Disclosure of Invention
The invention aims to provide an indoor hydraulic fracturing simulation device, an indoor hydraulic fracturing simulation system, a manufacturing method and a testing method, which can realize indoor hydraulic fracturing simulation by changing hydraulic fracturing parameters (pump pressure displacement and perforation arrangement) under the condition of simulating three-dimensional stress of a stratum, obtain real-time monitoring data of a stress field around a fracturing fracture and provide technical support for stress interference among hydraulic fracturing fractures of unconventional oil and gas reservoirs.
In order to achieve the above object, in a first aspect, the present invention provides an indoor hydraulic fracture simulation apparatus, including:
the test sample is provided with a blind hole along the horizontal direction and is used for simulating a horizontal shaft; an initial crack which is orthogonal and/or oblique to the blind hole is prefabricated on the sample; a main fracturing crack is preset on the sample at a crack opening close to the initial fracturing crack, and prefabricated drill holes are arranged on two sides close to the preset main fracturing crack;
the pressure box is fixedly arranged in the prefabricated drill hole;
the simulation sleeve is fixedly arranged in the blind hole, a spraying hole is formed in the simulation sleeve at a position corresponding to the initial crack opening, the spraying hole is used for spraying preset fracturing fluid into the initial crack opening, the first end of the simulation sleeve is a blind end, and the second end of the simulation sleeve is used for being connected with a hydraulic fracturing system.
Further, mechanical characteristics of the sample are adapted to the simulated rock formation, and the mechanical characteristics comprise strength and deformation stress characteristics.
Further, the sample is in the shape of a cube.
Furthermore, the blind hole is located at the center of the sample, and high-strength epoxy resin is sealed and fixed in the blind hole and the simulation sleeve.
Further, the prefabricated drill holes are multiple, each prefabricated drill hole is provided with the pressure box, and a gap between the pressure box and the prefabricated drill hole is filled with a concrete material.
In a second aspect, the present invention further provides an indoor hydraulic fracture simulation system, including:
a true triaxial fracture tester;
the indoor hydraulic fracture simulation device as described; when the test is carried out, the indoor hydraulic fracturing simulation device is arranged in the true triaxial fracturing tester, and the true triaxial fracturing tester is used for applying stratum three-way stress to the indoor hydraulic fracturing simulation device;
and the hydraulic fracturing system is connected with the simulation casing pipe of the indoor hydraulic fracturing simulation device and is used for pumping fracturing fluid into the simulation casing pipe.
In a third aspect, the present invention further provides a method for manufacturing the indoor hydraulic fracture simulation device, including:
selecting a sample, and determining a well type for simulating hydraulic fracturing, wherein the method specifically comprises the following steps: forming a blind hole in the horizontal direction of the sample for simulating a horizontal shaft; an initial crack which is orthogonal and/or oblique to the blind hole is prefabricated on the sample; arranging a plurality of groups of injection holes on the simulation sleeve, and then sending the simulation sleeve into the blind hole for fixing, so that each group of injection holes corresponds to the seam of the initial crack;
according to the setting condition of the ground stress of hydraulic fracturing, a main fracturing crack is preset on the sample close to the crack opening of the initial fracturing crack, and drill prefabricated drill holes are arranged on two sides close to the preset main fracturing crack;
and placing the pressure box into the prefabricated drill hole for fixing to obtain the indoor hydraulic fracturing simulation device.
Further, the step of feeding the simulation sleeve into the blind hole for fixing comprises:
feeding the simulated casing into the blind hole;
prefabricating a plurality of prefabricated perforations in the blind hole orthogonal and/or oblique to the blind hole,
after fracturing the plurality of preformed perforations, simulating an initial fracture initiation, specifically: and filling soluble salt into the prefabricated perforation, injecting epoxy resin between the simulation casing and the inner wall surface of the blind hole, dissolving salt filled in the simulation perforation section of the shaft by using clear water, and then pumping out the dissolved salt to form an effective fracturing section, namely the initial crack.
Further, the putting the pressure box into the prefabricated drill hole for fixing comprises:
and placing the pressure box in the prefabricated drill hole, filling a gap between the pressure box and the deep hole by adopting a high-strength concrete material, and leading out the lead of the pressure box from the prefabricated drill hole.
In a fourth aspect, the present invention further provides an indoor hydraulic fracture simulation test method, which is applied to the indoor hydraulic fracture simulation system, and the simulation test method includes:
connecting a second end of the simulated casing to the hydraulic fracturing system;
applying the stratum three-way stress to the indoor hydraulic fracturing simulation device by using the true triaxial fracturing tester;
controlling the hydraulic fracturing system to pump the preset fracturing fluid into the simulation casing according to a preset discharge capacity;
the method comprises the following steps of (1) collecting the running condition of the preset fracturing fluid after the preset fracturing fluid enters the blind hole in real time by using a pressure box while pumping the preset fracturing fluid, and monitoring the stress field around the crack during single-cluster fracturing physical simulation;
or when the synchronous initiation of the multiple clusters of initial fractures is completed after the pressure of the preset fracturing fluid rises to reach the fracture pressure and multiple clusters of through fracturing fractures are formed on the basis of the initial fractures, the flow distribution of the preset fracturing fluid in the multiple clusters of fracturing fractures and the acquisition of the characteristics of the fracturing fractures in the dynamic expansion process are realized.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
according to the indoor hydraulic fracturing simulation device and method provided by the invention, the pressure box capable of measuring the three-way stress is pre-embedded in the periphery of the natural unconventional compact sample and the preset fracturing, so that the three-way stress condition of a stratum can be simulated, the indoor hydraulic fracturing simulation is carried out by changing the hydraulic fracturing parameters, the real-time monitoring data of the stress field around the fracturing is obtained, and the real-time monitoring data and the pumping pressure curve are synchronously compared and analyzed, so that the technical support is provided for researching the stress interference between the hydraulic fracturing of the unconventional oil and gas reservoir. The method can be used for monitoring the stress field around the crack when the unconventional reservoir rock mass is subjected to single-cluster fracturing physical simulation, and can also be used for monitoring the stress field around the crack when other multi-cluster perforation synchronous fracturing and double-well synchronous or cross fracturing simulation are carried out, so that the applicability of the method is improved.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. 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 in accordance with the meanings 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.
In order to solve the technical problems, the general idea of the embodiment of the application is as follows:
in the method, a sample with mechanical characteristics suitable for the simulated rock stratum is selected to simulate the rock stratum in actual exploitation, a blind hole is formed in the sample to simulate a horizontal shaft, a simulation casing is arranged in the blind hole to simulate a field casing, and an initial fracture which is orthogonal and/or oblique to the blind hole is prefabricated on the sample to simulate a natural fracture. In the test process, a preset fracturing fluid is provided into the simulation sleeve through the hydraulic fracturing system, and the preset fracturing fluid is sprayed into the initial crack through the spraying holes in the simulation sleeve corresponding to the initial crack, so that the preset fracturing fluid enters a plurality of clusters of initial cracks to synchronously crack;
through the pressure box arranged in the prefabricated drill hole, the flow distribution of the preset fracturing fluid in the multiple clusters of fracturing fractures and the acquisition of the characteristics of the fracturing fractures in the dynamic expansion process can be monitored when the multiple clusters of initial fracturing fractures are synchronously fractured.
The method and the device solve the defect that the real reaction fracturing fracture can not truly analyze the characteristics of the surrounding stress field in the prior art, can simulate the three-dimensional stress condition of the stratum, carry out indoor hydraulic fracturing simulation by changing hydraulic fracturing parameters (pumping pressure displacement and perforation arrangement), obtain real-time monitoring data of the stress field around the fracturing fracture, and provide technical support for the stress interference among the hydraulic fracturing fractures of the unconventional oil and gas reservoir.
In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and the specific embodiments.
Example one
According to an exemplary embodiment of the present invention, there is provided an indoor hydraulic fracture simulation apparatus including:
the test sample is used for simulating tight oil and gas reservoir rocks and arranged in a true triaxial fracturing tester, the mechanical characteristics of the test sample are suitable for simulated rock stratums, the mechanical characteristics can comprise strength and deformation stress characteristics, the mechanical characteristics can also comprise material density, it needs to be explained that the rock stratums at different positions have different mechanical characteristics, and the mechanical characteristics of the test sample are selected according to the mechanical characteristics of the rock stratums needing to be researched. It should be noted that, according to the requirements of experimental research, different mechanical characteristics are selected, and different stratum three-dimensional stresses are applied through a true triaxial fracture tester, so that the influence of the ground stress characteristic parameters on the synchronous initiation and dynamic expansion of multiple fractures can be researched.
In the implementation process, the size specification of the sample is a cube of 300mm × 300mm × 300mm (or other specifications such as a cube of 500mm × 500mm × 500 mm), and the flatness of each end face is ensured.
The test sample is provided with a blind hole along the horizontal direction and is used for simulating a horizontal shaft; in the specific implementation process, the horizontal well fracturing design is adopted, a blind hole is formed in the center of one end face of 300mm multiplied by 300mm, and the blind hole with the diameter of 20mm and the depth of 170mm is drilled by a drill and used for simulating a horizontal shaft;
a plurality of prefabricated perforations are arranged in the blind holes and used for simulating initial crack initiation after fracturing; the preformed perforation in the embodiment of the invention is a seam opening of an initial crack, and the initial crack is formed after the preformed perforation is fractured.
Following the above example, a micro lateral drill bit is used to set a position in the simulated horizontal wellbore to initiate a fracture opening, the perforation diameter is 2mm, the perforation depth is 5mm, and the phase angle is 60 degrees, the initial fracture opening is used to simulate a natural fracture opening in the horizontal wellbore in the actual mining process, fracturing is formed under the pressure of fracturing fluid based on the initial fracture opening, the number of the initial fracture openings is a preset number, and two adjacent initial fracture openings are spaced at a preset interval. In the specific implementation process, the initial crack initiation quantity is preset, the preset interval can be set arbitrarily according to the test requirements, the different preset quantities are adjusted, the preset interval is preset, therefore, the embodiment is not limited to the test of single-cluster or double-cluster synchronous fracturing, multiple clusters of initial cracks can be formed, further, the test research of multiple clusters of synchronous fracturing can be carried out, different cluster intervals are researched simultaneously, the influence of different cluster numbers on the synchronous cracking and dynamic expansion of multiple clusters of cracks is not limited to the research of single clusters or double clusters in the prior art.
In addition, the initial crack initiation can be used for processing a simulated natural crack with a specific angle, length and orientation at any position of a sample according to the research requirement, so as to complete the preparation of the prefabricated crack.
A main fracturing crack is preset on the sample at a crack opening close to the initial fracturing crack, and prefabricated drill holes are arranged on two sides close to the preset main fracturing crack;
in the specific implementation process, according to the setting conditions of the ground stress of hydraulic fracturing, the direction of a horizontal shaft generally follows the direction of the horizontal minimum ground stress, the direction of a generated main hydraulic fracturing crack is vertical to the horizontal minimum ground stress, and the main fracture is close to the position of a perforation section;
the pressure box is fixedly arranged in the prefabricated drill hole;
in the specific implementation process, the small cube pressure box is placed into the four deep holes, and the three opposite faces of the cube are ensured to be consistent with the applied three-dimensional ground stress direction; filling the gap between the pressure box and the deep hole by adopting a high-strength concrete material, ensuring the compactness, and leading out 4 groups of pressure box leads from the deep hole; the number and the positions of the embedded pressure boxes can be increased or adjusted according to the research requirements, and the influence range of the pressure crack induced stress is further researched; after the pre-embedding is finished, maintaining under certain temperature and humidity conditions, and finishing the early preparation work of real-time monitoring and simulation of the crack induced stress field
The simulation sleeve is fixedly arranged in the blind hole, a spraying hole is formed in the simulation sleeve at a position corresponding to the initial crack opening, the spraying hole is used for spraying preset fracturing fluid into the initial crack opening, the first end of the simulation sleeve is a blind end, and the second end of the simulation sleeve is used for being connected with a hydraulic fracturing system.
In the specific implementation process, a simulation casing with the outer diameter of 18mm and the inner diameter of 16mm is adopted, a corresponding injection hole is preset in the casing, a hard paper sheet is plugged into the injection hole of the casing, the hard paper sheet extends out of the length of one end of the casing and is put into the casing to a preset injection position, the injection hole is opposite to the position of an initial crack opening on the wall surface of the well casing, and the injection hole is prevented from blocking the injection hole when a sealant filling ring is empty; and the sleeve and the simulated shaft annulus are sealed and fixed by high-strength epoxy resin.
The first end of the simulation sleeve is a blind end, the second end of the simulation sleeve is used for being connected with a hydraulic fracturing system, and the hydraulic fracturing system is used for providing preset fracturing fluid with preset discharge capacity for the simulation sleeve. The second end of the simulation sleeve is provided with internal threads, and the first end of the simulation sleeve is the end through which the preset fracturing fluid passes first according to the flowing direction of the preset fracturing fluid in the simulation sleeve.
The technical scheme in the embodiment of the application at least has the following technical effects or advantages:
in the application, the pressure box capable of measuring the three-dimensional stress is pre-embedded in the periphery of the natural unconventional compact sample and the preset fracturing fracture, so that the pressure box not only can be used for monitoring the stress field around the fracture during single-cluster physical fracturing simulation of unconventional reservoir rock bodies, but also can be used for monitoring the stress field around the fracture during synchronous fracture initiation of other multiple clusters of shooting holes and synchronous or cross fracturing simulation of double wells, and the applicability of the pressure box is improved.
Example two
The embodiment provides an indoor hydraulic fracturing simulation system, includes:
a true triaxial fracture tester;
the indoor hydraulic fracture simulation device as described; when the test is carried out, the indoor hydraulic fracturing simulation device is arranged in the true triaxial fracturing tester, and the true triaxial fracturing tester is used for applying stratum three-way stress to the indoor hydraulic fracturing simulation device;
and the hydraulic fracturing system is connected with the simulation casing pipe of the indoor hydraulic fracturing simulation device and is used for pumping fracturing fluid into the simulation casing pipe.
The technical scheme in the embodiment of the application at least has the following technical effects or advantages:
in this application, through to natural unconventional tight sample with predetermine the peripheral within range pre-buried pressure cell that can survey the three-dimensional stress of fracturing, can realize simulating stratum three-dimensional stress condition, carry out indoor hydraulic fracturing simulation through changing hydraulic fracturing parameter, obtain the fracturing fracture surrounding stress field real-time supervision data to with pump pressure curve synchronous contrastive analysis, provide technical support for studying unconventional oil gas reservoir water conservancy fracturing intervallic stress interference. The method can be used for monitoring the stress field around the crack when the unconventional reservoir rock mass is subjected to single-cluster fracturing physical simulation, and can also be used for monitoring the stress field around the crack when other multi-cluster perforation synchronous fracturing and double-well synchronous or cross fracturing simulation are carried out, so that the applicability of the method is improved.
EXAMPLE III
The present embodiment provides a method for manufacturing an indoor hydraulic fracture simulation device, as shown in fig. 1, including:
s101, selecting a sample, and determining a well type of the simulated hydraulic fracturing, wherein the method specifically comprises the following steps: forming a blind hole in the horizontal direction of the sample for simulating a horizontal shaft; arranging a plurality of prefabricated perforations in the blind hole, and simulating initial crack initiation after fracturing, wherein each prefabricated perforation is orthogonal and/or oblique to the blind hole; arranging a plurality of groups of injection holes on the simulation sleeve, and then sending the simulation sleeve into the blind hole for fixing, so that each group of injection holes corresponds to the prefabricated perforation one by one;
in the implementation process, the size specification of the sample is a cube of 300mm × 300mm × 300mm (or other specifications such as a cube of 500mm × 500mm × 500 mm), and the flatness of each end face is ensured.
Adopting a horizontal well fracturing design, forming a blind hole in the center of one end face of 300mm multiplied by 300mm, and specifically drilling the blind hole with the diameter of 20mm and the depth of 170mm to simulate a horizontal shaft;
a miniature side drill is adopted to set a prefabricated perforation in the simulated horizontal shaft, the diameter of the perforation is 2mm, the depth of the perforation is 5mm, and the phase angle is 60 degrees; a simulated cannula with an outer diameter of 18mm and an inner diameter of 16mm was used.
The method is characterized in that the prefabricated perforation fracture is used for simulating initial fracture initiation, and specifically comprises the following steps: filling fine salt into the shaft and the perforation hole by slight stirring in the perforation section of the shaft, and placing epoxy resin for sealing the shaft into the shaft and the perforation hole in the perforation section by taking plasticine as an interlayer on the upper part of the fine salt; the method comprises the following steps of inserting a steel chisel with the diameter of 5mm into a plasticine interlayer in a shaft through a sleeve to pierce solidified plasticine, injecting clear water into the shaft by using a lengthened injection needle cylinder, dissolving salt filled in a simulated injection hole section of the shaft by using the clear water, and then extracting the dissolved salt to form an effective fracturing section to finish sample preparation work;
step S102, presetting a main fracturing crack on the sample close to the prefabricated perforation according to the hydraulic fracturing ground stress setting conditions, and drilling prefabricated boreholes on two sides close to the preset main fracturing crack;
in the specific implementation process, according to the setting conditions of the ground stress of hydraulic fracturing, the direction of a horizontal shaft generally follows the direction of the horizontal minimum ground stress, the direction of the generated main hydraulic fracturing crack is vertical to the horizontal minimum ground stress, and the main fracture is close to the position of a perforation section;
and S103, placing the pressure box into the prefabricated drill hole for fixing to obtain the indoor hydraulic fracturing simulation device.
In the specific implementation process, the small cube pressure box is placed into the four deep holes, and the three opposite faces of the cube are ensured to be consistent with the applied three-dimensional ground stress direction; filling the gap between the pressure box and the deep hole by adopting a high-strength concrete material, ensuring the compactness, and leading out 4 groups of pressure box leads from the deep hole; and after pre-embedding is finished, maintaining under certain temperature and humidity conditions, and finishing the early preparation work of real-time monitoring and simulation of the crack inducing stress field. Multiple sets of pressure cells may also be used in other embodiments.
Example four
The embodiment provides an indoor hydraulic fracture simulation test method, which is applied to an indoor hydraulic fracture simulation system, and as shown in fig. 2, the simulation test method includes:
step S201, connecting a second end of the simulation casing pipe with the hydraulic fracturing system;
in the specific implementation process, the prefabricated thread at the second end of the simulation sleeve is connected with a hydraulic fracturing pump fluid outlet high-pressure hose by adopting a high-pressure hose connector, a servo control hydraulic fracturing pump is started, fracturing fluid is pumped into a space where the high-pressure hose is connected with the sleeve, the water pressure of 0.5MPa is set, and the sealing performance of each connection position is tested;
s202, applying three-dimensional stress to the stratum to the indoor hydraulic fracturing simulation device by using the true triaxial fracturing tester;
in the specific implementation process, the installation of the hydraulic fracturing true triaxial loading plate is completed, and a true triaxial model testing machine is started to apply three-dimensional stress to a set value according to the set three-dimensional stress conditions (the vertical stress is 20MPa, the horizontal maximum stress is 18MPa, and the horizontal minimum stress is 16 MPa);
s203, controlling the hydraulic fracturing system to pump the preset fracturing fluid into the simulation casing according to a preset discharge capacity;
the method comprises the following steps of (1) collecting the running condition of the preset fracturing fluid after the preset fracturing fluid enters the blind hole in real time by using a pressure box while pumping the preset fracturing fluid, and monitoring the stress field around the crack during single-cluster fracturing physical simulation;
or when the synchronous initiation of the multiple clusters of initial fractures is completed after the pressure of the preset fracturing fluid rises to reach the fracture pressure and multiple clusters of through fracturing fractures are formed on the basis of the initial fractures, the flow distribution of the preset fracturing fluid in the multiple clusters of fracturing fractures and the acquisition of the characteristics of the fracturing fractures in the dynamic expansion process are realized.
In the specific implementation process, a servo pump pressure control system is started to pump fracturing fluid according to the discharge capacity of 0.5ml/s, hydraulic fracturing tests are carried out, and automatic data acquisition software is adopted to acquire three-way stress real-time change data of 4 pressure boxes in the fracturing fluid pumping process and is used for analyzing the real-time change characteristics of the ground stress field around the hydraulic fracture initiation and expansion.
The technical scheme in the embodiment of the application at least has the following technical effects or advantages:
the pressure box capable of measuring the three-dimensional stress is pre-buried in the natural unconventional compact sample in a certain range of the preset fracturing, so that the three-dimensional stress condition of a simulated stratum can be realized, the indoor hydraulic fracturing simulation is carried out by changing hydraulic fracturing parameters (pumping pressure displacement and perforation arrangement), real-time monitoring data of a stress field around the fracturing is obtained, and the real-time monitoring data and a pumping pressure curve are synchronously compared and analyzed, so that technical support is provided for researching the stress interference between the unconventional oil and gas reservoir hydraulic fracturing. The method can be used for monitoring the stress field around the crack when the unconventional reservoir rock mass is subjected to single-cluster fracturing physical simulation, and can also be used for monitoring the stress field around the crack when other multi-cluster perforation synchronous fracturing and double-well synchronous or cross fracturing simulation are carried out, so that the applicability of the method is improved.
Finally, it should also be noted that 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.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.