CN113530516B - Pulsating CO 2 Foam fracturing and evaluation simulation integrated test device and method - Google Patents
Pulsating CO 2 Foam fracturing and evaluation simulation integrated test device and method Download PDFInfo
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- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
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Abstract
The invention discloses pulsating CO 2 Foam fracturing and evaluation simulation integrated test device and method, through CO 2 The pressurization liquefaction system and the foam fracturing fluid quantitative injection system realize CO with different foam qualities 2 Preparing foam fracturing fluid; the high-temperature high-pressure foam performance evaluation system can simulate and research CO with different proportions in a deep high-temperature high-pressure environment 2 Foam stability performance; the pulse fracturing control system can realize high-frequency large-amplitude pulse fracturing; the triaxial core holder can simulate a deep in-situ stress environment, and can be combined with an acoustic emission monitoring system to study the crack propagation and fracture energy law in the fracturing process; in addition, the triaxial core holder is combined with a permeability measuring system, so that the change condition of the permeability of the sample before and after fracturing can be evaluated; therefore, the invention can simulate unconventional natural gas reservoir pulsating CO 2 The foam fracturing process obtains test data of various different conditions, thereby being capable of treating CO 2 The proportion of the foam fracturing fluid is optimized, and the influence of different pulsation parameters on the fracturing effect can be researched.
Description
Technical Field
The invention relates to the technical field of unconventional natural gas exploitation, in particular to pulsating CO 2 Foam fracturing and evaluation simulation integrated test device and method.
Background
The unconventional natural gas (coal bed gas, shale gas, compact sandstone gas and the like) in China is abundant in resources, and the yield of the unconventional natural gas is about 1/10 of the national natural gas yield. Unconventional natural gas is a clean source of high heat that can be efficiently exploited to optimize energy consumption structures. However, the occurrence conditions of unconventional natural gas resources are complex, the effect of directly drilling a shaft or a borehole for extraction is not good, the commercialized extraction of unconventional natural gas cannot be realized, artificial fracturing and permeability increasing measures (hydraulic fracturing and the like) need to be adopted to perform volume fracturing on a reservoir stratum, and a gas diversion channel is added. The traditional hydraulic fracturing measures make excellent contribution to the aspect of unconventional natural gas exploitation, but the following problems still exist: firstly, the water consumption of the fracturing operation is huge, and the fracturing fluid seriously pollutes water resources; secondly, the large filtration loss affects the reservoir transformation effect; thirdly, the capacity of carrying the proppant is insufficient; and fourthly, the method is not suitable for the water resource deficient areas and the water sensitive stratum hydraulic fracturing technology. Based on the defects, the foam fracturing technology has the advantages of low water consumption, low filtration loss, strong proppant carrying capacity, good fracturing effect, high fracturing fluid flowback rate and the like. However, the foamed fracturing fluid is an unstable fluid, and the stable performance of the foamed fracturing fluid under high-temperature and high-pressure environments is very important. Because the viscosity of the foam fracturing fluid is higher, the fracture initiation pressure is increased, the fracture length is shorter, and the fracturing effect of a reservoir stratum is influenced.
Based on the above technical shortcomings, researchers have proposed pulsating CO 2 The foam fracturing technology utilizes a pulse pump to carry out pulse loading, causes fatigue damage to a reservoir, promotes the expansion of micro-pore fractures in the reservoir, forms a complex fracture network and increases the length of the reservoir fractures. CO 2 2 Gas adsorption is stronger than CH 4 Thus, CO 2 The injection of gas also creates a displacement effect in the reservoir, and it is possible to inject CO 2 Sealing underground to reduce CO 2 Is discharged to the air. However, the current pulseKinetic CO 2 The foam fracturing technology is only in a theoretical stage, and no research is provided on a concrete scheme for fracturing and determination of relevant parameters required by fracturing, so that the pulsed CO needs to be provided urgently 2 Foam fracturing and evaluation simulation integrated test device and method, so that CO can be tested 2 Parameters required by foam fracturing are tested and determined, and data support is provided for subsequent actual use.
Disclosure of Invention
In view of the problems of the prior art, the present invention provides a pulsating CO 2 Foam fracturing and evaluation simulation integrated test device and method, and CO can be carried out on coal rock mass under different confining pressure and axial pressure conditions 2 And (4) performing foam fracturing to obtain test data under different conditions, and providing data support for subsequent actual use.
In order to achieve the purpose, the invention adopts the technical scheme that: pulsating CO 2 The foam fracturing and evaluation simulation integrated test device comprises a data acquisition control system, a permeability measurement system, a triaxial core holder, an acoustic emission monitoring system, a pulse fracturing control system, a high-temperature high-pressure foam performance evaluation system, a foam fracturing fluid quantitative injection system and CO 2 A pressurized liquefaction system;
the triaxial core holder comprises a holder main body, a advection pump I, a left plug, a right plug and a plurality of sound wave conduction rods, wherein a triaxial loading mechanism is arranged in the holder main body, a core sample is arranged in the triaxial loading mechanism, and a drill hole is formed in the core sample; the constant-current pump I is connected with the triaxial loading mechanism through two branch pipelines and is used for controlling the triaxial loading mechanism to apply triaxial confining pressure on the rock core sample to simulate the actual underground stress condition; the two ends of the holder main body are provided with ports, and the left side plug and the right side plug are respectively arranged at the two ports and used for plugging the two ports; one ends of the sound wave conduction rods respectively extend into the holder main body and are in contact with the surface of the rock core sample in an attaching manner; the side part of each sound wave conduction rod is fixedly connected with the holder main body; the outer part of the clamp holder main body is wrapped by a first heating sleeve;
the acoustic emission monitoring system is connected with a plurality of acoustic wave conduction rods of the triaxial core holder and is used for monitoring the crack propagation rule and the energy release characteristic inside the sample in the fracturing process;
the CO is 2 The pressurized liquefaction system comprises CO 2 Gas cylinder, booster pump and high-pressure piston container III, CO 2 The gas cylinder is connected with a gas inlet of the high-pressure piston container III through a pipeline, and the booster pump is connected with the high-pressure piston container III through a pipeline to provide power for the high-pressure piston container III;
the foam fracturing fluid quantitative injection system comprises a constant-pressure pump II, a high-pressure piston container I, a high-pressure piston container II and a back-pressure device, wherein the constant-pressure pump II is respectively connected with the high-pressure piston container I and the high-pressure piston container II through pipelines to provide power for the high-pressure piston container I and the high-pressure piston container II; the port of the high-pressure piston container I is connected with the outlet of the high-pressure piston container III and the inlet of the back pressure device through pipelines, and the outlet of the back pressure device is connected with the port of the high-pressure piston container II through a pipeline;
the high-temperature high-pressure foam performance evaluation system comprises a foam generator, an industrial camera, a high-temperature high-pressure visual window, a stirring motor and a controller, wherein the stirring motor is arranged at the bottom of the foam generator, an output shaft of the stirring motor extends into the foam generator, and a stirrer fan blade is arranged on the output shaft of the stirring motor and used for stirring and foaming; the high-temperature high-pressure visible window is arranged on the side part of the foam generator, and the industrial camera is arranged on the camera bracket and is opposite to the high-temperature high-pressure visible window for shooting the form change of the foam in the foam generator under high temperature and high pressure; the outside of the foam generator is wrapped by the second heating sleeve; the controller is used for controlling the heating temperature of the heating sleeve II and the stirring speed of the stirring motor; an inlet of the foam generator is connected with an outlet of the back pressure device and a port of the high-pressure piston container II through a pipeline; an outlet of the foam generator is connected with one end of a fracturing pipeline, the other end of the fracturing pipeline is connected with one end of a liquid injection pipe, the other end of the liquid injection pipe is a liquid injection port, and the liquid injection port extends into the holder main body through a left plug and reaches the inside of a drill hole of the rock core sample; a back pressure valve is arranged on a liquid injection pipe between the foam generator and the holder main body;
the pulse fracturing control system comprises a servo variable frequency control system, a pulse pump and a servo pressure cylinder, wherein an outlet of the servo pressure cylinder is connected with a pressure port of a foam generator through a pipeline, an inlet of the servo pressure cylinder is connected with an output end of the pulse pump through a pipeline, and the servo variable frequency control system is used for controlling the pulse frequency and the pulse amplitude of the pulse pump;
the permeability measuring system comprises a gas source, a gas booster pump, a flowmeter, an inlet high-frequency pulse pressure sensor, a liquid discharge pipe, an outlet high-frequency pulse pressure sensor and a liquid discharge water cup; the gas source is connected with the inlet of a gas booster pump through a pipeline, and the outlet of the gas booster pump is connected with a fracturing pipeline between the backpressure valve and the clamp holder main body through a pipeline; one end of the liquid discharge pipe is in contact with the rock core sample, and the other end of the liquid discharge pipe is a liquid discharge outlet which extends out of the holder main body through the right plug and is connected with a liquid discharge cup; the flowmeter is arranged at an outlet of the gas booster pump, and the inlet high-frequency pulse pressure sensor is arranged on a fracturing pipeline positioned outside the clamp holder body; the outlet high-frequency pulse pressure sensor is arranged on a liquid discharge pipe positioned outside the gripper body;
the data acquisition control system is used for controlling the working states of the booster pump, the gas booster pump, the constant-flow pump I, the constant-flow pump II, the servo variable-frequency control system and the pulse pump; the flowmeter, the inlet high-frequency pulse pressure sensor, the outlet high-frequency pulse pressure sensor, the industrial camera, the controller, the heating sleeve I and the heating sleeve II are all connected to a data acquisition control system, and the data acquisition control system performs data calculation processing on received gas flow, inlet pressure, outlet pressure, foam form and heating temperature control data.
Furthermore, a first stop valve is arranged on a pipeline between the gas source and the gas booster pump; a second stop valve is arranged on a pipeline between the gas booster pump and the liquid injection pipe; a third stop valve and a fourth stop valve are respectively arranged on two branch pipelines between the first constant-current pump and the three-axis loading mechanism; a first pressure release valve and a first pressure gauge are arranged on the foam generator; a sixth stop valve is arranged on a pipeline between the constant-flow pump II and the high-pressure piston container I, and a fifth stop valve is arranged on a pipeline between the constant-flow pump II and the high-pressure piston container II; a second pressure gauge is arranged on the second high-pressure piston container, and a seventh stop valve is arranged at the port of the second high-pressure piston container; the first high-pressure piston container is provided with a pressure gauge IIIA fourth pressure gauge is arranged on a pipeline between the first high-pressure piston container and the back pressure device; a pipeline between the stop valve seventh and the back pressure device is provided with an injection pipe, and the injection pipe is provided with a stop valve ninth; a stop valve ten is arranged on a pipeline between the booster pump and the high-pressure piston container III; CO 2 2 A pipeline between the gas cylinder and the high-pressure piston container III is provided with a first stop valve; and a third pressure release valve and a fifth pressure gauge are arranged on the third high-pressure piston container, and a twelfth stop valve is arranged at the port of the third high-pressure piston container.
Further, the acoustic emission monitoring system comprises an acoustic signal processing computer, an acoustic emission collector, a plurality of acoustic signal amplifiers and a plurality of acoustic emission probes, wherein the acoustic signal processing computer is connected with the acoustic emission collector, and the acoustic emission collector is respectively connected with the acoustic emission probes through the plurality of acoustic signal amplifiers; each acoustic emission probe is respectively attached to the other end of each acoustic transmission rod.
Further, 8 sound wave conduction poles are divided into two groups, the two groups are respectively arranged at positions 25mm and 75mm of the height of the rock core sample, and the angle between the adjacent poles in the same group is 90 degrees.
Further, the core sample is diameter 50mm, high 100 mm's cylinder core, and the drilling diameter of core sample is 3mm, the degree of depth is 50mm and is used for simulating the fracturing pit shaft, stretches into the notes liquid mouth of the inside notes liquid pipe of drilling apart from drilling bottom 10mm, uses high strength bar planting to glue hole sealing 30mm between notes liquid pipe and the drilling inner wall, annotates the liquid pipe tip and is equipped with quick-operation joint and be used for the high-speed joint fracturing pipeline.
Furthermore, a staff gauge is arranged on the high-temperature high-pressure visual window.
Pulsating CO 2 The test method of the foam fracturing and evaluation simulation integrated test device comprises the following specific steps:
A. arranging an acoustic emission monitoring system: after the acoustic emission monitoring system is connected, fixing two acoustic emission probes at two ends of a cylindrical sample by using a vaseline coupling agent, and calibrating the sound velocity of the sample by using a lead-breaking experiment; then, connecting eight acoustic emission probes in the acoustic emission monitoring system with eight acoustic wave conduction rods by using vaseline coupling agent;
B. installing a core sample: preparing a plurality of core samples with the same size, drilling holes in the middle of each core sample, selecting one core sample, and sealing the hole between an injection pipe and the inner wall of the drilled hole of the core sample by using high-strength bar-planting glue; taking the left plug off the holder main body, putting the core sample into the holder main body, arranging the core sample in the three-axis loading mechanism, screwing the left plug, connecting the quick joint with an adjacent pipeline, then opening the third stop valve, controlling the three-axis loading mechanism to load confining pressure on the core sample to a set value by the first advection pump, then closing the third stop valve, opening the fourth stop valve, and controlling the three-axis loading mechanism to load axial pressure on the core sample to the set value by the first advection pump;
C. initial permeability determination: opening the first stop valve and the second stop valve, starting the gas booster pump to control gas in a gas source to enter the drill hole of the rock core sample in the step B through the liquid injection pipe, performing gas displacement on the rock core sample, monitoring gas flow, gas inlet pressure and gas outlet pressure by using a flowmeter, an inlet high-frequency pulse pressure sensor and an outlet high-frequency pulse pressure sensor, and feeding back the gas flow, the gas inlet pressure and the gas outlet pressure to the data acquisition control system; the data acquisition control system processes the acquired data to obtain the initial permeability of the rock core sample, and the specific formula is as follows:
in the formula: k is the permeability of the core sample, m 2 (ii) a q is the flow rate of the gas, m 3 S; s is the cross-sectional area of the specimen, m 2 (ii) a l is the length of the sample, m; mu is the aerodynamic viscosity coefficient, MPa · s; p is a radical of 0 Is atmospheric pressure, and 0.1MPa is taken; p is a radical of 1 Is the inlet pressure, MPa; p is a radical of 2 Is the pressure of the outlet gas, MPa;
D、CO 2 preparing the foam fracturing fluid: using CO 2 Liquefied gaseous CO of pressurized liquefaction system 2 Opening the stop valve ten and the stop valve eleven, CO 2 CO in gas cylinder 2 Gas enters high pressureC, plugging the container III, and closing the stop valve eleven; starting booster pump to discharge CO in high-pressure piston container 2 Pressurizing and liquefying the gas, and liquefying CO 2 Storing in a high-pressure piston container III, and maintaining liquid CO by regulating the pressure in the high-pressure piston container III with a back pressure device 2 Stabilizing; starting the foam fracturing fluid quantitative injection system, opening a seventh stop valve and a ninth stop valve, injecting quantitative foaming fluid into a second high-pressure piston container through an injection pipe, and closing the seventh stop valve and the ninth stop valve after completion; opening the stop valve twelve and the stop valve eight, and using the booster pump to pump the liquid CO in the high-pressure piston container three 2 Injecting the mixture into the first high-pressure piston container, and then closing the stop valve twelve and the stop valve eight; sequentially opening a stop valve six, a stop valve eight, a stop valve five and a stop valve seven, and sequentially controlling the liquid CO in the high-pressure piston container I by the constant-flow pump two 2 And the foaming liquid in the high-pressure piston container II is quantitatively injected into the foam generator, and then the stop valve six, the stop valve eight, the stop valve five and the stop valve seven are closed; the starting controller controls the stirring motor to stir the liquid CO in the foam generator at a set rotating speed 2 Mixing with foaming liquid under stirring to finally generate CO 2 Foam fracturing fluid, and stopping the stirring motor after completion; controlling heating jacket pair CO using controller 2 Heating the foam to obtain CO at high temperature and high pressure 2 Stability of the foamed fracturing fluid; scales for measuring CO 2 The foaming volume and the foam half-life period of the foam fracturing fluid, and an industrial camera is used for recording foam form change;
E. pulsating CO 2 And (3) foam fracturing: synchronously starting the pulse fracturing control system and the acoustic emission monitoring system, and controlling the pulse pump to pump CO at different frequencies, different amplitudes and different peak pressures by using the servo variable frequency control system 2 Foam fracturing fluid is injected into a drill hole of a rock core sample through an injection pipe, an acoustic emission monitoring system synchronously collects acoustic emission information of the rock core sample in the fracturing process, an inlet high-frequency pulse pressure sensor collects a pressure curve and feeds the pressure curve back to a data acquisition control system, when the pressure curve is suddenly released or the foam fracturing fluid is discharged from a liquid discharge water cup, the fracturing process is finished, and the pulse fracturing control system is closed at the momentAnd a harmonic emission monitoring system;
F. and (3) measuring the permeability after fracturing: c, repeatedly executing the step C to measure the permeability of the fractured core sample;
G. and (5) finishing the fracturing process: sequentially opening a third stop valve and a fourth stop valve, controlling a constant-flow pump to carry out confining pressure and axial pressure unloading on the rock core sample, then opening a left plug of a triaxial rock core holder, taking out the fractured rock core sample from the triaxial rock core holder, cleaning the fractured rock core sample, and simultaneously transmitting acoustic emission data and twice permeability measurement data obtained in the fracturing process to a data acquisition control system;
H. selecting a core sample, and resetting liquid CO 2 Mixing the foaming liquid and the confining pressure value and the axial pressure value of the triaxial loading mechanism, repeatedly executing the steps A to G to obtain CO of the mixing ratio under the condition of the current confining pressure value and the current axial pressure value 2 The acoustic emission data and the two-time permeability measurement data of the foam fracturing fluid in the rock core sample fracturing process are repeated for many times, and CO with different confining pressure values, axial pressure values and different mixing ratios can be obtained 2 Acoustic emission data and two-time permeability measurement data of the core sample fracturing process under the conditions of the foam fracturing fluid and different pulse parameters are used for subsequent actual adoption of CO 2 And determining the optimal implementation parameters when the foam fracturing fluid is fractured, and providing a data analysis sample.
Compared with the prior art, the invention adopts a data acquisition control system, a permeability measurement system, a triaxial core holder, an acoustic emission monitoring system, a pulsating fracturing control system, a high-temperature high-pressure foam performance evaluation system, a foam fracturing fluid quantitative injection system and CO 2 Combined pressurized liquefaction system by CO 2 The pressurizing liquefaction system and the foam fracturing fluid quantitative injection system realize CO with different foam qualities 2 Accurately preparing the foam fracturing fluid; the high-temperature high-pressure foam performance evaluation system can simulate and research CO with different proportions in deep high-temperature high-pressure environment 2 Foam stability performance; the pulse fracturing control system can realize stable high-frequency large-amplitude (the frequency is more than 20Hz, and the amplitude is 10MPa) pulse fracturing; triaxial core holder can simulate deep normal position stress ringThe system comprises a fracture surface, a fracture surface and a fracture surface, wherein eight sound wave conduction rods arranged on the fracture surface can be combined with a sound emission monitoring system to study the fracture expansion and fracture energy rule in the fracturing process; the invention combines a triaxial core holder and a permeability measuring system, and can be used for evaluating the change condition of the permeability of the sample before and after fracturing; therefore, the invention can simulate unconventional natural gas reservoir pulsating CO 2 The foam fracturing process obtains test data of various different conditions, thereby being capable of treating CO 2 The proportion of the foam fracturing fluid is optimized, the influence of different pulsation parameters on the fracturing effect can be researched, and the pulsation CO of the unconventional natural gas reservoir in the later stage can be researched 2 The development of the foam fracturing experiment provides scientific basis and theoretical basis.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic diagram of the construction of the permeability measurement system of the present invention;
FIG. 3 is a schematic view of a triaxial core holder according to the present invention;
FIG. 4 is a schematic layout of the acoustic wave conducting bar according to the present invention;
FIG. 5 is a top view of FIG. 4;
FIG. 6 is a schematic diagram of the construction of an acoustic emission monitoring system of the present invention;
FIG. 7 is a schematic diagram of the configuration of the pulsating fracturing control system of the present invention;
FIG. 8 is a schematic structural view of a high-temperature high-pressure foam property evaluation system according to the present invention;
FIG. 9 is a schematic diagram of the foam fracturing fluid dosing system of the present invention;
FIG. 10 shows CO in the present invention 2 The structure of the pressurized liquefaction system is shown schematically.
In the figure: 1. the device comprises a data acquisition control system, 2, an air source, 3, stop valves I and I, 4, a gas booster pump, 5, a flowmeter, 6, stop valves II and II, 7, an inlet high-frequency pulse pressure sensor, 8, stop valves III and III, 9, a advection pump I, 10, stop valves IV and 11, an outlet high-frequency pulse pressure sensor, 12, a liquid drainage cup, 13, a triaxial core holder, 13-1, a left plug, 13-2, a heating sleeve I, 13-3, a right plug, 13-4 parts of liquid discharge outlet, 13-5 parts of sound wave conduction rod, 13-6 parts of liquid injection port, 13-7 parts of holder main body, 13-8 parts of quick connector, 14 parts of core sample, 14-1 parts of drill hole, 14-2 parts of high-strength bar planting glue, 15 parts of sound emission monitoring system, 15-1 parts of sound signal processing computer, 15-2 parts of sound emission collector, 15-3 parts of sound signal amplifier, 15-4 parts of sound emission probe, 16-1 parts of pulse fracturing control system, 16-2 parts of servo variable frequency control system, 16-2 parts of pulse pump, 16-3 parts of servo pressurizing cylinder, 17 parts of back pressure valve, 18 parts of high-temperature and high-pressure foam performance evaluation system, 18-1 parts of industrial camera, 18-2 parts of camera support, 18-3 parts of stirrer blade, 18-4 parts of liquid injection port, 13-7 parts of holder main body, 13-8 parts of sound emission monitoring system, 15 parts of sound signal processing computer, and 3 parts of sound signal processing system, 18-5 parts of stirring motor, 18-6 parts of controller, 18-6 parts of heating sleeve II, 18-7 parts of high-temperature high-pressure visual window, 18-8 parts of scale, 18-9 parts of foam generator, 18-10 parts of pressure relief valve I, 18-11 parts of pressure gauge I, 19 parts of foam fracturing fluid quantitative injection system, 19-1 parts of advection pump II, 19-2 parts of stop valve V, 19-3 parts of stop valve VI, 19-4 parts of stop valve VI, high-pressure piston container I, 19-5 parts of high-pressure piston container II, 19-6 parts of pressure gauge II, 19-7 parts of stop valve VII, 19-8 parts of pressure relief valve II, 19-9 parts of stop valve V, 19-10 parts of pressure gauge III, 19-11 parts of pressure gauge IV, 19-12 parts of pressure gauge, back pressure device, 19-13 parts of stop valve V, 20 parts of CO 2 Pressurized liquefaction System, 20-1, CO 2 20-2 parts of gas cylinder, 20-3 parts of booster pump, 20-4 parts of stop valve eleven, 20-5 parts of stop valve eleven, 20-6 parts of high-pressure piston container III, 20-7 parts of pressure release valve III, 20-8 parts of pressure gauge V and twelve stop valves.
Detailed Description
The present invention will be further described below.
As shown in FIG. 1, a pulsating CO 2 The foam fracturing and evaluation simulation integrated test device comprises a data acquisition control system 1, a permeability measurement system, a triaxial core holder 13, an acoustic emission monitoring system 15, a pulsating fracturing control system 16, a high-temperature high-pressure foam performance evaluation system 18, a foam fracturing fluid quantitative injection system 19 and CO 2 A pressurized liquefaction system 20;
as shown in fig. 3 to 5, the triaxial core holder comprises a holder main body 13-7, a advection pump I9, a left plug 13-1, a right plug 13-3 and a plurality of sound wave conducting rods 13-5, wherein a triaxial loading mechanism is arranged in the holder main body 13-7, a core sample 14 is arranged in the triaxial loading mechanism, and a drill hole is arranged on the core sample 14; the core sample 14 is a cylindrical core with the diameter of 50mm and the height of 100mm, the drilling diameter of the core sample 14 is 3mm, the depth of the core sample is 50mm, the core sample is used for simulating a fracturing shaft, the distance between the injection port of an injection pipe extending into a drilling hole and the bottom of the drilling hole is 10mm, high-strength bar-planting glue 14-2 is used for sealing the hole between the injection pipe and the inner wall of the drilling hole by 30mm, and a quick connector 13-8 is arranged at the end part of the injection pipe and can be used for quickly connecting a fracturing pipeline; the advection pump I9 is connected with the three-axis loading mechanism through two branch pipelines and is used for controlling the three-axis loading mechanism to apply three-axis confining pressure on the rock core sample 14 to simulate the actual underground stress condition; the two ends of the clamp holder main body 13-7 are provided with ports, and the left plug 13-1 and the right plug 13-3 are respectively arranged at the two ports and used for plugging the two ports; one ends of a plurality of sound wave conduction rods 13-5 respectively extend into the holder main bodies 13-7 and are in contact with the surface of the core sample 14 in an attaching manner; and the side of each sound wave conduction rod 13-5 is fixedly connected with the holder body 13-7; the outside of the clamp holder body 13-7 is wrapped by a first heating sleeve 13-2; the number of the acoustic wave conduction rods 13-5 is 8, the acoustic wave conduction rods are divided into two groups, the two groups are respectively arranged at the positions 25mm and 75mm of the height of the rock core sample 14, and the angle between the adjacent rods in the same group is 90 degrees;
as shown in fig. 6, the acoustic emission monitoring system 15 includes an acoustic signal processing computer 15-1, an acoustic emission collector 15-2, a plurality of acoustic signal amplifiers 15-3, and a plurality of acoustic emission probes 15-4, the acoustic signal processing computer 15-1 is connected with the acoustic emission collector 15-2, and the acoustic emission collector 15-2 is respectively connected with the plurality of acoustic emission probes 15-4 through the plurality of acoustic signal amplifiers 15-3; each acoustic emission probe 15-4 is respectively attached to the other end of each acoustic transmission rod 13-5 and used for monitoring the internal crack propagation rule and the energy release characteristic of the sample in the fracturing process;
as shown in FIG. 10, the CO 2 The pressurized liquefaction system 20 includes CO 2 20-1 parts of gas cylinder, 20-2 parts of booster pump and three high-pressure piston containers, 20-5 parts of CO 2 The gas cylinder 20-1 is connected with a gas inlet of the high-pressure piston container III 20-5 through a pipeline, and the booster pump 20-2 is connected with the high-pressure piston container III 20-5 through a pipeline to provide power for the high-pressure piston container III;
as shown in fig. 9, the quantitative foam fracturing fluid injection system 19 comprises a constant-pressure pump II 19-1, a high-pressure piston container I19-4, a high-pressure piston container II 19-5 and a back-pressure device 19-12, wherein the constant-pressure pump II 19-1 is respectively connected with the high-pressure piston container I19-4 and the high-pressure piston container II 19-5 through pipelines to provide power for the constant-pressure pump II 19-1; the port of the high-pressure piston container I19-4 is connected with the outlet of the high-pressure piston container III 20-5 and the inlet of the back pressure device 19-12 through a pipeline, and the outlet of the back pressure device 19-12 is connected with the port of the high-pressure piston container II 19-5 through a pipeline;
as shown in FIG. 8, the high-temperature and high-pressure foam performance evaluation system 18 comprises a foam generator 18-9, an industrial camera 18-1, a high-temperature and high-pressure visual window 18-7, a stirring motor 18-4 and a controller 18-5, wherein the stirring motor 18-4 is arranged at the bottom of the foam generator 18-9, an output shaft of the stirring motor extends into the foam generator 18-9, and a stirrer blade 18-3 is arranged on the output shaft of the stirring motor 18-4 and is used for stirring and foaming; the high-temperature and high-pressure visual window 18-7 is arranged on the side part of the foam generator 18-9, a scale 18-8 is arranged on the high-temperature and high-pressure visual window 18-7, and the industrial camera 18-1 is placed on the camera support 18-2 and is opposite to the high-temperature and high-pressure visual window 18-7 and used for shooting the form change of foam in the foam generator 18-9 under high temperature and high pressure; the outside of the foam generator 18-9 is wrapped by a second heating sleeve 18-6; the controller 18-5 is used for controlling the heating temperature of the second heating sleeve 18-6 and the stirring speed of the stirring motor 18-4; the inlet of the foam generator 18-9 is connected with the outlet of the back pressure device 19-12 and the port of the high-pressure piston container II 19-5 through a pipeline; the outlet of the foam generator 18-9 is connected with one end of a liquid injection pipe, the other end of the fracturing pipeline is connected with one end of the liquid injection pipe, the other end of the liquid injection pipe is a liquid injection port 13-6, and the liquid injection port extends into the holder main body 13-7 through a left plug 13-1 and reaches the inside of a drill hole of a rock core sample 14; a back pressure valve 17 is arranged on a liquid injection pipe between the foam generator 18-9 and the holder body 13-7;
as shown in fig. 7, the pulse fracturing control system 16 comprises a servo variable frequency control system 16-1, a pulse pump 16-2 and a servo pressure cylinder 16-3, an outlet of the servo pressure cylinder 16-3 is connected with a pressure increasing port of a foam generator 18-9 through a pipeline, an inlet of the servo pressure cylinder 16-3 is connected with an output end of the pulse pump 16-2 through a pipeline, and the servo variable frequency control system 16-1 is used for controlling the pulse frequency and the pulse amplitude of the pulse pump 16-2;
as shown in fig. 2, the permeability measuring system comprises a gas source 2, a gas booster pump 4, a flow meter 5, an inlet high-frequency pulse pressure sensor 7, a liquid discharge pipe, an outlet high-frequency pulse pressure sensor 11 and a liquid discharge cup 12; the gas source 2 is connected with an inlet of the gas booster pump 4 through a pipeline, and an outlet of the gas booster pump 4 is connected with a fracturing pipeline between the backpressure valve 17 and the clamp body 13-7 through a pipeline; one end of the liquid discharge pipe is in contact with the core sample 14, the other end of the liquid discharge pipe is provided with a liquid discharge outlet 13-4, and the liquid discharge outlet 13-4 extends out of the holder main body 13-7 through a right side plug 13-3 to be connected with a liquid discharge cup 12; the flowmeter 5 is arranged at the outlet of the gas booster pump 4, and the inlet high-frequency pulse pressure sensor 7 is arranged on a fracturing pipeline outside the clamp body 13-7; an outlet high-frequency pulse pressure sensor 11 is arranged on a liquid discharge pipe outside the clamp body 13-7;
the data acquisition control system 1 is used for controlling the working states of the booster pump 20-2, the gas booster pump 4, the constant-flow pump I9, the constant-flow pump II 19-1, the servo variable-frequency control system 16-1 and the pulsation pump 16-2; the flowmeter 5, the inlet high-frequency pulse pressure sensor 7, the outlet high-frequency pulse pressure sensor 11, the industrial camera 18-1, the controller 18-5, the first heating sleeve 13-2 and the second heating sleeve 18-6 are all connected to the data acquisition control system 1, and the data acquisition control system 1 performs data calculation processing on received gas flow, inlet pressure, outlet pressure, foam form and heating temperature control data.
A first stop valve 3 is arranged on a pipeline between the gas source 2 and the gas booster pump 4; a second stop valve 6 is arranged on a pipeline between the gas booster pump 4 and the liquid injection pipe; a third stop valve 8 and a fourth stop valve 10 are respectively arranged on two branch pipelines between the first constant-current pump 9 and the triaxial loading mechanism; a pressure release valve I18-10 and a pressure gauge I18-11 are arranged on the foam generator 18-9; a pipeline between the second constant-flow pump 19-1 and the first high-pressure piston container 19-4 is provided with a stop valve six 19-3, and a pipeline between the second constant-flow pump 19-1 and the second high-pressure piston container 19-5 is provided with a stop valve five 19-2; a second pressure gauge 19-6 is arranged on the second high-pressure piston container 19-5, and a stop is arranged at the port of the second high-pressure piston container 19-5Valve seven 19-7; a third pressure gauge 19-10 and a second pressure release valve 19-8 are arranged on the first high-pressure piston container 19-4, a stop valve eighth 19-9 is arranged at the port of the first high-pressure piston container 19-4, and a fourth pressure gauge 19-11 is arranged on a pipeline between the first high-pressure piston container 19-4 and the back pressure device 19-12; a pipeline between the seven stop valves 19-7 and the back pressure device 19-12 is provided with an injection pipe, and the injection pipe is provided with nine stop valves 19-13; a stop valve ten 20-3 is arranged on a pipeline between the booster pump 20-2 and the high-pressure piston container three 20-5; CO 2 2 A pipeline between the gas cylinder 20-1 and the high-pressure piston container III 20-5 is provided with an eleventh stop valve 20-4; a pressure relief valve III 20-6 and a pressure gauge V20-7 are arranged on the high-pressure piston container III 20-5, and a stop valve twelve 20-8 is arranged at the port of the high-pressure piston container III 20-5.
Pulsating CO 2 The test method of the foam fracturing and evaluation simulation integrated test device comprises the following specific steps:
A. arranging an acoustic emission monitoring system: after the acoustic emission monitoring system 15 is connected, fixing two acoustic emission probes 15-4 at two ends of the cylindrical sample 14 by using vaseline coupling agent, and calibrating the sound velocity of the sample 14 by using a lead breaking experiment; then eight acoustic emission probes 15-4 in the acoustic emission monitoring system 15 are connected with eight acoustic wave conduction rods 13-5 by using vaseline coupling agent;
B. installing a core sample: preparing a plurality of core samples 14 with the same size, drilling holes in the middle of each core sample 14, selecting one core sample 14, and sealing the hole between an injection pipe and the inner wall of the drilling hole of the core sample 14 by using high-strength bar-planting glue 14-2; taking down the left choke plug 13-1 from the holder body 13-7, putting the core sample 14 into the holder body 13-7, arranging the core sample in the three-shaft loading mechanism, screwing down the left choke plug 13-1, connecting the quick connector 13-8 with the fracturing pipeline, then opening the third stop valve 8, controlling the three-shaft loading mechanism to load confining pressure on the core sample 14 to a set value by the first advection pump 9, then closing the third stop valve 8, opening the fourth stop valve 10, controlling the three-shaft loading mechanism to load axial pressure on the core sample 14 to the set value by the first advection pump 9;
C. initial permeability determination: opening the first stop valve 3 and the second stop valve 6, starting the gas booster pump 4 to control gas in the gas source 2 to enter the drill hole of the rock core sample 14 in the step B through the liquid injection pipe, performing gas displacement on the drill hole, monitoring gas flow, gas inlet pressure and gas outlet pressure by using a flowmeter 5, an inlet high-frequency pulse pressure sensor 7 and an outlet high-frequency pulse pressure sensor 11, and feeding back the gas flow, the gas inlet pressure and the gas outlet pressure to the data acquisition control system 1; the data acquisition control system 1 processes the acquired data to obtain the initial permeability of the core sample, and the specific formula is as follows:
in the formula: k is the permeability of the core sample, m 2 (ii) a q is the flow rate of the gas, m 3 S; s is the cross-sectional area of the specimen, m 2 (ii) a l is the length of the sample, m; μ is the aerodynamic viscosity coefficient, MPa · s; p is a radical of 0 Is atmospheric pressure, and 0.1MPa is taken; p is a radical of 1 Is the inlet pressure, MPa; p is a radical of 2 Is the pressure of the outlet gas, MPa;
D、CO 2 preparing the foam fracturing fluid: using CO 2 Pressurized liquefaction system 20 liquefies gaseous CO 2 Ten 20-3 and eleven 20-4 cut-off valves are opened, CO 2 CO in the gas cylinder 20-1 2 The gas enters a third high-pressure piston container 20-5, and a tenth stop valve 20-3 is closed; 20-2 pairs of high-pressure piston containers three 20-5 of CO in the booster pump are started 2 Pressurizing and liquefying gas, liquefied CO 2 Storing in a high pressure piston container III 20-5, and maintaining liquid CO by adjusting the pressure in the high pressure piston container III 20-5 using a back pressure device 19-12 2 Stabilizing; starting the foam fracturing fluid quantitative injection system 19, opening a stop valve seventh 19-7 and a stop valve ninth 19-13, injecting quantitative foaming fluid into a high-pressure piston container II 19-5 through an injection pipe, and closing the stop valve seventh 19-7 and the stop valve ninth 19-13 after completion; opening the stop valve twelve 20-8 and the stop valve eight 19-9, the booster pump 20-2 pumps the liquid CO in the high-pressure piston container three 20-5 2 Injecting the mixture into a first high-pressure piston container 19-4, and then closing a stop valve twelve 20-8 and a stop valve eight 19-9; opening stop valve six 19-3, stop valve eight 19-9, stop valve five 19-2 and stop valve seven 19-7 in sequence, and levelingThe flow pump II 19-1 sequentially controls the liquid CO in the high-pressure piston container I19-4 2 And the foaming liquid of the high-pressure piston container II 19-5 is quantitatively injected into the foam generator 18-9, and after the foaming liquid is completely injected, the stop valve six 19-3, the stop valve eight 19-9, the stop valve five 19-2 and the stop valve seven 19-7 are closed; the starting controller 18-5 controls the stirring motor 18-4 to control the liquid CO in the foam generator 18-9 at a set rotating speed 2 Mixing with foaming liquid under stirring to finally generate CO 2 Foaming the fracturing fluid, and stopping the stirring motor 18-4 after completion; the controller 18-5 is used to control the heating jacket 18-6 to CO 2 Heating the foam to obtain CO at high temperature and high pressure 2 Stability of the foamed fracturing fluid; scale 18-8 for measuring CO 2 The foaming volume and the foam half-life period of the foam fracturing fluid, and an industrial camera 18-1 is used for recording foam form change;
E. pulsating CO 2 And (3) foam fracturing: synchronously starting a pulse fracturing control system 16 and an acoustic emission monitoring system 15, and controlling a pulse pump 16-2 to pump CO by setting different frequencies, different amplitudes and different peak pressures by using a servo variable frequency control system 16-1 2 Injecting foam fracturing fluid into a drill hole of the rock core sample 14 through an injection pipe, synchronously acquiring acoustic emission information of the rock core sample 14 in the fracturing process by an acoustic emission monitoring system 15, acquiring a pressure curve by an inlet high-frequency pulse pressure sensor 7 and feeding back the pressure curve to a data acquisition control system, finishing the fracturing process when the pressure curve is suddenly relieved or the foam fracturing fluid is observed to be discharged from a liquid discharge water cup 12, and closing a pulse fracturing control system 16 and the acoustic emission monitoring system 15;
F. and (3) measuring the permeability after fracturing: c, repeatedly executing the step C to measure the permeability of the fractured rock core sample 14;
G. and (5) finishing the fracturing process: sequentially opening a third stop valve 8 and a fourth stop valve 10, controlling a first constant-flow pump 9 to unload confining pressure and axial pressure of a rock core sample 14, then opening a left plug 13-1 of a triaxial rock core holder 13, taking out and cleaning the fractured rock core sample 14 from the triaxial rock core holder 13, and simultaneously transmitting acoustic emission data and two times of permeability measurement data obtained in the fracturing process to a data acquisition control system 1;
H. selecting a core sample, and resetting liquid CO 2 Mixing the foaming liquid and the confining pressure value and the axial pressure value of the triaxial loading mechanism, repeatedly executing the steps A to G to obtain CO of the mixing ratio under the condition of the current confining pressure value and the current axial pressure value 2 The acoustic emission data and the two-time permeability measurement data of the foam fracturing fluid in the rock core sample fracturing process are repeated for many times, and CO with different confining pressure values, axial pressure values and different mixing ratios can be obtained 2 Acoustic emission data and two-time permeability measurement data of the core sample fracturing process under the conditions of the foam fracturing fluid and different pulse parameters are used for adopting CO for follow-up actual application 2 And determining the optimal implementation parameters when the foam fracturing fluid is fractured, and providing a data analysis sample.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention, and such modifications and adaptations are intended to be within the scope of the invention.
Claims (4)
1. Pulsating CO 2 The foam fracturing and evaluation simulation integrated test device is characterized by comprising a data acquisition control system, a permeability measurement system, a triaxial core holder, an acoustic emission monitoring system, a pulsating fracturing control system, a high-temperature high-pressure foam performance evaluation system, a foam fracturing fluid quantitative injection system and CO 2 A pressurized liquefaction system;
the triaxial core holder comprises a holder main body, a advection pump I, a left plug, a right plug and a plurality of sound wave conduction rods, wherein a triaxial loading mechanism is arranged in the holder main body, a core sample is arranged in the triaxial loading mechanism, and a drill hole is formed in the core sample; the constant-current pump I is connected with the triaxial loading mechanism through two branch pipelines and is used for controlling the triaxial loading mechanism to apply triaxial confining pressure on the rock core sample to simulate the actual underground stress condition; the two ends of the holder main body are provided with ports, and the left side plug and the right side plug are respectively arranged at the two ports and used for plugging the two ports; one ends of the sound wave conduction rods respectively extend into the holder main body and are in contact with the surface of the rock core sample in an attaching manner; the side part of each sound wave conduction rod is fixedly connected with the holder main body; the outer part of the clamp holder main body is wrapped by a heating sleeve I;
the acoustic emission monitoring system is connected with the plurality of acoustic wave conducting rods of the triaxial core holder and is used for monitoring the internal crack propagation rule and the energy release characteristic of the sample in the fracturing process, the acoustic emission monitoring system comprises an acoustic signal processing computer, an acoustic emission collector, a plurality of acoustic signal amplifiers and a plurality of acoustic emission probes, the acoustic signal processing computer is connected with the acoustic emission collector, and the acoustic emission collector is respectively connected with the plurality of acoustic emission probes through the plurality of acoustic signal amplifiers; each acoustic emission probe is respectively attached to the other end of each acoustic transmission rod;
the CO is 2 The pressurized liquefaction system includes CO 2 Gas cylinder, booster pump and high-pressure piston container III, CO 2 The air cylinder is connected with an air inlet of the high-pressure piston container III through a pipeline, and the booster pump is connected with the high-pressure piston container III through a pipeline to provide power for the high-pressure piston container III;
the quantitative foam fracturing fluid injection system comprises a constant-flow pump II, a high-pressure piston container I, a high-pressure piston container II and a back pressure device, wherein the constant-flow pump II is respectively connected with the high-pressure piston container I and the high-pressure piston container II through pipelines to provide power for the constant-flow pump II; the port of the high-pressure piston container I is connected with the outlet of the high-pressure piston container III and the inlet of the back pressure device through pipelines, and the outlet of the back pressure device is connected with the port of the high-pressure piston container II through a pipeline;
the high-temperature high-pressure foam performance evaluation system comprises a foam generator, an industrial camera, a high-temperature high-pressure visual window, a stirring motor and a controller, wherein the stirring motor is arranged at the bottom of the foam generator, an output shaft of the stirring motor extends into the foam generator, and a stirring fan blade is arranged on the output shaft of the stirring motor and used for stirring and foaming; the high-temperature high-pressure visible window is arranged on the side part of the foam generator, and the industrial camera is arranged on the camera bracket and is opposite to the high-temperature high-pressure visible window for shooting the form change of the foam in the foam generator under high temperature and high pressure; the outside of the foam generator is wrapped by a second heating sleeve; the controller is used for controlling the heating temperature of the heating sleeve II and the stirring speed of the stirring motor; an inlet of the foam generator is connected with an outlet of the back pressure device and a port of the high-pressure piston container II through a pipeline; an outlet of the foam generator is connected with one end of a fracturing pipeline, the other end of the fracturing pipeline is connected with one end of a liquid injection pipe, the other end of the liquid injection pipe is a liquid injection port, and the liquid injection port extends into the holder main body through a left plug and reaches the inside of a drill hole of the rock core sample; a backpressure valve is arranged on a fracturing pipeline between the foam generator and the holder main body, and a scale is arranged on the high-temperature high-pressure visual window;
the pulse fracturing control system comprises a servo variable frequency control system, a pulse pump and a servo pressure cylinder, wherein an outlet of the servo pressure cylinder is connected with a pressure port of a foam generator through a pipeline, an inlet of the servo pressure cylinder is connected with an output end of the pulse pump through a pipeline, and the servo variable frequency control system is used for controlling the pulse frequency and the pulse amplitude of the pulse pump;
the permeability measuring system comprises a gas source, a gas booster pump, a flowmeter, an inlet high-frequency pulse pressure sensor, a liquid discharge pipe, an outlet high-frequency pulse pressure sensor and a liquid discharge water cup; the gas source is connected with the inlet of the gas booster pump through a pipeline, and the outlet of the gas booster pump is connected with a fracturing pipeline between the backpressure valve and the holder main body through a pipeline; one end of the liquid discharge pipe is in contact with the rock core sample, and the other end of the liquid discharge pipe is a liquid discharge outlet which extends out of the holder main body through the right plug and is connected with a liquid discharge cup; the flowmeter is arranged at an outlet of the gas booster pump, and the inlet high-frequency pulse pressure sensor is arranged on a fracturing pipeline positioned outside the clamp holder body; the outlet high-frequency pulse pressure sensor is arranged on a liquid discharge pipe positioned outside the holder body;
the data acquisition control system is used for controlling the working states of the booster pump, the gas booster pump, the constant-flow pump I, the constant-flow pump II, the servo variable-frequency control system and the pulse pump; the flow meter, the inlet high-frequency pulse pressure sensor, the outlet high-frequency pulse pressure sensor, the industrial camera, the controller, the heating sleeve I and the heating sleeve II are all connected to a data acquisition control system, and the data acquisition control system performs data calculation processing on received gas flow, inlet pressure, outlet pressure, foam form and heating temperature control data;
a first stop valve is arranged on a pipeline between the gas source and the gas booster pump; a second stop valve is arranged on a pipeline between the gas booster pump and the liquid injection pipe; a third stop valve and a fourth stop valve are respectively arranged on two branch pipelines between the first constant-current pump and the three-axis loading mechanism; a first pressure release valve and a first pressure gauge are arranged on the foam generator; a sixth stop valve is arranged on a pipeline between the constant-flow pump II and the high-pressure piston container I, and a fifth stop valve is arranged on a pipeline between the constant-flow pump II and the high-pressure piston container II; a second pressure gauge is arranged on the second high-pressure piston container, and a seventh stop valve is arranged at the port of the second high-pressure piston container; a pressure gauge III and a pressure relief valve II are arranged on the high-pressure piston container I, a stop valve VIII is arranged at the port of the high-pressure piston container I, and a pressure gauge IV is arranged on a pipeline between the high-pressure piston container I and the back pressure device; a pipeline between the stop valve seventh and the back pressure device is provided with an injection pipe, and the injection pipe is provided with a stop valve ninth; a stop valve ten is arranged on a pipeline between the booster pump and the high-pressure piston container III; CO 2 2 A pipeline between the gas cylinder and the high-pressure piston container III is provided with a first stop valve; and a third pressure release valve and a fifth pressure gauge are arranged on the third high-pressure piston container, and a twelfth stop valve is arranged at the port of the third high-pressure piston container.
2. The pulsating CO of claim 1 2 Foam fracturing and evaluation simulation integration test device, its characterized in that, 8 are totaled to sound wave conduction pole, divide equally into two sets ofly, and two sets ofly arrange respectively in 25mm and 75mm department of rock core sample height, and the angle between the adjacent pole of same group is 90.
3. The pulsating CO of claim 1 2 Foam fracturing and evaluation simulation integration test device, its characterized in that, the rock core sample is diameter 50mm, high 100 mm's cylinder rock core, and the drilling diameter of rock core sample is 3mm, the degree of depth is used for simulating the fracturing pit shaft for 50mm, stretches into the inside notes liquid mouth apart from drilling bottom 10mm of annotating the liquid pipe of drilling, uses high strength bar planting to glue hole sealing 30mm between notes liquid pipe and the drilling inner wall, annotates liquid pipe tip and is equipped with quick-operation joint and be used for the high-speed joint fracturing pipeline.
4. A pulsed CO according to any one of claims 1 to 3 2 The test method of the foam fracturing and evaluation simulation integrated test device is characterized by comprising the following specific steps:
A. arranging an acoustic emission monitoring system: after the acoustic emission monitoring system is connected, fixing two acoustic emission probes at two ends of a cylindrical sample by using a vaseline coupling agent, and calibrating the sound velocity of the sample by using a lead-breaking experiment; then, connecting eight acoustic emission probes in the acoustic emission monitoring system with eight acoustic wave conduction rods by using vaseline coupling agent;
B. installing a core sample: preparing a plurality of rock core samples with the same size, forming drill holes in the middle of each rock core sample, selecting one rock core sample, and sealing holes between an injection pipe and the inner wall of each drill hole of the rock core sample by using high-strength rebar planting glue; taking the left plug off the holder main body, putting the core sample into the holder main body, arranging the core sample in the three-axis loading mechanism, screwing the left plug, connecting the quick joint with an adjacent pipeline, then opening the third stop valve, controlling the three-axis loading mechanism to load confining pressure on the core sample to a set value by the first advection pump, then closing the third stop valve, opening the fourth stop valve, and controlling the three-axis loading mechanism to load axial pressure on the core sample to the set value by the first advection pump;
C. initial permeability determination: opening the first stop valve and the second stop valve, starting the gas booster pump to control gas in a gas source to enter the drill hole of the rock core sample in the step B through the liquid injection pipe, performing gas displacement on the rock core sample, monitoring gas flow, gas inlet pressure and gas outlet pressure by using the flowmeter, the inlet high-frequency pulse pressure sensor and the outlet high-frequency pulse pressure sensor, and feeding back the gas flow, the gas inlet pressure and the gas outlet pressure to the data acquisition control system; the data acquisition control system processes the acquired data to obtain the initial permeability of the rock core sample, and the specific formula is as follows:
in the formula:kfor core testingPermeability of the sample, m 2 ；qIs the flow rate of the gas, m 3 /s；SIs the cross-sectional area of the sample, m 2 ；lIs the length of the sample, m;μis the aerodynamic viscosity coefficient, MPa · s;p 0 is atmospheric pressure, and 0.1MPa is taken;p 1 is the inlet pressure, MPa;p 2 is the pressure of the outlet gas, MPa;
D、CO 2 preparing a foam fracturing fluid: using CO 2 Liquefied gaseous CO of pressurized liquefaction system 2 Opening the stop valve ten and the stop valve eleven, CO 2 CO in gas cylinder 2 The gas enters a high-pressure piston container III, and a stop valve is closed; starting booster pump to discharge CO in high-pressure piston container 2 Pressurizing and liquefying gas, liquefied CO 2 Storing in a high-pressure piston container III, and maintaining liquid CO by regulating the pressure in the high-pressure piston container III with a back pressure device 2 Stabilizing; starting the foam fracturing fluid quantitative injection system, opening a seventh stop valve and a ninth stop valve, injecting quantitative foaming fluid into a second high-pressure piston container through an injection pipe, and closing the seventh stop valve and the ninth stop valve after completion; opening the stop valve twelve and the stop valve eight, and using the booster pump to pump the liquid CO in the high-pressure piston container three 2 Injecting the mixture into the first high-pressure piston container, and then closing the stop valve twelve and the stop valve eight; sequentially opening a stop valve six, a stop valve eight, a stop valve five and a stop valve seven, and sequentially controlling the liquid CO in the high-pressure piston container I by the constant-flow pump two 2 And the foaming liquid of the high-pressure piston container II is quantitatively injected into the foam generator, and then the stop valve six, the stop valve eight, the stop valve five and the stop valve seven are closed; the starting controller controls the stirring motor to stir the liquid CO in the foam generator at a set rotating speed 2 Mixing with foaming liquid under stirring to finally generate CO 2 Foam fracturing fluid, and stopping the stirring motor after completion; controlling the heating jacket two pairs of CO by using a controller 2 Heating the foam to obtain CO at high temperature and high pressure 2 Stability of the foamed fracturing fluid; scales for measuring CO 2 The foaming volume and the foam half-life period of the foam fracturing fluid, and an industrial camera is used for recording foam form change;
E. pulsating CO 2 And (3) foam fracturing: synchronously starting the pulse fracturing control system and the acoustic emission monitoring system, and controlling a pulse pump to pump CO at different frequencies, different amplitudes and different peak pressures by using a servo variable frequency control system 2 Injecting foam fracturing fluid into a drill hole of a rock core sample through an injection pipe, synchronously acquiring acoustic emission information of the rock core sample in a fracturing process by an acoustic emission monitoring system, acquiring a pressure curve by an inlet high-frequency pulse pressure sensor and feeding back the pressure curve to a data acquisition control system, finishing the fracturing process when sudden pressure relief of the pressure curve occurs or when foam fracturing fluid is observed to be discharged from a liquid discharge water cup, and closing a pulse fracturing control system and the acoustic emission monitoring system;
F. and (3) measuring the permeability after fracturing: c, repeatedly executing the step C to measure the permeability of the fractured core sample;
G. and (5) finishing the fracturing process: sequentially opening a third stop valve and a fourth stop valve, controlling a constant-flow pump to carry out confining pressure and axial pressure unloading on the rock core sample, then opening a left plug of a triaxial rock core holder, taking out the fractured rock core sample from the triaxial rock core holder, cleaning the fractured rock core sample, and simultaneously transmitting acoustic emission data and twice permeability measurement data obtained in the fracturing process to a data acquisition control system;
H. selecting a core sample, and resetting liquid CO 2 Mixing the foaming liquid with the foaming liquid and the confining pressure value and the axial pressure value of the triaxial loading mechanism, repeatedly executing the steps A to G to obtain CO of the mixing ratio under the condition of the current confining pressure value and the current axial pressure value 2 The acoustic emission data and the two-time permeability measurement data of the foam fracturing fluid in the rock core sample fracturing process are repeated for many times, and CO with different confining pressure values, axial pressure values and different mixing ratios can be obtained 2 Acoustic emission data and two-time permeability measurement data of the core sample fracturing process under the conditions of the foam fracturing fluid and different pulse parameters are used for adopting CO for follow-up actual application 2 And determining the optimal implementation parameters when the foam fracturing fluid is fractured, and providing a data analysis sample.
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| CN115217458B (en) * | 2022-05-25 | 2023-11-28 | 中国矿业大学 | Underground fracturing and proppant injection integrated device and construction method |
| CN115749713B (en) * | 2022-10-14 | 2023-06-16 | 中国矿业大学 | Rock stratum variable frequency pulse seam net fracturing method and equipment |
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| CN206740588U (en) * | 2017-05-24 | 2017-12-12 | 中国石油集团川庆钻探工程有限公司工程技术研究院 | A kind of carbon dioxide dry method fracturing fluid solid-carrying performance evaluating apparatus |
| CN107907431B (en) * | 2017-11-14 | 2019-08-06 | 中南大学 | Three axis load pulses hydraulically created fracture extended dynamic monitoring test devices |
| CN107942000B (en) * | 2017-11-16 | 2020-03-31 | 太原理工大学 | Multifunctional modular carbon dioxide foam fracturing test method for mine |
| CN108663298A (en) * | 2018-03-27 | 2018-10-16 | 西南石油大学 | True triaxial crack propagation simulation and permeability test integrated experimental device and method |
| CN109975140B (en) * | 2019-04-16 | 2022-02-22 | 重庆地质矿产研究院 | Supercritical carbon dioxide pulse fracturing and permeability testing integrated experimental device and method |
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