CN111236935A - Simulated CO2Experimental device and method for acid fracturing and acid etching crack process - Google Patents
Simulated CO2Experimental device and method for acid fracturing and acid etching crack process Download PDFInfo
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- CN111236935A CN111236935A CN202010120301.3A CN202010120301A CN111236935A CN 111236935 A CN111236935 A CN 111236935A CN 202010120301 A CN202010120301 A CN 202010120301A CN 111236935 A CN111236935 A CN 111236935A
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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
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
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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
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/164—Injecting CO2 or carbonated water
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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
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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
- E21B43/28—Dissolving minerals other than hydrocarbons, e.g. by an alkaline or acid leaching agent
- E21B43/283—Dissolving minerals other than hydrocarbons, e.g. by an alkaline or acid leaching agent in association with a fracturing process
Abstract
The invention discloses a simulated CO2The experimental device and the test method for the acid fracturing and acid etching crack process comprise CO2Conveying unit, acid liquor conveying unit and supercritical CO2The device comprises a liquid mixing tank for mixing with acid liquor and a rock plate clamp holder, wherein a rock plate is arranged in the rock plate clamp holder; CO 22The conveying unit and the acid liquor conveying unit respectively convey supercritical CO2Pumping the mixed fluid and the acid solution into a mixed fluid tank for mixing, injecting the obtained mixed fluid into a rock plate holder, and arranging a back pressure valve at a liquid outlet of the rock plate holder; the liquid mixing tank is a cylindrical tank body which is arranged in a sealing way, and supercritical CO is arranged at the bottom of the tank body2An inlet and a liquid inlet and outlet. A liquid outlet of the rock plate holder is sequentially connected with a back pressure valve, a cooling water jacket and CO2A separation tank, a waste liquid tank, CO2The separation tank is also connected withAnd (5) an acid liquor neutralization tank. The experimental device and method of the invention are used for accurately simulating CO2The real acid etching shape in acid fracturing provides special equipment and a test method.
Description
Technical Field
The invention relates to the technical field of oil and gas field exploitation, in particular to a CO simulation method applied to carbonate rock acid fracturing reformation2An experimental device and method for a process of acid fracturing and acid etching cracks.
Background
Acid fracturing is an important technical measure for the commissioning and production increase of carbonate oil and gas wells. The chemical reaction between acid liquid and rock on artificial (natural) crack wall to form high-seepage channel in the shape of channel or with raised surface can improve the seepage state of gas well and increase the yield of oil and gas well. However, when the conventional acid fracturing technology is adopted for low-pressure compact carbonate rock, two obvious limitations are realized: (1) the acid rock reaction rate is high, and the action distance in the acid stratum is small; (2) when a large amount of acid liquor enters the stratum, because the stratum pressure is low, the residual acid after reaction is difficult to flow back, and the damage to reservoir pores and acid fracturing cracks is increased due to the large retention of the acid liquor, so that the acid fracturing effect is reduced. CO 22Energizing acid fracturing, i.e. CO2Fluids for energy supplement of the formation and auxiliary fluids for slowing down the reaction rate of acid rock, CO in construction2The acid liquor and the ground surface are injected into the shaft separately and simultaneously, and then mixed in the shaft to form mixed fluid, and the mixed fluid enters the stratum, so that the reaction rate can be delayed, the using amount of the acid liquor can be reduced, the stratum energy can be increased, the liquid flowback efficiency can be improved, and the purpose of improving the acid fracturing effect can be realized; this technique has been tested for multiple wells at present abroad and has achieved good results (Sanchez Bernal, m., Tate, j., Idris, m., Soriano, j.e., Lopez, a.e.,&Fatkhutdinov,D..Acid Fracturing Tight Gas Carbonates Reservoirs Using CO2toAssist Stimulation Fluids:An Alternative to Less Water Consumption whileMaintaining Productivity[C]SPE 172913-MS), application No. 201910843809.3 also discloses a method for hypotonic heterogeneous carbonisationCO of sour rock gas reservoir2Acid fracturing method. CO 22In the process of energizing acid fracturing, CO2The phase state of the gas is influenced by temperature and pressure and is changed in a series, the gas is firstly stored in a liquid storage tank in a liquid form and then is injected into a shaft in the liquid form, and CO is generated under the combined action of high pressure at a well head and heating of the shaft2The temperature and pressure of the fluid gradually exceed CO2Critical point temperature, pressure (CO)2The critical temperature is 31 ℃, and the critical pressure is 7.38MPa), so as to reach a supercritical state; then supercritical CO2The mixed fluid with the acid liquor enters the hydraulic fracture and reacts with the rock on the wall surface of the fracture; CO 22The phase control and the control of the ratio in the mixed liquid (i.e. the degree of dryness of the foam) are CO2The key technology of the energizing acid fracturing process.
The experimental evaluation of the acid-etched crack flow conductivity is to know CO2The most direct and reliable means of the energy-increasing acid fracturing yield-increasing mechanism is also an important basis for acid fracturing construction design. CO 22The experimental simulation of the acid etching crack process after mixing with the acid liquor is the first step of experimental evaluation of the flow conductivity and is also an extremely complex and critical step; it simulates CO under reservoir conditions2In the energizing acid fracturing construction process, supercritical CO2The fluid mixed with the acid liquid flows in the hydraulic fracture and chemically reacts with the rock on the wall surface of the fracture, so that the real fracture form of the acid-etched rock sample is obtained, the acid-etched rock sample is provided for evaluating the flow conductivity of the acid-etched fracture, and meanwhile, the supercritical CO can be directly disclosed2The chemical reaction mechanism of the mixed fluid formed by the mixed fluid and the acid liquor and the rock is used for guiding and optimizing CO2The design of energy-increasing acid fracturing construction and the improvement of acid fracturing effect are of great significance.
At present, no simulated CO is seen in the published documents at home and abroad2The invention discloses an experimental device and method for acid etching crack process in acid fracturing process, and an invention patent with application number of 201010203373.0 discloses a test device and method for simulating acid etching crack flow conductivity, but the test device can not truly simulate CO2The main reason for acid etching cracks in energizing acid fracturing construction is that ① is lack of CO2Directly mixing with an acid liquid mixing device in a test pipeline to easily form a slug-shaped mixed fluid without② the rock sample holder has a long arc cylinder shape, the rock sample is loaded from the upper and lower parts of the cylinder cavity perpendicular to the flowing direction of the test medium, then two long arc cylinder pistons are installed, each piston has only one rubber ring for sealing, and the device can be used for carrying out CO mixing2The tail end waste liquid collection design in the ③ device process can not realize the gas-liquid separation of the mixed fluid, when the mixed fluid flows out of the back pressure valve, CO exists due to the sudden pressure reduction 2④ the whole flow pipeline is not designed with a heat insulation layer, so that heat loss and temperature are not easy to control in the flowing process of the tested fluid, and the supercritical CO in a stable phase state cannot be formed2Mixed fluid with acid liquor.
Therefore, it is urgently needed to develop a simulated CO2The experimental device and method for acid fracturing and acid etching of the crack process can accurately simulate CO2CO in acid fracturing construction process2The process of etching cracks with the mixed fluid formed by the acid liquor obtains the real acid etching appearance, provides samples for experimental evaluation of the flow conductivity, and simultaneously discloses the mechanism of etching rock samples with the mixed fluid to guide optimization of CO2The acid fracturing construction scheme is optimized and designed, and the acid fracturing effect is improved.
Disclosure of Invention
The invention aims to solve the problem that the prior art is lack of the capability of accurately simulating CO through experiment2The current situation of the acid fracturing and acid etching crack process provides a simulation CO2An experimental device and method for a process of acid fracturing and acid etching cracks.
The technical scheme is as follows:
the simulated CO provided by the invention2The experimental device for the acid fracturing and acid etching cracking process structurally comprises CO2Conveying unit, acid liquor conveying unit and supercritical CO2The device comprises a liquid mixing tank for mixing with acid liquor and a rock plate clamp holder, wherein a rock plate is arranged in the rock plate clamp holder; CO 22The conveying unit and the acid liquor conveying unit respectively convey supercritical CO2And pumping the mixed fluid into a mixed fluid tank with acid liquor to be mixed, injecting the obtained mixed fluid into the rock plate holder, and setting a back pressure valve at a liquid outlet of the rock plate holder.
The liquid mixing tank is a cylindrical tank body which is arranged in a sealing way, and supercritical CO is arranged at the bottom of the tank body2An inlet and a liquid inlet and outlet. And the outer surface of the liquid mixing tank is coated with a heat insulation material layer to completely wrap the liquid mixing tank. A temperature sensor and a pressure sensor are arranged in the liquid mixing tank, and a visual window and liquid volume scale marks are arranged on the liquid mixing tank.
A liquid outlet of the rock plate holder is sequentially connected with a back pressure valve, a cooling water jacket and CO2A separation tank, a waste liquid tank, CO2A separation tank and an acid liquor neutralization tank.
The acid liquor conveying unit comprises an acid liquor tank, a first plunger pump and a preheating device, the acid liquor tank is connected with the first plunger pump, a liquid outlet of the first plunger pump is connected with the preheating device, a liquid outlet pipe of the preheating device is connected with a three-way joint, and the other two interfaces of the three-way joint are respectively connected with the mixed liquor tank and the rock plate holder; valve switches are arranged on pipelines between the three-way joint and the preheating device, between the three-way joint and the liquid mixing tank and between the three-way joint and the rock plate holder; and pipeline heat-insulating layers are wrapped on the outer surfaces of the pipeline between the three-way joint and the mixed liquid tank and the pipeline between the three-way joint and the rock plate holder. And a second plunger pump and a liquid flowmeter are arranged on a pipeline between the three-way joint and the rock plate holder.
The CO is2The transport unit comprises CO2Gas cylinder, CO2Storage tank, cooling tank, CO2Booster pump, liquid flowmeter, electric heating jacket. CO 22Gas cylinder is connected with CO through gas pipeline2Storage tank, CO2The storage tank is arranged in a cooling tank, and the cooling tank is filled with liquid cooling medium to remove CO2The storage tank is completely wrapped in CO2Gas CO in storage tank2Cooling to liquid state; CO 22The liquid outlet of the storage tank is connected with CO2Booster pump, and in CO2Liquid outlet of storage tank and CO2A liquid flowmeter is arranged on a pipeline between the booster pumps; the liquid outlet of the booster pump is connected with the supercritical CO at the bottom of the liquid mixing tank2And (4) an inlet. On the gas line with CO2Storage tankOne end of the connection is spiral and is positioned in the cooling groove. The CO is2The connecting pipeline between the booster pump and the liquid mixing tank is CO-resistant2The outer wall of the corroded pipeline is provided with an electric heating jacket.
In the experimental device, the electric heating sleeve on the outer wall of the pipeline is used for heating liquid CO2Heating to supercritical CO2The required critical temperature is that the heat preservation of the mixed liquid tank is realized by the heat preservation material layer on the outer surface of the tank body, the heat preservation of the pipeline from the mixed liquid tank to the clamp holder is realized by the pipeline heat preservation layer, and the CO in the flowing system is ensured2Is in a supercritical state. CO 22Booster pump injecting supercritical CO2Entering a liquid mixing tank, and controlling the pressure of mixed fluid in the liquid mixing tank; the preheating device controls the temperature of the mixed fluid in the mixed fluid tank, a temperature sensor and a pressure sensor are arranged in the mixed fluid tank, and the pressure and the temperature of the fluid in the mixed fluid tank are monitored in real time; the liquid mixing tank is provided with a visual window, and the liquid interface and the fluid state change in the liquid mixing tank can be observed in real time. The pressure in the back pressure valve control system is higher than that of CO2Critical pressure to ensure CO in the mixed fluid2And simulating the real flow state of the mixed fluid under the reservoir condition in a supercritical state. The cooling water jacket cools the reacted mixed fluid, so that potential safety hazards caused by acid mist formed by high-temperature acid liquid during pressure sharp drop are effectively avoided. CO 22The separator can realize gas-liquid separation, the acid liquor flows out from the lower part and enters a waste liquid tank, and CO is discharged2The gas flows out from the upper part and enters an acid liquor neutralization tank; the acid liquor neutralization tank passes through NaOH and CO2Neutralizing reaction of small amount of acid mist in gas to separate high purity CO2And the gas enters the water tank to further dissolve acid mist, so that the safety of waste gas emission is ensured.
Adopt above-mentioned simulation CO2The method for carrying out the experiment test by the experiment device in the process of acid fracturing and acid etching cracks comprises the following steps:
(1) device installation: the experimental rock plate is arranged in a rock plate clamp holder and sealed, and a device is debugged to ensure that the pipeline has no leakage;
(2) preheating a device: respectively setting the working temperatures of the pipeline electric heating sleeve and the preheating device as the fluid temperatures of experimental design;
(3) fluid mixing: wait that pipeline heating jacket and preheating device temperature are steadyAfter the determination, pumping the acid liquor with the experimental design quantity into the liquid mixing tank by the plunger pump I; after the temperature and the pressure in the liquid mixing tank are stable, reading the volume V of the acid liquid from the visual window of the liquid mixing tankl(ii) a Then using CO2The booster pump can be used for supplying experimental design amount of supercritical CO at a certain flow rate2Also injected into the liquid mixing tank, requiring CO2The output pressure of the booster pump is more than 8 MPa; after the temperature and the pressure in the mixing tank are stable, closing all valves, starting a stirrer in the liquid mixing tank to stir and mix until the fluid is fully mixed and reaches the experimental design temperature, wherein the pressure in the tank is more than 8 MPa; reading the temperature T and the pressure p of the stable mixed fluid, and reading CO from a visual window of the mixed fluid tank2Volume V of mixed fluid formed with acid liquidmAt temperature T, pressure p, the foam dryness Γ is calculated according to the following formula:
(4) mixed fluid etching cracks: adjusting the pressure of a back pressure valve to 8MPa, injecting the mixed fluid in the mixed fluid tank into the rock plate holder by a plunger pump II, carrying out flow reaction along the fracture surface of the rock plate, and monitoring and recording the temperature T and the pressure p of the mixed tank and the flow of the mixed fluid in the displacement process in real time until the experiment is finished;
(5) etching the rock plate and post-treating: and after the experiment is finished, taking out the etched rock plate in the rock plate holder, carrying out laser scanning on the etched appearance of the surface of the rock sample, acquiring and analyzing the appearance data of the crack, and providing the acid-etched rock sample for the experimental test of the flow conductivity.
Compared with the prior art, the pipeline for conveying mixed fluid has the beneficial effects that the pipeline ① adopts a heat insulation layer design, and the outlet of the rock plate holder is provided with the back pressure valve, so that the supercritical CO in the fluid flowing process is ensured2Stable phase state, and can truly simulate CO2Acid pressure acid etching process ② CO2Booster pump injecting supercritical CO2Entering the mixed liquid tank, controlling the mixed liquid pressure in the mixed liquid tank, controlling the temperature of the mixed liquid in the mixed liquid tank by the pipeline electric heating jacket and the preheating device, and simultaneously, arranging a temperature sensor and a pressure sensor in the mixed liquid tank for monitoring the tank in real timeInternal temperature and pressure, and can realize supercritical CO in stable phase state2Mixing with acid solution uniformly to reach true simulation of supercritical CO2Mixing effect with acid liquor in a shaft; the liquid mixing tank is provided with a visual window and liquid volume scale marks, the volume of the mixed liquid can be accurately read, and CO can be calculated2③ the multistage separation method is used to cool the waste liquid and separate gas and liquid, and avoid CO from suddenly dropping2④ the device has the advantages of no CO 2⑤ the simulation device provided by the invention has reliable principle and feasible test method, can accurately simulate the formation conditions in the acid fracturing process to obtain the real acid-etched rock sample wall morphology, has good experimental result adaptability, and is suitable for researching supercritical CO2The acid fracturing provides a special experimental device and a test method; and is also suitable for nitrogen foam acid fracturing crack etching experiment simulation.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
FIG. 1, the simulated CO provided by the invention2The structural schematic diagram of the experimental device for the acid fracturing and acid etching cracking process.
Figure 2, outline drawing of the rock plate holder.
Figure 3, a cross-section of the rock plate holder shown in figure 2, taken in a horizontal section a-a.
Figure 4, a cross-section of the rock plate holder in longitudinal section B-B shown in figure 2.
Reference numbers in the figures:
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
As shown in FIG. 1, a simulated CO2The experimental device for the acid fracturing and acid etching cracking process structurally comprises CO2Conveying unit, acid liquor conveying unit and supercritical CO2The device comprises a liquid mixing tank 1 for mixing acid liquor and a rock plate holder 2, wherein a rock plate is arranged in the rock plate holder; CO 22The conveying unit and the acid liquor conveying unit respectively convey supercritical CO2And acid liquor is pumped into the mixed liquor tank 1 for mixing, and the obtained mixed fluid is injected into the rock plate holder 2. A liquid outlet of the rock plate holder is sequentially connected with a back pressure valve 3, a cooling water jacket 4 and CO2A separation tank 5, a waste liquid tank 6, CO2The separating tank is also connected with an acid liquor neutralizing tank 7. NaOH solution is filled in the acid liquor neutralization tank. The cooling water jacket cools the mixed fluid, so that potential safety hazards caused by acid mist formed by high-temperature acid liquid when the pressure drops sharply are effectively avoided. CO 22The separation tank can realize gas-liquid separation, the acid liquor flows out from the lower part and enters the waste liquid tank, and CO is discharged2The gas flows out from the upper part and enters an acid liquor neutralization tank; the acid liquor neutralization tank passes through NaOH and CO2Neutralizing reaction of small amount of acid mist in gas to separate high purity CO2And the gas enters the water tank to further dissolve acid mist, so that the safety of waste gas emission is ensured.
The liquid mixing tank 1 is a cylindrical tank body which is arranged in a sealing way, and supercritical CO is arranged at the bottom of the tank body2An inlet and a liquid inlet and outlet. The liquid mixing tank is made of heat preservation and insulation materials, and is further limited, and the outer surface of the liquid mixing tank is completely coated with a tank body heat preservation layer and used for preserving the heat of the liquid in the liquid mixing tank. And a temperature sensor 13 and a pressure sensor 14 are also arranged in the tank body, so that the pressure and the temperature of the fluid in the liquid mixing tank can be monitored in real time.
The acid liquor conveying unit comprises an acid liquor tank 15, a first plunger pump 16 and a preheating device 17. The acid liquor tank is connected with the first plunger pump 16, the liquid outlet of the first plunger pump 16 is connected with the preheating device 17, the acid liquor is preheated by winding an acid liquor pipeline on the heating rod, the liquid outlet pipe of the preheating device is connected with the three-way joint 36, and the other two interfaces of the three-way joint 36 are respectively connected with the mixed liquor tank 1 and the rock plate clamp holder 2. The preheating device 17 heats the acid liquor to the experimental design temperature (higher than CO)2The supercritical point temperature of 31 ℃). A valve switch 8 is arranged on a pipeline between the three-way joint 36 and the preheating device 17, a valve switch 9 is arranged on a pipeline between the three-way joint 36 and the mixed liquid tank 1, and a valve switch 10 is arranged on a pipeline between the three-way joint 36 and the rock plate holder 2. And the outer surfaces of the pipeline between the three-way joint 36 and the mixed liquid tank 1 and the pipeline between the three-way joint 36 and the rock plate holder 2 are wound with heat insulation layers 20 made of polyurethane heat insulation materials. The pipeline heat-insulating layer 20 realizes the heat insulation of the pipeline from the mixed liquid tank 1 to the clamp holder 2, and ensures CO in the flowing system2Is in supercritical state and stable. And a second plunger pump 18 and a liquid flow meter 19 are arranged on a pipeline between the three-way joint 36 and the rock plate holder 2.
The CO is2The transport unit comprises CO2Gas cylinder 21, CO2Storage tank 22, cooling tank 23, CO2A booster pump 24, a liquid flow meter 25 and an electric heating jacket 26. CO 22The gas cylinder 21 is connected with CO through a gas pipeline2Storage tank 22, CO2The storage tank 22 is arranged in a cooling tank 23, and the cooling tank 23 is filled with liquid cooling medium to remove CO2The storage tank 22 is completely wrapped in CO2CO gas in the storage tank 222Cooling to liquid state. The cooling medium is a mixed solution of water and ethanol, and the temperature of the cooling medium is 0-5 ℃. CO 22The liquid outlet of the storage tank 22 is connected with CO 224 of booster pump and in CO2The outlet of the storage tank 22 and CO2A liquid flow meter 25 is arranged on a pipeline between the booster pumps 24; CO 22The liquid outlet of the booster pump 24 is connected with the supercritical CO at the bottom of the liquid mixing tank 12Is imported and is in CO2A valve switch 11 is arranged on a pipeline between the booster pump 24 and the mixed liquid tank 1. On the gas line with CO2One end of the storage tank 22 is in a spiral shape and is positioned in the cooling tank23, adding CO gas2Residence time in cooling tank, so that CO2And fully liquefying. The CO is2The connecting pipeline between the booster pump 24 and the liquid mixing tank 1 is CO-resistant2The outer wall of the corroded pipeline is provided with an electric heating jacket 26. Electric heating jacket for mixing liquid CO2Is heated to a temperature greater than CO2The supercritical temperature of the mixed solution is 31 ℃, and CO is ensured to enter the mixed solution tank 12The phase state of (A) is supercritical state.
In another embodiment, the rock plate holder 2 may be a holder of the following construction. As shown in fig. 2-4, the main body of the rock plate holder 2 is a rectangular box body, the left end and the right end of the box body are respectively provided with a liquid inlet and a liquid outlet, the liquid inlet is connected with a liquid inlet piston 27, the liquid outlet is connected with a liquid outlet piston 28, a fluid flow passage in the piston is arranged into a horn-shaped diversion trench 29, the horns of the two pistons are arranged oppositely, and a cavity between the two pistons is a rock plate chamber. The liquid inlet piston and the liquid outlet piston are arranged on the box body through screws 35. The rock plate indoor installation is a pair of rock plates 30 which are horizontally placed and overlapped, a gap 37 is reserved between the two rock plates for simulating the width of a crack, and 4 side faces parallel to the length direction of the rock plates on the rock plates are completely pasted and covered with CO resistance2Corroding the rubber 31, covering a steel plate 32 on the outer side of the rubber, and vertically installing fastening screws 33 on 4 side faces of the box body, which are opposite to the steel plate. The upper side and the lower side are provided with at least 2 fastening screws. At least 4 fastening screws are arranged on the front side and the rear side. The gap between the two rock plates can be adjusted by adjusting the fastening screws on the upper side and the lower side, so that the width of the simulated crack is achieved. The steel plate is pushed to extrude the rubber to seal the side face of the rock plate by adjusting the fastening screws on the front side face and the rear side face. Ensuring that the mixed fluid flows and reacts only along the reserved cracks. A deep through hole, namely a heating hole 34, is drilled in the box body along the flowing direction of the fluid and is used for inserting an electric heating rod.
Using the simulated CO2The method for carrying out the experimental test by the experimental device for the acid fracturing and acid etching crack process comprises the following steps:
(1) device installation: firstly, cutting reservoir rock into a pair of rock plates 30 which accord with the size of an inner cavity of a rock plate holder, wherein the length of each rock plate is 176mm, the width is 36mm, and the thickness is 25 mm; two rock plates are horizontally weightedStacking, leaving gaps between the rock plates, and sticking CO-resistant films on four sides parallel to the length direction of the rock plates2Corroding the rubber 31, attaching a steel plate 32 on the outer surface of the rubber, and then placing the rock plate coated with the steel plate in a rock plate chamber of the rock plate holder 2; fastening the steel plate using a fastening screw 33; then a liquid inlet piston 27 and a liquid outlet piston 28 are additionally arranged to complete the installation of the rock plate holder 2; finally, further installing and debugging the whole set of test device to ensure that the pipeline has no leakage;
(2) preheating a device: setting the working temperature of the pipeline electric heating sleeve 26 and the preheating device 17 to be the fluid temperature of experimental design and preheating to the experimental design temperature, and inserting an electric heating rod into the heating hole 34 of the rock plate holder 2 to heat to the experimental design temperature;
(3) fluid mixing: after the temperature of the pipeline electric heating jacket 26 and the preheating device 17 is stable, the valve 8 and the valve 9 are opened, the valve 10 and the valve 11 are closed, and the first plunger pump 16 pumps the acid liquor with the experimental design quantity into the liquid mixing tank 1; after the temperature and the pressure in the liquid mixing tank 1 are stable, reading the volume V of the acid liquor from the visual window of the liquid mixing tankl(ii) a Opening valve 11, closing valve 8, valve 9 and valve 10, and adopting CO2The booster pump 24 will experimentally design the amount of supercritical CO at a certain flow rate2Also injected into the mixed liquid tank 1, and requires CO2The input pressure of the booster pump 24 is more than 8 MPa; after the temperature and the pressure in the mixing tank 1 are stable, all valves are closed, a stirrer in the mixing tank 1 is started to stir and mix until the fluid is fully mixed and reaches the experimental design temperature, and the pressure in the tank is more than 8 MPa; reading the temperature T and the pressure p of the stable mixed fluid, and reading CO from the visual window of the mixed fluid tank 12Volume V of mixed fluid formed with acid liquidmAt temperature T, pressure p, the foam dryness Γ is calculated according to the following formula:
for example, the temperature of the stable mixed fluid in the mixed fluid tank is 80.0 ℃, the pressure is 10.0MPa, and the volume V of the acid liquid is measured by experimentsl15L, volume V of mixed fluidmAt 21L, the calculated foam dryness was 28.6%.
(4) Mixed fluid etching cracks: opening a valve 9 and a valve 10, closing a valve 8 and a valve 11, adjusting the pressure of a back pressure valve 3 to 8MPa, injecting the mixed fluid in the mixed fluid tank 1 into the rock plate holder 2 by a plunger pump II 18, carrying out flow reaction along the fracture surface of the rock plate, and monitoring and recording the temperature and the pressure of the mixed fluid tank 1 and the flow 19 in the mixed fluid displacement process in real time until the experiment is finished;
(5) etching the rock plate and post-treating: and after the experiment is finished, taking out the etched rock plate 30 in the rock plate holder 2, carrying out laser scanning on the etched appearance of the surface of the rock sample, acquiring and analyzing the appearance data of cracks, and providing the acid-etched rock sample for the experimental test of the flow conductivity.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. Simulated CO2The experimental device for the acid fracturing and acid etching crack process is characterized by comprising CO2Conveying unit, acid liquor conveying unit and supercritical CO2The device comprises a liquid mixing tank for mixing with acid liquor and a rock plate clamp holder, wherein a rock plate is arranged in the rock plate clamp holder; CO 22The conveying unit and the acid liquor conveying unit respectively convey supercritical CO2Pumping the mixed fluid and the acid solution into a mixed fluid tank for mixing, injecting the obtained mixed fluid into a rock plate holder, and arranging a back pressure valve at a liquid outlet of the rock plate holder;
the liquid mixing tank is a cylindrical tank body which is arranged in a sealing way, and supercritical CO is arranged at the bottom of the tank body2An inlet and a liquid inlet and outlet;
a liquid outlet of the rock plate holder is sequentially connected with a back pressure valve, a cooling water jacket and CO2A separation tank, a waste liquid tank, CO2The separating tank is also connected with an acid liquor neutralizing tank;
the CO is2The transport unit comprises CO2Gas cylinder, CO2Gas cylinder is connected with CO through gas pipeline2Storage tank, CO2The storage tank is arranged in a cooling tank, and the cooling tank is filled with liquid cooling medium to remove CO2The storage tank is completely wrapped in CO2Gas CO in storage tank2Cooling to liquid state; CO 22The liquid outlet of the storage tank is connected with CO2Booster pump, and in CO2Liquid outlet of storage tank and CO2A liquid flowmeter is arranged on a pipeline between the booster pumps; the liquid outlet of the booster pump is connected with the supercritical CO at the bottom of the liquid mixing tank2And (4) an inlet.
2. The simulated CO of claim 12The experimental device for the acid fracturing acid etching cracking process is characterized in that the acid liquid conveying unit comprises an acid liquid tank, a first plunger pump and a preheating device, the acid liquid tank is connected with the first plunger pump, a liquid outlet of the first plunger pump is connected with the preheating device, a liquid outlet pipe of the preheating device is connected with a three-way joint, and the other two interfaces of the three-way joint are respectively connected with a liquid mixing tank and a rock plate clamp holder; valve switches are arranged on pipelines between the three-way joint and the preheating device, between the three-way joint and the liquid mixing tank and between the three-way joint and the rock plate holder; and pipeline heat-insulating layers are wrapped on the outer surfaces of the pipeline between the three-way joint and the mixed liquid tank and the pipeline between the three-way joint and the rock plate holder.
3. The simulated CO of claim 12The experimental device for the acid fracturing and acid etching crack process is characterized in that the gas pipeline is connected with CO2One end of the storage tank is in a spiral shape and is positioned in the cooling groove.
4. The simulated CO of claim 12The experimental device for the acid fracturing and acid etching crack process is characterized in that the CO is2The connecting pipeline between the booster pump and the liquid mixing tank is CO-resistant2The outer wall of the corroded pipeline is provided with an electric heating jacket.
5. The simulated CO of claim 12The acid fracturing experimental device is characterized in that the outer surface of the liquid mixing tank is coated with a heat preservation material layer to completely wrap the liquid mixing tank.
6. The simulated CO of claim 52The experimental device for the acid fracturing and acid etching cracking process is characterized in that a temperature sensor and a pressure sensor are arranged in the liquid mixing tank.
7. The simulated CO of claim 12The experimental device for the acid fracturing and acid etching cracking process is characterized in that a plunger pump II and a liquid flowmeter are arranged on a pipeline between the three-way joint and the rock plate holder.
8. Use of a simulated CO according to any of claims 1-72The method for carrying out the test experiment by using the experimental device for the acid fracturing and acid etching crack process comprises the following steps:
(1) device installation: the experimental rock plate is arranged in a rock plate clamp holder and sealed, and a device is debugged to ensure that the pipeline has no leakage;
(2) preheating a device: respectively setting the working temperatures of the pipeline electric heating sleeve and the preheating device as the fluid temperatures of experimental design;
(3) fluid mixing: after the temperature of the pipeline heating sleeve and the temperature of the preheating device are stable, pumping the acid liquor with the experimental design quantity into the liquid mixing tank by the plunger pump I; after the temperature and the pressure in the liquid mixing tank are stable, reading the volume V of the acid liquid from the visual window of the liquid mixing tankl(ii) a Then using CO2The booster pump can be used for supplying experimental design amount of supercritical CO at a certain flow rate2Also injected into the liquid mixing tank, requiring CO2The output pressure of the booster pump is more than 8 MPa; after the temperature and the pressure in the mixing tank are stable, closing all valves, starting a stirrer in the liquid mixing tank to stir and mix until the fluid is fully mixed and reaches the experimental design temperature, wherein the pressure in the tank is more than 8 MPa; reading the temperature T and the pressure p of the stable mixed fluid, and reading CO from a visual window of the mixed fluid tank2Volume V of mixed fluid formed with acid liquidmAt temperature T, pressure p, the foam dryness Γ is calculated according to the following formula:
(4) mixed fluid etching cracks: adjusting the pressure of the back pressure valve to 8 MPa; injecting the mixed fluid in the mixed fluid tank into the rock plate holder by the plunger pump II, performing flow reaction along the fracture surface of the rock plate, and monitoring and recording the temperature T and the pressure p of the mixed tank and the flow of the mixed fluid in the displacement process in real time until the experiment is finished;
(5) etching the rock plate and post-treating: and after the experiment is finished, taking out the etched rock plate in the rock plate holder, carrying out laser scanning on the etched appearance of the surface of the rock sample, acquiring and analyzing the appearance data of the crack, and providing the acid-etched rock sample for the experimental test of the flow conductivity.
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