CN112253074B - Method for improving bridge plug pumping efficiency by deep horizontal well fracturing - Google Patents
Method for improving bridge plug pumping efficiency by deep horizontal well fracturing Download PDFInfo
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Abstract
The invention discloses a method for improving pumping efficiency of a bridge plug by fracturing a deep horizontal well. The method comprises the following steps: (1) optimizing fracture parameters and fracturing construction parameters; (2) optimizing parameters of the shower holes; (3) acid pretreatment; (4) carrying out mixed pre-hydraulic fracturing and seam making; (5) adding sand into the soluble temporary plugging agent for fracturing; (6) fracturing 70-140 meshes of proppant by adding sand; (7) carrying out 40-70 mesh proppant long-section plug sand adding fracturing; (8) fracturing and filling the 30-50-mesh high-density proppant; (9) mixing and replacing. The invention realizes the promotion of seam height longitudinal extension, the promotion of proppant longitudinal settlement space and the provision of an effective flow channel for subsequent pumping bridge plug construction, thereby effectively relieving the high pumping pressure construction risk in the process of pumping the bridge plug after decompression and improving the pumping efficiency of the bridge plug.
Description
Technical Field
The invention relates to the technical field of oil and gas reservoir transformation, in particular to a method for improving bridge plug pumping efficiency by deep horizontal well fracturing.
Background
At present, the development proportion of oil and gas resources such as deep shale gas and deep sandstone oil and gas is higher and higher, and the wells are generally subjected to large-scale segmented fracturing modification after horizontal well casing is well-fixed. In order to ensure the effectiveness of staged fracturing, the isolation between fracturing sections, progressive perforation and staged fracturing are usually performed in a mode of combining a cable pumping bridge plug and perforation. However, deep oil and gas are buried deeply, the fracture forming width is limited, and in addition, the stratum closing pressure is high, at the later stage of construction, the migration of a propping agent in a fracture after the propping agent passes through a perforation hole becomes very difficult, so that a large amount of propping agent is accumulated at the position close to the well fracture, and therefore, the construction pumping stop pressure is high, sometimes, the pumping stop pressure of a well mouth is more than 70MPa, and even exceeds the highest well mouth pressure limit of a lower pumping bridge plug (the well mouth pressure limit of a common cable pumping bridge plug is more than 70 MPa). More disadvantageously, the pressure transmission efficiency is deteriorated due to the fact that a large amount of proppant is accumulated in the horizontal shaft close to the shaft of each cluster of crack inlets, in other words, the well shut-in pressure is slow, for example, the well shut-in pressure is reduced to the pressure limiting value of 70MPa of a pumping bridge plug, and sometimes the well shut-in pressure needs to be stopped for a quite long time, so that the fracturing construction progress is delayed, and the time cost is greatly increased. On the other hand, even if the pressure of the well head is reduced to be below the pressure limit of 70MPa, the pressure of the well head can be quickly increased to be above the pressure limit of 70MPa under the condition that the pumping displacement and the pumping speed are very low in the pumping process of the next section of bridge plug perforating gun combined tool, and at the moment, the construction of pumping the bridge plug and the perforating gun faces a great risk and the pumping operation must be stopped immediately.
At present, aiming at the technical problems that the pressure of a wellhead is difficult to diffuse and the pressure drops very slowly after the fracturing of a deep oil-gas well is stopped, and the next section of fracturing pumping construction is influenced, the main technical method is to open the well immediately after the pump is stopped to control open flow, so that a large amount of propping agents accumulated near the near well are regurgitated back to a horizontal shaft and are carried to the ground, and then a perforation hole is dredged to a near well crack and then to a flow channel of a far-end crack. Although the method is helpful for improving the pumping capacity of the next section, the flow conductivity of the crack after blowout is greatly reduced, especially the flow conductivity of the crack close to the well casing, because the liquid for subsequent sand addition is high-viscosity fracturing liquid, the viscosity is relatively high during flowback, and a large amount of propping agent at the seam is easily brought out. Meanwhile, along with the pumping operation, part of the propping agent flowing out of the seam during the original open flow process may flow back into the seam, so that the blocking effect on the operation of the pumping bridge plug may be generated again, and the low pressure of the pumping capacity is high.
The document ' application of a clustering perforation technology to shale gas wells ' (inner Mongolia petrochemical industry ' 2013, 10) introduces a cable perforation and hollow composite bridge plug fracturing combined technology, and provides a technical measure for ensuring pumping perforation by optimizing perforation diameter of a perforating bullet and reducing perforation friction when fracturing fluid enters a stratum; aiming at the condition that sand burial occurs in a well and a bridge plug cannot be normally pumped, a technical measure for establishing a pumping channel by using a coiled tubing to perform independent perforation is provided; aiming at the condition that sand grains are easy to accumulate near a deflecting point to influence a pumping bridge plug, a technical measure of cleaning a shaft by using glue solution with strong sand carrying capacity is provided.
The document mainly emphasizes some on-site response or emergency measures when the pumping bridge plug is in a condition, and the problems of high rock strength, high closing pressure, limited hydraulic fracturing fracture width, sensitive sand-liquid ratio and the like of deep shale, which cause high pumping stop pressure after fracturing, difficult pressure diffusion and slow falling, are not fundamentally solved, so that the construction of the pumping bridge plug of the next stage is influenced. No fundamental solutions are considered from the point of view of the fracturing process design itself and the overall implementation control. For example, the optimized perforation diameter of the perforating charge mentioned in the literature only plays a certain role in reducing the initial fracture initiation pressure of the rock, but has little influence on the whole fracturing construction; the single perforation of the coiled tubing is only a remedy measure which is taken when sand burial occurs in the well and the bridge plug cannot be pumped normally.
The method is characterized in that a conventional problem and a countermeasure for shale gas horizontal well pumping bridge plug perforation linkage operation (petroleum drilling and production process 2014 03) are provided, aiming at the problem that the pumping bridge plug is difficult to pump due to high pressure in the shale gas horizontal well pumping bridge plug perforation linkage staged fracturing practice, the main reasons are that shale gas fracturing mostly uses a slickwater and linear gel fracturing fluid system, the system is low in viscosity and poor in sand carrying performance, a small amount of settled sand existing in a horizontal section wellbore is accumulated in the bridge plug moving process, so that the pumping pressure is high, the cable lowering speed is low, the pumping pressure is limited to stop the pump when the pumping pressure is serious, and the tool stops moving; secondly, shale gas strata all belong to shale, and a large amount of liquid enters the strata during fracturing to cause the clay expansion of the strata, so that the strata are blocked and no liquid is fed, and the pressure of a pumping bridge plug is higher; thirdly, the pressure of the pump stopping in the former fracturing construction is high, and the bridge plug pumping cannot be carried out. Excessive displacement is carried out by using slickwater and highly viscous liquid in a displacement stage of fracturing, and settled sand in a horizontal well section is reduced; selecting proper type and dosage of the anti-swelling agent to reduce the clay swelling of the stratum; and a continuous oil pipe is adopted to jet the engineering hole, a stratum liquid inlet channel is established, and pumping pressure of a bridge plug is effectively reduced.
The literature mainly emphasizes some on-site countermeasures when the pumping bridge plug is in a state, and does not fundamentally solve the problems of high pressure of a pumping stop pump after fracturing, difficulty in pressure diffusion and slow falling caused by the problems of high rock strength, high closing pressure, limited hydraulic fracturing crack width, sensitive sand-liquid ratio and the like of deep shale, so that the construction of the pumping bridge plug of the next stage is influenced. No fundamental solutions are considered from the point of view of the fracturing process design itself and the overall implementation control. Preferably suitable anti-swelling agents such as those mentioned in the literature are not inherently related to reducing the pump-off pressure itself, and coiled tubing casing holes are only remedied for situations where high pump-off pressures are not conducive to normal wireline pumping operations.
The document ' difficult point and countermeasure of complex borehole trajectory pumping perforation ' (the ' 2016 (22) period of ' Chinese petroleum and chemical industry standards and quality ') analyzes the difficult points of cable twisting under large well body curvature, pipe string pump dropping, borehole sand setting, bridge blockage during pumping, complex borehole trajectory well cable jamming and the like in the complex borehole trajectory in the pumping stage, and provides a treatment measure. There is remaining sand to the horizontal segment, forms at the in-process of bridge plug pipe cluster motion and piles up, causes the hard and hinder, proposes through after fracturing at every turn, uses the high viscous liquid that is not less than 1.5 times pit shaft volume to replace, guarantees pumping channel's clean and reduction well sand bridge and piles up, and pumping process in-process reasonable control pumping speed and discharge capacity size to prevent that the pipe cluster meets and hinders and midway seat.
The document mainly emphasizes that corresponding treatment measures are provided for the difficulty of pumping perforation of a complex well track, and the treatment measures are general field operations. The problems of high rock strength, high closing pressure, limited hydraulic fracture forming width, sensitive sand-liquid ratio and the like of deep shale, which cause high pumping stop pressure after fracturing, difficult pressure diffusion and slow descending, are not fundamentally solved, so that the construction of the pumping bridge plug of the next stage is influenced. No consideration is given to the fundamental solution from the point of view of the fracturing process design itself and the full-scale implementation control. For example, in the literature, aiming at the problem of hard blockage of the bridge plug due to large change of curvature of a well track, residual sand in a horizontal section and the like, high-viscosity liquid displacement and reasonable control of pumping speed and discharge capacity are provided, and the method is not completely suitable for the problem that the bridge plug cannot be normally lowered due to high construction pressure of a deep well, high pump stopping pressure and slow pressure drop.
In the literature, "key control points and common problems of pumping bridge plug perforation combined operation" (chemical engineering and equipment, 2016, 10 th year), aiming at the characteristics of a horizontal well subsection multi-cluster pumping bridge plug perforation combined operation process, key control points such as grease injection sealing pressure, combined operation pipe string quality and length, pumping displacement and the like are determined by establishing an analysis model. Corresponding precautionary measures and solutions are made by combining the common problems of no-release of bridge plug seat seal, bridge plug pump release, accidental release of coiled tubing perforation and the like. For the case of pumping difficulties due to abnormal high pressure, the main reasons for literature analysis are: firstly, a shaft is not cleaned by organic solvent, so that a large amount of oily precipitates are accumulated in the pumping process; secondly, a small amount of settled sand exists in a shaft of the horizontal well section to form accumulation, so that the pumping pressure is too high; thirdly, a large amount of liquid enters the stratum during fracturing to cause clay expansion and cause difficulty in taking liquid; fourthly, the pressure of the pump stopping in the previous section is high, and no additional pressure space is pumped. The literature proposes soaking and flushing the wellbore with an organic solvent during the wellbore treatment process; after each stage of fracturing is finished, fully replacing by adopting glue solution and slick water, and completely ejecting sand into the stratum; for stratum with higher imbibition and pressure, acid liquor is used for treatment before and after fracturing, and if the problem can not be solved, a coiled tubing is used for setting a bridge plug and perforating.
The document mainly emphasizes that corresponding treatment measures are provided for potential risks in the process of pumping bridge plug perforation combined operation, and the treatment measures are general field operation. The problems that the rock strength of deep shale is high, the closing pressure is high, the hydraulic fracturing fracture forming width is limited, the sand-liquid ratio is sensitive and the like are not fundamentally solved, so that the pumping stop pressure after fracturing is high, the pressure is difficult to diffuse, and the pressure falls slowly, and further the construction of a pumping bridge plug of the next stage is influenced. No consideration is given to the fundamental solution from the point of view of the fracturing process design itself and the full-scale implementation control. For example, in the shaft treatment process proposed in the literature for the case of pumping difficulty caused by abnormal high pressure, the shaft is soaked and washed by using an organic solvent, so that the shaft treatment process only plays a certain role in solving the pollution in the shaft and has no internal connection for reducing the pump-stopping pressure after subsequent fracturing construction; after each section of fracturing proposed in the literature is finished, the glue solution and slick water are adopted for full replacement, so that the common operation on site cannot be realized fundamentally, an effective channel can be provided for subsequent pumping, and meanwhile, the effective filling in the full-seam high longitudinal direction can be realized; the coiled tubing set bridge plug and perforation proposed in the literature is a remedy measure for the pumping construction that the bridge plug cannot be normally set.
Therefore, there is a need to develop a new technology to fundamentally solve the above technical limitations.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for improving the pumping efficiency of a bridge plug by fracturing a deep horizontal well. Through the implementation of technologies such as the displacement is carried fast to leading high viscose liquid cooperation among the fracturing process, the former soluble temporary plugging agent of injection into earlier of sand construction, the later stage high density proppant is hit with the back to sand construction later stage, realize promoting seam height longitudinal extension, promote the vertical settlement space of proppant and provide effectual flow path for follow-up pumping bridge plug construction to pump the bridge plug in-process high pump pressure construction risk and the pumping efficiency who promotes the bridge plug after effective slow decompression.
The invention aims to provide a method for improving bridge plug pumping efficiency by deep horizontal well fracturing.
The method comprises the following steps:
optimizing fracture parameters and fracturing construction parameters;
step (2), optimizing the parameters of the shower holes;
step (3) acid pretreatment;
step (4), mixing the front hydraulic fracture;
adding sand into the soluble temporary plugging agent for fracturing;
step (6), adding sand into 70-140 meshes of proppant and fracturing;
step (7), carrying out 40-70 mesh proppant long-section plug sand adding fracturing;
step (8) fracturing and filling the 30-50-mesh high-density proppant;
and (9) mixing and replacing.
Wherein, the first and the second end of the pipe are connected with each other,
in the step (3), the discharge amount of acid is 1-2m 3 Min, acid dosage is 15-30m 3 After acid is injected, high-viscosity glue solution is adopted for replacing acid, and the discharge capacity of the acid replacing glue solution is increased to 2 times of the discharge capacity of the injected acid; when the acid liquid in the shaft reaches the blast hole, reducing the acid liquid to the previous acid injection discharge amount;
the viscosity of the high-viscosity glue solution is 60-80mPa & s.
In the step (4), all acid amount is completely replaced into the stratum until the construction pressure is not reduced any more, the discharge capacity of the high-viscosity glue solution is increased to the designed maximum discharge capacity within 1-2 minutes, and after 1.5-2 times of the wellbore volume high-viscosity glue solution is injected, the maximum discharge capacity is kept, and low-viscosity slick water is injected to further expand the seam; the injection amount of the low-viscosity slickwater is 4-5 times of the volume of the shaft;
the viscosity of the low-viscosity slickwater is 1-3mPa & s.
And (5) when the construction in the step (4) is completed, the seam length reaches 70-80% of the designed seam length, if the seam length does not reach the designed seam length, the pumping time of the preposed low-viscosity slickwater is prolonged, and the total liquid amount of the preposed high-viscosity liquid and the low-viscosity slickwater does not exceed 6 times of the volume of a shaft.
In the step (5), low-viscosity slick water is adopted to carry 70-140 meshes of temporary plugging agent, the temporary plugging agent is injected according to the sand-liquid ratio of 2% -4% -6% -8%, and the sand-liquid carrying amount of each step is 15-20m 3 (ii) a Then injecting the low-viscosity slick water carrying 30-50 meshes of temporary plugging agent according to the sand-liquid ratio of 6-8-10 percent, wherein the sand-liquid carrying amount of each step is 10-15m 3 。
In the step (6), after the temporary plugging agent is injected, 1.5-2 times of the low-viscosity slickwater with the shaft volume is replaced, the highest discharge capacity is kept, the low-viscosity slickwater is used for carrying 70-140 meshes of proppant slug type sand feeding, the initial sand-liquid ratio is 3%, the sand-carrying liquid slug liquid amount is 0.6-1.2 times of the shaft volume, then the low-viscosity slickwater with the same discharge capacity and the shaft volume of 0.5-1 times is injected as the spacer liquid, the sand-liquid ratio is gradually increased, and the increment of the sand-liquid ratio step is 1-2%. According to the field situation, 4-5 steps can be lifted generally.
In the step (7), the highest discharge capacity is kept, and 1-1.5 times of the volume of the shaft is replaced by high-viscosity slick water; carrying 40-70 meshes of propping agent with high-viscosity slick water to carry out continuous sand adding construction of a long section plug, wherein the initial sand-liquid ratio of the long section plug of the first section 40-70 meshes of propping agent is 3-5%; in the construction process of each long proppant slug, the sand-liquid ratio is increased by 2-3 steps according to 1% sand-liquid ratio step increment, the sand-carrying liquid amount is 3-5 times of the volume of a shaft, and high-viscosity slickwater 1-1.5 times of the volume of the shaft is pumped behind each long slug to serve as an isolation liquid;
repeating the initial sand-liquid ratio of the long section plug of the next-stage proppant for 2-3 times according to the highest sand-liquid ratio of the long section plug of the previous-stage proppant to complete 40-70 mesh proppant long section plug sand adding fracturing;
the viscosity of the high-viscosity slickwater is 12-15 mPa.s.
In the step (8), the highest discharge capacity is kept, and the high viscose liquid replaces 1-1.5 times of the volume of the shaft; carrying 30-50 mesh high-density proppant with high-viscosity glue; in the step (7), the highest sand-liquid ratio is taken as an initial value, 2-3 steps are gradually increased by 2% sand-liquid ratio increment, and the sand-carrying liquid amount of the 30-50-mesh high-density proppant is 1-2 times of the volume of the shaft;
the volume density of the proppant is higher than 1.8g/cm 3 The apparent density is 3.4g/cm 3 The above.
In the step (9), high-viscosity glue liquid with the volume 0.2-0.5 times of the shaft volume is replaced, and then low-viscosity slick water is replaced by a pump to inject the high-viscosity slick water with the volume 1-1.5 times of the shaft volume to perform the replacing operation.
The specific technical scheme of the invention is as follows:
(1) According to the design steps of a conventional shale gas well fracturing scheme, based on the evaluation of characteristic parameters of a reservoir before fracturing, optimizing fracture parameters including the length of a fracture, the number of fracture strips, the fracture conductivity and the like by adopting common oil reservoir numerical simulation software such as Eclipse and the like; and simulating and optimizing fracturing construction parameters matched with fracture parameters by using common shale gas fracturing fracture propagation simulation software such as Meyer and the like, wherein the fracturing construction parameters comprise liquid amount, propping agent amount, discharge amount, fracturing liquid systems with different viscosities, proportion and the like.
(2) And (3) according to the fracture parameters optimized in the step (1), combining the horizontal well while-drilling data and the well logging interpretation result, and specifically determining the fracture initiation position (namely the perforation position) and the bridge plug position. Except for the first section without a lower bridge plug, the subsequent fracturing section is subjected to bridge plug setting and step-by-step perforation according to the joint action of the bridge plug of a conventional cable pump and perforation, and according to the conventional method, spiral perforation is adopted, the hole density is 16-20 holes/meter, and the hole diameter is generally 9.5-13.9mm. After the perforation is finished, the cable is lifted up, the wellhead is reversely fractured, and the main fracturing flow is entered.
(3) Acid pretreatment is carried out before formal sand fracturing, and the acid dosage is generally 15-30m 3 The discharge capacity of the squeezed acid is generally 1-2m 3 And/min. After the acid is extruded, adopting glue solution with viscosity of 60-80mPa & s, quickly increasing the discharge capacity to the highest value within 1-2 minutes, promoting the seam to be high and quickly extended, and after injecting 1.5-2 times of shaft volume high viscosity glue solution, inverting 1-3mPa & s low viscosity slippery water for further seam expansion;
(4) Keeping the designed highest discharge capacity to continuously inject low-viscosity slickwater with the volume about 4-5 times of the shaft volume until the length of the seam reaches 70-80% of the designed seam length, respectively adopting the low-viscosity slickwater to carry 70-140 meshes of temporary plugging agents and 30-50 meshes of temporary plugging agents according to the sequence, carrying out pumping construction according to the designed sand-liquid ratio and the dosage, adding the temporary plugging agents in a stepped continuous sand-liquid extraction ratio mode, designing the 70-140 meshes of temporary plugging agents according to the sand-liquid ratio of 2% -4% -6% -8%, wherein the sand-liquid carrying capacity of each step is 15-20m 3 (ii) a The 30-50 mesh temporary plugging agent can be designed according to the sand-liquid ratio of 6-8-10 percent, and the sand-carrying liquid volume of each step is 10-15m 3 ；
(5) After the temporary plugging agent is pumped, replacing low-viscosity slickwater with 1.5-2 times of shaft volume, carrying out main proppant sand adding fracturing construction according to parameters such as design liquid amount, sand-liquid ratio, fracturing liquid viscosity and the like, and respectively carrying out 70-140 mesh proppant sand adding construction and 40-70 mesh proppant sand adding construction according to the sequence. The 70-140 mesh proppant is subjected to pumping construction by adopting a section-plug type sand adding mode of a section of sand carrying fluid and a section of isolation fluid, the sand carrying amount of each section plug of the 70-140 mesh proppant is 0.6-1.2 times of the volume of a shaft, and low-viscosity slickwater with 0.5-1 times of the volume of the shaft is replaced behind each section plug to serve as the isolation fluid; after pumping of all 70-140 meshes of propping agents is completed, the highest discharge capacity is kept, high-viscosity slickwater with the viscosity of 12-15mPa & s is changed to perform middle jacking, then the high-viscosity slickwater is used for carrying 40-70 meshes of propping agents to perform continuous sand adding construction of long section plugs, the sand carrying amount of each 40-70 meshes of propping agent long section plug is 3-5 times of the volume of a shaft, and the middle-viscosity slickwater with 1-1.5 times of the volume of the shaft is pumped to serve as a spacer fluid after each long section plug;
(6) After all the 40-70 mesh propping agents are added, the highest discharge capacity is kept, the high-viscosity glue solution with the pressure of 60-80mPa & s is switched, the high-viscosity glue solution with the grain size of 30-50 meshes and the volume density higher than 1.8g/cm is added after the high-viscosity glue solution with the volume of 1-1.5 times of the shaft is replaced 3 The apparent density is 3.4g/cm 3 The high-density proppant takes the highest sand-liquid ratio of 40-70 meshes as an initial value, and is gradually increased by 2-3 steps by 2% sand-liquid ratio increment, so that the whole sand adding construction is completed. The slug amount of the sand-carrying fluid with the grain diameter of 30-50 meshes in the stage is 1-2 times of the volume of the shaft;
(7) After the pumping construction of all the proppants is completed, high-viscosity glue liquid with the volume 0.2-0.5 times of the shaft volume is replaced, then low-viscosity slick water is replaced, and the displacement operation is performed by pumping with the volume 1-1.5 times of the shaft volume, so that the whole fracturing construction is completed.
By implementing the process and adding the hydration dissolution of the temporary plugging agent in advance near the end of the construction, the crack flow channel is further expanded, so that the rapid diffusion of the pressure of the pump stop after the construction is finished is facilitated, the pressure of the pump stop does not exceed the construction pressure limit of the pumping of the next-stage bridge plug, and the required discharge capacity of the pumping bridge plug of the next stage is facilitated to be established.
The invention has the following effects:
1) Construction for quickly lifting displacement by preposed high viscose
Due to the fact that the burial depth of deep shale or sandstone is increased, the closing pressure is increased, the minimum horizontal principal stress is relatively close to the vertical stress, the probability of horizontal bedding cracks or horizontal crack propagation in the fracturing process can be greatly increased, and therefore the crack height extension is limited. In the sand adding process, the propping agent is easy to be fully accumulated in the longitudinal direction of the fracture, so that the whole horizontal shaft is suppressed due to the lack of an effective flow channel after the last section of fracturing of the pumping bridge plug and the perforating tool after the fracturing, the bridge plug and the perforating gun cannot pump normally or the pumping displacement is relatively low, the operation efficiency is greatly reduced, and even the normal pumping operation cannot be performed possibly.
After the acid pretreatment, a high-viscosity glue solution and a rapid displacement increasing strategy are adopted, the viscosity of the glue solution is 60-80mPa & s, and the displacement is rapidly increased to the designed maximum displacement within 1-2 minutes. By implementation, relatively high wellbore pressure can be quickly suppressed in the horizontal wellbore, and the fractures at multiple cluster of jet holes in the section are ensured to be as synchronous as possible and quickly expanded on the fracture height. After the crack height is greatly expanded, all target layers are convenient to use in the longitudinal direction; and secondly, the settling height space of the proppant is increased, the proppant is difficult to be completely blocked in the longitudinal direction of the seam height, and in the process of pumping the next-stage bridge plug after pressing, pumping liquid is easy to flow in a channel which is not filled with the proppant and is positioned at the upper half seam height of the seam, so that the pumping operation of the next stage can be normally carried out.
2) Soluble temporary plugging agent construction before sand adding construction
Before formal sand adding, soluble temporary plugging agents with the particle size of 70-140 meshes are injected, so that after pressure continuously rises due to the fact that all perforation clusters in a fracturing construction section are fully filled and plugged, the temporary plugging agents which are settled previously are hydrated and dissolved along with the completion of construction, and the all perforation height direction is not completely filled any more, therefore, a new pumping liquid flowing channel is provided for the follow-up pumping bridge plug and perforating gun operation, and the risk of continuous pressure building of all well casings in the pumping process due to all perforation height plugging is reduced. In order to increase the plugging effect of the temporary plugging agent, a small part of the temporary plugging agent with the particle size of 30-50 meshes can be added at the tail end of the pumping and injecting stage of the temporary plugging agent so as to ensure that the temporary plugging effect is generated in the horizontal shaft.
3) High-density proppant for rear-end collision in later stage of sand addition
In the later stage of sand adding, if conventional density proppant or low density proppant is used, the fracture area is easily blocked at the middle upper part of the seam height, especially the fracture near the upper part of the seam height or even at the tip of the seam height, and because the seam width is relatively small, the proppant at the position can be mostly clamped by the fracture wall and cannot be settled, so that the final result is that the proppant almost completely fills the fracture area at the seam height, and the adverse situations that the wellhead pressure rises rapidly and the pumping output drops rapidly in the pumping process due to no flow channel in the subsequent pumping bridge plug and perforating gun processes are caused. By adopting the 30-50-mesh high-density proppant, on one hand, the requirement of filling with large particle size and improving the flow conductivity of the seam can be met; and on the other hand, the high-density large-particle size propping agent has high settling speed, can effectively reduce the plugging of cracks close to the upper part of the seam height and the seam height tip, and provides a flow channel for the pumped bridge plug after being pressed.
Drawings
FIG. 1 is a schematic diagram of the design of the displacement and sand-to-liquid ratio involved in the method of the present invention;
FIG. 2 is a cross-sectional view of the width of a slit along the length of the slit, obtained by the method of the present invention;
FIG. 3 is a cross-sectional view of a slit width along the slit length direction, which is obtained by a conventional process;
figure 4 graph of the construction of the J-well mini-test fracture in example 2.
Description of reference numerals:
1. construction displacement, sand-liquid ratio, acid pretreatment stage, mixed preposed hydraulic fracturing and crack-making stage, 5 soluble temporary plugging agent sand-adding fracturing stage, 6.70-140 meshes proppant sand-adding fracturing stage, 7.40-70 meshes proppant long-section plug sand-adding fracturing stage, 8.30-50 meshes large-particle-size high-density proppant fracturing and filling stage, and 9 mixed displacement stage.
The shale gas fracturing sand adding method disclosed by the invention has the following specific implementation mode by combining the attached drawings:
(1) And optimizing the fracture parameters and the fracturing construction parameters. According to the design steps of a conventional shale gas well fracturing scheme, based on the evaluation of reservoir characteristic parameters before fracturing, eclipse and other common reservoir numerical simulation software are adopted to optimize fracture parameters including fracture length, fracture number, fracture conductivity and the like; and simulating and optimizing fracturing construction parameters matched with fracture parameters by using common shale gas fracturing fracture propagation simulation software such as Meyer and the like, wherein the fracturing construction parameters comprise liquid amount, propping agent amount, discharge amount, fracturing liquid systems with different viscosities, proportion and the like.
(2) And optimizing the parameters of the shower holes. And (3) according to the fracture parameters optimized in the step (1), combining the horizontal well while-drilling data and the well logging interpretation result, and specifically determining the fracture initiation position (namely the perforation position) and the bridge plug position. Except for the first section without a lower bridge plug, the subsequent fracturing section is subjected to bridge plug setting and step-by-step perforation according to the joint action of the bridge plug of a conventional cable pump and perforation, and according to the conventional method, spiral perforation is adopted, the hole density is 16-20 holes/meter, and the hole diameter is generally 9.5-13.9mm. After the perforation is finished, the cable is lifted up, the wellhead is reversely fractured, and the main fracturing flow is entered.
(3) And (4) acid pretreatment. Such as "3. Acid pretreatment stage of FIG. 1", 1-2m before formal sand fracturing 3 Injecting 15-30m into the well bore by the displacement of/min 3 Hydrochloric acid with a concentration of 15%. After the acid is injected, the glue solution with the viscosity of 60-80mPa & s is changed over for replacing the acid, and the discharge capacity of the glue solution for replacing the acid can be increased to 4m 3 Min, when the acid liquor in the shaft reaches the blast hole, reducing the displacement of the acid-replacing glue liquor to 2m 3 The time of sufficient contact of the acid liquid and the blasthole is ensured so as to remove polluting plugs such as oil sludge and the like in a shaft and a perforation blasthole drilling well, and meanwhile, part of the acid liquid enters the stratum to perform chemical reaction with the rock, so that the initial fracture initiation pressure of the stratum can be reduced to a certain extent;
(4) Hybrid pre-hydraulic fracturing. Completely replacing all designed acid amount into the stratum by using glue solution according to the step (3) until the construction pressure is not reduced any more, rapidly increasing the discharge capacity of the glue solution to carry out pre-hydraulic crack formation after the change is stable (such as 4. A mixed pre-hydraulic fracturing crack formation stage of a figure 1), rapidly increasing the discharge capacity of the glue solution to the designed maximum discharge capacity within 1-2 minutes, keeping the designed maximum discharge capacity after injecting 1.5-2 times of shaft volume high-viscosity glue solution, inverting 1-3mPa.s of low-viscosity slickwater, and continuously injecting about 4-5 times of shaft volume low-viscosity slickwater to further expand the crack; the discharge capacity is rapidly improved through the preposed glue solution, and the further seam expansion of low-viscosity slick water is realized, so that the high direction of the longitudinal seam of the crack is fully extended;
through the implementation of the step (4), relatively high wellbore pressure can be quickly suppressed in the horizontal wellbore, and the fractures at multiple cluster jet holes in the section are ensured to be as synchronous as possible and quickly expanded on the fracture height. After the crack height is greatly expanded, all target layers are conveniently used in the longitudinal direction; and secondly, the settling height space of the proppant is increased, the proppant is difficult to be completely blocked in the longitudinal direction of the seam height, and in the process of pumping the next-stage bridge plug after pressing, pumping liquid is easy to flow in a channel which is not filled with the proppant and is positioned at the upper half seam height of the seam, so that the pumping operation of the next stage can be normally carried out.
(5) Adding sand into soluble temporary plugging agent for fracturing. After the step (4) is finished, the length of the seam at the moment is 70-80% of the designed seam length, if the specified seam length is not reached according to software simulation, the injection time of the preposed low-viscosity slickwater pump can be properly prolonged, and the total liquid volume of the preposed high-viscosity glue solution and the low-viscosity slickwater is generally not more than 6 times of the shaft volume. Then adding a soluble temporary plugging agent (as shown in figure 1, 5. A soluble temporary plugging agent adding sand fracturing stage), keeping the highest design discharge capacity, respectively adopting low-viscosity slick water to carry 70-140 meshes of temporary plugging agent and 30-50 meshes of temporary plugging agent according to the sequence, carrying out pumping construction according to the designed sand-liquid ratio and the dosage, completing the addition of the temporary plugging agent in a stepped continuous sand-liquid extraction ratio mode, designing the 70-140 meshes of temporary plugging agent according to the sand-liquid ratio of 2-4-6-8%, and carrying the sand-liquid quantity of each step to be 15-20m 3 (ii) a The 30-50 mesh temporary plugging agent can be designed according to the sand-liquid ratio of 6-8-10 percent, and the sand-carrying liquid volume of each step is 10-15m 3 ；
Through the implementation of the step (5), the continuous pressure rising effect caused by full-fracture high-filling blockage of each perforation cluster in a fracturing construction section can be prevented, along with the completion of the construction, the previously settled temporary plugging agent is hydrated and dissolved, and the full-fracture high direction is not completely filled any more, so that a new pumping liquid flowing channel is provided for the subsequent pumping bridge plug and perforating gun operation, and the risk of continuous full-wellbore pressure building in the pumping process caused by full-fracture high blockage is reduced.
(6) And fracturing by adding 70-140 meshes of proppant and sand. After the step (5) is finished, replacing low-viscosity slick water with 1.5-2 times of the volume of the shaft, keeping the highest discharge capacity, carrying out 'segment plug type' sand adding of 70-140 meshes of propping agent according to the designed liquid quantity and sand-liquid ratio (such as a 6.70-140 meshes of propping agent sand adding fracturing stage shown in figure 1), wherein the initial sand-liquid ratio of the 70-140 meshes of propping agent is 3%, the sand-carrying liquid slug liquid quantity is 0.6-1.2 times of the volume of the shaft, then injecting low-viscosity slick water with 0.5-1 times of the volume of the shaft as a spacer liquid with the same discharge capacity, gradually increasing the sand-liquid ratio, and increasing the step increment of the sand-liquid ratio by 1-2%, such as 3% -5% -7% -8% -9%, and carrying out the slug type sand adding;
(7) And (3) performing long-section sand-adding fracturing on the 40-70-mesh proppant. After the step (6) is finished, keeping the highest discharge capacity, replacing the low-viscosity slickwater with 1-3mPa s with the high-viscosity slickwater with 12-15mPa s to replace 1-1.5 times of the volume of the shaft, and then carrying out continuous sand adding construction on the long section plug by using the high-viscosity slickwater with 40-70 meshes of propping agent (such as a 7.40-70-mesh propping agent long section plug sand adding fracturing stage shown in the figure 1), wherein the initial sand-liquid ratio of the first section 40-70-mesh propping agent long section plug is 3-5% (specifically, the adjustment and confirmation can be carried out according to the actual situation on site), in the construction process of each long propping agent section plug, the sand-liquid ratio is slowly increased by 2-3 steps according to the increment of 1% sand-liquid ratio step, the sand-liquid carrying amount is 3-5 times of the volume of the shaft, the high-viscosity slickwater with 1-1.5 times of the volume of the shaft is pumped into each long section plug to serve as the spacer fluid, the initial sand-liquid ratio of the subsequent 40-70-mesh propping agent long section plug is designed as the highest sand-liquid-plug, and the step of the subsequent 40-70-mesh propping agent long section plug can be repeatedly carried out 2-70 times of the fracturing, and the step can be repeatedly carried out the step. In the stage, along with the increase of the sand-liquid ratio, the sand-carrying liquid amount of a single proppant long-section plug is gradually reduced;
through the implementation of the step (7), the sand adding efficiency can be effectively improved, and the construction period can be shortened.
(8) And fracturing and filling the high-density proppant with 30-50 meshes. After the step (6) is finished, keeping the highest discharge capacity, replacing the high-viscosity slickwater with 12-15 mPas with high-viscosity glue with 60-80 mPas to replace 1-1.5 times of the volume of the shaft, and then carrying out fracture sealing and sand adding construction (such as a fracturing and filling stage of 8.30-50-mesh large-particle-size high-density propping agent shown in figure 1) by using the high-viscosity glue and the 30-50-mesh large-particle-size high-density propping agent, wherein the volume density of the 30-50-mesh propping agent is higher than 1.8g/cm 3 The apparent density is 3.4g/cm 3 Taking the highest sand-liquid ratio of the 40-70-mesh proppant slug at the last section in the step (7) as an initial value, and gradually lifting the sand-liquid ratio by 2-3 steps according to the increment of 2% sand-liquid ratio step, so that the sand adding of the 30-50-mesh proppant can be completed, wherein the sand-carrying liquid slug amount of the 30-50-mesh proppant at the stage is 1-2 times of the volume of the shaft;
through the implementation of the step (8), on one hand, the requirement of filling with large particle size and improving the flow conductivity of the seam can be met; and on the other hand, the high-density large-particle size propping agent has high settling speed, can effectively reduce the plugging of cracks close to the upper part of the seam height and the seam height tip, and provides a flow channel for the pumped bridge plug after being pressed.
(9) And (4) mixing and replacing. After pump injection construction is completed on all proppants, high-viscosity glue liquid with the volume 0.2-0.5 times of that of the shaft is replaced, then low-viscosity slick water is replaced, and pump injection is performed on the high-viscosity glue liquid with the volume 1-1.5 times of that of the shaft, so that the whole fracturing construction is completed;
through the implementation of the steps (4) to (9), along with the hydration dissolution of the temporary plugging agent in the early stage and the rapid sedimentation of the high-density proppant with 30-50 meshes in the later stage when the construction is finished, the fracture cannot be blocked longitudinally, and a flow channel for communicating the fracture with the shaft is further expanded, so that the rapid diffusion of the pressure of the pump stop after the construction is finished is facilitated, the pressure of the pump stop cannot exceed the construction pressure limit of the well mouth of the pumping bridge plug of the subsequent fracturing section, and the displacement required by the pumping bridge plug of the next stage is facilitated to be established;
(10) The fracturing construction of other sections can be repeated in the steps (3) to (9) until all sections are pressed;
(11) The subsequent steps of drilling and plugging, flow back, production solving and the like are executed according to the conventional operation flow, and are not redundant.
Detailed Description
The present invention will be further described with reference to the following examples.
Example 1
The D well is a sea-facies deep shale gas horizontal well, the target layer of the well is a lower-mindset Longmaxi group-an upper-Otaogue Wufeng group, the middle part of the target layer is vertical deep 4115m, and the horizontal section is 1520m long. The average content of silicon, the average content of calcium and the brittleness index of 55-65 percent of the horizontal section of the well penetrating through a target layer are 43 percent, 15 percent and the average content of the calcium is 15 percent; young's modulus 33-35GPa, poisson's ratio 0.2-0.22, tensile strength 11.2-12.5MPa, and fracture toughness 0.6-1.5 MPa.m 0.5 (ii) a The maximum horizontal main stress is 105-118 MPa, the minimum horizontal main stress is 90-96 MPa, the absolute value difference of the two-direction horizontal stress is 21-24 MPa, and the difference coefficient of the horizontal stress is 0.22; seam and layer in the same directionThe seam is arranged and developed, and the high-angle natural crack is not developed. Generally, the target layer of the well is buried deeply, the rock strength is high, the difference of rock mechanical properties is large, the difficulty of rock initiation prediction is large, and the 12-18m of the well is calculated by referring to the extension pressure gradient of the fracture of the adjacent well 3 The construction pressure of a wellhead under the construction displacement per minute is 91-107MPa, and the well fracturing construction pressure is expected to be high. According to the judgment, because the fracture initiation pressure is high, the fracture construction pressure window is limited, and the difficulty of improving the net pressure, opening the micro-scale fracture and forming a complex fracture network is high; meanwhile, as the stratum closing pressure is high, the main fracture width and the flow conductivity can be influenced. If the effective supporting seam width and the ensured fracture connectivity cannot be formed in the fracturing construction process, and the natural fracture of the well does not develop, the pumping stop pressure of each stage of fracturing construction is high, and the pressure diffusion is slow. For general bridge plug pumping operation, the pressure limiting of a wellhead is 70MPa during pumping, and the pumping operation of the next stage of bridge plug after each section of pressure is finished cannot be carried out when the pressure limiting is exceeded; or the pressure drop is slow after the pump is stopped, the difference between the pressure drop and the limited pressure is less than 10MPa, the pumping operation of the next-stage bridge plug after the pressure is finished can be influenced, the pumping displacement can be strictly controlled to prevent overpressure in the pumping process of the bridge plug, the pumping time is greatly increased, and the whole operation efficiency is not improved. Therefore, the invention provides a method for improving the efficiency of a pumping bridge plug by horizontal well fracturing, namely in the fracturing construction process before pumping operation, by adopting some special processes and changing the fracturing pump injection mode, the effects of promoting seam height longitudinal extension, lifting a proppant longitudinal settling space, accelerating pressure diffusion, reducing pump stop pressure and providing an effective flow channel for subsequent pumping bridge plug construction are realized, so that the construction risk of high pumping pressure in the pumping bridge plug process after pressure relief and the pumping efficiency of the pumping bridge plug are effectively relieved. The specific implementation method will be described in detail with reference to this example as follows (fig. 1 is a typical construction displacement and sand-liquid ratio design diagram of the well):
(1) By adopting ECLIPSE oil and gas reservoir numerical simulation software for optimization, the horizontal section of the well is 1520m long, the designed fracturing 20 sections are 55 clusters in total, the half length of the optimized fracture is 270-300m, and the flow conductivity of the main fracture is 2-3D cm. Optimizing the parameters meeting the fracture by combining shale gas fracture propagation simulation software MEYERThe fracturing process parameters are as follows: single-stage hydrochloric acid 20m with concentration of 15% 3 (ii) a Single stage fracturing fluid volume 2200m 3 (including 350m of glue solution with viscosity of 80 mPas 3 Low viscosity slick water 880m with viscosity of 3 mPas 3 Viscosity of 15 mPas high viscosity slickwater 970m 3 ) (ii) a Single stage soluble temporary blocking dosage 6.3m 3 (including 70-140 mesh temporary plugging agent 3.4m 3 30-50 mesh temporary plugging agent 2.9m 3 ) (ii) a Single stage supported dose of 80m 3 (including 70-140 mesh pottery 17.4 m) 3 40-70 mesh low-density ceramsite 48.6m 3 30-50 meshes of high-density ceramsite 14m 3 ) (ii) a Optimized highest construction pump injection displacement of 18m 3 And/min. In the aspect of perforation parameter design, the number of perforation clusters is 2-3 clusters/section, the perforation length is 3 m/section, the hole density is 16 holes/m, the hole diameter is 13.9 mm/hole, and holes are spirally distributed. The cluster perforation positions in the sections are selected according to the principle that the layers are uniform, the gas content is high, and the lithological property, the electrical property and the mechanical property in the sections are consistent as much as possible;
(2) Well bore volume 60m 3 : based on step (1), press 2m 3 Injecting 15% hydrochloric acid 20m per min 3 Then, acid replacement is carried out by adopting glue solution with viscosity of 80mPa & s, and the discharge capacity of the acid replacement is 4m 3 And/min. The acid is quickly replaced to the hole, namely, the acid replacing glue solution is close to 40m 3 While reducing the discharge capacity to 2m 3 At the moment, the acid liquor begins to enter the stratum through the blast hole, and due to the removal of the pollution of the acid to the near well and the chemical reaction between the acid and the stratum rock, the rock cracking pressure is reduced, and the corresponding construction pressure is also reduced to a certain extent;
(3) According to the step (2), until the acid liquor is completely replaced into the stratum, the construction pressure changes stably, and the discharge capacity of the glue liquor is quickly increased to the designed maximum discharge capacity of 18m within 2 minutes 3 Permin for pad fluid fracture formation, 2 times of wellbore volume (about 120 m) is injected in a cumulative manner 3 ) After glue solution, low-viscosity slick water with the viscosity of 3mPa & s is changed, the designed maximum discharge capacity is kept, and the high-viscosity slick water is continuously injected into a 3-time shaft volume (about 180 m) 3 ) Low viscosity slickwater, the mixed preflush of the glue solution and the slickwater is injected into 300m in an accumulated way 3 The crack extends to about 70% of the designed crack length, and the pre-liquid crack making is completed;
(4) After the step (3) is finished, continuing to maintain 18m 3 And performing soluble temporary plugging agent sand fracturing at the discharge rate of/min. The initial sand-liquid ratio of the temporary plugging agent of 70-140 meshes is designed to be 2%, the sand-liquid ratio is increased to 8% by the increment of 2% sand-liquid ratio step (as shown in figure 1), and the sand-liquid ratio sand-carrying liquid amount of each step is 15-20m 3 I.e. 2% (15 m) 3 )-4％(15m 3 )-6％(15m 3 )-8％(20m 3 ) (ii) a Then replacing the temporary plugging agent with a 30-50-mesh soluble temporary plugging agent, wherein in the replacement process, in order to prevent an auger of a sand mixing truck from emptying, when sand is added to the last sand-liquid ratio of the previous 70-140-mesh temporary plugging agent, the flow of the 30-50-mesh soluble temporary plugging agent can be reversed in advance, the initial sand-liquid ratio of the 30-50-mesh soluble temporary plugging agent is designed to be 6%, the sand-liquid ratio is increased to 10% by 2% sand-liquid ratio step increment (as shown in figure 1), and the sand-liquid ratio sand-carrying liquid volume of each step is 10-15m 3 I.e. 6% (10 m) 3 )-8％(10m 3 )-10％(15m 3 ). At this stage, 70-140 mesh temporary plugging agent is added in an accumulated manner to form a mixture with a particle size of 3.4m 3 30-50 mesh temporary plugging agent 2.9m 3 . It should be noted that, according to the construction time of this example, the requirement for the dissolution time of the temporary plugging agent is 160min, that is, the temporary plugging agent is completely dissolved near the end of construction;
(5) After the step (4) is finished, keeping the maximum 18m 3 Displacement per minute, displacing 1.5 times the wellbore volume (about 90 m) 3 ) After the low-viscosity slickwater is low-viscosity slickwater, 70-140 meshes of propping agent (powder pottery) is added, the initial sand-liquid ratio of the powder pottery is designed to be 3%, the sand is added in a block type mode according to the mode of 'one-section sand carrying liquid + one-section isolation liquid', the sand carrying liquid amount of each block is 0.6-1 time of the volume of a shaft, then the low-viscosity slickwater with the same discharge capacity and 0.5-1 time of the volume of the shaft is injected to be used as the isolation liquid, the sand-liquid ratio is gradually increased to 9% by 1% -2% of the sand-liquid ratio step increment, and the isolation liquid behind each block is correspondingly increased along with the increase of the sand-liquid ratio. As shown in the "6.70-140 mesh proppant sand fracturing stage" of FIG. 1, the ratio of powder to ceramic sand liquid (sand carrying amount) and the amount of spacer liquid in this example are designed as follows: 3% (40 m) 3 )-30m 3 5% (50 m) of spacer fluid 3 )-40m 3 Isolation liquid-7% (50 m) 3 )-50m 3 Isolation liquid-8% (60 m) 3 )-60m 3 9% (60 m) of spacer fluid 3 ). At this stage, 70-140 mesh pottery powder of 17.4m is added 3 ；
(6) After the step (5) is finished, keeping the maximum of 18m 3 The displacement per min, the inversion viscosity of the high-viscosity slickwater with 15 mPas continuously replace 1.5 times of the shaft volume (90 m) 3 ) And then performing 40-70-mesh low-density ceramsite long-section sand filling construction. The initial sand-liquid ratio of the low-density ceramsite with the size of 40-70 meshes is designed to be 4%, the sand-liquid ratio is increased by 1% sand-liquid ratio step increment, the initial sand-liquid ratio of each subsequent long section plug is the highest sand-liquid ratio of the previous section, the sand-carrying liquid amount of each single long section plug is 3-5 times of the volume of a shaft, the sand-carrying liquid amount of each long section plug is gradually reduced along with the increase of the sand-liquid ratio, and 70-90m of displacement is carried out after each section plug 3 High viscosity slick water is used as the spacer fluid. As shown in the "7.40-70 mesh proppant long-section plug sand fracturing stage" of FIG. 1, the sand-liquid ratio (sand-carrying liquid amount) and the spacer liquid amount of the 40-70 mesh low-density ceramsite in this example are designed as follows: 4% (120 m) 3 )+5％(100m 3 )+6％(80m 3 )-70m 3 6% of spacer fluid (70 m) 3 )+7％(80m 3 )+8％(90m 3 )-80m 3 Isolation liquid-8% (70 m) 3 )+9％(60m 3 )+10％(60m 3 )-90m 3 And (4) isolating liquid. At this stage, 40-70 mesh low-density ceramsite 48.6m is added 3 ；
(7) After the step (6) is finished, keeping the maximum of 18m 3 The high-viscosity glue with the displacement per min and the reverse viscosity of 80 mPas continuously replaces 1.5 times of the shaft volume (90 m) 3 ) Then, carrying out 30-50 meshes of high-density ceramsite sand-adding construction, wherein the volume density of the high-density ceramsite is 1.8g/cm 3 Apparent density of 3.4g/cm 3 And (3) taking the highest sand-liquid ratio of the 40-70-mesh proppant slug at the last section in the step (6) as an initial value, gradually increasing the sand-liquid ratio to 14% according to the increment of the 2% sand-liquid ratio step, gradually reducing the sand-carrying liquid amount corresponding to each sand-liquid ratio along with the increase of the sand-liquid ratio, and taking the sand-carrying liquid slug of the 30-50-mesh proppant at the stage as 2 times of the volume of the well bore. As shown in the fracturing and filling stage of the 8.30-50 mesh large-particle-size high-density proppant in FIG. 1, the sand-liquid ratio (sand-carrying liquid amount) of the 30-50 mesh high-density ceramsite in this example is designed as follows: 10% (50 m) 3 )+12％(40m 3 )+14％(30m 3 ). At this stage, 30-50 mesh high-density ceramsite 14m is added 3 ；
(9) After step (7) is completed, the highest design is maintainedThe discharge capacity is 18m3/min, and 20m is replaced firstly 3 High viscosity glue, then switching 3 mPas low viscosity slickwater for continuously replacing 70m 3 And (5) left and right, finishing construction.
According to the construction parameter design of each fracturing stage of the embodiment, the fracture parameters are inverted by adopting fracture propagation simulation software MEYER (shown in figures 2 and 3). According to the invention, through implementation of measures such as rapid discharge of glue liquid for promoting seam height extension, adding a soluble temporary plugging agent with mixed particle size in the early stage, adding sand by force by using a long-section plug of low-density ceramsite with 40-70 meshes, and chasing 30-50 meshes of high-density ceramsite in the later stage of construction, compared with the traditional fracturing process of deep shale gas of an adjacent well (the discharge is controlled by the preposed glue liquid, the temporary plugging before sand addition is not considered, the dense sand addition of small-section plugs with 40-70 meshes and the chasing 30-50 meshes of low-density ceramsite are adopted), the seam length is reduced to a certain extent (the length of a fitting half seam is 321m, the design requirement can still be met), but the seam height, the seam width and the flow conductivity are obviously improved. Compared with the conventional fracturing method of adjacent sections, the method provided by the invention has the advantages that the seam length is reduced by 9.58%, the seam height is improved by 60.89%, the seam width is improved by 32.77%, and the flow conductivity is improved by 40.38%.
Example 2
The J well is a near-fault marine-phase deep shale gas horizontal well, the target layer of the well is a lower-mindset Longmaxi group-an upper-Otaogong Wufeng group, the middle part of the target layer is 3910m in vertical depth, and the horizontal section is 1500m in length. The average silicon content, the average calcareous content and the brittleness index of the horizontal section of the well penetrating through a target layer are respectively 51.8 percent, 9.5 percent and 66 to 74 percent respectively; young modulus 25.89-34.58GPa, poisson ratio 0.21-0.26; the maximum horizontal main stress is 96-108 MPa, the minimum horizontal main stress is 75-91 MPa, the absolute value difference of the two-direction horizontal stress is 13-17 MPa, and the difference coefficient of the horizontal stress is 0.14; horizontal seams and joints develop, and high-angle seams do not develop. Generally, the target layer of the well is buried deeply, the mechanical property difference of rocks is large, the predicted rock fracture pressure and the predicted extension pressure are high, particularly the vertical stress is close to the minimum horizontal main stress (the difference is 1.4 MPa), and horizontal bedding cracks are easy to open in the fracturing process, so that the filtration loss is increased, and the high construction pressure is possibly caused. Calculating the 12-18m of the well by referring to the fracture extension pressure gradient of the adjacent well 3 The construction pressure of a wellhead under the construction displacement per minute is 83-108MPa, and the well fracturing construction pressure is predictedThe force is high, and the fracturing construction pressure window and the pumping bridge plug construction pressure window are limited. According to the small-scale testing fracturing construction curve diagram of the J well in the figure 4, the fracturing construction has high pumping stop pressure and slow pressure diffusion, the difference between the wellhead pressure and the 70MPa wellhead pressure limiting required by pumping construction within 1 hour of pumping stop is within 10MPa, and the pumping operation of the next stage of bridge plug after being pressed can be influenced. Therefore, the well adjusts the subsequent main fracturing construction scheme according to the small fracturing test evaluation result, wherein in order to improve the overall fracturing-pumping operation efficiency, the method for improving the pumping bridge plug efficiency by horizontal well fracturing provided by the invention is adopted, namely in the fracturing construction process before pumping operation, the effects of promoting seam height longitudinal extension, improving the proppant longitudinal settlement space, accelerating pressure diffusion and reducing the pump stop pressure are realized by adopting some special processes and changing the fracturing pump injection mode, an effective flow channel is provided for the subsequent pumping bridge plug construction, and the high pumping pressure construction risk and the pumping efficiency of the bridge plug in the pumping bridge plug process after decompression are effectively relieved. The specific implementation method will be described in detail with reference to this example as follows:
(1) By adopting ECLIPSE oil and gas reservoir numerical simulation software for optimization, the horizontal section of the well is 1500m long, 61 clusters of 23 designed fractured sections are totally formed, the half length of the optimized fracture is 280-320m, and the flow conductivity of the main fracture is 1-2 D.cm. The fracturing process parameters meeting the fracture parameters are optimized by combining shale gas fracturing fracture propagation simulation software MEYER: single-stage hydrochloric acid 30m with concentration of 15% 3 (ii) a Single stage fracturing fluid volume 2200m 3 (including a glue solution with viscosity of 60 mPas of 300m 3 Low viscosity slickwater 950m with viscosity of 1 mPa.s 3 High viscosity of 12 mPas high viscosity slickwater 950m 3 ) (ii) a Single-stage soluble temporary plugging dosage of 7.6m 3 (including 70-140 mesh temporary plugging agent 4m 3 30-50 mesh temporary plugging agent 3.6m 3 ) (ii) a Single stage support dose of 79.6m 3 (comprising 70-140 mesh powder pottery 23m 3 40-70 mesh low-density ceramsite 45m 3 30-50 meshes of high-density ceramsite with the particle size of 11.6m 3 ) (ii) a Optimized highest construction pump injection displacement of 18m 3 And/min. In thatIn the aspect of perforation parameter design, the number of perforation clusters is 2-3 clusters/section, the perforation length is 3 m/section, the hole density is 16 holes/m, the hole diameter is 13.9 mm/hole, the holes are distributed spirally, and a part of well tracks pass across a plurality of small intervals to adopt a directional perforation mode. The cluster perforation position in the segment is selected on the principle that the gas content is high and the lithology, the electrical property and the mechanical property in the segment are as consistent as possible;
(2) Well bore volume 56m 3 : based on step (1), at 2m 3 Injecting 15% hydrochloric acid 30m per min 3 Then, acid replacement is carried out by adopting glue solution with the viscosity of 60mPa & s, and the discharge capacity of the acid replacement is 4m 3 And/min. The acid is quickly replaced to the hole, namely, the acid replacing glue solution is close to 26m 3 While reducing the discharge capacity to 2m 3 At the moment, the acid liquor begins to enter the stratum through the blast hole, and due to the removal of the pollution of the acid to the near well and the chemical reaction between the acid and the stratum rock, the rock cracking pressure is reduced, and the corresponding construction pressure is also reduced to a certain extent;
(3) According to the step (2), until the acid liquor is completely replaced into the stratum, the construction pressure changes stably, and the discharge capacity of the glue liquor is quickly increased to the designed maximum discharge capacity of 18m within 2 minutes 3 Permin pre-liquid seam making, and cumulatively injecting 100m 3 After the glue solution is added, the low-viscosity slickwater with the viscosity of 1mPa & s is switched, the highest designed discharge capacity is kept, and the glue solution is continuously injected into the water tank for 160m 3 Low viscosity slickwater, the mixed preflush of the glue solution and the slickwater is injected into 260m in an accumulated way 3 Finishing the preposed liquid seam making;
(4) After the step (3) is finished, continuing to maintain 18m 3 And carrying out soluble temporary plugging agent sand fracturing at the delivery rate of/min. The initial sand-liquid ratio of the temporary plugging agent with 70-140 meshes is designed to be 2%, the sand-liquid ratio is increased to 8% by the increment of 2% sand-liquid ratio step (as shown in figure 1), and the sand-liquid ratio sand-carrying liquid amount of each step is 20m 3 I.e. 2% (20 m) 3 )-4％(20m 3 )-6％(20m 3 )-8％(20m 3 ) (ii) a Then replacing the temporary plugging agent with a 30-50-mesh soluble temporary plugging agent, wherein in the replacement process, in order to prevent an auger of a sand mixing truck from emptying, when sand is added to the last sand-liquid ratio of the previous 70-140-mesh temporary plugging agent, the flow of the 30-50-mesh soluble temporary plugging agent can be reversed in advance, the initial sand-liquid ratio of the 30-50-mesh soluble temporary plugging agent is designed to be 6%, and the sand liquid is increased by increasing the 2% sand-liquid ratio to the step incrementThe sand-liquid ratio is 10 percent (as shown in figure 1), and the sand-liquid ratio of each step is 15m 3 I.e. 6% (15 m) 3 )-8％(15m 3 )-10％(15m 3 ). At this stage, 70-140 mesh temporary plugging agent 4m is added 3 30-50 mesh temporary plugging agent 3.6m 3 . It should be noted that, according to the construction time of this example, the requirement for the dissolution time of the temporary plugging agent is 160min, that is, the temporary plugging agent is completely dissolved near the end of construction;
(5) After the step (4) is finished, keeping the maximum 18m 3 Displacement at a rate of 80 m/min 3 After low-viscosity slick water, adding 70-140 meshes of propping agent (powder pottery) into the low-viscosity slick water, wherein the initial sand-liquid ratio of the powder pottery is 3%, and carrying out slug type sand adding according to a mode of 'first-stage sand-carrying liquid + first-stage spacer fluid', wherein the sand-carrying liquid amount of each slug is 40-60m 3 Then injecting 30-50m at the same displacement 3 The low-viscosity slick water is used as an isolation liquid, the sand-liquid ratio is gradually increased to 10 percent by 1 to 2 percent of sand-liquid ratio step increment, and the isolation liquid behind each slug is correspondingly increased along with the increase of the sand-liquid ratio. As shown in the "6.70-140 mesh proppant sand fracturing stage" of FIG. 1, the ratio of powder to ceramic sand liquid (sand carrying amount) and the amount of spacer liquid in this example are designed as follows: 3% (40 m) 3 )-30m 3 5% of spacer fluid (50 m) 3 )-30m 3 Isolation liquid-7% (60 m) 3 )-40m 3 Spacer fluid-8% (60 m) 3 )-50m 3 9% (60 m) of spacer fluid 3 )-50m 3 10% (50 m) of spacer fluid 3 ). At this stage, adding 70-140 mesh pottery powder 23m 3 ；
(6) After the step (5) is finished, keeping the maximum of 18m 3 The high-viscosity slickwater with the discharge capacity per min and the inversion viscosity of 12mPa & s continuously replaces 80m 3 And then performing 40-70-mesh low-density ceramsite long-section sand filling construction. The initial sand-liquid ratio of the low-density ceramsite of 40-70 meshes is designed to be 4%, the sand-liquid ratio is increased by 1% sand-liquid ratio step increment, the initial sand-liquid ratio of each subsequent long section plug is the highest sand-liquid ratio of the previous section, the sand-carrying liquid amount of a single long section plug is 3-5 times of the volume of a shaft, the sand-carrying liquid amount of the long section plug is gradually reduced along with the increase of the sand-liquid ratio, and 70-90m of displacement is carried out after each section plug 3 High viscosity slick water is used as the spacer fluid. The 7.40-70 mesh proppant long section plug sand adding pressure as shown in figure 1As shown in the cracking stage ", the sand-liquid ratio (sand-carrying liquid amount) and the partition liquid amount of the low-density ceramsite of 40 to 70 meshes in this example were designed as follows: 4% (120 m) 3 )+5％(80m 3 )+6％(80m 3 )-65m 3 6% isolation liquid (60 m) 3 )+7％(70m 3 )+8％(80m 3 )-65m 3 Isolation liquid-8% (70 m) 3 )+9％(60m 3 )+10％(55m 3 )-65m 3 And (4) isolating liquid. At this stage, 40-70 mesh low-density ceramsite 45m is added 3 ；
(7) After the step (6) is finished, keeping the maximum 18m 3 The high-viscosity adhesive with the discharge capacity per minute and the reverse viscosity of 60 mPas continuously replaces 80m 3 Then, carrying out 30-50 mesh high-density ceramsite sand adding construction, wherein the volume density of the high-density ceramsite is 1.85g/cm 3 Apparent density of 3.4g/cm 3 Taking the highest sand-liquid ratio of the 40-70-mesh proppant slug at the last section in the step (6) as an initial value, gradually increasing the sand-liquid ratio to 14% according to the increment of the 2% sand-liquid ratio step, gradually reducing the sand-carrying liquid amount corresponding to each sand-liquid ratio along with the increase of the sand-liquid ratio, and setting the sand-carrying liquid slug amount of the 30-50-mesh proppant at the stage as 100m 3 . As shown in the fracturing and filling stage of the 8.30-50 mesh large-particle-size high-density proppant in FIG. 1, the sand-liquid ratio (sand-carrying liquid amount) of the 30-50 mesh high-density ceramsite in this example is designed as follows: 10% (40 m) 3 )+12％(40m 3 )+14％(20m 3 ). At this stage, 30-50 mesh high-density ceramsite 11.6m is added 3 ；
(9) After the step (7) is finished, keeping the highest designed displacement of 18m 3 Min, first replace 20m 3 High viscosity glue, then switching 1 mPas low viscosity slickwater for continuously replacing 65m 3 And (5) left and right, finishing construction.
According to the design of construction parameters of each fracturing stage in the embodiment, the crack parameters are inverted by adopting crack propagation simulation software MEYER. The method has the advantages that the implementation of measures such as rapid increase of the discharge amount of glue solution to promote the extension of the seam height, addition of the soluble temporary plugging agent with mixed grain diameter in the early stage, forced sand addition of the long-section plug of the low-density ceramsite of 40-70 meshes, and tail dressing of the high-density ceramsite of 30-50 meshes in the later stage of construction is adopted, compared with the conventional fracturing method, the seam length is reduced by 8.23%, the seam height is increased by 61.34%, the seam width is increased by 31.42%, and the flow conductivity is increased by 38.67%.
By implementing the fracturing method provided by the invention, the flow conductivity of the cracks on the crack openings and the crack high sections is obviously improved, so that an effective flow channel is provided for pumping bridge plug operation before the subsequent fracturing section construction, and the pumping pressure is effectively controlled. Compared with the conventional method of the adjacent sections, the pressure drop of the fracturing bridge plug reaches 11.6MPa averagely after 30 minutes, the pumping pressure of the next section is reduced by 31.2% averagely when the pumping pressure of the last section is stopped, and the pressure of the same section is reduced by 16.4% averagely when the pumping pressure of the same section is stopped. Therefore, the construction risk of pumping bridge plugs before the next section of fracturing caused by high wellhead pressure and slow pressure drop after fracturing and pump stopping of the deep shale gas well is effectively avoided, and the pumping bridge plug operation efficiency is improved.
Claims (9)
1. A method for improving bridge plug pumping efficiency by deep horizontal well fracturing is characterized by comprising the following steps:
optimizing fracture parameters and fracturing construction parameters;
optimizing parameters of the shower holes;
step (3) acid pretreatment;
after acid injection is finished, replacing acid by adopting high-viscosity glue solution; the viscosity of the high-viscosity glue solution is 60-80mPa.s;
step (4), mixing the front hydraulic fracture;
after injecting high-viscosity glue solution with 1.5-2 times of shaft volume, keeping the highest discharge capacity and injecting low-viscosity slick water for further crack expansion; the injection amount of the low-viscosity slickwater is 4-5 times of the volume of the shaft;
adding sand into the soluble temporary plugging agent for fracturing;
adopting low-viscosity slickwater to carry 70-140 meshes of temporary plugging agent, and then injecting the low-viscosity slickwater to carry 30-50 meshes of temporary plugging agent;
step (6), adding sand into 70-140 meshes of propping agent for fracturing;
step (7), carrying out 40-70 mesh proppant long-section plug sand adding fracturing;
keeping the highest discharge capacity, and replacing 1-1.5 times of the volume of the shaft by adopting high-viscosity slick water; carrying 40-70 mesh proppant with high-viscosity slickwater to carry out continuous sand adding construction of long section plug, wherein the viscosity of the high-viscosity slickwater is 12-15mPa.s;
step (8) fracturing and filling 30-50 meshes of high-density proppant;
keeping the highest discharge capacity, and replacing 1-1.5 times of the volume of the shaft with high viscose; carrying 30-50 mesh high-density proppant with high-viscosity glue;
the proppant has a bulk density of greater than 1.8g/cm 3 The apparent density is 3.4g/cm 3 The above;
and (9) mixing and replacing.
2. The method of improving pumping efficiency of a bridge plug of claim 1, wherein:
in the step (3), the discharge amount of acid is 1-2m 3 Min, acid dosage is 15-30m 3 After acid injection is finished, high-viscosity glue is adopted for replacing acid, the discharge capacity of the acid replacing glue is increased to 2 times of the discharge capacity of the acid, and when the acid liquid in the shaft reaches the blast hole, the discharge capacity of the acid replacing glue is reduced to the discharge capacity of the prior acid injection.
3. The method of improving pumping efficiency of a bridge plug of claim 1, wherein:
in the step (4), all acid amount is completely replaced into the stratum until the construction pressure is not reduced any more, the discharge capacity of the high-viscosity glue solution is increased to the designed maximum discharge capacity within 1-2 minutes, and after 1.5-2 times of the shaft volume high-viscosity glue solution is injected, the maximum discharge capacity is kept and low-viscosity slick water is injected for further joint expansion; the injection amount of the low-viscosity slickwater is 4-5 times of the volume of the shaft;
the viscosity of the low-viscosity slickwater is 1-3mPa.s.
4. A method of improving pumping efficiency of a bridge plug as defined in claim 3, wherein:
and (4) when the construction in the step (4) is completed, the length of the seam reaches 70-80% of the designed seam length, if the length of the seam does not reach 70-80%, the pumping time of the preposed low-viscosity slickwater is prolonged, and the total liquid amount of the preposed high-viscosity glue solution and the low-viscosity slickwater does not exceed 6 times of the volume of the shaft.
5. The method of improving pumping efficiency of a bridge plug of claim 1, wherein:
in the step (5), low-viscosity slick water is adopted to carry the 70-140-mesh temporary plugging agent, the temporary plugging agent is injected according to the sand-liquid ratio of 2% -4% -6% -8%, and the sand-carrying liquid amount of each step is 15-20m for carrying the sand; and then pouring the low-viscosity slickwater carrying 30-50 meshes of temporary plugging agent according to the sand-liquid ratio of 6% -8% -10%, wherein the sand-liquid carrying amount of each step is 10-15m for carrying out the high-speed plantation.
6. The method of improving pumping efficiency of a bridge plug of claim 1, wherein:
in the step (6), after the temporary plugging agent is injected, 1.5-2 times of the low-viscosity slickwater with the shaft volume is replaced, the highest discharge capacity is kept, the low-viscosity slickwater is used for carrying 70-140 meshes of proppant slug type sand feeding, the initial sand-liquid ratio is 3%, the sand-carrying liquid slug liquid amount is 0.6-1.2 times of the shaft volume, then the low-viscosity slickwater with the same discharge capacity and the shaft volume of 0.5-1 times is injected as the spacer liquid, the sand-liquid ratio is gradually increased, and the increment of the sand-liquid ratio step is 1-2%.
7. The method of improving pumping efficiency of a bridge plug of claim 1, wherein:
in the step (7), the initial sand-liquid ratio of the first section of the long section plug of the 40-70-mesh proppant is 3% -5%; in the construction process of each long proppant slug, the sand-liquid ratio is increased by 2-3 steps according to 1% sand-liquid ratio step increment, the sand-carrying liquid amount is 3-5 times of the volume of a shaft, and high-viscosity slickwater 1-1.5 times of the volume of the shaft is pumped behind each long slug to serve as an isolation liquid;
and repeating the initial sand-liquid ratio of the long proppant section plug of the next stage for 2-3 times according to the highest sand-liquid ratio of the proppant section plug of the previous stage to complete 40-70-mesh proppant long section plug sand-adding fracturing.
8. The method of improving pumping efficiency of a bridge plug of claim 1, wherein:
in the step (8), the highest sand-liquid ratio in the step (7) is taken as an initial value, 2-3 steps are gradually increased by 2% sand-liquid ratio increment, and the sand-carrying liquid amount of the 30-50-mesh high-density proppant is 1-2 times of the volume of the shaft.
9. The method of improving pumping efficiency of a bridge plug of claim 1, wherein:
in the step (9), high-viscosity glue liquid with the volume 0.2-0.5 times of that of the shaft is replaced, and then low-viscosity slickwater is pumped to inject the high-viscosity glue liquid with the volume 1-1.5 times of that of the shaft for replacement operation.
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