CN113281182B - Multi-means integrated fracture quantitative evaluation method - Google Patents

Multi-means integrated fracture quantitative evaluation method Download PDF

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CN113281182B
CN113281182B CN202110569494.5A CN202110569494A CN113281182B CN 113281182 B CN113281182 B CN 113281182B CN 202110569494 A CN202110569494 A CN 202110569494A CN 113281182 B CN113281182 B CN 113281182B
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cylindrical sample
fracturing
sample
fracture
acquiring
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CN113281182A (en
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郭印同
应琪祺
杨春和
周俊
郭武豪
常鑫
王磊
杨涵志
张晓宇
毕振辉
赵国凯
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Wuhan Institute of Rock and Soil Mechanics of CAS
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    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G01N3/10Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
    • G01N3/12Pressure testing
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/08Investigating permeability, pore-volume, or surface area of porous materials
    • G01N15/082Investigating permeability by forcing a fluid through a sample
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    • G01MEASURING; TESTING
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    • G01N3/00Investigating strength properties of solid materials by application of mechanical stress
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    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014Type of force applied
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    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058Kind of property studied
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    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
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    • G01N2203/025Geometry of the test
    • G01N2203/0256Triaxial, i.e. the forces being applied along three normal axes of the specimen
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02Details not specific for a particular testing method
    • G01N2203/026Specifications of the specimen
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00Indexing codes associated with group G01N29/00
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    • G01N2291/0289Internal structure, e.g. defects, grain size, texture

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Abstract

A multi-means integrated quantitative evaluation method for fracturing fracture, the method comprising the steps of: preparing a cylindrical sample by using an unconventional compact reservoir underground full-diameter core; carrying out an indoor hydraulic fracturing physical simulation test on the cylindrical sample; acquiring the fracturing crack information of the cylindrical sample; acquiring strain information of the cylindrical sample in a fracturing process; carrying out crack surface stress sensitivity test on the cylindrical sample; acquiring the crack space characteristics of the cylindrical sample; preparing a standard cylinder sample by using the cylinder sample; carrying out an osmotic stress sensitivity test on the standard cylindrical sample; acquiring quantitative data of the crack surface of the standard cylinder sample; and carrying out comprehensive quantitative evaluation on the fracture surface. The method can be used for quantitatively evaluating the complexity and permeability characteristics of the fracturing fracture of the tight reservoir rock body with different burial depths under different stress characteristics and fracturing process parameters.

Description

Multi-means integrated quantitative evaluation method for fracturing fracture
Technical Field
The invention belongs to the technical field of unconventional tight reservoir reconstruction, and particularly relates to a multi-means integrated fracturing fracture quantitative evaluation method.
Background
Unconventional oil and gas resources have the characteristics of low reservoir porosity, low permeability and the like. In order to achieve efficient production of unconventional oil and gas resources, it must be commercially exploited by fracture modification to create artificial fracture networks. At present, a horizontal well staged fracturing mode is often adopted for a compact oil and gas reservoir, a large fracturing pump truck group is adopted to pump fracturing fluids with different types and different discharge capacities into the compact reservoir, and after the critical fracture pressure of the reservoir is reached, one or more fracturing fractures distributed in space are formed.
At present, the technical means for evaluating the expansion scale of the fracturing fracture in fracturing construction mainly comprise methods such as field micro-seismic monitoring, trace adding in fracturing fluid, a wide area electrical measurement method, an inclinometer and the like, but the technical methods are difficult to truly observe the characteristics and scale of the formed fracturing fracture, but are all obtained by indirect explanation of the fracturing modification evaluation result, and the reliability of the fracturing modification evaluation result needs to be further verified.
The currently common indoor hydraulic fracturing physical simulation test is the only technical method which can really obtain the fracture morphology and observe the fracture surface characteristic information, but the method only used for evaluating the fracture characteristics is not abundant enough, is difficult to quantify and is single.
Disclosure of Invention
In view of the above, the present invention provides a multi-means integrated quantitative fracture evaluation method that overcomes or at least partially solves the above-mentioned problems.
In order to solve the technical problem, the invention provides a multi-means integrated quantitative evaluation method for fracturing fracture, which comprises the following steps:
preparing a cylindrical sample by using an unconventional full-diameter underground core of a compact reservoir;
carrying out an indoor hydraulic fracturing physical simulation test on the cylindrical sample;
acquiring the fracturing crack information of the cylindrical sample;
acquiring strain information of the cylindrical sample in a fracturing process;
carrying out crack surface stress sensitivity test on the cylindrical sample;
acquiring the crack space characteristics of the cylindrical sample;
preparing a standard cylinder sample by using the cylinder sample;
carrying out an osmotic stress sensitivity test on the standard cylindrical sample;
acquiring quantitative data of the crack surface of the standard cylinder sample;
and carrying out comprehensive quantitative evaluation on the fracture surface.
Preferably, the preparation of the cylindrical sample by using the unconventional tight reservoir downhole full-diameter core comprises the following steps:
acquiring the underground full-diameter core of the unconventional tight reservoir;
preparing the underground full-diameter core of the unconventional tight reservoir into a cylindrical sample with a preset specification;
arranging a simulation shaft with a preset depth on the circular end face of the cylindrical sample;
filling a salt section with a preset height at a first end in the simulated shaft;
a plasticine layer is tightly arranged at the upper part of the salt section;
inserting a simulated casing from a second end of the simulated wellbore;
arranging sealing epoxy resin between the simulation casing and the inner wall of the simulation shaft;
injecting distilled water into the salt section through the epoxy resin and the plasticine layer using a syringe;
and after the salt section is completely dissolved, pumping the mixed solution away by using the syringe.
Preferably, the indoor hydraulic fracturing physical simulation test on the cylinder sample comprises the following steps:
preparing a three-axis testing machine;
placing the cylindrical sample between an upper pressure head and a lower pressure head of the triaxial tester;
packaging the cylindrical sample;
putting the cylindrical sample into a triaxial chamber of the triaxial testing machine;
starting the triaxial testing machine;
applying confining pressure and axial pressure to the cylindrical sample according to a preset stress;
keeping the confining pressure and the axial pressure unchanged and starting a servo pump pressure control system of the triaxial testing machine;
pumping simulated fracturing fluid into the triaxial chamber according to a preset discharge capacity;
stopping the servo pump pressure control system when the pump pressure curve reaches a preset turning point;
and acquiring the fractured complex cracks of the cylindrical sample.
Preferably, the step of obtaining the fracture information of the cylinder sample comprises the steps of:
arranging an acoustic emission data acquisition system around the cylindrical sample;
synchronously starting the acoustic emission data acquisition system when the indoor hydraulic fracture physical simulation test starts;
acquiring crack initiation and expansion information of the cylindrical sample in the injection process of the simulated fracturing fluid in real time through the acoustic emission data acquisition system;
positioning according to the crack initiation and the expansion information to obtain the crack three-dimensional space spread characteristics of the cylindrical sample;
and quantifying the data acquired by the acoustic emission data acquisition system to obtain the occurrence time and the proportion of the tension type cracks, the shear type cracks and the tension-shear composite cracks of the cylindrical sample.
Preferably, the acquiring strain information of the cylindrical sample in the fracturing process comprises the following steps:
arranging a radial strain sensor on the circumferential surface of the cylindrical sample;
arranging an axial strain sensor in the axial direction of the cylindrical sample;
acquiring radial strain data of the cylindrical sample through the radial strain sensor in a fracturing process;
and acquiring axial strain data of the cylindrical sample through the radial strain sensor in a fracturing process.
Preferably, the crack surface stress sensitivity test on the cylindrical test piece comprises the following steps:
acquiring a first confining pressure of the cylindrical sample in a first fracturing process;
after the first fracturing process is finished, the first confining pressure is increased to a second confining pressure;
keeping the second confining pressure in a second fracturing process stable;
pumping simulated fracturing fluid into a triaxial chamber of a triaxial testing machine according to a preset discharge capacity;
and determining seepage stress sensitivity data of the cylindrical sample after the second fracturing process is completed.
Preferably, the acquiring the fracture space characteristics of the cylindrical sample comprises the following steps:
obtaining the cylindrical sample which completes the fracturing test;
putting the cylindrical sample into a large core holder;
setting temperature parameters and pressure parameters of the large core holder;
simulating reservoir temperature for the cylindrical sample according to the temperature parameters;
simulating a reservoir pressure environment for the cylindrical sample according to the pressure parameters;
imaging and scanning the water space distribution characteristics inside the cylindrical sample;
quantitatively analyzing the three-dimensional space information of the pressing crack of the cylindrical sample;
quantitatively analyzing the size scale characteristics of the fracturing cracks of the cylindrical sample.
Preferably, the step of preparing a standard cylinder sample by using the cylinder sample comprises the steps of:
acquiring a tension type crack, a shear type crack and a tension-shear composite crack on the cylindrical sample;
classifying all the tension type fractures, the shear type fractures and the tension-shear composite type fractures;
positioning an axis containing the tension-type fracture, the shear-type fracture and the tension-shear composite fracture on the cylindrical sample;
and carrying out linear cutting on the cylindrical sample along the axis to obtain the standard cylindrical sample with a preset specification.
Preferably, the penetration stress sensitivity test for the standard cylindrical sample comprises the following steps:
sealing the outer peripheral surface of the standard cylindrical sample by using transparent epoxy resin;
preparing an MTS rock mechanical test system;
setting confining pressure parameters, axial prestress parameters and pore pressure parameters of the MTS rock mechanical test system;
determining the seepage stress sensitivity of the standard cylinder sample by using the MTS rock mechanical test system according to each parameter;
and acquiring the stress sensitivity parameters of the standard cylindrical sample.
Preferably, the step of obtaining quantitative data of the fracture surface of the standard cylinder sample comprises the steps of:
cutting the epoxy resin on the peripheral surface of the standard cylinder sample;
opening the standard cylinder sample along the original crack surface;
and acquiring the quantitative data of the crack surface of the standard cylindrical sample by adopting a high-precision morphology scanner.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: the multi-means integrated fracturing fracture quantitative evaluation method can be used for quantitatively evaluating the complexity and permeability characteristics of fracturing fractures of tight reservoir rock masses with different burial depths under different ground stress characteristics and fracturing process parameters, provides a technical means for optimizing fracturing design parameters, and has certain practical significance for promoting unconventional reservoir complex fracture forming mechanisms and technologies.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a multi-means integrated fracture quantitative evaluation method provided in an embodiment of the present invention.
Detailed Description
The present invention will be specifically explained below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented thereby. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Referring to fig. 1, in an embodiment of the present application, the present invention provides a multi-means integrated fracture quantitative evaluation method, including the steps of:
s1: preparing a cylindrical sample by using an unconventional compact reservoir underground full-diameter core;
in the embodiment of the application, the preparation of the cylindrical sample by using the underground full-diameter core of the unconventional tight reservoir in the step S1 comprises the following steps:
acquiring the underground full-diameter core of the unconventional tight reservoir;
preparing the unconventional tight reservoir underground full-diameter core into a cylindrical sample with a preset specification;
arranging a simulation shaft with a preset depth on the circular end face of the cylindrical sample;
filling a salt section with a preset height at a first end in the simulated shaft;
a plasticine layer is tightly arranged at the upper part of the salt section;
inserting a simulated casing from a second end of the simulated wellbore;
arranging sealing epoxy resin between the simulation casing and the inner wall of the simulation shaft;
injecting distilled water into the salt section through the epoxy resin and the plasticine layer using a syringe;
and after the salt section is completely dissolved, pumping the mixed solution away by using the syringe.
In the embodiment of the application, when the cylindrical sample is prepared by using the underground full-diameter core of the unconventional tight reservoir, specifically, the underground full-diameter core of the unconventional tight reservoir of shale gas is collected firstly to obtain a cylinder with the diameter of 100mm, and then the underground full-diameter core of the unconventional tight reservoir of shale gas is processed into the cylindrical sample with the diameter of 100mm and the height of 200mm by using a horizontal drilling machine, so that the parallelism of two end faces is ensured; then, drilling a central hole with the diameter of 8mm and the depth of 130mm on one circular end face of the cylindrical sample by using a straight diamond drill bit to serve as a simulated shaft; filling a salt section with the length of 60mm in the simulated shaft, and tightly placing a layer of plasticine on the upper part of the salt section to prevent epoxy resin from entering the salt section to block the reserved fracturing channel when the annular space of the simulated sleeve and the simulated shaft on the upper part is sealed by epoxy resin; then placing a simulation casing at the middle position of the upper simulation shaft, sealing the simulation casing and the annular space of the inner wall of the simulation shaft by using epoxy resin, and standing for 48 hours to enable the epoxy resin to reach the highest strength; injecting distilled water into the salt filling section through the end part of the simulation sleeve by using a medical syringe injector, and extracting the mixed solution after the salt is completely dissolved.
S2: carrying out an indoor hydraulic fracturing physical simulation test on the cylindrical sample;
in the embodiment of the present application, the performing of the indoor hydraulic fracture physical simulation test on the cylindrical sample in step S2 includes the steps of:
preparing a three-axis testing machine;
placing the cylindrical sample between an upper pressure head and a lower pressure head of the triaxial testing machine;
packaging the cylindrical sample;
putting the cylindrical sample into a triaxial chamber of the triaxial testing machine;
starting the triaxial testing machine;
applying confining pressure and axial pressure to the cylindrical sample according to a preset stress;
keeping the confining pressure and the axial pressure unchanged and starting a servo pump pressure control system of the triaxial testing machine;
pumping simulated fracturing fluid into the triaxial chamber according to a preset discharge capacity;
stopping the servo pump pressure control system when the pump pressure curve reaches a preset turning point;
and acquiring the fractured complex cracks of the cylindrical sample.
In the embodiment of the application, when an indoor hydraulic fracturing physical simulation test is carried out on the cylindrical sample, specifically, the prepared cylindrical sample is firstly placed between an upper pressure head and a lower pressure head of a triaxial chamber of a prepared triaxial testing machine, the upper port of a simulation sleeve is tightly connected with a built-in groove of the upper pressure head, and a pressure-resistant sealing ring is arranged in the groove to ensure the sealing property; then, a polyvinyl fluoride heat-shrinkable tube is adopted to enable the three to be in close contact by means of shrinkage of the heat-shrinkable tube, so that confining pressure oil in the triaxial chamber is prevented from entering the interior of the sample, and the packaged sample is placed in the triaxial chamber; starting a three-axis testing machine, applying confining pressure and axial pressure to a cylindrical sample according to a set stress condition, keeping the confining pressure and the axial pressure unchanged, starting a servo pump pressure control system, pumping simulated fracturing fluid into a three-axis chamber according to a set displacement parameter, rapidly increasing the pump pressure along with the increase of the pumped fracturing fluid, stopping the servo pump pressure control system when the pump pressure curve is obviously raised to a rapid drop point, and obtaining an unconventional reservoir sample fractured complex seam.
S3: acquiring the fracturing crack information of the cylindrical sample;
in the embodiment of the present application, the acquiring of the fracture information of the cylindrical sample in step S3 includes the steps of:
arranging an acoustic emission data acquisition system around the cylindrical sample;
synchronously starting the acoustic emission data acquisition system when the indoor hydraulic fracturing physical simulation test starts;
acquiring crack initiation and expansion information of the cylindrical sample in the injection process of the simulated fracturing fluid in real time through the acoustic emission data acquisition system;
positioning according to the crack initiation and the expansion information to obtain the crack three-dimensional space spread characteristics of the cylindrical sample;
and quantifying the data acquired by the acoustic emission data acquisition system to obtain the occurrence time and the proportion of the tension type cracks, the shear type cracks and the tension-shear composite cracks of the cylindrical sample.
In the embodiment of the application, when acquiring the fracturing crack information of the cylindrical sample, specifically, 8 high temperature and high pressure resistant acoustic emission probes are placed on the circumferential surface of the sample with the diameter of 100mm and the height of 200mm in two layers by adopting an elastic rigid ring, the lead of the acoustic emission probe is connected with a triaxial chamber base, the triaxial chamber is connected with a preamplifier and then connected with a DI sp acoustic emission data acquisition system, and the validity of a signal channel of equipment is checked before a test. Synchronously starting an acoustic emission data acquisition system in the fracturing test process, acquiring fracture initiation and expansion information of a sample in the fracturing fluid injection process in real time, and positioning according to the fracture initiation and expansion information to obtain the three-dimensional fracture distribution characteristic; after the fracturing test is finished, effective data acquired by the acoustic emission data acquisition system is deeply mined by adopting a moment tensor analysis technology, and the occurrence time and proportion of tension type, shear type and tension-shear composite type fractures are obtained quantitatively.
S4: acquiring strain information of the cylindrical sample in a fracturing process;
in an embodiment of the present application, the acquiring strain information of the cylindrical sample in the fracturing process in step S4 includes the steps of:
arranging a radial strain sensor on the circumferential surface of the cylindrical sample;
arranging an axial strain sensor in the axial direction of the cylindrical test sample;
acquiring radial strain data of the cylindrical sample through the radial strain sensor in a fracturing process;
and acquiring axial strain data of the cylindrical sample through the radial strain sensor in a fracturing process.
In the embodiment of the application, when strain information of the cylindrical sample in the fracturing process is obtained, specifically, a radial strain sensor is arranged on the peripheral surface of the sample with the diameter of 100mm and the height of 200mm, an LVDT sensor is axially adopted, whether a sensor connecting line is unblocked is checked before fracturing, then strain data of the sample are collected in real time through the radial strain sensor and the LVDT sensor in the fracturing process, and an obvious strain jump point correspondingly appears on the strain sensor corresponding to the generation of each fracturing, so that the maximum fracture geometric information corresponding to each fracturing fracture can be interpreted and obtained, and the maximum fracture geometric information is used for quantitatively evaluating data parameters such as the length and the width of the fracture.
S5: carrying out crack surface stress sensitivity test on the cylindrical sample;
in the embodiment of the present application, the crack surface stress sensitivity test on the cylindrical sample in step S5 includes the steps of:
acquiring a first confining pressure of the cylindrical sample in a first fracturing process;
after the first fracturing process is finished, the first confining pressure is increased to a second confining pressure;
maintaining the second confining pressure stable during a second fracturing process;
pumping simulated fracturing fluid into a triaxial chamber of a triaxial testing machine according to a preset displacement;
and determining seepage stress sensitivity data of the cylindrical sample after the second fracturing process is completed.
In the embodiment of the application, when a crack surface stress sensitivity test is performed on the cylindrical sample, specifically, after the cylindrical sample is fractured, the confining pressure is not removed temporarily, the confining pressure is increased to a pressure higher than the confining pressure of a fracturing test, then the confining pressure is kept unchanged, an original fracturing fluid injection pipeline is used as a pore pressure injection end, the pore pressure is set to be 5MPa, and then a pressure attenuation method is used for measuring the seepage stress sensitivity of the whole fractured sample; and repeating the process to obtain the integral stress sensitivity parameters of the quantified fracturing sample.
S6: acquiring the crack space characteristics of the cylindrical sample;
in the embodiment of the present application, the acquiring of the crack spatial characteristics of the cylindrical sample in step S6 includes the steps of:
acquiring the cylindrical sample which finishes a fracturing test;
putting the cylindrical sample into a large core holder;
setting temperature parameters and pressure parameters of the large core holder;
simulating the reservoir temperature of the cylindrical sample according to the temperature parameter;
simulating a reservoir pressure environment for the cylindrical sample according to the pressure parameters;
imaging and scanning the water space distribution characteristics inside the cylindrical sample;
quantitatively analyzing the three-dimensional space information of the pressing crack of the cylindrical sample;
quantitatively analyzing the size scale characteristics of the fracturing cracks of the cylindrical sample.
In an embodiment of the present application, when acquiring the fracture spatial characteristics of the cylindrical sample, the fracture spatial characteristics may be determined using a temperature-variable nmr analysis and imaging system. Specifically, a sample which is subjected to a fracturing test is placed in a large core holder, the temperature parameter and the pressure parameter of the large core holder are set to be used for simulating the reservoir temperature (100 ℃) and the confining pressure of 70MPa, and then the permeability parameter of the temperature of 100 ℃ and the confining pressure of 70MPa can be obtained; and then scanning the spatial distribution characteristics of the water inside the fractured rock core by using nuclear magnetic resonance imaging, and quantitatively analyzing the three-dimensional spatial information of the fracturing crack and the size and scale characteristics of the fracturing crack according to the distribution proportion of the water inside the rock core.
S7: preparing a standard cylinder sample by using the cylinder sample;
in the embodiment of the present application, the step S7 of preparing a standard cylindrical sample by using the cylindrical sample comprises the steps of:
acquiring a tension type crack, a shear type crack and a tension-shear composite crack on the cylindrical sample;
classifying all the tension type cracks, the shear type cracks and the tension-shear composite cracks;
positioning an axis containing the tension-type fracture, the shear-type fracture and the tension-shear composite fracture on the cylindrical sample;
and performing linear cutting on the cylindrical sample along the axis to obtain the standard cylindrical sample with a preset specification.
In the embodiment of the present application, when the standard cylinder sample is prepared by using the cylinder sample, specifically, the cracks (the tension type cracks, the shear type cracks, and the tension-shear composite cracks) obtained by analyzing the acoustic emission moment tensor are firstly classified, the standard cylinder sample containing different crack types (the tension type cracks, the shear type cracks, and the tension-shear composite cracks) and having a diameter of 25mm and a length of 50mm is obtained by processing the cylinder sample by using a linear cutting technique, and meanwhile, the crack surfaces (the tension type cracks, the shear type cracks, and the composite cracks) are basically located on the axis of the standard cylinder sample, so that the standard cylinder sample is mainly used for carrying out the test and study on the single crack permeability after the proppant is laid on the crack surfaces containing different types.
S8: carrying out an osmotic stress sensitivity test on the standard cylindrical sample;
in the embodiment of the present application, the step S8 of performing the penetration stress sensitivity test on the standard cylindrical sample includes the steps of:
sealing the outer peripheral surface of the standard cylindrical sample by using transparent epoxy resin;
preparing an MTS rock mechanical test system;
setting confining pressure parameters, axial prestress parameters and pore pressure parameters of the MTS rock mechanical test system;
determining the seepage stress sensitivity of the standard cylinder sample by using the MTS rock mechanical test system according to each parameter;
and acquiring the stress sensitivity parameters of the standard cylinder sample.
In the embodiment of the application, when the standard cylindrical sample is subjected to the penetration stress sensitivity test, specifically, the outer peripheral surface of the sample containing different types of crack surface characteristics and subjected to linear cutting is firstly sealed by transparent epoxy resin, so as to prevent pore water from overflowing from the peripheral surface of the sample and influencing the accuracy of the experimental result; secondly, carrying out a permeability stress sensitivity test study of cylindrical samples containing different types of crack surface characteristics obtained by carrying out linear cutting by adopting an MTS rock mechanical test system, sequentially setting confining pressure of the MTS rock mechanical test system to be 10MPa, 20MPa, 30MPa, 40MPa and 50MPa, axial prestress to be 2MPa and a pore pressure liquid inlet end to be 5MPa, and then measuring seepage stress sensitivity of the samples by adopting a pressure attenuation method; and repeating the processes at different confining pressures to obtain the finishing stress sensitivity parameters of the quantified fracturing sample.
S9: acquiring quantitative data of the crack surface of the standard cylinder sample;
in the embodiment of the present application, the acquiring of the quantitative data of the fracture surface of the standard cylindrical sample in step S9 includes the steps of:
cutting the epoxy resin on the peripheral surface of the standard cylinder sample;
opening the standard cylinder sample along the original crack surface;
and acquiring the quantitative data of the crack surface of the standard cylindrical sample by adopting a high-precision morphology scanner.
In the embodiment of the application, when quantitative crack surface data of the standard cylindrical sample are obtained, specifically, the cylindrical sample subjected to the permeability stress sensitivity test is opened along an initial crack pressing surface, a high-precision three-dimensional shape scanner is used for finely picking up the fluctuation degrees of different types of crack surfaces, and after-treatment is performed through software, quantitative parameters corresponding to different crack types can be obtained.
S10: and carrying out comprehensive quantitative evaluation on the fracture surface.
In the embodiment of the application, when comprehensive quantitative evaluation of fracture surfaces is performed, specifically, parameters such as fracture modes (tension type, shear type and tension-shear composite type), fracture length, fracture width, integral permeability of a fractured sample, single permeability change rules of different fracture types and the like of different fracture surfaces obtained in steps S1 to S9 are comprehensively analyzed and quantified, and then the complexity of fractures after underground core fracturing, the occupation ratios of different types of fractures and the permeability characteristics under reservoir conditions are comprehensively evaluated.
The multi-means integrated fracturing fracture quantitative evaluation method can be used for quantitatively evaluating the complexity and permeability characteristics of fracturing fractures of tight reservoir rock bodies with different burial depths under different stress characteristics and fracturing process parameters, provides a technical means for optimizing fracturing design parameters, and has certain practical significance for promoting unconventional reservoir complex fracture forming mechanisms and technologies.
It is noted that, in this document, relational terms such as "first" and "second," and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element. The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
In short, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A multi-means integrated quantitative evaluation method for fracturing fracture is characterized by comprising the following steps:
preparing a cylindrical sample by using an unconventional full-diameter underground core of a compact reservoir;
carrying out an indoor hydraulic fracturing physical simulation test on the cylindrical sample;
acquiring the fracturing crack information of the cylindrical sample;
acquiring strain information of the cylindrical sample in a fracturing process;
carrying out crack surface stress sensitivity test on the cylindrical sample;
acquiring the crack space characteristics of the cylindrical sample;
preparing a standard cylinder sample by using the cylinder sample;
carrying out an osmotic stress sensitivity test on the standard cylindrical sample;
acquiring quantitative data of the crack surface of the standard cylinder sample;
carrying out comprehensive and quantitative evaluation on fracture surfaces, wherein parameters of fracture modes, fracture lengths, fracture widths, integral permeability of samples after fracturing and single permeability change rules of different fracture types are comprehensively analyzed and quantified, and then the complexity of fractures after underground core fracturing, the occupation ratios of different types of fractures and the permeability characteristics under reservoir conditions are comprehensively evaluated;
the method for preparing the standard cylinder sample by using the cylinder sample comprises the following steps:
acquiring a tension type crack, a shear type crack and a tension-shear composite crack on the cylindrical sample;
classifying all the tension type fractures, the shear type fractures and the tension-shear composite type fractures;
positioning an axis containing the tension-type fracture, the shear-type fracture and the tension-shear composite fracture on the cylindrical sample;
and carrying out linear cutting on the cylindrical sample along the axis to obtain the standard cylindrical sample with a preset specification.
2. The quantitative evaluation method for fracturing fracture integrated by multiple sections according to claim 1, wherein the preparation of the cylindrical sample by using the underground full-diameter core of the unconventional tight reservoir comprises the following steps:
acquiring the underground full-diameter core of the unconventional tight reservoir;
preparing the underground full-diameter core of the unconventional tight reservoir into a cylindrical sample with a preset specification;
arranging a simulation shaft with a preset depth on the circular end face of the cylindrical sample;
filling a salt section with a preset height at a first end in the simulated shaft;
a plasticine layer is tightly arranged at the upper part of the salt section;
inserting a simulated casing from a second end of the simulated wellbore;
arranging sealing epoxy resin between the simulation casing and the inner wall of the simulation shaft;
injecting distilled water into the salt section through the epoxy resin and the plasticine layer using a syringe;
and after the salt section is completely dissolved, pumping the mixed solution away by using the syringe.
3. The quantitative evaluation method for fracturing fracture integrated by multiple means of claim 1, wherein the indoor hydraulic fracturing physical simulation test on the cylindrical sample comprises the following steps:
preparing a triaxial testing machine;
placing the cylindrical sample between an upper pressure head and a lower pressure head of the triaxial testing machine;
packaging the cylindrical sample;
putting the cylindrical sample into a triaxial chamber of the triaxial testing machine;
starting the triaxial testing machine;
applying confining pressure and axial pressure to the cylindrical sample according to a preset stress;
keeping the confining pressure and the axial pressure unchanged and starting a servo pump pressure control system of the triaxial testing machine;
pumping simulated fracturing fluid into the triaxial chamber according to a preset discharge capacity;
stopping the servo pump pressure control system when the pump pressure curve reaches a preset turning point;
and acquiring the fractured complex cracks of the cylindrical sample.
4. The quantitative evaluation method of fracturing fracture integrated with multiple segments as claimed in claim 1, wherein said obtaining fracturing fracture information of said cylindrical sample comprises the steps of:
arranging an acoustic emission data acquisition system around the cylindrical sample;
synchronously starting the acoustic emission data acquisition system when the indoor hydraulic fracturing physical simulation test starts;
acquiring crack initiation and expansion information of the cylindrical sample in the injection process of the simulated fracturing fluid in real time through the acoustic emission data acquisition system;
positioning according to the crack initiation and the expansion information to obtain the crack three-dimensional space spread characteristics of the cylindrical sample;
and quantifying the data acquired by the acoustic emission data acquisition system to obtain the occurrence time and the proportion of the tension type cracks, the shear type cracks and the tension-shear composite cracks of the cylindrical sample.
5. The quantitative evaluation method for fracturing fracture integrated with multiple sections according to claim 1, wherein the step of obtaining strain information of the cylindrical sample in the fracturing process comprises the following steps:
arranging a radial strain sensor on the circumferential surface of the cylindrical sample;
arranging an axial strain sensor in the axial direction of the cylindrical sample;
acquiring radial strain data of the cylindrical sample through the radial strain sensor in a fracturing process;
and acquiring axial strain data of the cylindrical sample through the axial strain sensor in the fracturing process.
6. The quantitative evaluation method of fracturing fracture integrated with multiple means according to claim 1, wherein said testing the stress sensitivity of fracture surface of said cylindrical sample comprises the steps of:
acquiring a first confining pressure of the cylindrical sample in a first fracturing process;
after the first fracturing process is finished, the first confining pressure is increased to a second confining pressure;
maintaining the second confining pressure stable during a second fracturing process;
pumping simulated fracturing fluid into a triaxial chamber of a triaxial testing machine according to a preset discharge capacity;
and determining seepage stress sensitivity data of the cylindrical sample after the second fracturing process is completed.
7. The multi-means integrated quantitative fracture evaluation method according to claim 1, wherein the obtaining of the fracture spatial characteristics of the cylindrical sample comprises the steps of:
obtaining the cylindrical sample which completes the fracturing test;
putting the cylindrical sample into a large core holder;
setting temperature parameters and pressure parameters of the large core holder;
simulating reservoir temperature for the cylindrical sample according to the temperature parameters;
simulating a reservoir pressure environment for the cylindrical sample according to the pressure parameters;
imaging and scanning the water space distribution characteristics inside the cylindrical sample;
quantitatively analyzing the three-dimensional space information of the pressing crack of the cylindrical sample;
quantitatively analyzing the size scale characteristics of the fracturing cracks of the cylindrical sample.
8. The quantitative evaluation method of fracturing fracture integrated with multiple segments as claimed in claim 1, wherein said test of osmotic stress sensitivity test on said standard cylindrical sample comprises the steps of:
sealing the outer peripheral surface of the standard cylindrical sample by using transparent epoxy resin;
preparing an MTS rock mechanical test system;
setting confining pressure parameters, axial prestress parameters and pore pressure parameters of the MTS rock mechanical test system;
determining the seepage stress sensitivity of the standard cylinder sample by using the MTS rock mechanical test testing system according to the parameters;
and acquiring the stress sensitivity parameters of the standard cylindrical sample.
9. The quantitative evaluation method of fracturing fracture integrated with multiple means according to claim 1, wherein the step of obtaining quantitative data of fracture surface of the standard cylinder specimen comprises the steps of:
cutting the epoxy resin on the peripheral surface of the standard cylinder sample;
opening the standard cylinder sample along the original crack surface;
and acquiring quantitative data of the crack surface of the standard cylindrical sample by adopting a high-precision morphology scanner.
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