CN108682270B - True triaxial fracturing simulation device for simulating proppant laying and working method thereof - Google Patents
True triaxial fracturing simulation device for simulating proppant laying and working method thereof Download PDFInfo
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- CN108682270B CN108682270B CN201810416413.6A CN201810416413A CN108682270B CN 108682270 B CN108682270 B CN 108682270B CN 201810416413 A CN201810416413 A CN 201810416413A CN 108682270 B CN108682270 B CN 108682270B
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- fracturing
- proppant
- shaft
- stirring tank
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
- G09B25/00—Models for purposes not provided for in G09B23/00, e.g. full-sized devices for demonstration purposes
- G09B25/02—Models for purposes not provided for in G09B23/00, e.g. full-sized devices for demonstration purposes of industrial processes; of machinery
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
Abstract
The device comprises a fracturing fluid stirring tank, a fracturing pump, a proppant stirring tank, a fracture expansion simulation assembly and an integrated control system, wherein the fracturing fluid stirring tank, the fracturing pump, the proppant stirring tank, the fracture expansion simulation assembly and the integrated control system are sequentially connected through a main pipeline. The proppant mixing tank has parallel branch lines. A steering switch is arranged between the fracturing pump and the proppant stirring tank to control the communication and the disconnection of the main pipeline, the proppant stirring tank and the branch pipeline; and a metal thread shaft with certain deformation is arranged in the fracturing simulation rock sample. According to the invention, by adding the independent proppant adding device and the steering switch, the shape of the shaft is improved, the fiber material is added, the sealing strength between the shaft and the rock sample contact surface is improved, the sand adding simulation in the crack initiation/expansion process can be realized, the purpose of improving the success rate of the experiment in the true triaxial fracturing room is improved, and the method has important guiding significance for researching the proppant migration rule and the optimization design of the fracturing construction scheme.
Description
Technical Field
The invention relates to a true triaxial fracturing simulation device for simulating proppant laying and a working method thereof, and belongs to the technical field of oil and gas field development.
Background
The unconventional oil and gas reservoirs in China are widely distributed, and due to the characteristics of low porosity, low permeability and the like, the seepage resistance of oil and gas in a reservoir matrix is extremely high, and the low permeability oil and gas reservoirs are usually economically and effectively exploited by depending on a fracturing production-increasing transformation technology. Hydraulic fracturing is a very complicated oil and gas well production increasing transformation process, a ground high-pressure pump set is utilized to pump fracturing fluid into a well at a discharge capacity exceeding the stratum absorption capacity, high pressure is suppressed at the bottom of the well, and when the pumping pressure overcomes the ground stress near the well wall to reach the tensile strength of rocks, cracks are generated at the bottom of the well; the mixed liquid of the fracturing fluid and the propping agent is continuously pumped, so that sand filling fractures which are long enough and have certain flow conductivity can be formed in the stratum, and a reservoir fluid seepage channel is provided.
In order to better study the fracture initiation/expansion rule of a fracture in a reservoir, a laboratory usually uses concrete, cement, sandstone, coal rock and other materials to manufacture a fracture rock sample to simulate an actual reservoir, a shaft device is arranged in the rock sample, liquid is pumped into the rock sample through a shaft, and high pressure is built in the rock sample until the fracture pressure of the fracture is reached to cause the fracture of the rock sample.
According to the hydraulic fracturing principle, the sealing between the contact surface of the shaft and the rock sample is the key of success or failure of the experiment, once the sealing is not tight, the liquid pumped into the rock sample overflows along the interface of the shaft and the rock sample, so that high pressure cannot be suppressed at the bottom of the well, and the rock sample cannot crack. In order to avoid the problems, laboratories generally adopt a method of reducing the diameter of a shaft to 3-10 mm (the inner diameter is 1-8 mm) to reduce a cementing interface so as to improve the sealing property between the shaft and a rock sample, so that the shaft is too thin to simulate the fracturing process of pumping a propping agent. In addition, the pressure range required by rock sample fracture is 20-80 MPa, the matched fracturing pump is required to be high-precision equipment capable of providing higher pressure, and the proppant particles are easy to wear working blades or pistons of the pump, so that the service life of the fracturing pump is shortened, and the fracturing pump is not suitable for pumping proppant materials (the proppant materials for fracturing are quartz sand or ceramsite particles with the particle size of 0.1-1.5 mm).
At present, due to the technical problem of sealing between a shaft and a rock sample and the problem that a high-pressure pump is easy to wear, the success rate of an experiment in a true triaxial fracturing room is low, and the simultaneous simulation of the fracture initiation/expansion and the fracturing sand-carrying process of the internal crack of the rock sample cannot be realized.
Disclosure of Invention
In order to solve the above problems in the prior art, the present invention provides a true triaxial fracture simulation apparatus for simulating proppant placement and a working method thereof.
The technical scheme of the invention is as follows:
a true triaxial fracturing simulator for simulating proppant laying is characterized in that a fracturing fluid stirring tank, a fracturing pump, a proppant stirring tank and a fracture expansion simulation assembly are sequentially connected through a main pipeline, wherein the proppant stirring tank is connected with branch pipelines which can be controlled to be communicated and cut off in parallel;
the fracturing fluid stirring tank comprises a stirrer inside, the upper part of the fracturing fluid stirring tank is provided with a fracturing fluid feeding hole, and the bottom of the side surface of the fracturing fluid stirring tank is provided with a discharging hole connected with a main pipeline;
the proppant stirring tank comprises a stirrer inside, the side surface of the proppant stirring tank is respectively provided with a fracturing fluid feed inlet and a sand-mixing fluid discharge outlet which are connected with a main pipeline, and the preferable position of the fracturing fluid feed inlet is higher than the sand-mixing fluid discharge outlet;
the fracturing simulation container is arranged on the periphery of the fracture expansion simulation assembly, a fracturing simulation rock sample is arranged in the fracturing simulation container, a shaft penetrating through an upper cover of the fracturing simulation container and communicated with a main pipeline is arranged in the fracturing simulation rock sample, perforation holes are distributed on the contact surface of the shaft and the fracturing simulation rock sample, and jacks are respectively connected in the front direction, the rear direction, the left direction, the right direction and the upper direction of the fracturing simulation rock sample;
an integrated control system is also included.
Preferably, a position finder for observing the liquid level position of the fracturing liquid in the tank in real time is arranged on the inner wall surface of the fracturing liquid stirring tank; the fracturing fluid feed inlet can be sealed by threads; the diameter of the fracturing fluid stirring tank is 1-80 cm, and the height of the fracturing fluid stirring tank is 1-80 cm; the position of a discharge port arranged on the side surface of the tank body is 0.1-30 cm away from the bottom of the tank.
Preferably, the diameter of the proppant stirring tank is 1-80 cm, and the height of the proppant stirring tank is 1-80 cm; the position of a sand mulling liquid discharge port on the side surface of the sand mulling liquid is 0.1-30 cm away from the bottom of the proppant stirring tank; the height difference of the position of the fracturing fluid feed inlet higher than the sand mixing fluid discharge outlet is 0.1-50 cm.
Preferably, the fracturing pump is a plunger pump with a head of 0.1-104kPa; and an electromagnetic flowmeter is arranged at the outlet of the fracturing pump.
Preferably, a steering switch is arranged at the connection position of the branch pipeline and the main pipeline.
The preferable raw material of the fracturing simulation rock sample comprises fibers, wherein the length of the fibers is 0.1-10 cm, and the content of the fibers is 1-60%.
Preferably, the shaft is a metal shaft with threads on the surface, the cross section of the shaft is circular or oval with twist in the axial direction, and the axial twist angle is 0-360 degrees; a sealing cover is arranged at the tail end of the shaft; the radius of the shaft with the circular cross section is 1-150 mm; the short radius of the shaft with the oval cross section is 1-75 mm, and the ratio of the long axis to the short axis is 1-2; the difference value between the major diameter D and the minor diameter D of the threads on the surface of the shaft is 0.1-5 cm, and the thread pitch of the threads is 0.1-15 cm; the number of the shafts is 1-5, the shaft type is a vertical shaft and/or a horizontal shaft, and the length of the shaft is 5-400 cm.
The surface of the preferable shaft is uniformly or in a cluster distribution with perforation holes, the diameter of each perforation hole is 1-20 mm, the phase of each perforation hole is 0-180 degrees, the density of each perforation hole is 8-96/m, and the number of the perforation holes is adjusted in a nut sealing mode.
The integrated control system preferably controls power switches of the fracturing pump, the electric mixer and the jack device; and a system control panel of the integrated control system is provided with a frequency adjusting button of the fracturing pump, a pressure adjusting button of the jack, a displacement display and a pressure display.
The working method of the simulation device is characterized by comprising the following steps of:
(1) assembling a shaft device, installing a tail end sealing cover, and determining the density of holes; preferably using nuts to seal the excess perforations while installing a crossover joint at the top of the wellbore;
(2) preparing raw materials required for manufacturing a rock sample comprising fibers and cement and/or concrete and/or coal rock, consolidating the raw materials together with a shaft to manufacture a reservoir simulation rock sample, and airing the rock sample to a state required by an experiment;
(3) installing a rock sample and a shaft to the inside of the fracturing simulation container, and fixing a jack on the front, rear, left, right and upper 5 wall surfaces of the rock sample;
(4) preparing a fracturing fluid system for experiments, and preparing a proppant material for fracturing;
(5) arranging a laboratory, moving experimental equipment to a proper position, connecting all experimental pipelines of the equipment, and checking the tightness of the pipelines;
(6) pouring the fracturing fluid material into a fracturing fluid stirring tank, so that the volume of the fluid accounts for 80-90% of the volume of the tank; filling a proppant material into a proppant stirring tank, wherein the volume of the proppant accounts for 3-25% of the volume of the tank;
(7) starting the jack device, and setting the confining pressure in the front-back direction, the left-right direction and the up-down direction;
(8) cutting off the communication between the main pipeline and the proppant stirring tank, communicating the branch pipeline, and starting the fracturing fluid electric stirrer;
(9) starting a fracturing pump and adjusting the frequency to the required discharge capacity, pumping the fracturing fluid into a shaft through the fracturing pump, and building high pressure in the rock sample to crack the rock sample;
(10) observing a rock sample pressure change curve of the integrated control display interface, and judging whether the rock sample cracks or not according to the curve;
(11) starting a propping agent electric stirrer after the rock sample is fractured;
(12) communicating a proppant stirring tank, closing a branch pipeline, allowing the fracturing fluid to enter the proppant stirring tank, mixing with the proppant to form a sand mixing fluid, allowing the sand mixing fluid to flow into a shaft through an adapter, and allowing the sand mixing fluid to enter artificial cracks in the rock sample;
(13) repeating the step (8-12), and simulating an actual fracturing process on site;
(14) after the experiment is finished, closing the fracturing pump, the electric stirrer and unloading the pressure of the jack;
(15) storing and copying experimental data, and closing the integrated control system;
(16) and taking out the simulated rock sample, observing the expansion form of the fractured crack, analyzing the laying rule of the propping agent in the crack, arranging experimental instruments and materials, and cleaning a laboratory.
The invention has the following effects:
(1) the invention adds an independent proppant adding device and a branch pipeline which can be controlled by a steering switch, and can control the connection and disconnection of a main pipeline and a proppant stirring tank; when the main pipeline is communicated with the proppant stirring tank, the fracturing fluid flows into the proppant stirring tank and is mixed with the proppant to form sand-carrying fluid, and then the sand-carrying fluid and the sand-carrying fluid are pumped into the shaft and flow into artificial cracks formed in the rock sample; and on the contrary, the fracturing fluid is pumped into the shaft alone to press the crack open. The simulation of the fracture initiation/expansion and the fracturing sand-carrying process of the internal fracture of the rock sample and the laying of the proppant can be realized in the true triaxial fracturing experiment process, and the fracturing construction process of the proppant slug can be simulated.
(2) The experimental device can effectively improve the sealing strength of the interface between the shaft and the rock sample and improve the success rate of the real triaxial fracturing indoor experiment by improving the shape of the shaft (a smooth cylindrical shaft is improved into a threaded elliptic cylinder with a certain rotation angle) and adding fiber materials into the rock sample. According to the classic anchoring theory, the adhesive force between the metal bar and the concrete mainly comprises four types, the metal bars with different surface characteristics are stressed differently, the smooth metal bar is stressed by chemical adhesive force and friction force, the threaded metal bar generates occlusion force with the concrete due to uneven surface, and the cold-rolled steel bar generates mechanical anchoring force due to surface protrusion, distortion or change of cross section geometric shape besides the 3 types of force, so that the adhesive strength between the cold-rolled steel bar and the concrete can be obviously enhanced; in addition, dispersed fibers are randomly and uniformly mixed into cement or concrete in a mechanical, air pressure or water pressure mode, and the like, and the fibers are distributed in a net shape in the mixture, so that the tensile stress generated by the axial load effect in the test piece can be effectively borne, the lateral deformation of the structure can be prevented, and the sealing effect between the metal rod and the concrete can be improved.
(3) The experimental device can realize the integrated control of equipment switching, parameter adjustment, data display and data processing, and improve the safety of experimental operation.
(4) The experimental device provided by the invention can realize the fracturing process simulation of a 'well factory' by installing different types (vertical or horizontal) and different quantities of well shafts, better understand the laying and moving rule of the propping agent in the fracturing fracture (especially a complex fracture network), and has important guiding significance for the optimization design of a field fracturing construction scheme.
Drawings
FIG. 1 is a schematic view of the overall structure of the apparatus of the present invention;
the various reference numbers in the figures are listed below:
1, a fracturing fluid stirring tank; 2, an electric stirrer; 3 a position finder; 4, a fracturing fluid feed port; 5 a fracturing pump; 6 an electromagnetic flow meter; 7, a proppant stirring tank; 8 proppant feed inlets; 9 a main pipeline; 10 a steering switch; 11 pipelines; 12, a crossover joint; 13 fracturing the simulated container; 14 fracturing the simulated rock sample; 15 jack; 16 a wellbore; 17 sealing the nut; 18 universal wheels; 19 integrated control system.
Detailed Description
The invention is described in detail below with reference to the following examples and the accompanying drawings.
Example 1
As shown in fig. 1, a fracturing fluid stirring tank 1, a fracturing pump 5, a proppant stirring tank 7, and a fracture propagation simulation assembly are sequentially connected to a main pipeline 9, wherein the proppant stirring tank is connected in parallel with a branch pipeline, and a steering switch 10 is arranged at a parallel connection interface; the top of the fracturing fluid stirring tank 1 is provided with a fracturing fluid feeding port 4, and the bottom of the side surface is provided with a discharging port which is connected with a main pipeline 9; the inside of the proppant stirring tank 7 comprises a stirrer 2, the axial side surface of the proppant stirring tank is respectively provided with a fracturing fluid feed inlet and a sand mulling fluid discharge outlet which are connected with a main pipeline, the position of the fracturing fluid feed inlet is higher than that of the sand mulling fluid discharge outlet, and the top of the proppant stirring tank is provided with a proppant feed inlet 8; the periphery of the fracture expansion simulation assembly is provided with a fracturing simulation container 13, a fracturing simulation rock sample 14 is arranged in the fracture expansion simulation assembly, a shaft 16 which penetrates through an upper cover of the fracturing simulation container and is communicated with the main pipeline 9 is arranged in the fracturing simulation rock sample 14, perforation holes are distributed on the contact surface of the shaft 16 and the fracturing simulation rock sample 14, and jacks 15 are respectively connected in the front direction, the rear direction, the left direction, the right direction and the upper direction of the fracturing simulation rock sample 14; an integrated control system 19 is also included.
The well bore 16 is threaded and has an elliptical cross-section and a 120 degree twist is applied in the axial direction to increase the strength of the cement.
By adding the independent proppant adding device 7 and the pipeline steering switch 10 and improving the shape of the shaft 16, the sealing strength of the shaft and the rock sample interface can be effectively improved, and the purposes of simulating and improving the success rate of the experiment in the true triaxial fracturing chamber while the fracture initiation/expansion and fracturing sand-carrying process in the rock sample are realized.
An electric stirrer 2 is arranged at the center of the inner parts of the fracturing fluid stirring tank 1 and the proppant stirring tank 7, and a position finder 3 is arranged close to the inner wall surface to observe the liquid level position of the fracturing fluid in the tank in real time; according to the embodiment, the diameter of the fracturing fluid stirring tank 1 and the proppant stirring tank 7 is 40cm, and the height of the fracturing fluid stirring tank and the proppant stirring tank is 60 cm; the position of a discharge port arranged on the side surface of the fracturing fluid mixing tank is 10cm away from the bottom of the tank, the position of a fracturing fluid feed port on the side surface of the proppant mixing tank is higher than a sand mulling fluid discharge port, and the height difference is 10 cm.
The fracturing pump 5 is a high-precision plunger pump with a delivery head of 0.1-104kPa, an electromagnetic flowmeter 6 is arranged at an outlet; a pipeline steering switch 10 is arranged between the fracturing pump 5 and the proppant stirring tank 7 to control the communication and disconnection of the branch pipeline and the main pipeline of the proppant stirring tank 7; when the main pipeline 9 is communicated with the proppant stirring tank 7, the fracturing fluid flows into the proppant stirring tank 7 to be mixed with the proppant to form sand mixing fluid, and then the sand mixing fluid is pumped into the shaft 16 and flows into the artificial cracks formed in the rock sample; and on the contrary, the fracturing fluid is pumped into the shaft alone to press the crack open.
The fracturing simulation container 13 is a cuboid container, the box body is connected with the upper cover through nuts 17, and the number of the nuts is 4-8, preferably 6; the fracturing simulation container is 200cm in length, 100cm in width and 200cm in height; 4 universal wheels 18 are arranged at the bottom of the container, so that the equipment can be conveniently moved and transported.
The shape of the fracturing simulation rock sample 14 is a cuboid, the length is 80cm, the width range is 60cm, and the height is 80 cm; the device is arranged in the fracturing simulation container 13, the front direction, the back direction, the left direction, the right direction and the upper direction of the device are respectively connected with a jack 15 device, the jack device is used for providing confining pressure for the reservoir stratum so as to simulate the stress state of the underground reservoir stratum, and the confining pressure in the front direction, the back direction, the left direction and the upper direction is not necessarily the same. The fracturing simulation rock sample can be made of one or more materials of concrete, silicate cement, aluminate cement, gravel, sandstone, coal rock and the like in combination with fibers, and can simulate reservoir layers with different lithologies or heterogeneous lithologies respectively.
A shaft device is arranged in the fracturing simulation rock sample 14, the shaft is a metal threaded shaft 16, and the axial torsion angle is 0-360 degrees; the cross section of the shaft is oval, and the tail end of the shaft is provided with a sealing cover to adjust the flow of the perforation hole.
According to the embodiment, the difference between the major diameter D and the minor diameter D of the thread on the surface of the wellbore 16 is 3cm, and the thread pitch is 10 cm; the short radius of the cross section of the shaft is 50mm, and the ratio of the long axis to the short axis is 1.5; the number of the well bores is 1, the type of the well bores is a vertical well bore, and the length of the well bore is 200 cm.
According to the embodiment, perforations are uniformly distributed on the surface of the shaft 16, the diameter of each perforation is 5mm, the phase of each perforation is 0-180 degrees, the density of each perforation is 20/m, and the number of the perforations can be adjusted in a nut sealing mode.
The top of the shaft device is provided with an adapter 12, the cross section of one end of the adapter 12 connected with the shaft is oval, and the adapter is connected with the shaft by threads; the cross section of one end of the adapter connected with the main pipeline is circular and is in threaded connection with the pipeline;
the integrated control system 19 controls power switches of the fracturing pump 5, the electric mixer 2 and the jack device 15; a frequency adjusting button, a discharge capacity display and a rock sample internal pressure change display of the fracturing pump are arranged on the control panel of the integrated control system; and a pressure adjusting button and a pressure display of the jack are arranged on the control panel of the integrated control system.
Example 2
The embodiment is a working method of the above device, including the steps of:
(1) assembling a shaft device 16, installing a tail end sealing cover, determining the density of holes, using nuts to seal redundant holes if needed, and installing an adapter 12 at the top of the shaft;
(2) preparing raw materials required for manufacturing rock samples such as cement, concrete, coal rock, fiber and the like, consolidating with a shaft to manufacture a reservoir simulation rock sample 14 with a certain size, and airing the rock sample to a state required by an experiment;
(3) installing a rock sample 14 and a shaft 16 into the fracturing simulation container 13, and fixing a jack 15 on the front, rear, left, right and upper 5 wall surfaces of the rock sample;
(4) preparing a fracturing fluid system for experiments, and preparing a proppant material for fracturing;
(5) arranging a laboratory, moving the laboratory equipment to a proper position, connecting all experimental pipelines 9 of the equipment, and checking the tightness of the pipelines;
(6) pouring the fracturing fluid material into a fracturing fluid stirring tank 1, so that the volume of the fluid accounts for 80-90% of the volume of the tank; filling a proppant material into a proppant stirring tank 7, wherein the volume of the proppant accounts for 3-25% of the volume of the tank;
(7) starting the jack device 15, and setting the confining pressure in the front-back direction, the left-right direction and the up-down direction;
(8) rotating a pipeline steering switch 10, cutting off the communication between the main pipeline and the proppant stirring tank, and starting the fracturing fluid electric mixer 2;
(9) starting a fracturing pump 5, adjusting the frequency to the required discharge capacity, starting an electromagnetic flowmeter 6, pumping fracturing fluid into a shaft 16 through the fracturing pump, and building high pressure in the rock sample to crack the rock sample;
(10) observing a rock sample pressure change curve of the integrated control 19 display interface, and judging whether the rock sample cracks according to the curve;
(11) after the rock sample is fractured, starting the proppant electric stirrer 2;
(12) a pipeline steering switch 10 is rotated to communicate the pipeline with a proppant stirring tank, fracturing fluid enters the proppant stirring tank, is mixed with proppant to form sand mixing fluid, flows into a shaft 16 through a conversion joint 12 and enters artificial cracks in a rock sample;
(13) repeating the step (8-12), and simulating an actual fracturing process on site;
(14) after the experiment is finished, the fracturing pump 5, the electric stirrer 2 and the unloading jack 15 are closed in sequence;
(15) storing and copying the experimental data, and closing the integrated control system 19;
(16) and taking out the simulated rock sample, observing the expansion form of the fractured crack, analyzing the laying rule of the propping agent in the crack, arranging experimental instruments and materials, and cleaning a laboratory.
The above embodiments are merely examples regarding dimensions, materials, and the like, and are not limited thereto. The effects of the present invention can be further preferably achieved within the following ranges: the diameter of the fracturing fluid stirring tank is 30-80 cm, and the height of the fracturing fluid stirring tank is 30-80 cm; the position of a discharge port arranged on the side surface of the tank body is 0.1-30 cm away from the bottom of the tank; preferably, the diameter of the proppant stirring tank is 30-80 cm, and the height of the proppant stirring tank is 30-80 cm; the position of a sand mulling liquid discharge port on the side surface of the sand mulling liquid is 0.1-30 cm away from the bottom of the proppant stirring tank; the height difference of the position of the fracturing fluid feed inlet and the position of the fracturing fluid discharge outlet is 5-50 cm; the three-dimensional size of the selected crack propagation container is 30-300 cm; the three-dimensional size of the used crack expansion simulation rock sample is 5-100 cm; the used shaft device is a metal thread shaft, and the axial twist angle is 0-360 degrees; the short radius of the cross section of the shaft is 1-75 mm, and the ratio of the long axis to the short axis is 1-2; clustering or uniformly perforating on the surface of a shaft, wherein the diameter of each eyelet is 1-20 mm, the density of each eyelet is 16-48/m, and the phase of each eyelet is 0-90 degrees; the number of the shafts is 1-5, the type of the shaft is a vertical shaft or a horizontal shaft, and the length of the shaft is 5-400 cm; the particle size of the used propping agent is 20-100 meshes; the fracturing fluid adopts active water fracturing fluid and the like.
Claims (10)
1. A true triaxial fracturing simulator for simulating proppant laying is characterized in that a fracturing fluid stirring tank, a fracturing pump, a proppant stirring tank and a fracture expansion simulation assembly are sequentially connected through a main pipeline, wherein the proppant stirring tank is connected with branch pipelines which can be controlled to be communicated and cut off in parallel;
the fracturing fluid stirring tank comprises a stirrer inside, the upper part of the fracturing fluid stirring tank is provided with a fracturing fluid feeding hole, and the bottom of the side surface of the fracturing fluid stirring tank is provided with a discharging hole connected with a main pipeline;
the proppant stirring tank comprises a stirrer inside, and a fracturing fluid feeding port and a sand-mixing fluid discharging port which are connected with a main pipeline are respectively arranged on the side surfaces of the stirrer;
the fracturing simulation container is arranged on the periphery of the fracture expansion simulation assembly, a fracturing simulation rock sample is arranged in the fracturing simulation container, a shaft penetrating through an upper cover of the fracturing simulation container and communicated with a main pipeline is arranged in the fracturing simulation rock sample, perforation holes are distributed on the contact surface of the shaft and the fracturing simulation rock sample, and jacks are respectively connected in the front direction, the rear direction, the left direction, the right direction and the upper direction of the fracturing simulation rock sample;
an integrated control system is also included.
2. The simulation device of claim 1, wherein a position finder for observing the liquid level position of the fracturing fluid in the tank in real time is arranged on the inner wall surface of the fracturing fluid stirring tank; the diameter of the fracturing fluid stirring tank is 1-80 cm, and the height of the fracturing fluid stirring tank is 1-80 cm; the position of a discharge port arranged on the side surface of the tank body is 0.1-30 cm away from the bottom of the tank.
3. The simulation device of claim 1, wherein the proppant mixing tank has a diameter of 1-80 cm and a height of 1-80 cm; the position of a sand mulling liquid discharge port on the side surface of the sand mulling liquid is 0.1-30 cm away from the bottom of the proppant stirring tank; the height difference of the position of the fracturing fluid feed inlet higher than the sand mixing fluid discharge outlet is 0.1-50 cm.
4. The simulation device of claim 1, wherein the fracturing pump is a plunger pump with a head of 0.1-104kPa; and an electromagnetic flowmeter is arranged at the outlet of the fracturing pump.
5. The simulation apparatus of claim 1, wherein a steering switch is provided at a junction of the branch pipeline and the main pipeline.
6. The simulation device of claim 1, wherein the raw material of the fracture simulation rock sample comprises fibers, the length of the fibers is 0.1-10 cm, and the content of the fibers is 1-60%.
7. The simulation device of claim 1, wherein the shaft is a metal shaft with a thread on the surface, the cross section of the shaft is circular or oval with a twist in the axial direction, and the axial twist angle is 0-360 °; a sealing cover is arranged at the tail end of the shaft; the radius of the shaft with the circular cross section is 1-150 mm; the short radius of the shaft with the oval cross section is 1-75 mm, and the ratio of the long axis to the short axis is 1-2; the difference value between the major diameter D and the minor diameter D of the threads on the surface of the shaft is 0.1-5 cm, and the thread pitch of the threads is 0.1-15 cm; the number of the shafts is 1-5, the shaft type is a vertical shaft and/or a horizontal shaft, and the length of the shaft is 5-400 cm.
8. The simulation device of claim 7, wherein the surface of the shaft is uniformly or in clusters distributed with perforation holes, the diameter of each perforation hole is 1-20 mm, the phase of each perforation hole is 0-180 degrees, the density of the perforation holes is 8-96/m, and the number of the perforation holes is adjusted by means of nut sealing.
9. The simulation apparatus of claim 1, wherein the integrated control system controls power switches of the fracturing pump, electric blender, jack apparatus; and a system control panel of the integrated control system is provided with a frequency adjusting button of the fracturing pump, a pressure adjusting button of the jack, a displacement display and a pressure display.
10. Method of operating a simulation device according to any of the claims 1-9, characterized in that it comprises the following steps:
(1) assembling a shaft device, installing a tail end sealing cover, and determining the density of holes;
(2) preparing raw materials required by the preparation of a rock sample comprising fibers, consolidating the raw materials together with a shaft to prepare a reservoir simulation rock sample, and airing the rock sample to a state required by an experiment;
(3) installing a rock sample and a shaft to the inside of the fracturing simulation container, and fixing a jack on the front, rear, left, right and upper 5 wall surfaces of the rock sample;
(4) preparing a fracturing fluid system for experiments, and preparing a proppant material for fracturing;
(5) arranging a laboratory, moving experimental equipment to a proper position, connecting all experimental pipelines of the equipment, and checking the tightness of the pipelines;
(6) pouring the fracturing fluid material into a fracturing fluid stirring tank, so that the volume of the fluid accounts for 80-90% of the volume of the tank; filling a proppant material into a proppant stirring tank, wherein the volume of the proppant accounts for 3-25% of the volume of the tank;
(7) starting the jack device, and setting the confining pressure in the front-back direction, the left-right direction and the up-down direction;
(8) cutting off the communication between the main pipeline and the proppant stirring tank, communicating the branch pipeline, and starting the fracturing fluid electric stirrer;
(9) starting a fracturing pump and adjusting the frequency to the required discharge capacity, pumping the fracturing fluid into a shaft through the fracturing pump, and building high pressure in the rock sample to crack the rock sample;
(10) observing a rock sample pressure change curve of the integrated control display interface, and judging whether the rock sample cracks or not according to the curve;
(11) starting a propping agent electric stirrer after the rock sample is fractured;
(12) communicating a proppant stirring tank, closing a branch pipeline, allowing the fracturing fluid to enter the proppant stirring tank, mixing with the proppant to form a sand mixing fluid, allowing the sand mixing fluid to flow into a shaft through an adapter, and allowing the sand mixing fluid to enter artificial cracks in the rock sample;
(13) repeating the steps (8) to (12), and simulating the actual fracturing process on site;
(14) after the experiment is finished, closing the fracturing pump, the electric stirrer and unloading the pressure of the jack;
(15) storing and copying experimental data, and closing the integrated control system;
(16) and taking out the simulated rock sample, observing the expansion form of the fractured crack, analyzing the laying rule of the propping agent in the crack, arranging experimental instruments and materials, and cleaning a laboratory.
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| CN109297830A (en) * | 2018-11-27 | 2019-02-01 | 山东大学 | A kind of refracturing laboratory testing rig and its operating method |
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| CN110331970B (en) * | 2019-07-02 | 2021-07-02 | 中国石油天然气股份有限公司 | Multistage fracturing simulation experiment device |
| CN110685660B (en) * | 2019-11-01 | 2024-04-16 | 西南石油大学 | Device and method for realizing accurate control of concentration of sand-carrying fluid in proppant conveying experiment |
| CN113550725B (en) * | 2020-04-26 | 2024-04-09 | 四川宏华石油设备有限公司 | Electric fracturing operation system |
| CN111734376B (en) * | 2020-06-05 | 2022-12-20 | 西安科技大学 | Downhole high pressure liquid CO 2 Method for designing complete equipment for fracturing permeability-increasing coal rock |
| CN114062144A (en) * | 2020-08-03 | 2022-02-18 | 中国石油天然气股份有限公司 | Hydraulic sand fracturing experiment system and method |
| CN114607331B (en) * | 2020-11-24 | 2023-09-26 | 中国石油天然气股份有限公司 | Horizontal well sectional volume fracturing simulation test device and method |
| CN112943233B (en) * | 2021-04-23 | 2023-10-20 | 重庆大学 | Method for simulating proppant transport under reservoir conditions |
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| CN114320261B (en) * | 2022-01-17 | 2023-03-14 | 中国科学院武汉岩土力学研究所 | Migration simulation method of proppant in fracturing under true triaxial condition |
| CN115639083B (en) * | 2022-12-06 | 2023-03-21 | 新疆斐德莱布能源科技有限公司 | True triaxial hydraulic fracturing simulation experiment method and device for mine field level |
| CN117569788B (en) * | 2024-01-15 | 2024-03-29 | 中国矿业大学 | Deep thermal storage fracturing, seepage and displacement integrated testing device and method |
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