CN113008941B - Method for testing saturation-resistance increase coefficient of bedding joint development shale - Google Patents
Method for testing saturation-resistance increase coefficient of bedding joint development shale Download PDFInfo
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- 238000012360 testing method Methods 0.000 title claims abstract description 11
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
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- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
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- B25B11/00—Work holders not covered by any preceding group in the subclass, e.g. magnetic work holders, vacuum work holders
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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
- G01N15/088—Investigating volume, surface area, size or distribution of pores; Porosimetry
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Abstract
The invention discloses a method for testing saturation-resistance increasing coefficient of bedding joint development shale, which is based on a resistivity tester, wherein the resistivity tester comprises a resistivity meter, a rock core holder, an air source and a metering balance; the core holder comprises a kettle body shell, a rubber sleeve arranged in the kettle body shell, a kettle body plunger, a core upper plunger and a core lower plunger; the upper end of the kettle body shell is provided with an opening, and the kettle body plunger is plugged at the upper end of the kettle body shell; the rubber sleeve and the kettle body shell are arranged in a split mode, the space between the inner wall of the kettle body shell and the outer wall of the rubber sleeve is a cavity in the kettle body, and non-conductive silicone oil is filled in the cavity in the kettle body; the upper core plunger and the lower core plunger are respectively blocked at the upper end and the lower end of the rubber sleeve, and a clamping space for holding the core is formed between the upper core plunger and the lower core plunger; this application is in whole experimentation, and the sample keeps motionless in the gum cover, avoids damaging the sample because of reasons such as artificial removal, plays the purpose of protection sample.
Description
Technical Field
The invention relates to the technical field of reservoir evaluation of oil and gas reservoirs, in particular to a method for testing the saturation-resistance increase coefficient of bedding joint developed shale.
Background
The porosity and permeability of the shale matrix are generally low, and a large number of developed bedding seams are important factors for improving the oil and gas storage and transportation characteristics of the shale. Fractures refer to various fractures or fracture surfaces in the rock that occur due to loss of cohesion, and the presence of bedding cracks in shale significantly affects the distribution and migration of the original fluids in the formation. The Archie's formula is the preferred model for solving formation oil and water saturation using electrical logging. The method for estimating the reservoir water saturation based on the Archie formula is one of important means for evaluating the oil-gas saturation of the stratum rock. According to the method, the stratum oil and gas saturation is obtained by reducing the rock water saturation and establishing a corresponding relation (RI-SW curve) of the saturation and the resistivity to obtain the Archie parameter.
The fracture and the matrix porosity together constitute the pore system of the rock. Reducing water saturation in the rock pore system is a necessary means to obtain the Archie parameters. For rock without fractures (i.e., rock matrix pore systems), centrifugation (driving water) and gas driving (water) are common methods to reduce the water saturation of the rock. However, in the case of shale with developed bedding seams, the sample itself has a fragile nature, and thus centrifugation is not suitable in the first place. The method for reducing the saturation degree of the rock core through gas drive is characterized in that gas is injected from the upper part of the rock core holder device, the gas is diffused from the upper part to the lower part of the wrapped plunger, and part of water in the wrapped plunger is driven out through a pore system, so that the aim of reducing the saturation degree of water and obtaining the Archie parameters is fulfilled.
When existing gas drive equipment is designed, a kettle body shell and a rubber sleeve are installed together, a core needs to be manually filled into a cavity of the rubber sleeve before an experiment begins, then a system is loaded to carry out the experiment under confining pressure, and the core is manually pushed out of the cavity of the rubber sleeve by a push rod after the experiment is finished. The problem of adhesion between the rock core and the rubber sleeve often appears after the confining pressure of the system is released after the experiment is finished, the brittleness of the shale sample is high, and the rock core is easily damaged due to uneven stress in the moving process, so that the experiment fails.
Also, for shale, the heavily developed bedding joints form through channels in the shale core, and these fractures, which are much more permeable than the matrix pores, form the dominant seepage channels in the rock. When fluid flows through the rock pore system, the matrix pores are avoided and these highly permeable fractures are selected as preferential seepage channels. This results in that the existing gas displacement desaturation method (gas displacement method) can only displace water in shale cracks but can not displace water in matrix pores. That is, the water saturation in the fracture decreases most, and the water saturation in the surrounding pores hardly changes. Rock resistivity test experiments based on the Archie's formula are carried out in the shale with developed cracks, and only the conduction rule reflecting the change of the saturation degree of the crack fluid can be obtained. The saturation in the matrix pores is not obviously reduced, so that the method is difficult to represent the conduction rule of matrix pore fluid, the resistance increase coefficient and the saturation relation in a complete shale pore system cannot be represented, and the experimental result cannot provide accurate parameters for evaluating the oil saturation of the shale formation.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for testing the saturation-resistance increasing coefficient of the bedding joint developed shale.
The technical scheme adopted by the invention is as follows:
the method is based on a resistivity tester, and the resistivity tester comprises a resistivity meter, a core holder, an air source and a metering balance; the core holder comprises a kettle body shell, a rubber sleeve arranged in the kettle body shell, a kettle body plunger, a core upper plunger and a core lower plunger; the upper end of the kettle body shell is provided with an opening, and the kettle body plunger is plugged at the upper end of the kettle body shell; the rubber sleeve and the kettle body shell are arranged in a split mode, the space between the inner wall of the kettle body shell and the outer wall of the rubber sleeve is a cavity in the kettle body, and non-conductive silicone oil is filled in the cavity in the kettle body; the core upper plunger and the core lower plunger are respectively blocked at the upper end and the lower end of the rubber sleeve, and a clamping space for clamping the core is formed between the core upper plunger and the core lower plunger; the gas source is connected to the upper end of the clamping space through a gas inlet pipeline, and the metering balance is connected to the lower end of the clamping space through a gas outlet pipeline; the resistivity meter is respectively connected with the lower core plunger and the upper core plunger through a positive electrode lead and a negative electrode lead;
the test method comprises the following steps:
s1, manufacturing and drying a core with a regular shape, and measuring the dry weight m of the dried coredLength L and diameter d, and calculating the total volume V of the core according to the length L and the diameter ddWherein Vd＝π*d^2*L/4；
S2, preparing a simulated formation aqueous solution, saturating the core for 24 hours under the pressure of 30MPa to ensure that the pores of the core are completely filled with formation water, and weighing the mass m of the saturated cores；
S3, measuring the resistivity R of the formation water solutionw；
S4, calculating the water-containing mass and the pore volume of the core, wherein the water-containing mass of the core is mw0＝ms-mdPore volume of Vw0＝mw0/ms*Vd＝(ms-md)/ms*Vd；
S5, filling the saturated rock core into a rubber sleeve, placing the rubber sleeve into a kettle body, and setting system confining pressure to simulate a formation pressure state;
s6, after the confining pressure of the system is stable, calculating the total volume of the compressed rock according to the reading c of the micrometer on the core holder, wherein the volume is the total volume of the rock under the formation pressure state and is recorded as VcIn which V isc＝π*(d-c)^2*(L-c)/4；
S7, calculating the compression coefficient cc of the pore volume of the core and the porosity of the compressed core
Wherein cc ═ Vd–Vc)/Vd，
S8, the mass of water contained in the pores of the compressed core is equal to the mass m of water contained in the total pores of the core under the formation pressure state0，
S9, measuring the resistance of the rock core under the confining pressure state, namely the resistivity R of the saturated rock under the formation pressure0；
S10, measuring the water saturation S in the process of desaturation under the confining pressure statewAnd a resistance increase coefficient RI, the process comprises two stages of gas drive and throughput;
s101, reducing the water saturation of the crack by adopting a gas water-driving mode; opening an upper plunger and a lower plunger valve of the rock core, and using nitrogen to displace water in the rock core, wherein the water in the crack can quickly drop out of the rock core;
s102, measuring mass m of discharged water by using a metering balanceiCollecting core resistivity R by using resistivity meteriCalculating the saturation Sw and the resistance increase coefficient RI; wherein Sw ═ m0-mi)/(m0)*100％，RI＝Ri/R0；
S103, reducing the porosity saturation of the matrix in a throughput mode, wherein the step comprises 4 steps:
a. swallowing: opening an air inlet valve of an upper plunger piston of the rock core and closing an air outlet valve of a lower plunger piston of the rock core, and injecting a determined amount of carbon dioxide into the rock core;
b. stewing: closing an air inlet valve of a plunger piston on the rock core, sealing carbon dioxide in the rock core, enabling gas to diffuse into pores, and maintaining for about 2-12 hours;
c. spit: opening a gas outlet valve of a lower plunger of the rock core, releasing gas pressure, and removing water carried by carbon dioxide molecules out of matrix pores;
d. gas drive: opening an upper plunger air inlet valve, and introducing nitrogen to wash out moisture attached to the surfaces of the cracks and in the air outlet pipeline;
repeating the steps S102 and S103 for 5-7 times to obtain Sw and RI in each state; and S11, drawing a saturation-resistance increase coefficient graph.
Further, still include the confining pressure pump, this confining pressure pump pass through oil pipe with internal cavity intercommunication of cauldron.
Further, still include earial drainage jar and earial drainage pipe, cauldron body shell bottom is equipped with the relief valve, the one end and the relief valve of earial drainage pipe are connected, the other end with earial drainage jar is connected.
Further, the kettle comprises a tripod which is supported at the bottom of the kettle shell.
Further, the device also comprises a computer, wherein the output end of the resistivity meter is connected with the input end of the computer.
Further, a plurality of insulating joints are arranged on the kettle body plunger, and the gas inlet pipeline, the gas outlet pipeline, the positive electrode lead and the negative electrode lead respectively enter the cavity inside the kettle body through the insulating joints.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
Fig. 1 is a schematic structural view of a core holder for bedding fracture-developing shale provided in example 1 of the present application;
fig. 2 is a schematic structural diagram of a resistivity tester for bedding fissured shale according to embodiment 2 of the present application.
The reactor comprises a reactor shell 1, a reactor plunger 2, a rubber sleeve 3, a core upper plunger 4, a core lower plunger 5, a core 6, a confining pressure pump 7, a drainage pipe 8, a drainage tank 9, a tripod 10, a resistivity meter 11, a computer 12, an air source 13, a metering balance 14, an air inlet pipeline 15, a negative electrode lead 16, a positive electrode lead 17 and an air outlet pipeline 18.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.
It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the invention pertains.
Example 1
Referring to fig. 1, in this embodiment, the application provides a core 6 holder for bedding joint developing shale, which includes a kettle housing 1, a rubber sleeve 3 arranged in the kettle housing 1, a kettle plunger 2, a core upper plunger 4, and a core lower plunger 5; the upper end of the kettle body shell 1 is opened, and the kettle body plunger 2 is blocked at the upper end of the kettle body shell 1; the rubber sleeve 3 and the kettle body shell 1 are arranged in a split mode, the space between the inner wall of the kettle body shell 1 and the outer wall of the rubber sleeve 3 is a cavity in the kettle body, and non-conductive silicone oil is filled in the cavity in the kettle body; and the core upper plunger 4 and the core lower plunger 5 are respectively blocked at the upper end and the lower end of the rubber sleeve 3, and a clamping space for clamping the core 6 is formed between the core upper plunger 4 and the core lower plunger 5.
During the use, through encapsulating rock core 6 in gum cover 3, and be located the rock core and go up plunger 4 and rock core 6 and make between the plunger and can carry out the confining pressure experiment. This application is through setting up gum cover 3 and the 1 components of a whole that can function independently of cauldron body shell, and gum cover 3 direct encapsulation is on the sample, and in whole experimentation, the sample keeps motionless in gum cover 3, avoids damaging the sample because of reasons such as artificial removal, plays the purpose of protection sample.
Preferably, the device further comprises a confining pressure pump 7, the confining pressure pump 7 is communicated with the cavity in the kettle body through an oil pipe, silicone oil can be injected into the cavity in the kettle body through the confining pressure pump 7, and covering pressure is provided for the rock core 6 so as to simulate the bottom pressure state.
For the convenience of the pressure release, this application still includes earial drainage jar 9 and earial drainage pipe 8, and 1 bottom of cauldron body shell is equipped with the relief valve, and earial drainage pipe 8's one end is connected with the relief valve, and the other end is connected with earial drainage jar 9. When the pressure of the cavity in the kettle body is too high, the pressure release valve can be opened, and the silicone oil can flow into the drainage tank 9 through the drainage pipe 8 so as to release the silicone oil in the cavity in the kettle body.
Preferably, a tripod 10 is further included, and the tripod 10 is supported at the bottom of the kettle shell 1 and supports the kettle.
Example 2
In this embodiment, the present application provides an electrical resistivity tester for bedding joint developing shale, including an electrical resistivity meter 11, a computer 12, a core 6 holder, an air source 13, and a metering balance 14, where the core 6 holder is the above core 6 holder; the gas source 13 is connected to the upper end of the clamping space through a gas inlet pipeline 15, and the metering balance 14 is connected to the lower end of the clamping space through a gas outlet pipeline 18; the resistivity meter 11 is respectively connected with the core lower plunger 5 and the core upper plunger 4 through a positive electrode lead 17 and a negative electrode lead 16; the output end of the resistivity meter 11 is connected with the input end of the computer 12.
Specifically, a plurality of insulating joints are arranged on the kettle plunger 2, and the gas inlet pipeline 15, the gas outlet pipeline 18, the positive electrode lead 17 and the negative electrode lead 16 respectively enter the cavity inside the kettle through the insulating joints.
When the device is used, the gas source 13 releases displacement gas, and the displacement gas enters the upper end of the rock core 6 through the gas inlet pipeline 15 and displaces fluid in the pores of the rock core 6; the gas passing through the core 6 and the fluid displaced from the core 6 are discharged out of the kettle body through a gas outlet pipeline 18 at the lower end of the core 6 and enter a metering balance 14, a measuring cylinder is placed on the metering balance 14, the displaced fluid is discharged into the measuring cylinder, the mass of the fluid is weighed by the metering balance 14, and the current saturation is calculated; meanwhile, the resistivity meter 11 collects the resistance values at both ends of the core 6 through the positive electrode lead 17 and the negative electrode lead 16, and outputs the collected resistivity data through the computer 12. By the equipment, the mass and the resistivity of the core 6 in a confining pressure state can be collected, and the water saturation and the resistance increase coefficient of the core 6 are calculated according to the mass and the resistivity, so that a graph of the saturation-resistance increase coefficient (Sw-RI) of the core 6 is obtained.
Example 3
In this embodiment, the application provides a method for testing saturation-resistance increase coefficient of a bedding joint developing shale, which adopts the above resistivity tester, and includes the following steps:
s1, manufacturing and drying a core with a regular shape, and measuring the dry weight m of the dried coredLength L and diameter d, and calculating the total volume V of the core according to the length L and the diameter ddWherein Vd＝π*d^2*L/4。
Specifically, step S1 includes the following steps:
s101, processing a shale sample into a plunger core with the diameter d of 2.54cm and the length L of 3-5 cm.
S102, drying the plunger core, and measuring dry weight m of the plunger coredThe unit is g, and the total volume V of the dried core is calculated according to the length L and the diameter d of the cored，VdPi d 2L/4 in cm3。
S2, preparing a simulated formation aqueous solution, saturating the core for 24 hours under the pressure of 30MPa to ensure that the pores of the core are completely filled with formation water, and weighing the mass m of the saturated coresCalculating to obtain the total volume V of the saturated rock cores。
S3, measuring the resistivity R of the formation water solutionwAnd the unit is omega.
S4, calculating the water-containing mass and the pore volume of the core, wherein the water-containing mass of the core is mw0＝ms-mdPore volume of Vw0＝mw0/ms*Vd＝(ms-md)/ms*Vd。
S5, filling the saturated rock core into a rubber sleeve, placing the rubber sleeve into the kettle body in the embodiment 2, and setting system confining pressure to simulate a formation pressure state; in order to protect the core and ensure the integrity of the core, the subsequent test is completed in the core holder, and the core is not taken out of the core holder for testing.
S6, after the confining pressure of the system is stable, calculating the total volume of the compressed rock according to the reading c of the micrometer on the core holder, wherein the volume is the total volume of the rock under the formation pressure state and is recorded as VcIn which V isc＝π*(d-c)^2*(L-c)/4；
S7, calculatingCore pore volume compressibility cc and post-compression core porosity
Wherein cc ═ Vd–Vc)/Vd，
S8, the mass of water contained in the pores of the compressed core is equal to the mass m of water contained in the total pores of the core under the formation pressure state0，
S9, measuring the resistance of the rock core under the confining pressure state, and recording as R0，R0I.e. the resistivity of saturated rock at formation pressure.
S10, measuring the water saturation S in the process of desaturation under the confining pressure statewAnd the resistance increase coefficient RI, which comprises two stages of gas drive and throughput.
Specifically, step S10 includes the following steps:
s101, reducing the water saturation of the crack by adopting a gas water-driving mode; and opening the upper plunger and the lower plunger valve of the rock core, and displacing water in the rock core by using nitrogen or carbon dioxide, wherein the water in the crack can quickly separate from the rock core.
S102, measuring mass m of discharged water by using a metering balanceiCollecting core resistivity R by using resistivity meteriCalculating the saturation Sw and the resistance increase coefficient RI; wherein Sw ═ m0-mi)/(m0)*100％，RI＝Ri/R0。
S103, reducing the porosity saturation of the matrix in a throughput mode, wherein the step comprises 4 steps:
a. swallowing: and opening an air inlet valve of the upper plunger piston of the rock core and closing an air outlet valve of the lower plunger piston of the rock core, and injecting a determined amount of carbon dioxide into the rock core.
b. Stewing: closing the plunger piston air inlet valve on the rock core, sealing carbon dioxide in the rock core, and enabling gas to diffuse into the pores for about 2-12 hours.
c. Spit: and opening a gas outlet valve of the lower plunger of the rock core, releasing gas pressure, and removing the carbon dioxide molecules carrying water out of the matrix pores.
d. Gas drive: and opening an air inlet valve of the upper plunger, and introducing nitrogen to wash out the moisture attached to the surfaces of the cracks and in the air outlet pipeline.
Repeating the steps S102 and S103 for 5-7 times to obtain Sw and RI in each state; that is, the saturation of the pores of the substrate is decreased a plurality of times in 4 steps of "throughput", and the mass and the resistance of the discharged water are measured by the method of step S102 after each decrease of the saturation of the pores of the substrate, thereby calculating the saturation and the resistance increase coefficient after each decrease of the saturation of the pores of the substrate.
S11, obtaining the water saturation S according to the step S10wAnd the resistance increase coefficient RI plots the saturation-resistance increase coefficient.
The method adopts a combination of a gas displacement method and a gas swallowing and spitting method to reduce the water saturation of the shale fracture, wherein the gas comprises nitrogen and carbon dioxide; the gas displacement saturation reduction method is characterized in that nitrogen is injected into a rock core wrapped by confining pressure from an inlet end of a core barrel, water in a crack is driven out of a pore system by utilizing the displacement capacity of gas, the driven water flows out from an outlet end of the core barrel, the purpose of reducing the rock water saturation is achieved, and valves at the gas inlet end and the gas outlet end are in an open state in the whole gas displacement process. And after the process of gas displacement saturation reduction is finished, carrying out a gas huff and puff method to reduce the saturation of the matrix pores. The gas throughput saturation degree reducing method comprises three parts of swallowing, stewing and spitting, and the used gas medium is carbon dioxide. The 'swallowing' is that a certain amount of pressurized gas is injected into the confined and wrapped rock core from the inlet end of the core barrel, and the valve at the inlet end is opened while the valve at the outlet end is closed; then, after the gas reaches a certain pressure, closing the valve at the inlet end, sealing the gas in the pores of the rock core for a certain time, wherein the sealed gas can be diffused in the pore system of the shale, the valves at the inlet end and the outlet end are closed at the moment, the process is called as 'braising', and the pressure of the gas sealed in the pores is gradually reduced in the process; finally, after the pressure of the stewing well is reduced to a certain value, entering a spitting stage, wherein the spitting is a pressure releasing process, an outlet end valve needs to be opened to release gas in the process, and the high-pressure gas can carry part of the fluid in the pores to be separated from the rock core; the aim of reducing the water saturation of the pores of the rock matrix is achieved through three steps of swallowing, stewing and spitting, and the problem that dehydration cannot be achieved in the pores of the shale matrix by an air-flooding method is solved. The RI-SW curve drawn according to the experimental result of the method can reflect the Archie parameters of the electrical characteristics of the whole pore system including the cracks and the matrix pores in the shale, and can provide more accurate parameters for evaluating the oil saturation of the shale formation.
In this application, unless expressly stated or limited otherwise, the terms "connected," "secured," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral combinations thereof; may be an electrical connection; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the description of the present invention, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, systems, and techniques have not been shown in detail in order not to obscure an understanding of this description.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, system, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, systems, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.
Claims (6)
1. The method for testing the saturation-resistance increase coefficient of the bedding joint development shale is characterized by being based on a resistivity tester, wherein the resistivity tester comprises a resistivity meter (11), a rock core (6) holder, an air source (13) and a metering balance (14); the core (6) holder comprises a kettle body shell (1), a rubber sleeve (3) arranged in the kettle body shell (1), a kettle body plunger (2), a core upper plunger (4) and a core lower plunger (5); the upper end of the kettle body shell (1) is opened, and the kettle body plunger (2) is plugged at the upper end of the kettle body shell (1); the rubber sleeve (3) and the kettle body shell (1) are arranged in a split mode, the space between the inner wall of the kettle body shell (1) and the outer wall of the rubber sleeve (3) is a cavity in the kettle body, and non-conductive silicone oil is filled in the cavity in the kettle body; the core upper plunger (4) and the core lower plunger (5) are respectively plugged at the upper end and the lower end of the rubber sleeve (3), and a clamping space for clamping the core (6) is formed between the core upper plunger (4) and the core lower plunger (5); the gas source (13) is connected to the upper end of the clamping space through a gas inlet pipeline (15), and the metering balance (14) is connected to the lower end of the clamping space through a gas outlet pipeline (18); the resistivity meter (11) is respectively connected with the rock core lower plunger (5) and the rock core upper plunger (4) through a positive electrode lead (17) and a negative electrode lead (16);
the test method comprises the following steps:
s1, manufacturing and drying a core with a regular shape, and measuring the dry weight m of the dried coredLength L and diameter d, and calculating the total volume V of the core according to the length L and the diameter ddWherein Vd＝π*d^2*L/4；
S2, preparing a simulated formation aqueous solution, saturating the core for 24 hours under the pressure of 30MPa to ensure that the pores of the core are completely filled with formation water, and weighing the mass m of the saturated cores；
S3, measuring the resistivity R of the formation water solutionw；
S4, calculating the water-containing mass and the pore volume of the core, wherein the water-containing mass of the core is mw0＝ms-mdPore volume of Vw0＝mw0/ms*Vd＝(ms-md)/ms*Vd；
S5, filling the saturated rock core into a rubber sleeve, placing the rubber sleeve into a kettle body, and setting system confining pressure to simulate a formation pressure state;
s6, after the confining pressure of the system is stable, calculating the total volume of the compressed rock according to the reading c of the micrometer on the core holder, wherein the volume is the total volume of the rock under the formation pressure state and is recorded as VcIn which V isc＝π*(d-c)^2*(L-c)/4；
S7, calculating the compression coefficient cc of the pore volume of the core and the porosity of the compressed core
Wherein cc ═ Vd–Vc)/Vd，
S8, the mass of water contained in the pores of the compressed core is equal to the mass m of water contained in the total pores of the core under the formation pressure state0，
S9, measuring the resistance of the rock core under the confining pressure state, namely the resistivity R of the saturated rock under the formation pressure0；
S10, measuring the water saturation S in the process of desaturation under the confining pressure statewAnd a resistance increase coefficient RI, the process comprises two stages of gas drive and throughput;
s101, reducing the water saturation of the crack by adopting a gas water-driving mode; opening an upper plunger and a lower plunger valve of the rock core, and using nitrogen to displace water in the rock core, wherein the water in the crack can quickly drop out of the rock core;
s102, measuring mass m of discharged water by using a metering balanceiCollecting core resistivity R by using resistivity meteriCalculating the saturation Sw and the resistance increase coefficient RI; wherein Sw ═ m0-mi)/(m0)*100％，RI＝Ri/R0；
S103, reducing the porosity saturation of the matrix in a throughput mode, wherein the step comprises 4 steps:
a. swallowing: opening an air inlet valve of an upper plunger piston of the rock core and closing an air outlet valve of a lower plunger piston of the rock core, and injecting a determined amount of carbon dioxide into the rock core;
b. stewing: closing an air inlet valve of a plunger piston on the rock core, sealing carbon dioxide in the rock core, enabling gas to diffuse into pores, and maintaining for about 2-12 hours;
c. spit: opening a gas outlet valve of a lower plunger of the rock core, releasing gas pressure, and removing water carried by carbon dioxide molecules out of matrix pores;
d. gas drive: opening an upper plunger air inlet valve, and introducing nitrogen to wash out moisture attached to the surfaces of the cracks and in the air outlet pipeline;
repeating the steps S102 and S103 for 5-7 times to obtain Sw and RI in each state;
and S11, drawing a saturation-resistance increase coefficient graph.
2. The test method for the saturation-resistance increasing coefficient of the bedding joint developing shale according to claim 1, characterized by further comprising a confining pressure pump (7), wherein the confining pressure pump (7) is communicated with the cavity inside the kettle body through an oil pipe.
3. The method for testing the saturation-resistance increase coefficient of the bedding crack developing shale according to claim 2, characterized by further comprising a drainage tank (9) and a drainage pipe (8), wherein a pressure release valve is arranged at the bottom of the kettle body shell (1), one end of the drainage pipe (8) is connected with the pressure release valve, and the other end of the drainage pipe is connected with the drainage tank (9).
4. The test method for the saturation-resistivity coefficient of increase of bedding joint developing shale according to any one of claims 1 to 3, characterized by further comprising a tripod (10), wherein the tripod (10) is supported at the bottom of the kettle shell (1).
5. The resistivity tester for bedding developing shale according to claim 4, further comprising a computer (12), wherein an output end of the resistivity meter (11) is connected with an input end of the computer (12).
6. The resistivity tester for bedding developing shale according to claim 5, wherein a plurality of insulating joints are arranged on the kettle plunger (2), and the gas inlet pipeline (15), the gas outlet pipeline (18), the positive electrode lead (17) and the negative electrode lead (16) respectively enter the cavity inside the kettle through the insulating joints.
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