CN114893147B - Multi-scale crack plugging simulator and multi-scale crack plugging simulation experiment device - Google Patents

Multi-scale crack plugging simulator and multi-scale crack plugging simulation experiment device Download PDF

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CN114893147B
CN114893147B CN202210433859.6A CN202210433859A CN114893147B CN 114893147 B CN114893147 B CN 114893147B CN 202210433859 A CN202210433859 A CN 202210433859A CN 114893147 B CN114893147 B CN 114893147B
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shaft
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CN114893147A (en
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马成云
邓金根
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China University of Petroleum Beijing
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    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B33/00Sealing or packing boreholes or wells
    • E21B33/10Sealing or packing boreholes or wells in the borehole
    • E21B33/13Methods or devices for cementing, for plugging holes, crevices or the like
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01FMIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/60Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis
    • B01F27/72Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis with helices or sections of helices
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00Survey of boreholes or wells
    • E21B47/005Monitoring or checking of cementation quality or level

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Abstract

The invention discloses a multi-scale crack leakage stoppage simulator and a multi-scale crack leakage stoppage simulation experiment device, wherein the multi-scale crack leakage stoppage simulator comprises a well cylinder part and a crack simulation part, wherein a cylinder top liquid inlet and a cylinder bottom liquid outlet are respectively arranged at two ends of the well cylinder part, at least two mutually independent and long and narrow through cracks are arranged in the crack simulation part, and liquid inlet ends of the through cracks are respectively communicated with the inside of the well cylinder part; the multi-scale crack leakage stoppage simulation experiment device comprises a leakage stoppage slurry blending device and the multi-scale crack leakage stoppage simulator, wherein the leakage stoppage slurry blending device comprises a plurality of leakage stoppage slurry tanks, a stirrer, a leakage stoppage slurry output pipe, a liquid return pipe and a waste liquid tank. The multi-scale fracture leakage stoppage simulator and the multi-scale fracture leakage stoppage simulation experiment device disclosed by the invention can optimize the design of the multi-scale fractured stratum leakage stoppage material while performing a fracture leakage stoppage simulation experiment, and provide theoretical guidance for realizing the simulation of the underground leakage stoppage process under complex working conditions.

Description

Multi-scale crack plugging simulator and multi-scale crack plugging simulation experiment device
Technical Field
The invention relates to the technical field of oil and gas exploitation, in particular to a multi-scale fracture leakage stoppage simulator and a multi-scale fracture leakage stoppage simulation experiment device.
Background
The well leakage is a phenomenon that various working fluids such as drilling fluid, cement slurry, completion fluid and other fluids leak into a stratum under the action of pressure difference in various downhole operations such as well drilling, well cementing and well logging. Drilling fluid loss is a common downhole complication in drilling operations. Once the leakage occurs, not only the drilling time is delayed, the drilling fluid is lost, the geological logging work is disturbed, but also a series of complex conditions and accidents such as well collapse, drilling sticking, blowout and the like can be caused, and even the well hole is scrapped, so that the great economic loss is caused. If the well leakage occurs in the oil-gas layer, the damage to the production layer is easily caused, the production is influenced, the production test and the sample test fail due to the leakage, and the production efficiency is reduced due to the blockage of the production layer. To some extent, lost circulation is more costly to oil and gas exploration and development than some drilling incidents. Therefore, in the drilling process, various plugging materials are required to be added into the drilling fluid to plug the cracks. The selection of the plugging material needs to consider factors in multiple aspects such as formation physical and chemical properties, formation pressure bearing capacity and the like, and the common plugging materials comprise graphite particles, calcium carbonate particles and various polymers.
Studies have shown that the vast majority of lost circulation is fractured. The crack leakage has the defects of undefined opening degree, low leakage stopping efficiency and the like. Currently, bridging plugging is the primary method of treating fractured losses. The matching precision of the grade distribution of the plugging material and the size of the leakage passage is a key factor for determining the once plugging success rate of the fractured leakage. The academia has developed a mature set of solutions to the problem of fissured leakages. Nevertheless, the success rate of field one-time plugging of complex fractured formations is low. The dimension span of the complex fractured formation fracture is large, so the complex fractured formation fracture is called as a multi-dimension fracture, the fracture causing the loss of drilling fluid is composed of fractures with various widths, the previous plugging research takes the migration and accumulation process of a plugging material in a single fixed fracture as a research object, the plugging material design takes the width of a single fracture as a reference, and an experimental device taking the multi-dimension fracture as a research object is lacked, so the migration and bridging plugging process of the plugging material in the multi-dimension fracture cannot be well researched, and the guidance of theory and method cannot be provided for the multi-dimension fractured formation plugging design.
Disclosure of Invention
The invention aims to provide a multi-scale fracture plugging simulator and a multi-scale fracture plugging simulation experiment device, which are used for researching the migration and bridging plugging processes of plugging materials in multi-scale fractures and providing guidance of theories and methods for multi-scale fractured formation plugging design.
The invention provides a multi-scale crack plugging simulator, which comprises a well bore part and a crack simulation part, wherein a barrel top liquid inlet and a barrel bottom liquid outlet are respectively arranged at two ends of the well bore part, at least two mutually independent and long and narrow through cracks are arranged in the crack simulation part, liquid inlet ends of the through cracks are respectively communicated with the inside of the well bore part, and liquid outlet ends of the through cracks are converged to form a simulator liquid outlet end;
after the plugging slurry is injected into the liquid inlet at the top of the cylinder, the residual liquid after plugging in the through crack can reach the liquid outlet end of the simulator, and can directly flow out from the liquid outlet at the bottom of the cylinder.
Preferably, the fracture simulating part is tightly attached to the side wall of the well cylinder part to form a whole; three mutually independent and long and narrow through cracks are arranged in the multi-scale crack simulator.
Preferably, a plurality of first pressure sensors are sequentially arranged in each penetrating crack along the longitudinal direction of the crack, and each first pressure sensor is connected with a first pressure gauge.
Preferably, the liquid outlet end of the simulator is connected with a recovery tank through a recovery tank branch pipe, and a first electromagnetic valve is arranged on the recovery tank branch pipe;
when the plugging slurry is injected into the liquid inlet at the top of the cylinder, the part of the plugging slurry which passes through the through crack and reaches the liquid outlet end of the simulator flows into the recovery tank.
Preferably, a shaft liquid inlet pipe and a shaft liquid outlet pipe are respectively communicated with the cylinder top liquid inlet and the cylinder bottom liquid outlet of the cylinder part, the inner end of the shaft liquid inlet pipe is in butt joint with the cylinder top liquid inlet, and the exposed outer end of the shaft liquid inlet pipe is used as a liquid inlet of externally connected leakage-stopping slurry of the multi-scale crack simulator; the inner end of the shaft liquid outlet pipe is butted with the liquid outlet at the bottom of the cylinder, and the exposed outer end of the shaft liquid outlet pipe is used as a liquid return port of the multi-scale crack simulator for externally connecting leaking stoppage slurry; and a second pressure gauge and a third pressure gauge are respectively arranged on the shaft liquid inlet pipe and the shaft liquid outlet pipe.
Preferably, a back-pressure valve is further arranged on the shaft liquid outlet pipe; the plugging slurry is injected from a shaft liquid inlet pipe to a cylinder top liquid inlet, when the pressure in the through crack is smaller than the back pressure set value of the back pressure valve, the plugging slurry gradually forms a bridge in the through crack plugging process, and after the residual liquid reaches the liquid outlet end of the simulator, the residual liquid flows into the recovery tank through the recovery tank branch pipe; when the pressure in the through crack reaches or exceeds the back pressure set value of the back pressure valve, the blocking slurry in the shaft barrel part directly flows out of the barrel bottom liquid outlet and then flows into the shaft liquid outlet pipe.
The invention also relates to a multi-scale crack leaking stoppage simulation experiment device, which comprises a leaking stoppage slurry blending device and the multi-scale crack leaking stoppage simulator, wherein the leaking stoppage slurry blending device comprises a plurality of leaking stoppage slurry tanks, a stirrer, a leaking stoppage slurry output pipe, a liquid return pipe and a waste liquid pool, and the leaking stoppage slurry tanks are used for storing the leaking stoppage slurry with concentration gradient; the top end of each leaking stoppage slurry tank is communicated with the stirrer through a leaking stoppage slurry pipe; the liquid outlet of the stirrer is communicated with the liquid inlet of the shaft liquid inlet pipe through the leaking stoppage slurry output pipe; and the waste liquid pool is communicated with a liquid return port of the shaft liquid outlet pipe through a liquid return pipe.
Preferably, the leakage-stopping slurry tank also comprises a clean water tank, the shape and the size of each leakage-stopping slurry tank are the same, a piston is arranged in each leakage-stopping slurry tank, and the piston divides the leakage-stopping slurry tank into an upper part and a lower part; the clean water tank is respectively communicated with the lower parts of the leaking stoppage slurry tanks through clean water pipes, the lower parts of the leaking stoppage slurry tanks are used for loading clean water, the upper parts of the leaking stoppage slurry tanks are used for loading drilling fluid, and the leaking stoppage slurry is sequentially loaded on the upper parts of the leaking stoppage slurry tanks according to concentration gradient; and the clean water pipes are respectively provided with a displacement pump and a second electromagnetic valve.
Preferably, the stirrer comprises an intermediate container, a stirring shaft and a rotating motor, wherein the power input end of the stirring shaft is in butt joint with the output shaft of the rotating motor, the stirring shaft penetrates into the intermediate container from the end part of the intermediate container, and stirring blades are arranged on the stirring shaft; the side surface of the middle container of the stirrer is provided with a plurality of liquid inlets, and the top end of each leaking stoppage slurry tank is communicated with the liquid inlet of the middle container of the stirrer through a leaking stoppage slurry pipe; a third electromagnetic valve and a fourth pressure gauge are arranged on each leaking stoppage slurry pipe; and a liquid outlet is formed in the end face of the end part, far away from the stirring shaft, of the intermediate container, and the liquid outlet of the intermediate container is communicated with a liquid inlet of a shaft liquid inlet pipe through a leaking stoppage slurry output pipe.
Preferably, a fourth electromagnetic valve is arranged on the leaking stoppage slurry output pipe.
Compared with the prior art, the invention has the beneficial effects that:
the invention discloses a multi-scale fracture leaking stoppage simulator and a multi-scale fracture leaking stoppage simulation experiment device, which dynamically allocate the particle proportion in the leaking stoppage slurry proportions of coarse particles, particles and fine particles by adjusting the frequency of a displacement pump of a leaking stoppage slurry allocating device, so as to quickly and continuously complete the allocation of a leaking stoppage material of a multi-scale fractured stratum; the multi-scale fracture simulator can be used for simulating the migration and bridging plugging processes of the plugging material in the multi-scale fracture. The multi-scale fracture simulator and the multi-scale fracture leaking stoppage simulation experiment device disclosed by the invention can optimize the design of the multi-scale fractured stratum leaking stoppage material while performing a fracture leaking stoppage simulation experiment, and provide theoretical guidance for realizing the simulation of the underground leaking stoppage process under complex working conditions.
Drawings
FIG. 1 is a schematic structural diagram of a multi-scale fracture plugging simulator provided in example 1 of the present invention;
fig. 2 is a schematic structural view of a multi-scale fracture leakage stoppage simulator provided in embodiment 1, where two ends of a shaft portion are connected to a shaft liquid inlet pipe and a shaft liquid outlet pipe;
fig. 3 is a schematic structural view of a pipeline formed by communicating the plugging slurry blending device and the wellbore part according to embodiment 2 of the present invention;
fig. 4 is a schematic structural diagram of a multi-scale fracture plugging simulation experiment device provided in embodiment 2 of the present invention.
Description of the reference numerals:
1-a shaft cylinder part, 11-a cylinder top liquid inlet, 12-a cylinder bottom liquid outlet, 13-a shaft liquid inlet pipe, 14-a shaft liquid outlet pipe, 130-a second pressure gauge and 140-a third pressure gauge;
2-a crack simulation part, 21-a through crack, 22-a simulator liquid outlet end, 23-a first pressure gauge, 24-a recovery tank branch pipe, 25-a recovery tank and 26-a first electromagnetic valve; 20-a blocking layer and 200-a back pressure valve;
3-leaking stoppage slurry blending device, 30-piston, 31-clean water tank, 310-displacement pump, 311-clean water pipe, 312-second electromagnetic valve; 32-slurry leakage tank, 321-slurry leakage blocking pipe, 322-third electromagnetic valve, 323-fourth pressure gauge; 33-stirrer, 331-intermediate container, 332-stirring shaft, 333-rotating motor, 334-stirring blade; 34-leaking stoppage slurry output pipe, 341-fourth electromagnetic valve, 35-liquid return pipe, and 36-waste liquid pool.
Detailed Description
The invention discloses a multi-scale fracture plugging simulator and a multi-scale fracture plugging simulation experiment device, wherein a plugging slurry blending device is used for blending plugging slurry to realize rapid and continuous completion of the configuration of plugging materials of multi-scale fractured strata; the multi-scale fracture simulator can be used for simulating the migration and bridging plugging processes of the plugging material in the multi-scale fracture, can optimize the design of the multi-scale fractured stratum plugging material while performing a fracture plugging simulation experiment, and provides theoretical guidance for truly simulating the underground plugging process under complex working conditions.
Example 1: multi-scale crack leakage stoppage simulator
Example 1 a multi-scale fracture plugging simulator is provided, the structure of which is described in detail below with reference to fig. 1 and 2.
Referring to fig. 1, the multi-scale fracture simulator includes a wellbore section 1, a fracture simulation section 2, a recovery pond leg 24 and a recovery pond 25,
the two ends of the well cylinder part 1 are respectively provided with a cylinder top liquid inlet 11 and a cylinder bottom liquid outlet 12, and the crack simulation part 2 is tightly attached to the side wall of the well cylinder part 1 to form a whole;
at least two mutually independent and long and narrow through cracks 21 are arranged in the crack simulation part 2, liquid inlet ends of the through cracks 21 are respectively communicated with the inside of the shaft part 1, and liquid outlet ends of the through cracks 21 are converged to form a simulator liquid outlet end 22.
After the plugging slurry is injected into the liquid inlet 11 at the top of the cylinder, the residual slurry can reach the liquid outlet end 22 of the simulator after plugging in the through crack 21, and can directly flow out from the liquid outlet 12 at the bottom of the cylinder.
Preferably, three independent and elongated through-slits 21 are provided in the multi-scale slit simulator.
In order to facilitate observation of pressure changes of the plugging slurry in the through cracks 21, a plurality of first pressure sensors are sequentially arranged in each through crack 21 along the longitudinal direction of the crack, and each first pressure sensor is connected with a first pressure gauge 23.
In order to discharge the leaking stoppage slurry in the experimental process or after the experiment is finished, the liquid outlet end 22 of the simulator is connected with a recovery tank 25 through a recovery tank branch pipe 24, and a first electromagnetic valve 26 is arranged on the recovery tank branch pipe 24, which is used for communicating the recovery tank 25 with the liquid outlet end 22 of the simulator.
When the plugging slurry is injected into the liquid inlet 11 at the top of the cylinder, the part of the plugging slurry which passes through the through crack 21 and reaches the liquid outlet end 22 of the simulator flows into a recovery tank 25.
In order to convey plugging slurry, referring to fig. 2, a shaft liquid inlet pipe 13 and a shaft liquid outlet pipe 14 are respectively communicated with a cylinder top liquid inlet 11 and a cylinder bottom liquid outlet 12 of a well cylinder part 1, the inner end of the shaft liquid inlet pipe 13 is butted with the cylinder top liquid inlet 11, and the exposed outer end is used as a liquid inlet of the multi-scale crack simulator for externally connecting the plugging slurry; the inner end of a shaft liquid outlet pipe 14 is in butt joint with a cylinder bottom liquid outlet 12, and the exposed outer end is used as a liquid return port of the multi-scale crack simulator for externally connecting leaking stoppage slurry.
In order to observe the pressure change of the plugging slurry in the shaft liquid inlet pipe 13 and the shaft liquid outlet pipe 14, a second pressure gauge 130 and a third pressure gauge 140 are respectively arranged on the shaft liquid inlet pipe 13 and the shaft liquid outlet pipe 14.
In order to restrict the flow of plugging slurry from the wellbore outlet 14 so that the plugging slurry in the wellbore section 1 flows into the through-fractures 21 as preferentially as possible, the wellbore outlet 14 is also provided with a back-pressure valve 200.
Plugging slurry is injected into the barrel top liquid inlet 11 from the shaft liquid inlet pipe 13, when the pressure in the through crack 21 is smaller than the back pressure set value of the back pressure valve 200, bridging is gradually formed in the plugging process in the through crack 21 by the plugging slurry, and after the residual liquid reaches the simulator liquid outlet end 22, the residual liquid flows into the recovery tank 25 through the recovery tank branch pipe 24; when the pressure in the through fracture 21 reaches or exceeds the back pressure setting value of the back pressure valve 200, the plugging slurry in the well bore part 1 directly flows out from the bore bottom outlet 12 and then flows into the well bore outlet 14.
Example 2: multi-scale crack leakage stoppage simulation experiment device
Example 2 provides a multi-scale fracture plugging simulation experiment device, and the structure thereof is described in detail below with reference to fig. 3 and 4.
The multi-scale fracture leakage stoppage experimental device comprises a multi-scale fracture leakage stoppage simulator and a leakage stoppage slurry blending device 3 in the embodiment 1,
referring to fig. 3 and 4, the plugging slurry preparing apparatus 3 includes a plurality of plugging slurry tanks 32, a stirrer 33, a plugging slurry output pipe 34, a liquid return pipe 35 and a waste liquid tank 36,
the plurality of plugging slurry tanks 32 are used for storing the plugging slurry with concentration gradient respectively;
the top end of each plugging slurry tank 32 is respectively communicated with the stirrer 33 through a plugging slurry pipe 321;
the liquid outlet of the stirrer 33 is communicated with the liquid inlet of the shaft liquid inlet pipe 13 through a leakage-stopping slurry output pipe 34;
waste reservoir 36 communicates with the return port of well bore effluent line 14 via return line 35.
In order to convey the leaking stoppage slurry in a plurality of leaking stoppage slurry tanks 32 into a stirrer 33, specifically, the shape and the size of each leaking stoppage slurry tank 32 are the same, a piston 30 is arranged in each leaking stoppage slurry tank 32, and the piston 30 divides the leaking stoppage slurry tank 32 into an upper part and a lower part; the plugging slurry blending device 3 further comprises a clean water tank 31, the clean water tank 31 is communicated with the lower portions of the multiple plugging slurry tanks 32 through clean water pipes 311 respectively, the lower portions of the plugging slurry tanks 32 are used for loading clean water, the upper portions of the plugging slurry tanks 32 are used for loading plugging slurry, the plugging slurry is sequentially loaded on the upper portions of the multiple plugging slurry tanks 32 according to concentration gradient, when the clean water tank 31 injects clean water into the plugging slurry tanks 32 through the clean water pipes 311, the clean water pushes the pistons 30 to extrude the plugging slurry in the plugging slurry tanks 32, and the plugging slurry is forced to be conveyed into the stirrer 33.
More specifically, a clean water inlet is arranged at the bottom end of each leaking stoppage slurry tank 32, the water outlet of the clean water tank 31 is communicated with the clean water inlets of the leaking stoppage slurry tanks 32 through clean water pipes 311, and the clean water pipes 311 are provided with displacement pumps 310 and second electromagnetic valves 312.
Specifically, the stirrer 33 comprises an intermediate container 331, a stirring shaft 332 and a rotating motor 333, wherein the power input end of the stirring shaft 332 is in butt joint with the output shaft of the rotating motor 333, the stirring shaft 332 penetrates into the intermediate container 331 from the end part of the intermediate container 331, and the stirring shaft 332 is provided with stirring blades 334;
the side surface of the middle container 331 of the stirrer 33 is provided with a plurality of liquid inlets, and the top end of each plugging slurry tank 32 is respectively communicated with the liquid inlet of the middle container 331 of the stirrer 33 through a plugging slurry pipe 321; each leaking stoppage grout pipe 321 is provided with a third electromagnetic valve 322 and a fourth pressure gauge 323.
A liquid outlet is arranged on the end surface of the end part of the middle container 331 far away from the stirring shaft 332, and the liquid outlet of the middle container 331 is communicated with the liquid inlet of the shaft liquid inlet pipe 13 through the plugging slurry output pipe 34.
In order to control the leakage stoppage slurry flowing from the intermediate container 331 to the well bore liquid inlet pipe 13, the leakage stoppage slurry outlet pipe 34 is provided with a fourth electromagnetic valve 341.
The method for carrying out the experiment by using the multi-scale crack plugging simulation experiment device is briefly introduced as follows, which mainly comprises the following two steps:
and (3) blending of plugging slurry: one or more displacement pumps 310 and second electromagnetic valves 312 thereof are opened, clean water in the clean water tank 31 is respectively injected into the leakage stoppage slurry tank 32 through the clean water pipe 311, and the clean water pushes the piston 30 upwards to extrude the leakage stoppage slurry in the leakage stoppage slurry tank 32; according to the requirement of the plugging simulation experiment, the third electromagnetic valve 322 on one or more corresponding plugging slurry pipes 321 is opened, and the plugging slurry in the corresponding plugging slurry tank 32 enters the middle container 331 of the stirrer 33 through the plugging slurry pipe 321; starting the rotating motor 333, driving the stirring blade 334 to rotate by the stirring shaft 332, and stirring the plugging slurry in the stirrer 33 until the plugging slurry is uniformly stirred;
multi-scale fracture plugging simulation: and opening the fourth electromagnetic valve 341 on the plugging slurry output pipe 34, conveying the uniformly stirred plugging slurry to the shaft liquid inlet pipe 13 through the plugging slurry output pipe 34, and flowing into the shaft part 1 from the cylinder top liquid inlet 11, wherein part of the plugging slurry penetrates through the through crack 21 of the crack simulation part 2, so as to simulate the multi-scale crack plugging.
Example 3: an experimental method for multi-scale fracture plugging simulation,
embodiment 3 provides an experimental method for multi-scale fracture plugging simulation, which adopts the multi-scale fracture plugging simulation experimental apparatus provided in embodiment 2, and includes a multi-scale fracture plugging simulator and a plugging slurry blending apparatus 3, wherein the multi-scale fracture simulator includes a fracture simulation part 2, at least two mutually independent and long and narrow through fractures 21 are provided in the fracture simulation part 2, before an experiment is carried out, the plugging slurry with concentration gradient is respectively stored in the upper parts of a plurality of plugging slurry tanks 32, and the experimental method includes the following steps:
dynamically blending the plugging slurry to obtain ideal plugging slurry;
introducing ideal plugging slurry into a multi-scale crack plugging simulator, and simulating the process of bridging the plugging slurry in the through crack 21 to form a plugging layer 20;
the maximum pressure-bearing capacity of the plugging layer 20 is determined.
Wherein, the dynamic allocation of the plugging slurry comprises the following steps:
step A1: selecting three plugging slurry tanks 32, and adding plugging slurry containing coarse particles, medium particles and fine particles into the three plugging slurry tanks 32 to form a first plugging slurry tank, a second plugging slurry tank and a third plugging slurry tank;
step A2: determining a first back pressure setting P, e.g., P =5MPa, of the back pressure valve 200;
step A3: opening all the second electromagnetic valves 312 and all the third electromagnetic valves 322, opening all the displacement pumps 310, injecting clean water in the clean water tank 31 into the plurality of plugging slurry tanks 32 through clean water pipes 311 respectively, pushing the pistons 30 upwards by the clean water, conveying the plugging slurry into the intermediate container 331 of the stirrer 33 forcibly, and stopping all the displacement pumps 310 after the plugging slurry is filled;
step A4: starting the rotating motor 333, driving the stirring shaft 332 to drive the stirring blade 334 to rotate, and stirring the plugging slurry in the stirrer 33 until the plugging slurry is uniformly stirred, for example, mixing for 5 minutes;
step A5: opening all the displacement pumps 310 and the fourth electromagnetic valves 341 again, pushing the piston 30 upwards by clean water, forcibly conveying the plugging slurry into the middle container 331 of the stirrer 33, promoting the uniformly-stirred plugging slurry to be conveyed into the shaft liquid inlet pipe 13 through the plugging slurry outlet pipe 34 and to flow into the shaft part 1 from the shaft top liquid inlet 11, and enabling part of the plugging slurry to pass through the through cracks 21 of the crack simulation part 2;
step A6: carrying out an experiment for simulating multi-scale crack plugging;
step A7: if the plugging slurry is not bridged and blocked in the through crack 21, adjusting the frequency of all the displacement pumps 310, adjusting the proportion of coarse, medium and fine plugging slurries output by the first plugging slurry tank, the second plugging slurry tank and the third plugging slurry tank together, continuously repeating the experiment for simulating the multi-scale crack plugging in the step A6 until the plugging slurry is bridged in the through crack 21, and simultaneously determining that the plugging slurry obtained by proportioning the coarse particles, the medium particles and the fine particles in the three plugging slurry tanks 32 is the ideal plugging slurry.
The multi-scale fracture plugging simulation method comprises the following steps:
step B1: determining a first back pressure setting P, e.g., P =5MPa, of the back pressure valve 200;
and step B2: all the second electromagnetic valves 312, all the third electromagnetic valves 322 and all the fourth electromagnetic valves 341 are opened, all the displacement pumps 310 are opened, clean water in the clean water tank 31 is respectively injected into the plurality of leaking stoppage slurry tanks 32 through the clean water pipes 311, the clean water pushes the piston 30 upwards, and the leaking stoppage slurry is forcedly conveyed into the middle container 331 of the stirrer 33;
and step B3: the plugging slurry is conveyed to the shaft liquid inlet pipe 13 through the plugging slurry outlet pipe 34 and flows into the shaft part 1 from the top liquid inlet 11, the plugging slurry firstly passes through the through crack 21 of the crack simulation part 2 and is blocked at the first electromagnetic valve 26, and the pressure in the through crack 21 is gradually increased;
and step B4: when the pressure values of the second pressure gauge 130 and the first pressure gauge 23 reach 1/5 of the first back pressure valve setting value P, namely 1MPa, the first electromagnetic valve 26 is opened, the plugging slurry passes through the first electromagnetic valve 26 and flows into the recovery tank 25 through the recovery tank branch pipe 24, and meanwhile the plugging slurry bridges in the through crack 21;
and step B5: the position of the bridging formation plugging layer 20 in each through crack 21 is respectively judged through a plurality of first pressure gauges 23, and the method specifically comprises the following steps:
firstly, comparing the pressure values of a plurality of first pressure gauges 23 respectively connected with a plurality of first pressure sensors in the same penetrating crack 21, and if the pressure value of the first pressure gauge 23 connected with the first pressure sensor behind along the flowing direction of the plugging slurry is smaller than that of the first pressure gauge 23 in the front, indicating that the bridging formation plugging layer 20 in the penetrating crack 21 is positioned between the installation position of the first pressure sensor connected with the first pressure gauge 23 with the smaller pressure value and the installation position of the first pressure sensor nearest to the first pressure sensor;
next, the next through-cracks 21 are compared one by one, and the position where the bridging layer 20 is formed in each through-crack 21 is found.
Step B6: bridging and accumulating the plugging slurry in the through crack 21 to gradually form a plugging layer 20, gradually increasing the pressure in the well bore part 1 until the pressure of the second pressure gauge 130 and the third pressure gauge 140 reaches the first back pressure setting value P =5MPa, and then allowing the plugging slurry to enter the waste liquid pool 36 through the back pressure valve 200;
and step B7: keeping all the displacement pumps 310 open, continuing to displace for a period of time, such as 10 minutes, and continuously simulating the process of bridging the plugging slurry in the through cracks 21 to form the plugging layer 20;
and step B8: increasing 1MPa on the basis of the first back pressure setting value P, adjusting the back pressure of the back pressure valve 200 to be a second back pressure setting value Q, wherein the second back pressure setting value Q = P +1MPa, continuing to displace for a period of time, such as 10 minutes, and simulating the process of bridging and forming the plugging layer 20 in the through crack 21 by the plugging slurry again;
and step B9: observing whether the pressure values of the second pressure gauge 130 and the third pressure gauge 140 are changed and whether the volume of the liquid in the recovery tank 25 is increased, if the second pressure gauge 130, the third pressure gauge 140 and the back pressure valve 200 are all stabilized at the second back pressure setting value Q and the volume of the liquid in the recovery tank 25 is not increased or slightly increased, indicating that the plugging layer 20 in each through crack 21 is well plugged, otherwise, indicating that at least one of the plugging layers 20 in the through cracks 21 is damaged;
and step B10: and (4) increasing the pressure by 1MPa each time on the basis of the last back pressure setting value, continuously adjusting the back pressure setting value of the back pressure valve 200, continuously displacing for a period of time, continuously simulating the process of bridging the leakage-stopping slurry in the through crack 21 to form the blocking layer 20, and repeating the step B9 until the blocking layer 20 in the through crack 21 is damaged.
The method for determining the maximum pressure-bearing capacity of the plugging layer 20 specifically comprises the following steps:
and determining the pressure values of the second pressure gauge 130 and the third pressure gauge 140 which are the last time before the damage in the experimental process as the maximum pressure-bearing value of the blocking layer 20.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (4)

1. A multi-scale crack leakage stoppage simulation experiment device is characterized by comprising a leakage stoppage slurry blending device (3) and a multi-scale crack leakage stoppage simulator,
the leakage-stopping slurry blending device (3) comprises: a plurality of plugging slurry tanks (32), a stirrer (33), a plugging slurry output pipe (34), a liquid return pipe (35) and a waste liquid pool (36),
the plurality of leakage stopping slurry tanks (32) are used for storing leakage stopping slurry with concentration gradient;
the top end of each leaking stoppage slurry tank (32) is respectively communicated with the stirrer (33) through a leaking stoppage slurry pipe (321);
the liquid outlet of the stirrer (33) is communicated with the liquid inlet of the shaft liquid inlet pipe (13) through a plugging slurry output pipe (34);
the waste liquid pool (36) is communicated with a liquid return port of the shaft liquid outlet pipe (14) through a liquid return pipe (35);
the multi-scale fracture plugging simulator comprises: a well bore part (1) and a crack simulation part (2),
a cylinder top liquid inlet (11) and a cylinder bottom liquid outlet (12) are respectively arranged at two ends of the well cylinder part (1),
at least two mutually independent and long and narrow through cracks (21) are arranged in the crack simulation part (2), liquid inlet ends of the through cracks (21) are respectively communicated with the inside of the well bore part (1), and liquid outlet ends of the through cracks (21) are converged to form a simulator liquid outlet end (22);
after the plugging slurry is injected into the liquid inlet (11) at the top of the cylinder, the residual liquid of the plugging slurry can reach the liquid outlet end (22) of the simulator after plugging in the through crack (21) and can directly flow out of the liquid outlet (12) at the bottom of the cylinder;
a barrel top liquid inlet (11) and a barrel bottom liquid outlet (12) of the barrel part (1) are respectively communicated with a barrel shaft liquid inlet pipe (13) and a barrel shaft liquid outlet pipe (14), the inner end of the barrel shaft liquid inlet pipe (13) is in butt joint with the barrel top liquid inlet (11), and the exposed outer end is used as a liquid inlet of the multi-scale crack simulator for external connection leakage plugging slurry; the inner end of the shaft liquid outlet pipe (14) is butted with the cylinder bottom liquid outlet (12), and the exposed outer end is used as a liquid return port of the multi-scale crack plugging simulator for externally connecting plugging slurry;
a second pressure gauge (130) and a third pressure gauge (140) are respectively arranged on the shaft liquid inlet pipe (13) and the shaft liquid outlet pipe (14);
a back pressure valve (200) is also arranged on the shaft liquid outlet pipe (14);
injecting plugging slurry into the barrel top liquid inlet (11) from the shaft liquid inlet pipe (13), gradually forming a bridge in the plugging process of the through cracks (21) when the pressure in the through cracks (21) is smaller than the back pressure set value of the back pressure valve (200), and allowing residual liquid to flow into a recovery tank (25) through a recovery tank branch pipe (24) after the residual liquid reaches a simulator liquid outlet end (22); when the pressure in the through crack (21) reaches or exceeds the back pressure set value of the back pressure valve (200), the plugging slurry in the shaft part (1) directly flows out from the cylinder bottom liquid outlet (12) and then flows into the shaft liquid outlet pipe (14).
2. The multi-scale crack plugging simulation experiment device according to claim 1, further comprising a clean water tank (31),
the shape and the size of each leaking stoppage slurry tank (32) are the same, a piston (30) is arranged in each leaking stoppage slurry tank (32), and the piston (30) divides the leaking stoppage slurry tank (32) into an upper part and a lower part;
the clean water tank (31) is respectively communicated with the lower parts of the leaking stoppage slurry tanks (32) through clean water pipes (311), the lower parts of the leaking stoppage slurry tanks (32) are used for loading clean water, the upper parts of the leaking stoppage slurry tanks (32) are used for loading drilling fluid, the leaking stoppage slurry is sequentially loaded on the upper parts of the leaking stoppage slurry tanks (32) according to concentration gradient, when the clean water tank (31) injects clean water into the leaking stoppage slurry tanks (32) through the clean water pipes (311), the clean water pushes the piston (30) to extrude the leaking stoppage slurry in the leaking stoppage slurry tanks (32), and the leaking stoppage slurry is forcedly conveyed into the stirrer (33);
the clean water pipes (311) are respectively provided with a displacement pump (310) and a second electromagnetic valve (312).
3. The multi-scale fracture plugging simulation experiment device according to claim 2,
the stirrer (33) comprises an intermediate container (331), a stirring shaft (332) and a rotating motor (333), wherein the power input end of the stirring shaft (332) is in butt joint with the output shaft of the rotating motor (333), the stirring shaft (332) penetrates into the intermediate container (331) from the end part of the intermediate container (331), and stirring blades (334) are arranged on the stirring shaft (332);
the side surface of the middle container (331) of the stirrer (33) is provided with a plurality of liquid inlets, and the top end of each leaking stoppage slurry tank (32) is respectively communicated with the liquid inlets of the middle container (331) of the stirrer (33) through leaking stoppage slurry pipes (321); each leaking stoppage slurry pipe (321) is provided with a third electromagnetic valve (322) and a fourth pressure gauge (323);
a liquid outlet is formed in the end face of the end part, far away from the stirring shaft (332), of the middle container (331), and the liquid outlet of the middle container (331) is communicated with a liquid inlet of the shaft liquid inlet pipe (13) through a leaking stoppage slurry output pipe (34).
4. The multi-scale fracture plugging simulation experiment device according to claim 3,
and a fourth electromagnetic valve (341) is arranged on the leaking stoppage slurry output pipe (34).
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