Device and method for evaluating flow conductivity of propping agent cracks under acidizing and fracturing actions
Technical Field
The invention relates to a device and a method for evaluating conductivity of a proppant fracture under an acid fracturing action, and belongs to the technical field of petroleum and natural gas engineering.
Background
With the change of oil and gas reservoir development from a conventional reservoir to an unconventional reservoir, the hydraulic fracturing generally utilizes preposed acid liquor to erode reservoir rock, reduces fracture pressure, forms a complex fracture network, prevents the fracture from closing after fracturing is finished by pumping fracturing fluid carrying proppant, maintains a high-conductivity fracture with a certain width, becomes an oil and gas high-speed seepage channel, and improves the recovery ratio. Injecting acid liquor after fracturing is finished, so that gel breaking of the fracturing fluid can be accelerated, residues can be dissolved, and the flow conductivity of the fracture can be further improved; in addition, for the fractured low-yield old well, the purpose of restoring the productivity is achieved by injecting acid liquor to remove the blockage. In the acid liquor treatment process, the proppant particles are dissolved, the volume and the mass are reduced, the compressive strength is reduced, and the effective fracture width and the final flow conductivity are difficult to maintain, so the real flow conductivity of the fracture after acid etching needs to be further evaluated.
The conventional fracture conductivity evaluation is to test the conductivity of the fracture under different closing pressure conditions by taking fracturing fluid as fluid, and the influence of acid liquid on proppant particles is not considered; then, researchers design a fracture conductivity testing device for acid fracturing, but only test the conductivity after acid etching, and do not evaluate the damage degree of the conductivity before and after acid etching; in addition, the reaction of acid and proppant under simulated reservoir temperature conditions can better characterize real formation conditions.
Therefore, research on an evaluation device for fracture conductivity of the acid fracturing propping agent under the condition of simulating the reservoir is urgently needed.
Disclosure of Invention
Aiming at the problem of the conventional fracture conductivity evaluation, the invention provides a proppant fracture conductivity evaluation device and method under the action of acidizing fracturing, namely, the corrosion action of acid liquid on proppant particles and rock plates is considered, the acid resistance and the conductivity maintaining capacity of the proppant particles are evaluated by testing the conductivity of the proppant fracture before and after acidizing, and the optimization of proper proppant is facilitated.
An evaluation device for fracture conductivity of acidizing fracturing propping agent comprises a flow guide chamber 1, a differential pressure sensor 2, a constant-speed constant-pressure pump 3, an acid liquid container 4, a fracturing liquid container 5, a first gas supply device 6, a pressure reducing valve 7, a heater 8, a vacuum pump 9, a back pressure valve 10, a second gas supply device 11, an acid liquid collector 12 and a fracturing liquid collector 13,
the constant-speed constant-pressure pump 3 is communicated with an acid liquid container 4 through a first pressure supply pipe, the constant-speed constant-pressure pump 3 is communicated with a fracturing liquid container 5 through a second pressure supply pipe, a lower rock plate and an upper rock plate which are matched with a cavity in the flow guide chamber 1 are arranged in the flow guide chamber 1, a propping agent is filled between the lower rock plate and the upper rock plate, a first conveying pipe communicated with the flow guide chamber 1 is arranged at the inlet end of the flow guide chamber 1, the acid liquid container 4 is communicated with the first conveying pipe through a first acid liquid pipe, the fracturing liquid container 5 is communicated with the first conveying pipe through a first fracturing liquid pipe, a first air supply device 6 is communicated with the first conveying pipe through a first air supply pipe, the outlet of the flow guide chamber 1 is communicated with a vacuum pump 9 and a back-pressure valve 10 through a vacuum pipe and a second conveying pipe respectively, the back-pressure valve 10 is communicated with an acid liquid collector 12 through a second acid liquid pipe, and the back-pressure valve 10 is communicated with a fracturing liquid collector 13 through a second fracturing liquid pipe;
the first conveying pipe is provided with a heater 8, and a second air supply device 11 is communicated with a back pressure valve 10 through a second air supply pipe;
the inlet end, the middle part and the outlet end of the diversion chamber 1 are respectively provided with a pressure measuring point A, a pressure measuring point B and a pressure measuring point C, and a differential pressure sensor 2 is arranged among the pressure measuring point A, the pressure measuring point B and the pressure measuring point C.
Acid liquor is stored in an acid liquor container 4, fracturing fluid is stored in a fracturing fluid container 5, when acid fracturing is simulated, the acid liquor is injected into the diversion chamber 1 at a constant speed through the constant-speed constant-pressure pump 3, and due to the corrosivity of the acid liquor, the acid liquor flowing out of the diversion chamber 1 is collected by an acid liquor collector 12; injecting fracturing fluid into the flow guide chamber 1 at a constant speed through the constant-speed constant-pressure pump 3, collecting the fracturing fluid flowing out of the flow guide chamber 1 by a fracturing fluid collector 13 with a precision balance, and calculating the flow;
the first gas supply device 6 is a first nitrogen bottle, nitrogen is pumped and flows through the flow guide chamber 1, and after the flow guide capacity of the fracturing fluid in the previous stage is measured, the fracturing fluid in the flow guide chamber 1 and the pipeline is removed by using gas to prevent the acid liquor in the next stage from being diluted; after acid fracturing is simulated, the gas is used again to remove acid liquor in the diversion chamber 1 and the pipeline.
An upper piston hole and a lower piston hole are formed in the middle of the diversion chamber 1, an upper piston 1.1 matched with the upper piston hole is arranged in the upper piston hole in a sliding mode, an upper piston horizontal plate is arranged at the top end of the upper piston 1.1, a lower piston 1.2 matched with the lower piston hole is arranged in the lower piston hole in a sliding mode, a lower piston horizontal plate is arranged at the bottom end of the lower piston 1.2, and a photoelectric displacement sensor 1.3 is arranged on the lower piston horizontal plate; the photoelectric displacement sensor 1.3 is used for monitoring the width change of the support crack in the experimental process;
during fracture diversion test of the acidizing fracturing propping agent, a polished lower rock plate is filled in a filling chamber, propping agent particles are laid on the lower rock plate, the propping agent is filled in simulated stratum rock fractures, and then an upper rock plate is placed on the propping agent particles; and pressurizing the upper piston 1.1 and the lower piston 1.2 by using a pressurizing machine to simulate the closing pressure of the formation fracture.
A pressure reducing valve 7 is arranged at the outlet end of the first gas supply device 6, a first heating sleeve is arranged on the outer side wall of the acid liquid container 4, a second heating sleeve is arranged on the outer side wall of the fracturing liquid container 5, a temperature sensor T2 is arranged in the fracturing liquid container 5, a temperature sensor T3 is arranged in the acid liquid container 4, a temperature sensor T4 is arranged in the heater 8, a temperature sensor T1 is arranged in the diversion chamber 1, a pressure sensor P1 is arranged at the inlet end of the diversion chamber 1, a pressure sensor P2 is arranged at the outlet end of the diversion chamber 1, a pressure sensor P3 is arranged on the first gas supply pipe, and a pressure sensor P4 is arranged in the back-pressure valve 10; the fluid flowing through the diversion chamber 1 is controlled to flow out under the condition of stable pressure by a back pressure valve 10, so that the flow is kept stable;
a first pressure measuring pipe, a second pressure measuring pipe and a third pressure measuring pipe which are sequentially communicated are arranged between a pressure measuring point A and a pressure measuring point B of the diversion chamber 1, the first pressure measuring pipe is communicated with the pressure measuring point A, the third pressure measuring pipe is communicated with the pressure measuring point B, a third pressure measuring pipe, a fourth pressure measuring pipe and a fifth pressure measuring pipe which are sequentially communicated are arranged between the pressure measuring point B and the pressure measuring point C, the fourth pressure measuring pipe is communicated with the second pressure measuring pipe, the junction of the first pressure measuring pipe and the second pressure measuring pipe is an intersection C, the junction of the fourth pressure measuring pipe and the fifth pressure measuring pipe is an intersection D, and a differential pressure sensor 2 is arranged between the intersection C and the intersection D;
by utilizing different combinations among the pressure measuring points A, B and C, the pressure difference of the front end, the rear end and the whole of the crack can be tested, and the flow conductivity at different positions can be calculated.
The first pressure supply pipe is provided with a first control valve 22, the second pressure supply pipe is provided with a second control valve 23, the first fracturing liquid pipe is provided with a third control valve 24, the first acid liquid pipe is provided with a fourth control valve 25, the first gas supply pipe is provided with a fifth control valve 26, the first conveying pipe is provided with a sixth control valve 27, the first pressure measurement pipe is provided with a seventh control valve 28, the fifth pressure measurement pipe is provided with an eighth control valve 29, the second pressure measurement pipe is provided with a ninth control valve 30, the fourth pressure measurement pipe is provided with a tenth control valve 31, the vacuum pipe is provided with an eleventh control valve 32, the second conveying pipe is provided with a twelfth control valve 33, the second gas supply pipe is provided with a thirteenth control valve 34, the second acid liquid pipe is provided with a fourteenth control valve 35, and the second fracturing liquid pipe is provided with a fifteenth control valve 36.
The diversion chamber is a standard API diversion chamber, the length is 17.78cm, the width is 3.81cm, and the distance between pressure measuring points at two ends is 12.7cm.
The structural parts and pipelines of the device for evaluating the fracture conductivity of the acid fracturing propping agent adopt Hastelloy, have high compressive strength and high temperature resistance, can simulate the reservoir conditions with the highest temperature of 150 ℃ and the highest closing pressure of 200MPa, and ensure the safety of the experiment.
A fracture conductivity evaluation method of an acid fracturing propping agent adopts the fracture conductivity evaluation of the acid fracturing propping agent, and comprises the following specific steps:
s1, preparing a flow guide chamber: placing the cut and polished lower rock plate in a cavity of a diversion chamber, laying proppant particles with preset thickness on the lower rock plate, then placing an upper rock plate on the proppant particles, and pressurizing the upper rock plate and the lower rock plate by using a pressurizing machine through an upper piston and a lower piston to simulate formation fracture closing pressure; meanwhile, heating the acid liquid in the acid liquid container to a preset temperature through a first heating sleeve sleeved on the outer side of the acid liquid container, and heating the fracturing liquid in the fracturing liquid container to the preset temperature through a second heating sleeve sleeved on the outer side of the fracturing liquid container to reach the temperature and pressure conditions of the diversion capability test;
s2, vacuumizing: vacuumizing the flow guide chamber through a vacuum tube and a vacuum pump to ensure that the flow guide chamber can be completely filled with subsequent injected fluid, namely fracturing fluid or acid liquid;
s3, testing the flow conductivity of the early-stage fracturing fluid: opening a constant-speed constant-pressure pump, setting the flow of fracturing fluid of an experiment, injecting the fracturing fluid into a flow guide chamber through a first fracturing fluid pipe, opening a heater to heat the fracturing fluid in the first fracturing fluid pipe, opening a back pressure valve, setting back pressure, testing the differential pressure of different pressure measurement points of the flow guide chamber through a differential pressure sensor, and calculating to obtain the flow guide capacity k of the fracturing fluid in the early stage of the supporting crack 1 W f1 。
S4, primary gas injection and evacuation: after the test of the flow conductivity of the early-stage fracturing fluid is finished, closing the constant-speed constant-pressure pump, the fracturing fluid container and the differential pressure gauge, starting the gas supply device to inject gas into the flow guide chamber, and discharging residual fracturing fluid;
s5, acid injection and acidification: opening the constant-speed constant-pressure pump, setting the acid liquid flow of the experiment, closing the differential pressure meter, injecting the acid liquid into the diversion chamber through the first acid liquid pipe for acidification treatment, and controlling the volume of the acid liquid injected into the diversion chamber and the acidification treatment time according to the experimental design;
s6, secondary gas injection and evacuation: before the flow conductivity of the fracturing fluid is tested in the later period, the acid liquid container is closed, and the gas supply device supplies gas to the flow guide chamber for the second time to evacuate residual acid liquid;
s7, testing the flow conductivity of the later-stage fracturing fluid: opening a constant-speed constant-pressure pump, setting the flow of fracturing fluid for an experiment, injecting the fracturing fluid into the flow guide chamber through a first fracturing fluid pipe, opening a heater to heat the fracturing fluid in the first fracturing fluid pipe, opening a back pressure valve, setting the back pressure, and testing the flow guide chamber through a differential pressure sensor without changing the flow guide chamberCalculating the differential pressure of the same pressure measurement point to obtain the fracture conductivity k after acidification 2 W f2 ;
S8, fracture conductivity evaluation of the acid fracturing propping agent: testing flow conductivity kW of supporting crack according to Darcy's law f ,
In the formula: kW (power of kilowatt) f Mu m for proppant fracture conductivity 2 Cm; k is the propping crack permeability, μm 2 (ii) a Q is the flow through the fracture in cm 3 S; μ is the fluid viscosity, mPa · s; l is the length between the pressure ports, cm; a is the supporting crack sectional area in cm 2 (ii) a w is the width of the diversion chamber, cm; Δ P is the pressure difference between the test points, 10 5 Pa;
The thickness of the proppant in the diversion chamber, namely the width of the crack is W f The flow conductivity of the supporting fracture is k.W f For units corresponding to the experiment, then:
A=3.81×W f
in the formula: kW (power of kilowatt) f Mu m for proppant fracture conductivity 2 Cm; q is the flow through the fracture, ml/min; delta P is the pressure difference, KPa, between the test points;
the upper rock plate, the lower rock plate and the propping agent are not filled initially in the test, and when the upper piston contacts with the lower piston, the distance H between the horizontal plate of the upper piston and the horizontal plate of the lower piston 1 (ii) a Total thickness H of upper and lower rock plates 2 (ii) a In the process of testing the flow conductivity, the distance H between the upper piston horizontal plate and the lower piston horizontal plate 3 Width of crack W f =H 3 -H 2 -H 1 ;
The viscosity of the fracturing fluid is obtained by viscosity test after the fracturing fluid is prepared in the early stage.
The invention has the beneficial effects that:
(1) The method comprises the steps of dividing an acidification flow conductivity test into three stages, injecting fracturing fluid at the early stage, injecting acid at the middle stage and injecting fracturing fluid at the later stage, quantitatively representing the influence degree of acidification on the flow conductivity of a proppant fracture, evaluating the acid resistance of the proppant and guiding the optimization of the acidification fracturing proppant;
(2) Acid liquor in the diversion chamber is removed through gas injection in the middle stage of the experiment, the differential pressure sensor is prevented from being corroded, the high-precision differential pressure sensor is used for testing the pressure difference between different positions of the crack, and compared with the conventional device for testing the pressure calculation pressure difference between the inlet and the outlet of the diversion chamber, the method has higher precision.
Drawings
FIG. 1 is a schematic structural diagram of an apparatus for evaluating fracture conductivity of an acid fracturing proppant;
fig. 2 is an exploded view of the baffle compartment;
in the figure, 1-diversion chamber, 1.1-upper piston, 1.2-lower piston, 1.3-photoelectric displacement sensor, 2-differential pressure sensor, 3-constant speed constant pressure pump, 4-acid liquid container, 5-fracturing liquid container, 6-first gas supply device, 7-pressure reducing valve, 8-heater, 9-vacuum pump, 10-back pressure valve, 11-second gas supply device, 12-acid liquid collector, 13-fracturing liquid collector, 14-temperature sensor T2, 15-temperature sensor T3, 16-pressure sensor P3, 17-temperature sensor T4, 18-pressure sensor P1, 19-temperature sensor T1, 20-pressure sensor P2, 21-pressure sensor P4, 22-first control valve, 23-second control valve, 24-third control valve, 25-fourth control valve, 26-fifth control valve, 27-sixth control valve, 28-seventh control valve, 29-eighth control valve, 30-ninth control valve, 31-tenth control valve, thirteenth control valve, twelfth control valve, 34-fourteenth control valve, and fifteenth control valve, 35-fifteenth control valve.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the description.
Example 1: an evaluation device for fracture conductivity of acidizing fracturing propping agent comprises a flow guide chamber 1, a differential pressure sensor 2, a constant-speed constant-pressure pump 3, an acid liquid container 4, a fracturing liquid container 5, a first gas supply device 6, a pressure reducing valve 7, a heater 8, a vacuum pump 9, a back pressure valve 10, a second gas supply device 11, an acid liquid collector 12 and a fracturing liquid collector 13,
the constant-speed constant-pressure pump 3 is communicated with an acid liquid container 4 through a first pressure supply pipe, the constant-speed constant-pressure pump 3 is communicated with a fracturing liquid container 5 through a second pressure supply pipe, a lower rock plate and an upper rock plate which are matched with a cavity in the flow guide chamber 1 are arranged in the flow guide chamber 1, a propping agent is filled between the lower rock plate and the upper rock plate, a first conveying pipe communicated with the flow guide chamber 1 is arranged at the inlet end of the flow guide chamber 1, the acid liquid container 4 is communicated with the first conveying pipe through a first acid liquid pipe, the fracturing liquid container 5 is communicated with the first conveying pipe through a first fracturing liquid pipe, a first air supply device 6 is communicated with the first conveying pipe through a first air supply pipe, the outlet of the flow guide chamber 1 is respectively communicated with a vacuum pump 9 and a back-pressure valve 10 through a vacuum pipe and a second conveying pipe, the back-pressure valve 10 is communicated with the acid liquid collector 12 through a second acid liquid pipe, and the back-pressure valve 10 is communicated with the fracturing liquid collector 13 through a second fracturing liquid pipe;
a heater 8 is arranged on the first conveying pipe, and a second air supply device 11 is communicated with a back pressure valve 10 through a second air supply pipe;
the inlet end, the middle part and the outlet end of the diversion chamber 1 are respectively provided with a pressure measuring point A, a pressure measuring point B and a pressure measuring point C, and a differential pressure sensor 2 is arranged among the pressure measuring point A, the pressure measuring point B and the pressure measuring point C;
acid liquor is stored in an acid liquor container 4, fracturing fluid is stored in a fracturing fluid container 5, when acid fracturing is simulated, the acid liquor is injected into the diversion chamber 1 at a constant speed through the constant-speed constant-pressure pump 3, and due to the corrosivity of the acid liquor, the acid liquor flowing out of the diversion chamber 1 is collected by an acid liquor collector 12; injecting fracturing fluid into the flow guide chamber 1 at a constant speed through the constant-speed constant-pressure pump 3, collecting the fracturing fluid flowing out of the flow guide chamber 1 by a fracturing fluid collector 13 with a precision balance, and calculating the flow;
the first gas supply device 6 is a first nitrogen bottle, nitrogen is pumped and flows through the flow guide chamber 1, and after the flow guide capacity of the fracturing fluid in the previous stage is measured, the fracturing fluid in the flow guide chamber 1 and the pipeline is removed by using gas to prevent the acid liquor in the next stage from being diluted; after acid fracturing is simulated, removing acid liquor in the diversion chamber 1 and the pipeline by using gas again;
an upper piston hole and a lower piston hole are formed in the middle of the diversion chamber 1, an upper piston 1.1 matched with the upper piston hole is arranged in the upper piston hole in a sliding mode, an upper piston horizontal plate is arranged at the top end of the upper piston 1.1, a lower piston 1.2 matched with the lower piston hole is arranged in the lower piston hole in a sliding mode, a lower piston horizontal plate is arranged at the bottom end of the lower piston 1.2, and a photoelectric displacement sensor 1.3 is arranged on the lower piston horizontal plate; the photoelectric displacement sensor 1.3 is used for monitoring the width change of the support crack in the experimental process;
during fracture diversion test of the acidizing fracturing propping agent, a polished lower rock plate is filled in a filling chamber, propping agent particles are laid on the lower rock plate, the propping agent is filled in simulated stratum rock fractures, and then an upper rock plate is placed on the propping agent particles; pressurizing the upper piston 1.1 and the lower piston 1.2 by using a pressurizing machine to simulate the closing pressure of the formation fracture;
a pressure reducing valve 7 is arranged at the outlet end of the first gas supply device 6, a first heating sleeve is arranged on the outer side wall of the acid liquid container 4, a second heating sleeve is arranged on the outer side wall of the fracturing liquid container 5, a temperature sensor T2 is arranged in the fracturing liquid container 5, a temperature sensor T3 is arranged in the acid liquid container 4, a temperature sensor T4 is arranged in the heater 8, a temperature sensor T1 is arranged in the diversion chamber 1, a pressure sensor P1 is arranged at the inlet end of the diversion chamber 1, a pressure sensor P2 is arranged at the outlet end of the diversion chamber 1, a pressure sensor P3 is arranged on the first gas supply pipe, and a pressure sensor P4 is arranged in the back-pressure valve 10; the fluid flowing through the diversion chamber 1 is controlled to flow out under the condition of stable pressure through the back pressure valve 10, so that the flow is kept stable;
a first pressure measuring pipe, a second pressure measuring pipe and a third pressure measuring pipe which are sequentially communicated are arranged between a pressure measuring point A and a pressure measuring point B of the diversion chamber 1, the first pressure measuring pipe is communicated with the pressure measuring point A, the third pressure measuring pipe is communicated with the pressure measuring point B, a third pressure measuring pipe, a fourth pressure measuring pipe and a fifth pressure measuring pipe which are sequentially communicated are arranged between the pressure measuring point B and the pressure measuring point C, the fourth pressure measuring pipe is communicated with the second pressure measuring pipe, the junction of the first pressure measuring pipe and the second pressure measuring pipe is an intersection C, the junction of the fourth pressure measuring pipe and the fifth pressure measuring pipe is an intersection D, and a differential pressure sensor 2 is arranged between the intersection C and the intersection D;
by utilizing different combinations among the pressure measuring point A, the pressure measuring point B and the pressure measuring point C, the pressure difference of the front end, the rear end and the whole body of the crack can be tested, and the flow conductivity at different positions can be calculated;
a first control valve 22 is arranged on the first pressure supply pipe, a second control valve 23 is arranged on the second pressure supply pipe, a third control valve 24 is arranged on the first fracturing liquid pipe, a fourth control valve 25 is arranged on the first acid liquid pipe, a fifth control valve 26 is arranged on the first pressure supply pipe, a sixth control valve 27 is arranged on the first conveying pipe, a seventh control valve 28 is arranged on the first pressure measuring pipe, an eighth control valve 29 is arranged on the fifth pressure measuring pipe, a ninth control valve 30 is arranged on the second pressure measuring pipe, a tenth control valve 31 is arranged on the fourth pressure measuring pipe, an eleventh control valve 32 is arranged on the vacuum pipe, a twelfth control valve 33 is arranged on the second conveying pipe, a thirteenth control valve 34 is arranged on the second pressure measuring pipe, a fourteenth control valve 35 is arranged on the second acid liquid pipe, and a fifteenth control valve 36 is arranged on the second fracturing liquid pipe;
the diversion chamber is a standard API diversion chamber, the length is 17.78cm, the width is 3.81cm, and the distance between pressure measuring points at two ends is 12.7cm;
the structural parts and pipelines of the device for evaluating the fracture conductivity of the acidizing and fracturing propping agent adopt Hastelloy, have high compressive strength and high temperature resistance, can simulate the reservoir conditions with the maximum temperature of 150 ℃ and the maximum closing pressure of 200MPa, and ensure the safety of the experiment.
Example 2: a fracture conductivity evaluation method of an acid fracturing propping agent adopts the fracture conductivity evaluation of the acid fracturing propping agent, and comprises the following specific steps:
s1, preparing a flow guide chamber: placing a cut and polished lower rock plate in a cavity of a diversion chamber, laying proppant particles with preset thickness on the lower rock plate, placing an upper rock plate on the proppant particles, and pressurizing the upper rock plate and the lower rock plate through an upper piston and a lower piston by using a pressurizing machine to simulate formation crack closing pressure; meanwhile, heating the acid liquid in the acid liquid container to a preset temperature through a first heating sleeve sleeved on the outer side of the acid liquid container, and heating the fracturing liquid in the fracturing liquid container to the preset temperature through a second heating sleeve sleeved on the outer side of the fracturing liquid container to reach the temperature and pressure conditions of the diversion capability test;
s2, vacuumizing: vacuumizing the flow guide chamber through a vacuum tube and a vacuum pump to ensure that the flow guide chamber can be completely filled with subsequent injected fluid, namely fracturing fluid or acid liquid;
s3, testing the flow conductivity of the early-stage fracturing fluid: opening a constant-speed constant-pressure pump, setting the flow of fracturing fluid of an experiment, injecting the fracturing fluid into a flow guide chamber through a first fracturing fluid pipe, opening a heater to heat the fracturing fluid in the first fracturing fluid pipe, opening a back pressure valve, setting back pressure, testing the differential pressure of different pressure measurement points of the flow guide chamber through a differential pressure sensor, and calculating to obtain the flow guide capacity k of the fracturing fluid in the early stage of the supporting crack 1 W f1 。
S4, primary gas injection and evacuation: after the test of the flow conductivity of the early-stage fracturing fluid is finished, closing the constant-speed constant-pressure pump, the fracturing fluid container and the differential pressure gauge, starting the gas supply device to inject gas into the flow guide chamber, and discharging residual fracturing fluid;
s5, acid injection and acidification: opening the constant-speed constant-pressure pump, setting the acid liquid flow of the experiment, closing the differential pressure meter, injecting the acid liquid into the diversion chamber through the first acid liquid pipe for acidification treatment, and controlling the volume of the acid liquid injected into the diversion chamber and the acidification treatment time according to the experimental design;
s6, secondary gas injection and evacuation: before the flow conductivity of the fracturing fluid is tested in the later period, the acid liquid container is closed, and the gas supply device supplies gas to the flow guide chamber for the second time to evacuate residual acid liquid;
s7, testing the flow conductivity of the later-stage fracturing fluid: opening a constant-speed constant-pressure pump, setting the flow of fracturing fluid for an experiment, injecting the fracturing fluid into a flow guide chamber through a first fracturing fluid pipe, opening a heater to heat the fracturing fluid in the first fracturing fluid pipe, opening a back pressure valve, setting the back pressure, testing the differential pressure of different pressure measurement points of the flow guide chamber through a differential pressure sensor, and calculating to obtain the acidized fracture conductivity k 2 W f2 ;
S8, fracture conductivity evaluation of the acid fracturing propping agent: testing according to Darcy's LawFlow conductivity kW of support crack f ,
In the formula: kW (power of kilowatt) f Mu m for proppant fracture conductivity 2 Cm; k is the propping crack permeability, μm 2 (ii) a Q is the flow through the fracture in cm 3 S; μ is the fluid viscosity, mPa · s; l is the length between the pressure ports, cm; a is the supporting crack sectional area in cm 2 (ii) a w is the width of the diversion chamber, cm; Δ P is the pressure difference between the test points, 10 5 Pa;
The thickness of the proppant in the diversion chamber, namely the width of the crack is W f The flow conductivity of the supporting fracture is k.W f Corresponding to the unit and experiment, then
A=3.81×W f
In the formula: kW (kilo power) f Mu m for proppant fracture conductivity 2 Cm; q is the flow through the fracture, ml/min; delta P is the pressure difference, KPa, between the test points;
the upper rock plate, the lower rock plate and the propping agent are not filled initially in the test, and when the upper piston contacts with the lower piston, the distance H between the horizontal plate of the upper piston and the horizontal plate of the lower piston 1 (ii) a Total thickness H of upper and lower rock plates 2 (ii) a In the process of testing the flow conductivity, the distance H between the upper piston horizontal plate and the lower piston horizontal plate 3 Width of crack W f =H 3 -H 2 -H 1 ;
The viscosity of the fracturing fluid is obtained by performing viscosity test after the fracturing fluid is prepared in the early stage.
Example 2: this embodiment is a specific set of experimental diversion capability test examples to illustrate specific experimental operation steps and calculation methods, and the specific steps are as follows:
s1, preparing acid liquor: preparing an experimental acid solution of 12 percent by adopting HCL with the concentration of 38 percent and HF with the concentration of 40 percent;
s2, selection of a propping agent and a fracturing fluid: in the experiment, 30/50-mesh quartz sand proppant is adopted, and the mass is weighed to be 64.52g; selecting 0.02% of slickwater fracturing fluid as the fracturing fluid, and testing the viscosity of the fracturing fluid to be 2.62mPa & s at the temperature of 70 ℃ in an experiment;
s3, preparing a flow guide chamber: firstly, a lower piston of a diversion chamber is installed, a lower rock plate is arranged on the lower piston in the diversion chamber, a quartz sand propping agent weighed in advance is laid on the lower rock plate, an upper rock plate is laid above the propping agent, and finally the upper piston is inserted; simulating formation rock by using a rock plate in the diversion chamber, applying pressure by using a press to simulate fracture closure, wherein the pressure is set to be 20MPa, and the propping agent prevents the fracture closure and fills a channel for oil-gas migration formed between the fractures;
s4, vacuumizing: the vacuum tube and the vacuum pump carry out vacuum pumping treatment on the diversion chamber to ensure that the diversion chamber can be completely filled with subsequent injected fluid (fracturing fluid or acid liquid);
s5, testing the early-stage flow conductivity: injecting fracturing fluid into the diversion chamber by using a constant-speed constant-pressure pump, testing the flow rate to be 5ml/min, testing the differential pressure between the pressure testing points 1 and 3 to be 3.204kPa, and testing by using a photoelectric displacement sensor to obtain the width W of the crack f1 6.125mm, and calculating the flow conductivity k of the early fracturing fluid by a calculation formula 1 W f1 Is 22.71 mu m 2 ·cm;
S6, primary gas injection and evacuation: after the test of the flow conductivity of the early-stage fracturing fluid is finished, closing the constant-speed constant-pressure pump, the fracturing fluid container and the differential pressure gauge, starting the gas supply device to inject gas into the flow guide chamber, and discharging residual fracturing fluid;
s7, acid injection and acidification: opening an acid liquid container, opening a constant-speed constant-pressure pump, continuously injecting acid liquid into the flow guide chamber at a flow rate of 2ml/min, and stopping injection when the acid liquid starts to flow out from the acid liquid collection container, so that the acid liquid in the flow guide chamber is continuously subjected to acidification reaction with the propping agent and the rock plate for 2 hours;
s8, secondary gas injection emptying: before the flow conductivity of the fracturing fluid is tested in the later period, the acid injection container and the corresponding pipeline control valve are closed, and a gas supply device injects gas into the flow guide chamber to evacuate residual acid liquid;
s9, testing the later-stage flow conductivity: injecting fracturing fluid into the flow guide chamber again by using a constant-speed constant-pressure pump, wherein the test flow is 5ml/min, the differential pressure between the test pressure points 1 and 3 is 4.381kPa, the acidizing propping agent is corroded with the surface of the rock plate, the crack width is reduced, and the crack width W is obtained by testing through a photoelectric displacement sensor f2 5.854mm, and calculating the flow conductivity k of the early fracturing fluid by a calculation formula 1 W f1 Is 16.61 mu m 2 ·cm:
S10, analyzing an experimental result: under the action of acidification, the width of the crack is reduced by 4.42%, and the conductivity is reduced by 26.9%.
In the experimental device designed by the invention, the design experiment can evaluate the capability of the proppant for maintaining the flow conductivity of the fracture under the action of acidification, and provides reference for designing optimal proppant for field fracturing.
While the present invention has been described in detail with reference to the specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention.