CN115680591A - Chemical flooding three-dimensional fracturing process suitable for interactive distribution of thin and thick oil layers - Google Patents
Chemical flooding three-dimensional fracturing process suitable for interactive distribution of thin and thick oil layers Download PDFInfo
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Abstract
The invention relates to a chemical flooding three-dimensional fracturing process suitable for the interactive distribution of a thin and thick oil layer. Comprises the following steps: the overall design method comprises the following steps: by adopting a staged design, various oil layers are planned to be transformed in steps, and the injection and production capacity of thin and thick oil layers is balanced, wherein the three main aspects comprise well selection, layer selection and construction scale; the local multi-well group design method comprises the following steps: the local multi-well group design method is based on a staged design strategy, and is characterized in that when a plurality of well groups with similar dynamic and static characteristics appear in block connection, on the basis of the original single injection and production well design, a single well design is expanded into a multi-well synchronous design by combining a dynamic development index and a dynamic monitoring index, a geological design synchronous construction design is combined, a fracturing target layer is combined, and the connection well groups are subjected to fracturing reconstruction as a whole. The three-dimensional fracturing technology advances the transformation time of the thin oil layer or transforms the thin oil layer and the thick oil layer synchronously; the synchronous thick oil layer of the thin and poor oil layer is effected, and the relative synchronous use of the thin and thick oil layer in the peak period is realized.
Description
The technical field is as follows:
the invention relates to the technical field of oil extraction in oil fields, in particular to a chemical flooding three-dimensional fracturing process suitable for interactive distribution of thin and thick oil layers.
Background art:
in the process of developing large continental facies sandstone oil reservoirs, when chemical flooding development is carried out, the fracturing design method is single injection-production well design, an injection well is selected to reach the injection allocation rate of below 70 percent as a standard, a production well is selected to take the degree of effectiveness as a standard, a well with large reduction amplitude of produced liquid and water is preferably selected, a fracturing thick layer is mainly used in the blank period, the injection-gathering period, the main section plug initial period and the peak period, and a submerging thin-difference layer is mainly used in the main section plug later period.
In the process of developing a large-scale continental-facies sandstone oil reservoir, when chemical flooding development is carried out, the fracturing design method is a single injection-production well design, an injection well is selected on the basis that the top allowable pressure reaches below 70% of injection allocation, a production well is selected on the basis of the degree of effectiveness, a well with large liquid production and water content reduction amplitude is preferably selected, a single fracturing thick layer is mainly used in the blank, injection and gathering period, the initial period and the peak period of a main section plug, and a potential thin difference layer is mainly dug in the later period of the main section plug. The original method has better promotion effect on the river channel sand with the grain size of more than 1m and the main body sand, the utilization ratio reaches more than 85 percent, and the recovery ratio is improved by more than 16 percent.
Along with the continuous progress and deepening of oil field development, a development object gradually becomes worse, the oil layer span is large, and the oil reservoir characteristics of the interactive distribution of the thin and thick oil layers are formed. At present, the oil layer span of a chemical development object is about 50m, which is 2 times of the original similar development object. The reserve of the oil layer with the thickness less than 1m already exceeds 50 percent, the thickness proportion exceeds 50 percent, and the number proportion exceeds 80 percent. The original design method has poor transformation effect on the thin and poor oil layer below 1m, and the utilization ratio only reaches 40 percent. According to the formula of recovery R ＝Ev﹡E D Calculating (E) R Recovery factor, ev-swept coefficient, E D Displacement efficiency), the sweep efficiency is approximately taken as a utilization ratio, the utilization ratio of an oil layer below 1m needs to reach more than 70 percent to achieve the aim of improving the overall recovery ratio by 16 percent, and the prior art cannot meet the requirement.
The invention content is as follows:
the invention aims to overcome the problems in the background technology and provides a chemical flooding three-dimensional fracturing process suitable for the interactive distribution of a thin oil layer and a thick oil layer. The chemical-flooding three-dimensional fracturing process suitable for the interactive distribution of the thin and thick oil layers controls the displacement of the classified oil layers, realizes the relative balance of the utilization degree of the thin and thick oil layers, achieves the utilization ratio of the thin and thick oil layers below 1m to be more than 70 percent, and achieves the purpose of improving the recovery ratio of the thin and thick oil layers by chemical flooding of the interactive distribution oil reservoir to be more than 16 percent.
The invention can solve the problems by the following technical scheme: the chemical flooding three-dimensional fracturing process suitable for the interactive distribution of the thin and thick oil layers comprises the following two methods:
the overall design method comprises the following steps:
the chemical driving development process is divided into a plurality of stages according to the injection condition, the whole design method adopts the staged design of the development process, various oil layers are planned to be transformed step by step, the injection and production capacity of thin and thick oil layers is balanced, and the method comprises three main aspects of well selection, layer selection and construction scale:
a well selection method comprises the following steps: widening the well selection range of the modified injection and production well, wherein the injection well is mainly improved in a part of stages, the injection and production well is synchronously modified in a part of stages, and the production well is mainly improved in a part of stages;
b, layer selection method: selecting layers according to the layer selection sequence and the layer section combination; in the aspect of layer selection sequence, the transformation time of the thin difference layer is advanced, or the transformation is carried out synchronously with the thick oil layer; in the aspect of layer section combination, a permeability grade difference method is adopted for layer section combination;
c, construction scale: calculating a target layer comprehensive index by using common parameters, and designing a construction scale by using the target layer comprehensive index so that the development of various modified oil layers all reaches the highest extraction degree under the optimal penetration ratio;
the local multi-well group design method comprises the following steps:
the local multi-well group design method is based on a staged design strategy, and is characterized in that when a plurality of well groups with similar dynamic and static characteristics appear in block connection, on the basis of the original single injection and production well design, a single well design is expanded into a multi-well synchronous design by combining a dynamic development index and a dynamic monitoring index, a geological design synchronous construction design is combined, a fracturing target layer is combined, and the connection well groups are subjected to fracturing reconstruction as a whole.
Further, the chemical flooding development process is divided into seven stages according to the injection condition: (1) a blank water injection stage; (2) a pre-slug injection stage; (3) primary slug stage; (4) a main section plug peak period stage; (5) a main slug late stage; (6) a secondary slug injection stage; (7) and turning to a subsequent water injection stage.
Further, the specific method for widening and modifying the well selection range of the injection and production well comprises the following steps: three types of injection wells are added in the stages (1), (2) and (3): (1) completing injection allocation of more than 70 percent, and allowing injection pressure difference to be within 1 Mpa; (2) the injection section is not balanced, and the suction proportion of a single small layer exceeds 30 percent; (3) the injection-production ratio is below 0.8, and the injection intensity is lower than the average level of the whole area by 20 percent; fracturing a production well which takes effect synchronously while adding three types of injection wells in the first three stages in the stage (4); and (5) excavating the potential of the residual oil in the stages (5) and (6), and fracturing the production well with the cumulative oil production per unit thickness being more than 50% of the average level of the block.
Further, according to the specific method for widening the well selection range, the extraction end can be matched with the same layer of the injection end to be synchronously transformed; according to the specific method for excavating the potential of the residual oil, the injection well can be matched with the same layer of the extraction end to perform synchronous reconstruction.
Further, the specific method for advancing the transformation time of the thin difference layer or synchronously transforming the thin difference layer and the thick oil layer comprises the following steps: preferably, the thin difference layer is firstly reformed in the (1), (2) and (3) stages; synchronously transforming the thin and thick oil layers in the (4) stage; thick oil layer reconstruction is not used in the (5) stage and the (6) stage;
in the aspect of interval combination, the interval combination is carried out by adopting a permeability grade difference method.
Further, the method for combining the intervals by the permeability step method comprises the following steps: the interlayer contradiction is relieved by segmentation, so that the cracks are relatively uniformly distributed in the oil layer; increasing the number of fracturing sections of the whole well, and increasing the number of layers of the reconstruction number; the permeability grade difference in the fracturing section is within 20 percent of the permeability grade difference of the well; when the permeability grading method is used, the grading range is reduced along with the increase of the highest permeability of the target layer: when the highest permeability is below 70 millidarcies, the effect of the intra-stage difference is small; when the highest permeability is 70-200 millidarcy, the range of the difference in the fracturing section is kept in a range of 1-2; when the highest permeability is higher than 200 millidarcies, the difference of the stages in the fracturing stage ranges from 1 to 1.2.
Further, the method for calculating the target layer comprehensive index comprises the following steps: calculating the average sandstone thickness, the average effective thickness, the average permeability and the number of communication directions according to the layers by taking the target layer as the center; classifying the calculation results, multiplying the classification results by corresponding coefficients respectively and then summing to obtain a target measurement comprehensive index; according to the method for selecting the construction scale of the target layer, the construction scale is selected according to the comprehensive index of the target layer, different crack radiuses can be generated by different construction scales, and the different crack radiuses correspond to different crack penetration ratios and different extraction degrees, namely, the optimal construction scale corresponds to the highest extraction degree; when different requirements of multiple well groups in multiple directions are balanced on a plane, the total penetration ratio of the optimal directions of all well point planes is required to be not higher than 35%, so that the block water containing problem caused by violent flooding can be effectively avoided when the development is carried out to the last two stages.
Further, the local multi-well group design method specifically comprises the following steps:
step 1: determining a transformation range and the number of wells according to dynamic development indexes, wherein the number of related adjacent well groups is not less than 4, and changing the original single well group analysis into multi-well group analysis; the reference dynamic development index is characterized in that more than 80% of indexes in the well selection range are lower than 80% of the average level of the whole area, and the number of modified wells in the range reaches more than 70%;
and 2, step: according to dynamic monitoring indexes, well monitoring and other dynamic and static data which are easily acquired by an oil field are utilized to carry out multi-well synchronous geological and scale design on the same sedimentary plan; the method aims to utilize development geological data to guide scale design and meet the development geological requirements through the scale design;
and 3, step 3: and combining the fracturing target layers, and further reducing the range of range by a refined permeability level difference method to reduce the number of small layers in the fracturing layer section to 2-3 layers.
And furthermore, the method for synchronously designing the geology and the scale of the multiple wells in the step 2 comprises the steps of radiating to the communication wells from the central well of the first well group on the edge, then radiating to the multiple communication wells according to the divergent design of the well row where the central well is located, determining well point targets one by one, and simultaneously carrying out the scale design.
Furthermore, the principle of determining the well point target is a draw difference principle, the general monitoring data shows that the draw difference is less than 25% of the whole well, and the standard range can be determined to be 20-30% according to the actual situation of the block.
Compared with the background technology, the chemical flooding three-dimensional fracturing process applicable to the interactive distribution of the thin and thick oil layers has the following beneficial effects:
(1) Compared with the original method, the method has stronger strategic thinking by adopting the overall design method. The overall planning and the ordered arrangement of the well selection, the layer selection and the scale of the block are tactical means, and are more favorable for improving the pertinence of block development and reducing the blindness.
(2) Compared with the original method, the local multi-well group design method has the advantages that the transformation range is expanded, the action area of measure transformation is increased, the effect is obviously superior to the original single-well design, and the effect of solving the problem that local injection is difficult and mining is difficult during the peak period of the main section plug is ideal.
(3) The reconstruction time of the thin difference layer is advanced, so that the repeated construction rate of an injection well can be reduced.
(4) By adopting a permeability stage difference method, the number of the fracturing stages of the whole well can be increased, the number of the fracturing stages of the whole well is increased from 3.5 to 6.5, the number of layers for improving the purpose is increased, the number of the layers for improving the purpose is increased from 7 to 13, and the injection condition of more thin difference layers is improved.
(5) After the well selection range is widened, the water absorption capacity of the thin and differential layer can be further enhanced by improving the added three types of wells, the interlayer contradiction is relieved, and the integral injection strength of the block is improved.
(6) By adopting the permeability grade difference method to combine the intervals, the contradiction between the intervals can be relieved by subsection, which is beneficial to reducing the bad result generated by the dominant channel in the fracturing process and ensuring that the cracks are relatively uniformly distributed in the oil layer.
(7) In the aspect of construction scale, the fracturing scale of the thin and thick oil layer of the produced well is respectively optimized in the peak period of the main section plug, the single-layer scale of the first three stages is gradually decreased by 20-30%, and the minimum is not lower than 4m < 3 >; the scale of the later two stages is gradually increased by 20-30% to a maximum of 25m 3 . The design can ensure that the crack is extended to the optimal penetration ratio to reach the maximum production degree of a single layer from the development stage to the peak stage.
(8) The thin and thick oil layer respectively achieves the optimal fracture penetration ratio and the highest extraction degree by controlling the whole well fracturing length, good and bad and balanced transformation, and the production potential of the thin and thick oil layer is synchronously exerted.
When the three-dimensional fracturing design process is implemented on the field chemical flooding development block in the south Sagnan development area, the actual water content and the extraction degree are both higher than the digital analog level.
When the three-dimensional fracturing design process block is applied to the on-site chemical flooding development block in the south Sagnan development area, the oil layer utilization ratio below 1m reaches 77.8%, the block stage extraction degree reaches 19.3%, and the recovery ratio is improved by 16.26%.
Description of the drawings:
FIG. 1 is a graph of recovery from a test area according to an embodiment of the present invention;
FIG. 2 is a graph showing enhanced oil recovery comparison in the same PV in the experimental zones of the examples of the present invention;
FIG. 3 is an equivalent graph of effective thickness in the test area according to an embodiment of the present invention; (test area in black frame)
FIG. 4 is a graph of permeability equivalence for a test zone according to an embodiment of the present invention; (test area in black frame)
FIG. 5 is a single layer plan view of a test zone according to an embodiment of the present invention.
The specific implementation mode is as follows:
various exemplary embodiments, features, etc. aspects of the disclosure are described in detail below with reference to the figures.
The invention discloses a chemical flooding three-dimensional fracturing design method for a thin and thick oil layer interactive distribution oil reservoir, which is divided into an integral design method and a local multi-well group design method.
(I) Overall design method
The chemical development process is divided into the following seven stages according to the injection condition: (1) a blank water injection stage (2), a front slug injection stage (3), a main slug early stage (4), a main slug peak period stage (5), a main slug later stage (6), an auxiliary slug injection stage (7) and a subsequent water injection stage. The overall design method adopts a staged design in the development process, plans to modify various oil layers in steps, balances the injection and production capacity of thin and thick oil layers, and comprises three main aspects of well selection and layer selection and construction scale;
a well selection method
The specific method for widening the well selection range of the modified injection and production well comprises the following steps: three types of injection wells are added in the stages (1), (2) and (3): (1) completing injection allocation of more than 70 percent, and allowing injection pressure difference to be within 1 Mpa; (2) the injection section is not uniform, and the suction proportion of a single small layer exceeds 30 percent; (3) the injection-production ratio is less than 0.8, and the injection strength is lower than the average level of the whole area by 20 percent. And (4) fracturing a synchronously effective production well while adding three types of injection wells in the first three stages in the stage (4). And (5) excavating the potential of the residual oil in the stages (5) and (6), and fracturing the production well with the cumulative oil production per unit thickness being more than 50% of the average level of the block. This stage is governed by engineering and other factors, and the actual well ratio is below 5%.
B layer selection method
In the aspect of layer selection sequence, the transformation sequence of the original method of firstly thick and then thin is changed, and the transformation time of the thin-difference layer is advanced or is synchronously transformed with the thick oil layer. The specific method comprises the following steps: in the (1), (2) and (3) stages, the thin difference layer is preferably firstly reformed; synchronously transforming the thin and thick oil layers in the (4) stage; the thick oil layer is not used for reconstruction in the stages (5) and (6).
In the aspect of interval combination, the interval combination is carried out by adopting a permeability grade difference method. The extending direction of the crack is more prone to be deviated to a stratum with higher permeability and better communication, so that the permeability grade difference in the section has higher influence on the trend of the crack, the greater the range is, the more prominent the interlayer contradiction is, the crack is more easy to open in the dominant direction, and the balanced exploitation of other oil layers is not facilitated. The method is characterized in that the permeability grade difference in the fracturing section is within 20% of the permeability grade difference of the well, except for the influence of engineering factors such as an interlayer and the like. When the permeability grading method is used, the grading range is reduced along with the increase of the highest permeability of the target layer. When the highest permeability is below 70 millidarcies, the effect of the intra-stage difference is small; when the highest permeability is 70-200 millidarcy, the range of the difference in the fracturing section is kept in a range of 1-2; when the highest permeability is higher than 200 millidarcies, the difference of the levels in the fracturing stage ranges from 1 to 1.2.
The method relieves the interlayer contradiction by sections, is favorable for reducing the bad results generated by the dominant channel in the fracturing process, and ensures that the cracks are relatively uniformly distributed in the oil layer. By adopting a permeability stage difference method, the number of the fracturing stages of the whole well can be increased, the number of the fracturing stages of the whole well is increased from 3.5 to 6.5, the number of layers for improving the purpose is increased, the number of the layers for improving the purpose is increased from 7 to 13, and the injection condition of more thin difference layers is improved. It should be noted that when the number of combined story segments exceeds the current construction limit, the alteration can be done in batches, but still the order of story selection is kept consistent with the whole area.
C construction Scale
The construction scale is an important component of the fracturing design method, the reasonable construction scale and the scientific scale design can ensure the efficient development of the oil reservoir. Original design separately goes on geological design and construction design, and design scale is lower with the oil reservoir matching degree, and it is not enough to cause some target stratum to reform transform, and some target stratum excessively reform transform.
By calculating the comprehensive indexes of the target layer, matching the optimal construction scale, effectively combining geological design and construction design, and improving the effective rate of target layer reconstruction, all development layers reach the highest extraction degree. The method for calculating the comprehensive index of the target layer comprises the following steps: calculating the average sandstone thickness, the average effective thickness, the average permeability and the number of communication directions according to the layers by taking the target layer as a center; and (4) taking values of the calculation results according to the range, multiplying the value taking coefficients and the empirical weights respectively, and summing to obtain the target measurement comprehensive index. And (3) utilizing a construction design template, corresponding the comprehensive index of the target layer to the construction scale, and respectively optimizing the fracturing scale of the thin and thick oil layers of the produced well in the peak period of the main section plug. The single-layer scale of the first three stages is gradually decreased by 20-30%, and the minimum is not less than 4m 3 (ii) a The scale of the later two stages is gradually increased by 20-30% to a maximum of 25m 3 。
The design can ensure that the crack is extended to the optimal penetration ratio to reach the maximum production degree of a single layer from the development stage to the peak stage.
The main section plug peak period is a key period for fracturing promotion of a production well, a thin difference layer is added as a modification object on the basis of the original design, a target layer comprehensive index is calculated (see table 1 as a target layer reference comprehensive index calculation template), and the construction scale is matched according to the index (table 2 is the construction scale under the target layer reference comprehensive index). And optimizing the fracturing scale in a layering manner by calculation, improving the single-seam scale of the thin-difference oil layer and controlling the single-seam scale of the thick oil layer. By controlling the length, the difference and the weight of the whole well fracturing, and balanced reconstruction, the thin and thick oil layers respectively reach the optimal fracture penetration ratio and the highest extraction degree, and the production potential of the thin and thick oil layers is synchronously exerted.
The calculation formula of the comprehensive index in table 1 is:
p＝h1*0.55+h2*0.5+q*0.45+n*0.4；
wherein: p target layer comprehensive indexes; h1 average sandstone thickness coefficient; h2 average effective thickness coefficient; q mean permeability coefficient; n is a connectivity coefficient; 0.55, 0.5, 0.45 and 0.4 are empirical weight values.
The calculation formula of the construction scale in table 2 is: v = π R 2 h; t = R/well spacing;
wherein: r is the crack radius; h is the width of the crack and takes the value of 4mm; the well spacing is the distance between the injection well and the production well;
TABLE 1
Note: because the coefficient and the index calculation method are different due to different development blocks, the empirical algorithm of the developed similar blocks is referred. The calculation formula of the comprehensive index in the table is p = h1, 0.55+ h2, 0.5+ q, 0.45+ n, 0.4
TABLE 2
Note: 1, the optimal penetration ratio in a table is changed along with the injection-production well spacing; 2 the construction scale is influenced by the comprehensive index and simultaneously changes along with the injection stage
Local multi-well group design method
The local multi-well group design method is an important constituent part of the overall design method, is based on a staged design strategy, and is characterized in that when a plurality of well groups with similar and static characteristics appear in block connection, a single well design is expanded into a multi-well synchronous design by combining a dynamic development index and a dynamic monitoring index on the basis of the original single injection and production well design, a geological design synchronous construction design is combined, a fracturing target layer is combined, and the connection well groups are used as a whole for fracturing reconstruction.
Compared with the original method, the local multi-well group design method enlarges the transformation range, increases the action area of measure transformation, has obviously better effect than the original single-well design, and has ideal effect on solving the problem of local difficult injection and difficult extraction in the peak period of the main section plug. The design steps are as follows:
the method comprises the following steps: determining the transformation range and the number of wells as required, wherein the number of related adjacent well groups is not less than 4, and changing the original single well group analysis into multi-well group analysis. And referring to dynamic development indexes, more than 80% of indexes in the range are lower than 80% of the average level of the whole area, and the number of modified wells in the range reaches more than 70%.
Step two: well monitoring and other dynamic and static data which are easily obtained by an oil field are utilized to carry out multi-well synchronous geological and scale design on the same sedimentary plane map. The method aims to utilize the development geological data to guide scale design and meet the development geological requirements through the scale design. The method comprises the steps of radiating to a communication well from a central well of a first well group on the edge, then radiating to a plurality of communication wells according to the divergent design of the well row where the central well is located, determining well point targets one by one, and simultaneously carrying out scale design. The principle of determining the target is the differential draw, generally the differential draw is less than 25%, and the standard range can be determined to be 20-30% according to the actual situation of the block. When different requirements of multiple well groups in multiple directions are balanced on a plane, the total penetration ratio of the optimal directions of all well point planes is required to be not higher than 35%, so that the block water containing problem caused by violent flooding can be effectively avoided when the development is carried out to the last two stages. The design scale of the well point can be referred to tables 1 and 2. The method is more favorable for the transformation effectiveness of the thin differential layer and improves the stage utilization degree of the thin differential layer.
Step three: the target fracturing layers are combined, the range of range is further reduced by a refined permeability level difference method, even a single thin difference layer can be singly pressed by a single clamp, and the pertinence of oil layer reconstruction below 1m is improved.
Example 1
In order to make the purpose, technical scheme and advantages of the present invention clearer, the following will take an example of a specific implementation process of the chemical-driven three-dimensional fracturing process applicable to the interactive distribution of thin and thick oil layers in a ternary composite drive block in a para-sagan development area, and further describe in detail the implementation mode of the present invention with reference to the attached drawings.
The three-element composite flooding block has the effective jet thickness of 7.9m and the permeability of 220mD, and has 271 ports, wherein a 161 port of an injection well and 110 ports of a production well are arranged. And the injection-production well spacing is 125m, and the oil production five-point method is used for area well pattern well arrangement. Wherein, the proportion of the number of oil layers below 1m is 83.1 percent, and the proportion of the thickness is 52.8 percent.
The specific implementation process of the chemical flooding three-dimensional fracturing process applicable to the interactive distribution of the thin and thick oil layers in a certain three-component composite flooding block is as follows:
the application of the integral design: after the well selection condition is expanded, 25 injection wells are added for fracturing reconstruction, the part of wells are divided into three types, (1); (2) the injection section of the 5 ports is not balanced, and the suction proportion of a single small layer exceeds 30 percent; (3) the injection-production ratio of 9 ports is less than 0.8, and the injection strength is lower than the average level of the whole area by 20 percent. The 85 well times of fracturing injection wells are accumulated, the fracturing target layers are 680, the average single-layer thickness is 0.9m, and the average single-layer sand adding amount is 9.0m 3 . Wherein the target layer with a thickness of less than 1m is 70% or more, the average single-layer thickness is 0.5m, and the average single-layer sand adding amount is 12m 3 。
Compared with the original design, the fracturing proportion of the injection well is improved by 15.5%, the single-layer thickness of a target layer is reduced by 59%, the number of fracturing target layers is increased by 46%, and the single-layer sand adding amount is increased by 50%.
TABLE 3
The fracturing effect comparison of the method of the invention and the existing design method is shown in table 3, the comparison before and after fracturing of table 3 shows that the fracturing object of the original design method is a thick oil layer with the thickness of more than 1m, the fracturing object of the three-dimensional fracturing design method is a thin difference layer with the thickness of less than 1m, the permeability of the comparison fracturing object is lower, the sand adding amount of the designed single layer is larger, the pressure reduction amplitude is relatively smaller, the daily injection increasing level of a single well is equivalent (table 3), and the application obtains better effect. The oil layer utilization below 1m is improved to 77.8% (Table 4), and the recovery ratio is improved by 16.26%. The utilization condition of the classified oil layer after the three-dimensional fracturing design is shown in the table 4.
TABLE 4
| <1m | 1-2m | >2m | Total up to | |
| Blank water flooding | 48.3 | 54.3 | 61.4 | 52.4 |
| Front-mounted slug | 75 | 77.7 | 97.5 | 77.2 |
| Three-element main slug | 77.8 | 87.8 | 100 | 82.2 |
The transformation time of the thin difference layer is advanced, and the repeated construction rate of an injection well is reduced. The statistics of the number of the staged fracturing wells are shown in a table 5, after the staged fracturing of the stages (3) and (4), the repeated fracturing proportion of the peak period reaches 50%, and after the fracturing of the blank water flooding stage, the repeated fracturing proportion of the peak period is 34.3%, and the repeated construction rate is reduced by 15.7% (shown in a table 5).
TABLE 5
The three-element block recovery curve of the test area of the embodiment is shown in fig. 1, the third curve from top to bottom is the actual water content of the block, and the water content value is lower than that of the second simulation curve from top to bottom; the third curve from bottom to top is the actual extraction degree curve of the block, and the extraction degree value is higher than that of the second simulation curve from bottom to top. The experimental zones of this example are shown in FIG. 2 versus the enhanced recovery ratio for the same PV; the uppermost first curve represents the block in which the present invention frac design process is performed, which has the highest enhanced recovery margin. When the three-dimensional fracturing design process block is implemented on the field chemical flooding development block in the Saran development area, the oil layer utilization ratio below 1m reaches 77.8%, the block stage recovery degree reaches 19.3% (shown in figure 2), and the recovery ratio is increased by 16.26% (shown in figure 1).
(II) application of local multi-well group design:
step 1: 10 well groups which are adjacent and take the oil well as the center are determined as test areas, and 18 injection wells and 10 extraction wells are totally used.
The plot of the effective thickness equivalent of the test area is shown in FIG. 3; test zones the plot of permeability equivalences for the test zones is shown in figure 4. Static characteristics were general poor development (see fig. 3, 4, test zones in black boxes), with an average single well thickness of 6.9m below the average level of the block of 12.7%. Wherein the oil layer with the thickness less than 1m accounts for 85.4 percent, and the thickness accounts for 58.3 percent. The test zone permeability was 190mD, which was 13.6% below the mean level of the block, with 74.1% of the perforation well points permeability being below 150mD.
The dynamic characteristics of the test area are that the injection and production capacity is poor, the injection pressure is high, the injection amount is low, the injection strength is low, the liquid production amount is low, the liquid production strength is low, and the oil layer utilization ratio below 1m is 35.9 percent and is lower than 25.7 percent of the block. (see table 6 for comparison of test area and block dynamics indicators).
TABLE 6
Step 2: the single-layer plane design diagram is shown in figure 5, and a target layer can not be made for a well injection point with or without production; the small layers which are good in one-way communication and high in utilization ratio are not used as target layers; for jetting pure sandstone extraction wells with the diameter of more than 1m, surrounding injection wells are developed well and can be used as target layers. And manually marking scale design results on the graph according to template data, so that adjustment and modification among well groups are facilitated. And a test area is provided with 17 injection wells and 8 extraction wells, wherein the number of the fracturing wells is 89.2%. 232 layers with the number of the fracturing layers is fractured, and the proportion of the fracturing layers is 77.1 percent.
And step 3: and (3) combining the intervals according to a permeability grade difference method to perform multi-crack fracturing, wherein engineering factors need to be considered in the practical application process. The test area permeability difference method layer section combination is shown in table 7, the combination result is shown in brackets, the thickness of the lower interlayer of the second small layer of the third section in the figure is influenced, the construction requirement cannot be met, only one layer can be expanded downwards, and the target layer cannot be influenced in the construction process due to the fact that the permeability of the expanded small layer is 119mD, the effective thickness is 0.2 m. If the permeability of the expanded layer is equal to that of the target layer, a selective fracturing mode is designed, and the expanded layer is constructed after being plugged by pitching according to the thickness.
The effective thickness of the average single well fracturing is 3.5m, the fracturing is 4.6 sections, 8.5 seams are pressed open, the fracturing thickness proportion is 50.7%, wherein the oil layer with the thickness of less than 1m accounts for 73.9%, and the number accounts for 83.5%.
TABLE 7
In the original design method, the number of the average small layers in the fracturing section is 4.2, the reconstruction proportion of the target layer is only 47.6%, and the difficulty of judging the crack opening layer is high, so that the subsequent reconstruction and layer selection are not facilitated. By using the method, in the multi-well combined design, the number of the average small layers in the fracturing section is thinned to 2.1 in a local range, the transformation proportion of the target layer reaches 95.2 percent, the transformation proportion of the target layer is greatly improved, the accuracy of oil layer transformation is ensured, and the correspondence and timeliness are improved.
The test area is completely implemented in one month, after the implementation, the average single-well injection pressure drop amplitude is higher than the average level of 2.1MPa, and the injection strength is improved by 1.2m 3 The oil layer consumption ratio below 1 m/m reaches more than 80%, and the fracturing effective period of the injection well is more than 3 months above the average level. The water cut at the test zone stage was 16.36% lower than 6.05 percentage points above the full zone, the enhanced recovery was 8.51, and 0.56 percentage points above the full zone at the same PV.
Claims (10)
1. A chemical flooding three-dimensional fracturing process suitable for the interactive distribution of thin and thick oil layers is characterized by comprising the following two designs:
the overall design method comprises the following steps:
the chemical driving development process is divided into a plurality of stages according to the injection condition, the whole design method adopts the staged design of the development process, various oil layers are planned to be transformed step by step, the injection and production capacity of thin and thick oil layers is balanced, and the method comprises three main aspects of well selection, layer selection and construction scale:
a well selection method comprises the following steps: widening the well selection range of the transformed injection and production well, wherein the injection well is mainly improved in a part of stages, the injection and production well is synchronously transformed in a part of stages, and the production well is mainly improved in a part of stages;
b, layer selection method: selecting layers according to the layer selection sequence and the layer section combination; in the aspect of layer selection sequence, the transformation time of the thin difference layer is advanced, or the transformation is synchronous with the transformation of the thick oil layer; in the aspect of layer section combination, a permeability grade difference method is adopted for layer section combination;
c, in the aspect of construction scale: calculating a target layer comprehensive index by using common parameters, and designing a construction scale by using the target layer comprehensive index so that the development of various modified oil layers all reaches the highest extraction degree under the optimal penetration ratio;
the local multi-well group design method comprises the following steps:
the local multi-well group design method is based on a staged design strategy, and is characterized in that when a plurality of well groups with similar dynamic and static characteristics appear in block connection, on the basis of the original single injection and production well design, a single well design is expanded into a multi-well synchronous design by combining a dynamic development index and a dynamic monitoring index, a geological design synchronous construction design is combined, a fracturing target layer is combined, and the connection well groups are subjected to fracturing transformation as a whole.
2. The chemical flooding three-dimensional fracturing process suitable for the interactive distribution of thin and thick oil layers according to claim 1, characterized in that: the chemical flooding development process is divided into seven stages according to the injection condition: (1) a blank water injection stage; (2) a pre-slug injection stage; (3) primary slug stage; (4) a main section plug peak period stage; (5) a main slug late stage; (6) a secondary slug injection stage; (7) and turning to a subsequent water injection stage.
3. The chemical flooding three-dimensional fracturing process suitable for the interactive distribution of thin and thick oil layers according to claim 1 or 2, characterized in that:
the specific method for widening the well selection range of the modified injection and production well comprises the following steps: three types of injection wells are added in the stages (1), (2) and (3): (1) completing injection allocation of more than 70 percent, and allowing injection pressure difference to be within 1 Mpa; (2) the injection section is not balanced, and the suction proportion of a single small layer exceeds 30 percent; (3) the injection-production ratio is less than 0.8, and the injection strength is lower than the average level of the whole area by 20 percent; fracturing a production well which takes effect synchronously while adding three types of injection wells in the first three stages in the stage (4); and (5) excavating the potential of the residual oil in the stages (5) and (6), and fracturing the production well with the cumulative oil production per unit thickness being more than 50% of the average level of the block.
4. The chemical flooding three-dimensional fracturing process suitable for the interactive distribution of thin and thick oil layers according to claim 3, characterized in that: according to the specific method for widening the well selection range, the extraction end can be matched with the same layer of the injection end to perform synchronous modification; according to the specific method for excavating the potential of the residual oil, the injection well can be matched with the same layer of the extraction end to perform synchronous reconstruction.
5. The chemical flooding three-dimensional fracturing process suitable for the interactive distribution of thin and thick oil layers according to claim 1 or 2, characterized in that:
the specific method for advancing the transformation time of the thin difference layer or synchronously transforming the thin difference layer and the thick oil layer comprises the following steps: in the (1), (2) and (3) stages, the thin difference layer is preferably firstly reformed; synchronously transforming a thin and thick oil layer in the (4) stage; thick oil layer reconstruction is not used in the (5) stage and the (6) stage;
in the aspect of interval combination, the interval combination is carried out by adopting a permeability grade difference method.
6. The chemical flooding three-dimensional fracturing process suitable for the interactive distribution of thin and thick oil layers according to claim 5, characterized in that: the method for combining the intervals by the permeability step method comprises the following steps: the interlayer contradiction is relieved by subsection, so that cracks are relatively uniformly distributed in an oil layer; increasing the number of fracturing sections of the whole well, and increasing the number of layers of the reconstruction number; the permeability grade difference in the fracturing section is within 20 percent of the permeability grade difference of the well; when using the permeability step method, the step range is reduced as the highest permeability of the target layer is increased: when the highest permeability is below 70 millidarcies, the effect of the intra-stage difference is small; when the highest permeability is 70-200 millidarcy, the range of the grade difference in the fracturing section is kept between 1 and 2; when the highest permeability is higher than 200 millidarcies, the difference of the levels in the fracturing stage ranges from 1 to 1.2.
7. The chemical flooding three-dimensional fracturing process suitable for the interactive distribution of thin and thick oil layers according to claim 1, characterized in that: the method for calculating the target layer comprehensive index comprises the following steps: calculating the average sandstone thickness, the average effective thickness, the average permeability and the number of communication directions according to the layers by taking the target layer as the center; classifying the calculation results, multiplying the classification results by corresponding coefficients respectively and then summing to obtain a target measurement comprehensive index; the method for selecting the construction scale of the target layer selects the construction scale according to the comprehensive index of the target layer, different construction scales can generate different crack radiuses, and the different crack radiuses correspond to different crack penetration ratios and extraction degrees, namely, the optimal construction scale corresponds to the highest extraction degree; when different requirements of multiple well groups in multiple directions are balanced on a plane, the total penetration ratio of the optimal directions of all well point planes is required to be not higher than 35%, and thus the problem of block water containing caused by violent flooding can be effectively avoided when the development reaches the last two stages.
8. The chemical flooding three-dimensional fracturing process suitable for the interactive distribution of thin and thick oil layers according to claim 1, characterized in that: the local multi-well group design method specifically comprises the following steps:
step 1: determining a transformation range and the number of wells according to dynamic development indexes, wherein the number of related adjacent well groups is not less than 4, and changing the original single well group analysis into multi-well group analysis; the reference dynamic development index is characterized in that more than 80% of indexes in the well selection range are lower than 80% of the average level of the whole area, and the number of modified wells in the range reaches more than 70%;
step 2: according to dynamic monitoring indexes, well monitoring and other dynamic and static data which are easily acquired by an oil field are utilized to carry out multi-well synchronous geological and scale design on the same sedimentary plan; the method aims to utilize development geological data to guide scale design and meet the development geological requirements through the scale design;
and step 3: and combining the fracturing target layers, and further reducing the range of range by a refined permeability level difference method to reduce the number of small layers in the fracturing layer section to 2-3 layers.
9. The chemical flooding three-dimensional fracturing process suitable for the interactive distribution of thin and thick oil layers according to claim 8, characterized in that: and 2, carrying out multi-well synchronous geological and scale design by a method that the central well of the first well group at the edge is radiated to the communication wells, then the communication wells are divergently designed according to the well row where the central well is located, then the communication wells are radiated to the plurality of communication wells, well point targets are determined one by one, and scale design is carried out simultaneously.
10. The chemical flooding three-dimensional fracturing process suitable for the interactive distribution of thin and thick oil layers according to claim 9, characterized in that: the principle of determining the well point target is a draw difference principle, the general monitoring data shows that the draw difference is 25 percent lower than that of the whole well, and the standard range can be determined to be 20-30 percent according to the actual situation of a block.
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