CN116380752B - Evaluation method for shielding effect of degradable sinking agent artificial interlayer - Google Patents
Evaluation method for shielding effect of degradable sinking agent artificial interlayer Download PDFInfo
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- 238000011156 evaluation Methods 0.000 title claims abstract description 25
- 230000000694 effects Effects 0.000 title claims abstract description 21
- 239000011229 interlayer Substances 0.000 title claims description 44
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 73
- 239000011435 rock Substances 0.000 claims abstract description 48
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 18
- 239000008398 formation water Substances 0.000 claims abstract description 10
- 239000002253 acid Substances 0.000 claims description 25
- 239000012530 fluid Substances 0.000 claims description 15
- 238000006073 displacement reaction Methods 0.000 claims description 14
- 239000007788 liquid Substances 0.000 claims description 10
- 238000005530 etching Methods 0.000 claims description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 7
- 229910052802 copper Inorganic materials 0.000 claims description 7
- 239000010949 copper Substances 0.000 claims description 7
- 238000004062 sedimentation Methods 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 claims description 5
- 230000008859 change Effects 0.000 claims description 4
- 230000000593 degrading effect Effects 0.000 claims description 4
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000004804 winding Methods 0.000 claims description 3
- 238000012544 monitoring process Methods 0.000 claims description 2
- 230000009467 reduction Effects 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 claims 1
- 230000004888 barrier function Effects 0.000 abstract description 4
- 238000011161 development Methods 0.000 abstract description 3
- 239000000706 filtrate Substances 0.000 description 15
- 238000001914 filtration Methods 0.000 description 14
- 230000009471 action Effects 0.000 description 10
- 230000000903 blocking effect Effects 0.000 description 9
- 238000012360 testing method Methods 0.000 description 9
- 230000015556 catabolic process Effects 0.000 description 7
- 238000006731 degradation reaction Methods 0.000 description 7
- 239000007789 gas Substances 0.000 description 7
- 239000002245 particle Substances 0.000 description 7
- 230000035699 permeability Effects 0.000 description 7
- 239000004576 sand Substances 0.000 description 6
- 230000008569 process Effects 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000013461 design Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 230000000087 stabilizing effect Effects 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000003094 microcapsule Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
- G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/0806—Details, e.g. sample holders, mounting samples for testing
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Abstract
本发明公开了一种可降解下沉剂人工隔层遮挡效果评价方法，包括：制备带有碳酸盐岩天然裂缝的模拟岩心柱样品；在模拟岩心柱样品内填充下沉剂；在将模拟岩心柱样品放入第二岩心夹持器内，利用动态稳定渗流评价仪加入模拟地层水，并测得带有碳酸盐岩天然裂缝的模拟岩心柱样品的下沉剂人工隔层承压的压力值；还原模拟岩心柱样品，测得无碳酸盐岩天然裂缝的下沉剂人工隔层承压的压力值；对模拟岩心柱样品进行降解；利用导流能力评价仪测得稳定时的压力值和流量值；求得裂缝导流能力值。通过上述方案，本发明具有逻辑简单、准确可靠等优点，在气田开发技术领域具有很高的实用价值和推广价值。
The invention discloses a method for evaluating the shielding effect of a degradable subsidence agent artificial barrier, comprising: preparing a simulated core column sample with natural cracks in carbonate rock; filling the simulated core column sample with a subsidence agent; The core column sample was put into the second core holder, and the simulated formation water was added using the dynamic and stable seepage evaluation instrument, and the pressure of the subsidence agent artificial barrier of the simulated core column sample with natural fractures in carbonate rock was measured. Pressure value; restore the simulated core column sample, and measure the pressure value of the subsidence agent artificial barrier without natural fractures in carbonate rock; degrade the simulated core column sample; use the conductivity evaluation instrument to measure the stable pressure value Pressure value and flow rate value; obtain fracture conductivity value. Through the above scheme, the present invention has the advantages of simple logic, accuracy and reliability, etc., and has high practical value and popularization value in the technical field of gas field development.
Description
Technical Field
The application relates to the technical field of gas field development, in particular to a method for evaluating shielding effect of an artificial interlayer of a degradable sinking agent suitable for deep carbonate acid fracturing.
Background
Because of the general poor physical conditions of deep high-temperature carbonate gas reservoirs, most gas wells can obtain industrial productivity through acid fracturing transformation, and the acid fracturing transformation technology has become one of core technologies for increasing yield and effectively developing carbonate reservoirs. The deep carbonate bottom water and gas reservoir is small in stress difference of a reservoir interlayer, so that the seam height can not be controlled in the process of acidizing and fracturing transformation, the water layer is easy to communicate, the water yield after acid fracturing is greatly increased, the water locking effect is serious, and the productivity of a gas well is restricted.
At present, most of oil fields in China adopt a manner of establishing an artificial interlayer by using a sinking agent to increase the stress difference of the interlayer, but common carbonate rock is buried deeply, a well completion manner is open hole well completion, if conventional sinking agents are used, once underground sand blocking or sand setting accidents occur, the underground sand blocking or sand setting accidents are difficult to clean, subsequent fracturing construction is hindered, and therefore, degradable sinking agent materials are generated, and the degradable sinking agent materials are dissolved after the underground sand blocking or sand setting accidents occur for a few hours. The degradable sinking agent contains a degradation agent (microcapsule gel breaker) which can enable the degradation agent to break gel and self-degrade in a certain time under the high-temperature condition of the reservoir.
However, in the prior art, no corresponding evaluation method exists for the shielding effect of the degradable sinking agent at present, and the shielding effect cannot be reflected numerically.
Therefore, it is highly desirable to provide a simple, accurate and reliable evaluation method for blocking strength and restoration of diversion capability after degradation of a degradable sinking agent suitable for deep carbonate acid fracturing.
Disclosure of Invention
Aiming at the problems, the application aims to provide a method for evaluating the shielding effect of an artificial interlayer of a degradable sinking agent, which adopts the following technical scheme:
the method for evaluating the shielding effect of the artificial interlayer of the degradable sinking agent adopts a diversion capacity evaluating instrument and a dynamic stable seepage evaluating instrument for monitoring, wherein a first core holder is arranged in the diversion capacity evaluating instrument; a second core holder, an intermediate container and a metering container are arranged in the dynamic stable seepage evaluation instrument; the second core holder is longitudinally arranged; the first core holder is transversely arranged. Filling a sinking agent in the simulated rock core column sample; adding simulated formation water into a simulated core column sample in a second core holder by using a dynamic stable seepage evaluator in FIG. 2, and measuring the pressure value of the artificial interlayer bearing of the sinking agent of the simulated core column sample with the natural cracks of the carbonate rock; reducing the simulated core column sample, and measuring the pressure value of the artificial interlayer bearing of the sinking agent without the natural crack of the carbonate rock; degrading the simulated core column sample; measuring a pressure value and a flow value when the flow conductivity evaluation instrument in FIG. 1 is stable; and obtaining the fracture conductivity value.
The method for evaluating the shielding effect of the degradable sinking agent artificial interlayer comprises the following steps:
s1, taking a plurality of natural core columns from a carbonate stratum, and preparing a simulated core column sample with natural cracks of the carbonate stratum;
s2, filling a sinking agent into the simulated rock core column sample, placing the simulated rock core column sample into a second rock core holder, performing free sedimentation of the sinking agent, and adjusting the confining pressure of the second rock core holder to 15MPa;
s3, placing the simulated core column sample in the step S2 into a second core holder, adding simulated formation water by using a dynamic stable seepage evaluation instrument, and presetting the initial inlet pressure of the second core holder to be 1MPa; observing whether fracturing fluid flows into the metering container or whether the pressure of the second core holder is suddenly changed; if no fracturing fluid flows in or the pressure of the second core holder is not suddenly changed, the step S4 is carried out; otherwise, recording the current inlet pressure value;
step S4, boosting by adopting a pressure gradient of 1MPa, and keeping for 10min after boosting by any gradient until a large amount of fracturing fluid flows into a metering container or pressure is suddenly changed; recording the current pressure value of the artificial interlayer bearing of the sinking agent;
s5, replacing the simulated core column sample, and repeating the steps S2 to S4 to obtain pressure values of the artificial interlayer bearing of the sinking agent with a plurality of cracks;
s6, performing carbonate natural fracture removal and reduction on the simulated rock core column sample, placing the simulated rock core column sample with the carbonate natural fracture removed into a second rock core holder, adding simulated formation water by using a dynamic stable seepage evaluation instrument, and presetting the initial inlet pressure of the second rock core holder to be 0.5MPa; observing whether fracturing fluid flows into the metering container or whether the pressure of the second core holder is suddenly changed; if no fracturing fluid flows in or the pressure of the second core holder is not suddenly changed, the step S7 is carried out; otherwise, recording the current inlet pressure value;
step S7, the displacement pressure of the second core holder is increased to 1Mpa, and the confining pressure is kept to be 1.5Mpa higher than the displacement pressure; boosting by adopting a pressure gradient of 1MPa, and keeping for 5min after boosting by any gradient; until a large amount of fracturing fluid flows into the metering container or a sudden pressure change occurs; recording the current pressure value, namely the pressure value of the artificial interlayer bearing of the sinking agent without the natural crack of the carbonate rock;
step S8, placing the simulated core column sample in the step S7 into a high-temperature reaction kettle, and degrading for 12 hours at 160 ℃;
s9, placing the degraded simulated core column sample into a first core holder, and increasing confining pressure to 2.5MPa; presetting a first flow of the flow conductivity evaluation instrument in fig. 1, and measuring a pressure value and a flow value when the pressure and the flow are stable by using the flow conductivity evaluation instrument;
step S10, regulating the first flow to obtain a plurality of pressure values and flow values when the pressure and the flow are stable;
step S11, according to the flow Q, the length of the simulated core column sample, the natural fracture information of the carbonate rock and the displacement pressure differenceAnd obtaining a fracture conductivity value.
Compared with the prior art, the application has the following beneficial effects:
(1) According to the application, the natural rock core column is taken and split in half, the gaskets are adopted to simulate natural cracks with different slit widths, the rock core holder is required to be placed vertically, the underground real crack form and the sinking agent sedimentation process are simulated, and when the diversion recovery capability under the effect of residual acid is simulated, the gaskets are required to be replaced by copper sheets, so that the gaskets are prevented from being corroded and loosened by the residual acid.
(2) According to the application, the pressure value of the artificial interlayer bearing of the sinking agent of the simulated rock core column sample with the natural crack of the carbonate rock and the pressure value of the artificial interlayer bearing of the sinking agent without the natural crack of the carbonate rock are tested, so that the simulated rock core column sample has the advantages of simulating the bearing performance under two conditions and being more similar to the real condition of the stratum.
(3) According to the application, the pressure-bearing capacity of the sinking agent material under the condition of different crack widths is obtained by simulating carbonate rock natural crack cores with different crack widths; and (3) taking out gaskets of the cores with different slit widths, testing the artificial interlayer bearing experiment under the action of the closing stress, and evaluating the artificial interlayer bearing strength and the fluid loss property under the action of the closing stress.
In conclusion, the application has the advantages of simple logic, accuracy, reliability and the like, and has high practical value and popularization value in the technical field of gas field development.
Drawings
For a clearer description of the technical solutions of the embodiments of the present application, the drawings to be used in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and should not be considered as limiting the scope of protection, and other related drawings may be obtained according to these drawings without the need of inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a conductivity evaluator in accordance with the present application.
FIG. 2 is a schematic diagram of a dynamic stabilization seepage evaluation instrument in the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the present application will be further described with reference to the accompanying drawings and examples, which include, but are not limited to, the following examples. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In this embodiment, the term "and/or" is merely an association relationship describing the association object, and indicates that three relationships may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone.
The terms first and second and the like in the description and in the claims of the present embodiment are used for distinguishing between different objects and not for describing a particular sequential order of objects. For example, the first target object and the second target object, etc., are used to distinguish between different target objects, and are not used to describe a particular order of target objects.
In embodiments of the application, words such as "exemplary" or "such as" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "e.g." in an embodiment should not be taken as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.
In the description of the embodiments of the present application, unless otherwise indicated, the meaning of "a plurality" means two or more. For example, the plurality of processing units refers to two or more processing units; the plurality of systems means two or more systems.
The embodiment provides a degradable sinking agent artificial interlayer shielding effect evaluation method, which is characterized in that a natural core column is taken, split into halves, a gasket is adopted to simulate natural cracks with different slit widths, a second core holder is required to be placed vertically, the underground real crack form and the sinking agent sedimentation process are simulated, and when the diversion recovery capacity under the effect of residual acid is simulated, the gasket is required to be replaced by a copper sheet, so that the gasket is prevented from being corroded and loosened by the residual acid.
The basic components of the flow conductivity evaluation device in fig. 1 and the functions thereof are as follows: the leftmost side is a horizontal pump connected with the middle container, and is mainly used for providing pressure for the middle container and displaying pressure readings to displace the liquid in the middle container into the first core holder. Finally, the liquid was dropped into the metering tube from the outlet of the first core holder. In this example, the intermediate vessel was used primarily to hold simulated formation water (8% wtkcl), simulating a subsurface fluid environment; a six-way valve is arranged between the intermediate container and the first core holder, and a six-way valve is arranged between the hand pump and the first core holderAnd a through valve, the two six-way valves acting to connect the plurality of displacement lines. The first core holder is a container for placing an experimental core column. In addition, the hand pump is used for applying confining pressure to the first core holder and simulating the pressure around the stratum; metering tube is a measuring device for measuring the flow rate (cm) of liquid passing through the first core holder 3 And/s) is the volume dropped per second. In fig. 1, the conductivity of the core is obtained by pressure readings of the advection pump, the flow measured by the metering tube, the diameter and length of the core initially measured.
The basic components of the dynamic stabilization seepage evaluation instrument in fig. 2 and the functions thereof are as follows:
the main loop is: the nitrogen bottle is arranged at the leftmost side, and is used for providing displacement pressure, displacing liquid in the middle container into the second core holder, and finally the liquid drops into the metering container. Wherein the intermediate vessel in fig. 2 is primarily used to hold simulated formation water (8% wtkcl), simulating a subsurface liquid environment; a pressure gauge is arranged on the intermediate container and used for detecting the pressure of the gas cylinder displaced to the intermediate container; the pressure gauge on the second core holder detects the pressure displaced to the second core holder, and the circulating pump eliminates the pressure transmission loss between the middle container and the second core holder, and maintains the same pressure gauge numbers on the left side and the right side. In this embodiment, the second core holder is a container with an experimental core column placed upright, which simulates the formation seepage situation. In addition, the manual booster pump is connected with the second core holder, and the manual booster pump is used for applying confining pressure to the second core holder and simulating the pressure around the stratum. The metering container is used for recording the volume of liquid displaced every minute, calculating the fluid loss rate through the rock core, and judging the pressure bearing capacity of the sinking agent through the readings of the two pressure gauges and the fluid loss rate measured by the metering container.
The specific experimental operation steps comprise:
step 1, taking a natural core column from a carbonate stratum, splitting the core column, and winding gaskets with different widths by iron wires to simulate carbonate natural cracks with different underground seam widths;
step 2, measuring the diameter D and the length L of the rock sample by using a vernier caliper;
step 3, the process of filling the sinking agent material into the carbonate rock natural fracture core column is a simulated particle free sedimentation process, free stacking is carried out among particles, a filled core is put into the first core holder, the first core holder is placed vertically to simulate the form of an underground natural fracture, and then the confining pressure of the first core holder is regulated to 15MPa;
step 4, adding simulated formation water (8% wtKCl) into an intermediate container of the dynamic stability seepage evaluation instrument in fig. 2, vertically placing the second core holder, simulating the sedimentation of a sinking agent in a crack, setting the initial inlet pressure to be 1MPa, opening a circulation system, observing the pressure change of the pressure sensor, and observing whether fracturing fluid flows into the filtrate collection tank; if the inlet pressure is stable and the filtrate is small or none, the blocking pressure-bearing capacity of the sinking agent is larger than the displacement pressure at the moment;
and 5, setting the pressure gradient to be 1MPa, and carrying out gradient boosting, wherein each pressure point is kept for 10min. When the inlet pressure is gradually increased from 0 to 7MPa, no filtrate flows out of the outlet section, so that the pressure bearing and compactness of the artificial interlayer shielding of the sinking agent are better; when the inlet pressure is continuously increased to 8-9 MPa, filtrate slowly flows out from the outlet end, the filtration rate is 0.033-0.034 ml/min, and the flow rate of the liquid at the outlet end is stable; after the pressure of the inlet end is continuously increased, the filtration stall rate is steadily increased, and when the filtration stall rates are respectively increased to 10MPa, the filtration loss rate is 0.088ml/min; when the pressure is raised to 11MPa, the filtration rate is 0.334ml/min; when the pressure is raised to 12MPa, the filtration rate is 0.600ml/min; when the pressure is raised to 13MPa, the filtration rate is 0.865ml/min; at this time, the inlet end has reached the maximum measurable pressure, but the artificial barrier shielding of the sinking agent is still not broken through, and the ultimate bearing capacity is not reached. Therefore, under the condition of 1.5mm seam width, the bearing capacity of the consolidation-degradable organic solid particle type sinking agent is more than or equal to 13MPa;
step 6, replacing carbonate rock natural fracture cores with different fracture widths, when the fracture width is 3mm, operating the steps as above, starting increasing from an initial pressure of 1MPa, pressurizing 1MPa each time, and stabilizing for 10min;
step 7, when the inlet pressure is gradually increased from 0 to 6MPa, the outlet section does not flow out filtrate, and the pressure bearing and compactness of the artificial interlayer shielding of the sinking agent are better; when the inlet pressure is continuously increased to 7-9 MPa, filtrate slowly flows out from the outlet end, the flow rate of the outlet end is stable under each inlet pressure stage, but the filtration rate is slowly increased along with the increase of the pressure of the inlet end, and is respectively 0.021ml/min, 0.037ml/min and 0.045ml/min; when the inlet pressure is continuously increased to 10MPa, the filter loss of the outlet end is suddenly increased, the filter stall rate reaches 2.050ml/min within 0-1 min, and the filter stall rate is increased to 8.16ml/min within 1-3 min. The artificial interlayer shielding of the sinking agent is broken through, the filtration stall rate is suddenly increased, and the artificial shielding limit bearing capacity of the sinking agent is reached. Therefore, under the condition of 3mm seam width, the limit bearing capacity of the consolidation-degradable organic solid particle type sinking agent is considered to be more than 9MPa;
step 8, replacing natural fracture cores with different fracture widths, when the fracture width is 4mm, operating steps are the same as above, starting increasing from 1MPa initial pressure, pressurizing 1MPa each time and stabilizing for 10min;
step 9, when the inlet pressure is gradually increased from 0 to 4MPa, the outlet section does not flow out of filtrate, and the pressure bearing and compactness of the artificial interlayer shielding of the sinking agent are better; when the inlet pressure is continuously increased to 5-6 MPa, filtrate slowly flows out from the outlet end, the flow rate of the outlet end is stable in each inlet pressure stage, but the filtration rate is slowly increased along with the increase of the pressure of the inlet end, and is respectively 0.024ml/min and 0.041ml/min; when the inlet pressure is continuously increased to 7MPa, the filter loss of the outlet end is suddenly increased, the filter stall rate reaches 3.445ml/min within 0-2 minutes, and the filter stall rate is increased to 5.180ml/min within 2-4 minutes. The artificial interlayer shielding of the sinking agent is broken through, the filtration stall rate is suddenly increased, and the artificial shielding limit bearing capacity of the sinking agent is reached. Therefore, under the condition of 4mm seam width, the limit bearing capacity of the consolidation-degradable organic solid particle type sinking agent is considered to be more than 6MPa;
step 10, replacing carbonate rock natural fracture cores with different fracture widths, when the fracture width is 5mm, operating the steps as above, starting increasing from an initial pressure of 1MPa, pressurizing 1MPa each time and stabilizing for 10min;
step 11, when the inlet pressure is gradually increased from 0 to 3MPa, the outlet section does not flow out filtrate, and the pressure bearing and compactness of the artificial interlayer shielding of the sinking agent are better; when the inlet pressure is continuously increased to 4-5 MPa, filtrate slowly flows out from the outlet end, the flow rate of the outlet end is stable in each inlet pressure stage, but the filtration rate is slowly increased along with the increase of the pressure of the inlet end, and is respectively 0.057ml/min and 0.062ml/min; when the inlet pressure is continuously increased to 6MPa, the filter loss of the outlet end is suddenly increased, the filter stall rate reaches 3.615ml/min within 0-2 minutes, and the filter stall rate is increased to 8.890ml/min within 2-4 minutes. At the moment, the shielding of the artificial interlayer of the sinking agent is broken through, the filtration stall rate is suddenly increased, and the artificial shielding limit bearing capacity of the sinking agent is reached. Therefore, under the condition of 5mm seam width, the limit bearing capacity of the consolidation-degradable organic solid particle type sinking agent is considered to be more than 5MPa;
step 12, evaluating the pressure-bearing strength and fluid loss performance of the artificial interlayer under the action of the closing stress through an artificial interlayer pressure-bearing test experiment under the action of the closing stress;
step 13, taking out gaskets of the cores with different seam widths, testing the artificial interlayer bearing experiment under the action of the closing stress, and evaluating the artificial interlayer bearing strength and the fluid loss performance under the action of the closing stress;
step 14, adding simulated formation water (8% wtKCl) into an intermediate container of a dynamic stable seepage evaluation instrument, vertically placing the second core holder, simulating the sedimentation of a sinking agent in a crack, opening a circulation system, observing the pressure change of the pressure sensor, and observing whether fracturing fluid flows into the filtrate collection tank; if the inlet pressure is stable and the filtrate is little or no, the blocking pressure-bearing capacity of the sinking agent is larger than the displacement pressure at the moment under the closing pressure;
and 15, raising the displacement pressure to 1MPa, and always keeping the confining pressure to be larger than the displacement pressure by 1.5MPa. Setting the pressure gradient to be 1MPa, carrying out gradient boosting, and keeping each pressure point for 5min;
step 16, under the action of closed stress, when the inlet pressure is gradually increased from 0 to 7MPa, no filtrate flows out of the outlet section, and the fact that the pressure bearing and compactness of the artificial interlayer shielding of the sinking agent are better is shown; continuously and synchronously increasing the closing stress and the inlet pressure, when the inlet pressure reaches 8MPa, the filtrate slowly flows out from the outlet end, the filtration rate is 0.46ml/min, and the flow of the liquid at the outlet end is stable; however, as the closing stress continues to increase, the pressure at the inlet end continues to increase (8-10 MPa), and the fluid loss rate is reduced from 0.46ml/min to 0.34ml/min; when the closing stress is continuously increased and the pressure at the inlet end is continuously increased to 11-13 MPa, the fluid loss rate is 0ml/min, no filtrate flows out of the outlet section at this time, and the pressure bearing and compactness of the artificial interlayer of the sinking agent are recovered. Analysis shows that the crack edge of the inlet end pressure (8-10 MPa) can possibly show signs of blocking breakthrough of the sinking agent, but the blocking breakthrough is restrained and the blocking effect is recovered along with the continuous increase of the closing stress. Therefore, the shielding effect of the sinking agent in the seam width of 2mm under the action of the closing stress is considered to be good, and when the closing stress is more than 14.5MPa, the pressure bearing capacity of the organic solid particle type sinking agent is more than or equal to 13MPa;
step 17, measuring and evaluating the restoration of the fracture conductivity under the action of no acid etching;
step 18, placing the real core column after testing the bearing capacity into a high-temperature reaction kettle, setting the reaction temperature to 160 ℃ for simulating the formation temperature, and degrading for 12 hours;
and 19, taking out the core subjected to high-temperature degradation, then placing the core into a core holder, and testing the permeability of the core until the confining pressure is 2.5 MPa.
Step 20, a power supply of a advection pump is turned on, after five minutes of preheating, different flow rates are set, the pressure of the inlet end of the rock core is measured when the set flow rates are set, and the flow rate of the outlet end of the rock core is measured by a measuring cup and a stopwatch; and when the data of the pressure gauge tend to be stable and the outlet flow velocity is stable, recording the pressure and the flow at the moment, and calculating the rock diversion capacity. The statistical table of the experimental results of the permeability test of the core sinking agents with different slit widths after high-temperature degradation is shown in table 1:
table 1 statistical table of experimental results of permeability test of core sinkers with different slit widths after high-temperature degradation
Step 21, the fracture conductivity decreases sharply with increasing closing stress, and the fracture conductivity is substantially lost when the closing stress increases above 20 MPa. Therefore, the wall surface of the crack is considered to be blocked by the sinking agent, when the wall surface of the crack is not etched by the acid liquor, the crack can lose the diversion capability under the action of the closing pressure after the degradation of the sinking agent, and the risk of communicating with a water layer is reduced.
In this embodiment, the average fracture conductivity of the rock sample can be determined by measuring three flow rates, and the permeability formula can be calculated from the following formula:
wherein, a=slit width w×rock plate (core) width D, a fracture conductivity evaluation formula can be deduced:
wherein,,representing the flow rate; />Indicating the viscosity of the liquid->Representing the length of the simulated core column sample; />Representing the width of a simulated core column sample; />Representing the displacement differential pressure.
Step 22, recovering and evaluating the flow conductivity of the crack after the residual acid acts;
step 23, padding copper sheets on two sides of the core column, winding the copper sheets by using iron wires, and hanging the copper sheets on two sides of a beaker; residual acid is stored in the beaker.
Step 24, circularly injecting the residual acid into the crack for 5 minutes, and simulating the residual acid to flow through the crack;
step 25, measuring the diversion capacity of the fracture core after acid etching, and carrying out recovery evaluation on the diversion capacity by the same steps; the statistics of the experimental results of the permeability test of the carbonate rock core after acid etching are shown in table 2:
table 2 statistical table of experimental results of permeability test after acid etching of carbonate core
Step 26, along with the increase of the closing stress, the fracture conductivity is sharply reduced, when the closing stress is increased to more than 10MPa, the fracture conductivity retention rate is only 13.41%, and when the closing stress is increased to more than 50MPa, the fracture conductivity retention rate is only 2.95%, but at the moment, the fracture conductivity is still much larger than that of the fracture conductivity without acid etching. Therefore, the crack wall surface subjected to acid etching by the residual acid is considered to have certain permeability, namely, the upper crack control reserve and the seepage channel are recovered in the longitudinal direction of the artificial interlayer, and the influence of the artificial interlayer on the acid etching seam height is reduced.
The above embodiments are only preferred embodiments of the present application and are not intended to limit the scope of the present application, but all changes made by adopting the design principle of the present application and performing non-creative work on the basis thereof shall fall within the scope of the present application.
Claims (6)
1. The method for evaluating the shielding effect of the artificial interlayer of the degradable sinking agent adopts a diversion capability evaluating instrument and a dynamic stable seepage evaluating instrument for monitoring, and is characterized in that a first core holder is arranged in the diversion capability evaluating instrument; a second core holder, an intermediate container and a metering container are arranged in the dynamic stable seepage evaluation instrument; the second core holder is longitudinally arranged; the first core holder is transversely arranged;
the method for evaluating the shielding effect of the degradable sinking agent artificial interlayer comprises the following steps:
s1, taking a plurality of natural core columns from a carbonate stratum, and preparing a simulated core column sample with natural cracks of the carbonate stratum;
s2, filling a sinking agent into the simulated rock core column sample, placing the simulated rock core column sample into a second rock core holder, performing free sedimentation of the sinking agent, and adjusting the confining pressure of the second rock core holder to 15MPa;
s3, placing the simulated core column sample in the step S2 into a second core holder, adding simulated formation water by using a dynamic stable seepage evaluation instrument, and presetting the initial inlet pressure of the second core holder to be 1MPa; observing whether fracturing fluid flows into the metering container or whether the pressure of the second core holder is suddenly changed; if no fracturing fluid flows in or the pressure of the second core holder is not suddenly changed, the step S4 is carried out; otherwise, recording the current inlet pressure value;
step S4, boosting by adopting a pressure gradient of 1MPa, and keeping for 10min after boosting by any gradient until a large amount of fracturing fluid flows into a metering container or pressure is suddenly changed; recording the current pressure value of the artificial interlayer bearing of the sinking agent;
s5, replacing the simulated core column sample, and repeating the steps S2 to S4 to obtain pressure values of the artificial interlayer bearing of the sinking agent with a plurality of cracks;
s6, performing carbonate natural fracture removal and reduction on the simulated rock core column sample, placing the simulated rock core column sample with the carbonate natural fracture removed into a second rock core holder, adding simulated formation water by using a dynamic stable seepage evaluation instrument, and presetting the initial inlet pressure of the second rock core holder to be 0.5MPa; observing whether fracturing fluid flows into the metering container or whether the pressure of the second core holder is suddenly changed; if no fracturing fluid flows in or the pressure of the second core holder is not suddenly changed, the step S7 is carried out; otherwise, recording the current inlet pressure value;
step S7, the displacement pressure of the second core holder is increased to 1Mpa, and the confining pressure is kept to be 1.5Mpa higher than the displacement pressure; boosting by adopting a pressure gradient of 1MPa, and keeping for 5min after boosting by any gradient; until a large amount of fracturing fluid flows into the metering container or a sudden pressure change occurs; recording the current pressure value, namely the pressure value of the artificial interlayer bearing of the sinking agent without the natural crack of the carbonate rock;
step S8, placing the simulated core column sample in the step S7 into a high-temperature reaction kettle, and degrading for 12 hours at 160 ℃;
s9, placing the degraded simulated core column sample into a first core holder, and increasing confining pressure to 2.5MPa; presetting a first flow of a diversion capacity evaluation instrument, and measuring a pressure value and a flow value when the pressure and the flow are stable by using the diversion capacity evaluation instrument;
step S10, regulating the first flow to obtain a plurality of pressure values and flow values when the pressure and the flow are stable;
step S11, obtaining a fracture conductivity value according to the flow Q, the length of the simulated core column sample, the natural fracture information of the carbonate and the displacement pressure difference; the expression of the fracture conductivity value is as follows:
wherein Q represents flow; μ represents the viscosity of the liquid; l represents the length of the simulated core column sample; d represents the width of the simulated core column sample; Δp represents the displacement differential pressure.
2. The method for evaluating the shielding effect of the artificial interlayer of the degradable sinking agent according to claim 1, wherein the preparation of the simulated core column sample comprises the following steps:
and uniformly splitting the natural core column into two parts, and winding the split natural core column with a plurality of gaskets to obtain a simulated core column sample with natural cracks of carbonate rock.
3. The method for evaluating the shielding effect of the artificial interlayer of the degradable sinking agent according to claim 2, wherein the width of the gasket is 1.5-5mm; the range of the carbonate natural fracture of the simulated core column sample is 1-4mm.
4. The method for evaluating the shielding effect of the artificial interlayer of the degradable sinking agent according to claim 2, wherein the method for removing and reducing the natural cracks of the carbonate rock from the simulated core column sample comprises the following steps: and (5) removing the gasket wound on the split natural core column.
5. The method for evaluating the shielding effect of an artificial interlayer of a degradable sinking agent according to claim 2, further comprising: and replacing the gasket with a copper sheet with the same width, and repeating the steps S1 to S11 to measure the conductivity value of the fracture core after acid etching.
6. The method for evaluating the shielding effect of an artificial interlayer of a degradable sinking agent according to claim 5, further comprising: and after the gasket is replaced by a copper sheet with the same width, injecting residual acid after the reaction of the gelled acid and the carbonate rock into the simulated rock core column sample for 5min.
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