CN114352238A - Device and method for testing flow conductivity of natural gas hydrate production increasing seam - Google Patents
Device and method for testing flow conductivity of natural gas hydrate production increasing seam Download PDFInfo
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- CN114352238A CN114352238A CN202111655012.4A CN202111655012A CN114352238A CN 114352238 A CN114352238 A CN 114352238A CN 202111655012 A CN202111655012 A CN 202111655012A CN 114352238 A CN114352238 A CN 114352238A
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Abstract
The invention is suitable for the technical field of natural gas exploitation, and particularly relates to a device and a method for testing the flow conductivity of a natural gas hydrate production increasing seam, wherein the device comprises: gas injection unit, notes liquid unit, temperature control unit, crack water conservancy diversion appearance, export control unit and data processing unit, the gas injection unit all is connected with crack water conservancy diversion appearance with annotating the liquid unit, and crack water conservancy diversion appearance sets up in temperature control unit, and the crack water conservancy diversion appearance is linear flow water conservancy diversion room, and export control unit is connected with crack water conservancy diversion appearance, and data processing unit is connected with gas injection unit, notes liquid unit, temperature control unit, crack water conservancy diversion appearance and export control unit for data acquisition and data processing carry out. The method has the characteristic of truly simulating the natural gas hydrate reservoir reconstruction yield-increasing seam, can apply different closing pressures to carry out gas measurement and liquid measurement on the yield-increasing seam conductivity under the condition of ensuring that the hydrate is not decomposed, can research the evolution law of the yield-increasing seam conductivity in the hydrate decomposition process, and preferably adopts a natural gas hydrate reservoir fracture support scheme.
Description
Technical Field
The invention belongs to the technical field of natural gas exploitation, and particularly relates to a device and a method for testing the flow conductivity of a natural gas hydrate production increasing seam.
Background
The hydrate resource amount in the sea area of China is huge, the hydrate is expected to become an important clean alternative energy, and the safe and efficient development of the hydrate has important significance for guaranteeing the national energy safety. At present, sea hydrate trial production makes an important breakthrough, but the daily gas production of a single well is low, the difference from the commercial production requirement is large, and a yield increasing technology is urgently needed. Reservoir transformation such as hydraulic cutting and hydraulic fracturing is considered as a necessary auxiliary production increasing means for sea area hydrate depressurization and exploitation, and the existing indoor experiments and numerical simulation researches show that the hydraulic cutting and hydraulic cutting technology can construct a hypertonic artificial fracture channel in a hydrate reservoir. The existence of the artificial fracture channel can increase the pressure relief area and improve the seepage condition of the reservoir, thereby expanding the hydrate decomposition array surface, improving the decomposition rate of the natural gas hydrate and realizing the yield increase of the hydrate. After the natural gas hydrate reservoir is modified, the artificial yield increasing fracture channel is used as a channel for rapid seepage of hydrate decomposition gas, and the change of the flow conductivity of the channel is related to the yield increasing effect of reservoir modification. Therefore, the test and research on the conductivity of the production joint for the natural gas hydrate reservoir transformation have important guiding significance for the natural gas hydrate reservoir transformation.
At present, a great deal of research is carried out on the flow conductivity of fracturing and supporting fractures in unconventional oil and gas reservoirs such as shale gas and coal bed gas at home and abroad, and various fracture flow conductivity detection devices and methods are invented, but the device and the method are still not suitable for natural gas hydrate reservoirs. The conductivity test of the yield joint for the natural gas hydrate reservoir transformation has the particularity that:
firstly, a testing device needs to meet the condition that a hydrate stably exists, the hydrate exists in a low-temperature high-pressure environment, the existing crack conductivity testing device cannot meet the low-temperature high-pressure condition, the in-situ generation of the natural gas hydrate cannot be carried out, and the natural gas hydrate cannot be guaranteed not to be decomposed in the crack conductivity testing process;
secondly, the testing device needs to have the functions of quantitative gas injection, quantitative constant-pressure liquid injection, gas-liquid separation and outlet gas flow detection, the quantitative gas injection and the quantitative constant-pressure liquid injection can be used for hydrate synthesis and flow conductivity testing, gas and liquid can be used for conveniently detecting gas production/water production in the hydrate decomposition process, the outlet gas flow detection is used for calculating crack flow conductivity, hydrate decomposition amount, hydrate residual amount and the like, and the conventional crack flow conductivity detection device cannot simultaneously meet the functions;
thirdly, the temperature and the pressure in the diversion chamber and the temperature of the fluid entering the diversion chamber need to be regulated and controlled in the diversion capability test process of the production joint, in order to ensure that the hydrate is not decomposed in the diversion capability test process, the temperature and the pressure in the diversion chamber are above the phase equilibrium condition of the hydrate, the temperature of the fluid entering the diversion chamber is basically consistent with the temperature of the diversion chamber, and the influence of the temperature and the pressure in the diversion chamber and the temperature of the injected fluid is not considered in the current diversion capability test method.
In a word, the existing diversion capability testing device and method cannot be applied to research on the aspect of natural gas hydrate reservoir transformation. Therefore, a device and a method for testing the flow conductivity of the natural gas hydrate production increasing seam, which are suitable for the natural gas hydrate reservoir, need to be developed.
Disclosure of Invention
The embodiment of the invention aims to provide a device for testing the flow conductivity of a natural gas hydrate production increasing seam, and aims to solve the problems in the background art.
The embodiment of the invention is realized in such a way that the device for testing the flow conductivity of the natural gas hydrate production increasing joint comprises: the gas injection unit and the liquid injection unit are connected with the crack flow guide instrument, the gas injection unit is used for injecting CH4 gas required by hydrate synthesis into the crack flow guide instrument and controlling the flow and pressure of the injected CH4 gas, the liquid injection unit is used for injecting water and saturated sediments for hydrate synthesis into the crack flow guide instrument and controlling the flow and pressure of injected liquid, the crack flow guide instrument is arranged in the temperature control unit, the temperature control unit is used for controlling the temperature of the crack flow guide instrument and injected fluid, the crack flow guide instrument is a linear flow guide chamber and is used for simulating the support crack parameters of a modified hydrate reservoir stratum, the outlet control unit is connected with the crack flow guide instrument and is used for collecting produced gas and detecting the gas flow, the liquid flow and the corresponding output pressure of the gas and the liquid, the data processing unit is connected with the gas injection unit, the liquid injection unit, the temperature control unit, the crack flow guide instrument and the outlet control unit and is used for data acquisition and data processing.
Preferably, the gas injection unit comprises a CH4 gas cylinder, a first stop valve, a pressure reducing valve, a first pressure sensor, a gas mass flow controller and a second stop valve, wherein the CH4 gas cylinder, the first stop valve, the pressure reducing valve, the first pressure sensor, the gas mass flow controller and the second stop valve are sequentially connected in series.
Preferably, the liquid injection unit comprises a first balance, a first beaker, a constant-pressure constant-flow pump, a third stop valve, a second pressure sensor, a stirring piston tank, a fourth stop valve and a fifth stop valve, the first beaker is arranged on the first balance, the constant-pressure constant-flow pump is connected with the first beaker through a pipeline, the constant-pressure constant-flow pump, the third stop valve, the second pressure sensor and the fifth stop valve are connected in series, and the stirring piston tank is connected with the fourth stop valve in series and then connected with the fifth stop valve in parallel.
Preferably, the fracture guiding instrument comprises an injection fluid precooler, a first temperature sensor, a fracture guiding chamber, a closed pressure hydraulic loader, a displacement sensor, a differential pressure sensor, a second temperature sensor, a third pressure sensor and a fourth pressure sensor, wherein the injection fluid precooler, the first temperature sensor, the closed pressure hydraulic loader, the displacement sensor, the differential pressure sensor, the second temperature sensor, the third pressure sensor and the fourth pressure sensor are all connected with the fracture guiding chamber, and the closed pressure hydraulic loader is used for pressurizing the fracture guiding chamber.
Preferably, a refrigeration cavity and a diversion chamber cavity are arranged in the crack diversion chamber, an upper piston and a lower piston are respectively arranged at two ends of the diversion chamber cavity in a sliding mode, the closed pressure hydraulic loading machine is installed on one side, away from each other, of the upper piston and the lower piston, a propping agent filling layer is arranged between the upper piston and the lower piston, an upper sediment is arranged between the propping agent filling layer and the upper piston, and a lower sediment is arranged between the propping agent filling layer and the lower piston.
Preferably, the outlet control unit comprises a fifth pressure sensor, a back pressure valve, a gas-liquid separator, a second beaker, a second balance, a dryer, a sixth stop valve, a first mass flowmeter, a seventh stop valve, a second mass flowmeter and a gas storage tank, wherein the gas storage tank is connected with the first mass flowmeter and the second mass flowmeter, the first mass flowmeter and the second mass flowmeter are respectively connected with the dryer through the sixth stop valve and the seventh stop valve, the dryer is connected with the crack flow guide instrument sequentially through the back pressure valve and the gas-liquid separator, the second beaker is arranged on the second balance, and the gas-liquid separator is connected with the second beaker through a pipeline.
Another purpose of an embodiment of the present invention is to provide a method for testing a flow conductivity of a gas hydrate stimulation joint, where the method includes:
preparing a sample from the deposit: filling the in-situ hydrate reservoir sediment mixed with a certain mass of water or configured sediment into a mold, applying load in layers to compress the sediment, and pressing to obtain a lower sediment;
filling a sample: and placing the prepared sediment sample into a crack diversion chamber to flatten the sediment sample, pouring a certain amount of proppant filling layer into the upper part of the sediment sample, scraping the proppant filling layer by using a scraper, and then filling another upper sediment above the proppant filling layer.
Connecting equipment: filling an upper piston in the crack diversion chamber, and connecting joints of the crack diversion chamber; applying a closing pressure of 1.0MPa by a closing pressure hydraulic loader to ensure that the lower sediment and the upper sediment, the proppant filling layer, the upper piston and the lower piston are tightly attached, injecting CH4 gas, and checking the air tightness of the system;
hydrate synthesis: quantitatively injecting CH4 gas through a CH4 gas cylinder, a pressure reducing valve and a gas mass flow controller, stopping injecting the gas when the pressure reaches a set value, closing all valves, starting low-temperature water bath equipment and an injection fluid precooling circulating pump, and cooling a crack flow guide chamber until the crack flow guide chamber reaches the set temperature; monitoring the temperature and pressure change of the crack diversion chamber in real time, and when the temperature and pressure change of the crack diversion chamber does not exceed a preset value, determining that the generation of the hydrate is finished;
and (3) testing the flow conductivity: the conductivity test comprises gas conductivity measurement, liquid conductivity measurement and gas conductivity measurement in the hydrate decomposition process;
disassembling and cleaning the instrument: after the experiment was completed, the instrument was disassembled and all vessels and lines were cleaned, keeping the equipment clean.
Preferably, the process of the conductivity test specifically includes:
gas measurement of flow conductivity: setting a backpressure valve to enable backpressure to be pressure after hydrate synthesis, controlling a closed pressure hydraulic loader, setting different closed pressures, quantitatively injecting CH4 gas refrigerated by an injection fluid precooler into a crack diversion chamber, detecting outlet gas flow by using a first mass flowmeter and a second mass flowmeter, detecting pressure change of a differential pressure sensor and displacement change of a displacement sensor in real time, and calculating diversion capacity of a supporting crack layer according to a gas Darcy formula;
liquid measurement of flow conductivity: setting a back pressure valve to enable the back pressure to be the pressure after hydrate synthesis, injecting distilled water into a crack flow guiding chamber by using a constant-pressure constant-flow pump to enable a sediment sample to be saturated, controlling a closed-pressure hydraulic loading machine, setting different closed pressures, quantitatively injecting the liquid refrigerated by an injection fluid precooler into the crack flow guiding chamber by using the constant-pressure constant-flow pump and a stirring piston tank, detecting the flow rate of an outlet until the flow rate is stable, detecting the pressure change of a differential pressure sensor and the displacement change of a displacement sensor in real time, and calculating the flow guiding capacity of a supporting crack layer according to a liquid Darcy formula;
gas measurement conductivity during hydrate decomposition: setting a back pressure valve to enable the back pressure to be lower than the hydrate phase equilibrium pressure, controlling a closed pressure hydraulic loader, keeping the closed pressure not to inject CH4 gas which is refrigerated by an injection fluid precooler into a crack flow guide chamber in a fixed quantity, detecting the flow of gas at an outlet by using a first mass flow meter and a second mass flow meter, measuring the output change of the gas, calculating the hydrate decomposition amount by using a mass balance formula, detecting the pressure change of a differential pressure sensor and the displacement change of a displacement sensor in real time, and calculating the flow guide capacity in the hydrate decomposition process according to a gas Darcy formula.
The invention provides a device for testing the flow conductivity of a natural gas hydrate production joint, which has the characteristic of truly simulating a natural gas hydrate reservoir reconstruction production joint, can apply different closing pressures to carry out gas measurement and liquid measurement on the flow conductivity of the production joint under the condition of ensuring that a hydrate is not decomposed, can research the evolution law of the flow conductivity of the production joint in the decomposition process of the hydrate, and preferably selects a natural gas hydrate reservoir fracture support scheme.
Drawings
Fig. 1 is a schematic structural diagram of a natural gas hydrate stimulation fracture conductivity testing device provided in an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a fracture guiding chamber according to an embodiment of the present invention.
In the drawings: 1. a CH4 gas cylinder; 2. a first shut-off valve; 3. a pressure reducing valve; 4. a first pressure sensor; 5. a gas mass flow controller; 6. a second stop valve; 7. a first balance; 8. a first beaker; 9. a constant-pressure constant-flow pump; 10. a third stop valve; 11. a second pressure sensor; 12. a stirring piston tank; 13. a fourth stop valve; 14. a fifth stop valve; 15. low-temperature water bath equipment; 16. injecting a fluid precooling circulating pump; 17. a diversion chamber refrigeration circulating pump; 18. an injection fluid precooler; 19. a first temperature sensor; 20. a crack diversion chamber; 21. closing the pressure hydraulic loader; 22. a displacement sensor; 23. a differential pressure sensor; 24. a second temperature sensor; 25. a third pressure sensor; 26. a fourth pressure sensor; 27. a fifth pressure sensor; 28. a back pressure valve; 29. a gas-liquid separator; 30. a second beaker; 31. a second balance; 32. a dryer; 33. a sixth stop valve; 34. a first mass flow meter; 35. a seventh stop valve; 36. a second mass flow meter; 37. a gas storage tank; 38. a data conversion module; 39. a data processing module; 40. a lower piston; 41. an upper piston; 42. a lower deposit; 43. an upper sediment; 44. a proppant pack; 45. a diversion chamber cavity; 46. a refrigeration cavity.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Specific implementations of the present invention are described in detail below with reference to specific embodiments.
As shown in fig. 1, a schematic structural diagram of a natural gas hydrate stimulation fracture conductivity testing apparatus provided in an embodiment of the present invention is shown, where the apparatus includes: the gas injection unit and the liquid injection unit are connected with the crack flow guide instrument, the gas injection unit is used for injecting CH4 gas required by hydrate synthesis into the crack flow guide instrument and controlling the flow and pressure of the injected CH4 gas, the liquid injection unit is used for injecting water and saturated sediments for hydrate synthesis into the crack flow guide instrument and controlling the flow and pressure of injected liquid, the crack flow guide instrument is arranged in the temperature control unit, the temperature control unit is used for controlling the temperature of the crack flow guide instrument and injected fluid, the crack flow guide instrument is a linear flow guide chamber and is used for simulating the support crack parameters of a modified hydrate reservoir stratum, the outlet control unit is connected with the crack flow guide instrument and is used for collecting produced gas and detecting the gas flow, the liquid flow and the corresponding output pressure of the gas and the liquid, the data processing unit is connected with the gas injection unit, the liquid injection unit, the temperature control unit, the crack flow guide instrument and the outlet control unit and is used for data acquisition and data processing.
In the embodiment, the gas injection unit can control the flow and pressure of the injected gas, is used for injecting CH4 gas required by hydrate synthesis into the fracture flow guide instrument, and is also used for quantitatively injecting CH4 gas to measure the fracture flow guide capacity; the liquid injection unit can control the flow and pressure of injected liquid, is used for injecting water and saturated sediments for synthesizing hydrate into the crack flow guide instrument, and is also used for quantitatively injecting liquid to measure the flow guide capacity of the crack; the temperature control unit is used for controlling the temperature of the crack flow guide instrument and the injected fluid, providing a low-temperature environment for hydrate synthesis, and regulating and controlling the decomposition of hydrate in the process of testing the crack flow guide capacity; the fracture flow guide instrument is a linear flow guide chamber specified by API standard, can simulate the parameters of the support fracture of the modified hydrate reservoir, realizes in-situ generation of hydrate, and can detect a plurality of parameters such as differential pressure, temperature and displacement; the outlet control unit can measure the gas and liquid flow in the crack flow conductivity test process, can also be used for controlling the output pressure of the gas and water for simulated exploitation, and can collect the gas for exploitation; the data processing unit is used for collecting and processing data of the experimental device such as temperature, pressure, displacement, flow and the like, and can draw temperature, pressure, displacement, flow curves and the like.
As shown in fig. 1, as a preferred embodiment of the present invention, the gas injection unit includes a CH4 gas cylinder 1, a first cut-off valve 2, a pressure reducing valve 3, a first pressure sensor 4, a gas mass flow controller 5, and a second cut-off valve 6, and the CH4 gas cylinder 1, the first cut-off valve 2, the pressure reducing valve 3, the first pressure sensor 4, the gas mass flow controller 5, and the second cut-off valve 6 are connected in series in this order.
As shown in fig. 1, as a preferred embodiment of the present invention, the liquid injection unit includes a first balance 7, a first beaker 8, a constant-pressure constant-flow pump 9, a third cut-off valve 10, a second pressure sensor 11, a stirring piston tank 12, a fourth cut-off valve 13, and a fifth cut-off valve 14, the first beaker 8 is placed on the first balance 7, the constant-pressure constant-flow pump 9 is connected to the first beaker 8 through a pipeline, the constant-pressure constant-flow pump 9, the third cut-off valve 10, the second pressure sensor 11, and the fifth cut-off valve 14 are connected in series, and the stirring piston tank 12 is connected in series with the fourth cut-off valve 13 and then connected in parallel with the fifth cut-off valve 14.
As shown in fig. 1, as a preferred embodiment of the present invention, the fracture guiding instrument includes an injection fluid precooler 18, a first temperature sensor 19, a fracture guiding chamber 20, a closed pressure hydraulic loader 21, a displacement sensor 22, a differential pressure sensor 23, a second temperature sensor 24, a third pressure sensor 25 and a fourth pressure sensor 26, the injection fluid precooler 18, the first temperature sensor 19, the closed pressure hydraulic loader 21, the displacement sensor 22, the differential pressure sensor 23, the second temperature sensor 24, the third pressure sensor 25 and the fourth pressure sensor 26 are all connected to the fracture guiding chamber 20, and the closed pressure hydraulic loader 21 is used for pressurizing the fracture guiding chamber 20.
In the present embodiment, the gas injection unit includes a CH4 gas cylinder 1, a first shutoff valve 2, a pressure reducing valve 3, a first pressure sensor 4, a gas mass flow controller 5, a second shutoff valve 6; the pressure reducing valve 3 is used for adjusting the pressure of injected gas; the gas mass flow controller 5 can realize the quantitative injection of CH4 gas, and the flow rate of the CH4 gas is 0-20L/min under the standard condition; the constant-pressure constant-flow pump 9 is mainly used for constant-pressure/quantitative injection of liquid; the stirring piston tank 12 is mainly used for injecting fracturing fluid, brine and suspension containing particles; the temperature control unit comprises a low-temperature water bath device 15, an injection fluid precooling circulating pump 16 and a diversion room refrigerating circulating pump 17; the low-temperature water bath equipment 15 is used for refrigerating the ethylene glycol aqueous solution; the injection fluid precooling circulating pump 16 and the diversion room refrigerating circulating pump 17 are used for circulating low-temperature ethylene glycol aqueous solution, and respectively refrigerate the injection fluid device and the crack diversion room 20.
As shown in fig. 2, as a preferred embodiment of the present invention, a refrigeration cavity 46 and a diversion chamber cavity 45 are disposed in the fracture diversion chamber 20, an upper piston 41 and a lower piston 40 are slidably disposed at two ends of the diversion chamber cavity 45, respectively, the closing pressure hydraulic loader 21 is mounted on a side of the upper piston 41 and the lower piston 40 away from each other, a proppant pack 44 is disposed between the upper piston 41 and the lower piston 40, an upper deposit 43 is disposed between the proppant pack 44 and the upper piston 41, and a lower deposit 42 is disposed between the proppant pack 44 and the lower piston 40.
In the present embodiment, the fracture guiding instrument includes an injection fluid precooler 18, a first temperature sensor 19, a fracture guiding chamber 20, a closed pressure hydraulic loader 21, a displacement sensor 22, a differential pressure sensor 23, a second temperature sensor 24, a third pressure sensor 25, a fourth pressure sensor 26; an injection fluid precooler 18 is used to refrigerate the injected fluid; the first temperature sensor 19 is used to measure the temperature of the injected fluid; crack diversion chamber 20 is withstand voltage 35MPa, the temperature control range is-20-100 ℃, the internal cavity is a linear flow guide chamber specified by API standard, the width is 3.81cm, the length is 17.78cm, the thickness of the proppant filling layer C is 0.25-1.27cm, the thickness is adjustable, and the test area is 64.5cm2(ii) a The crack diversion chamber 20 comprises an upper piston 41 and a lower piston 40, the cavity of the crack diversion chamber can accommodate 2 lower sediments 42 containing hydrate and upper sediments 43, and the height of the sediments is 1-5 cm; the closing pressure hydraulic loader 21 is in contact with an upper piston 41 and a lower piston 40 in the fracture diversion chamber 20, and closing pressure of 0-100MPa can be applied to the lower sediment 42, the upper sediment 43 and the proppant pack C through the upper piston 41 and the lower piston 40; the displacement sensor 22 mainly measures the displacement of the upper piston; three pressure measuring ports of the differential pressure sensor 23 are provided, and the differential pressure values of two distances can be measured by opening and closing the matched ball valve, so that whether the proppant is uniformly paved or not can be analyzed; the second temperature sensor 24 is used for measuring the temperature of the crack diversion chamber; both the third pressure sensor 25 and the fourth pressure sensor 26 are used to measure the pressure of the fracture guiding chamber 20.
As shown in fig. 1, as a preferred embodiment of the present invention, the outlet control unit includes a fifth pressure sensor 27, a back pressure valve 28, a gas-liquid separator 29, a second beaker 30, a second balance 31, a dryer 32, a sixth stop valve 33, a first mass flow meter 34, a seventh stop valve 35, a second mass flow meter 36 and a gas tank 37, the gas tank 37 is connected to the first mass flow meter 34 and the second mass flow meter 36, the first mass flow meter 34 and the second mass flow meter 36 are connected to the dryer 32 through the sixth stop valve 33 and the seventh stop valve 35, the dryer 32 is connected to the crack flow meter through the back pressure valve 28 and the gas-liquid separator 29 in sequence, the second beaker 30 is placed on the second balance 31, and the gas-liquid separator 29 is connected to the second beaker 30 through a pipe.
In the present embodiment, the outlet control unit includes a fifth pressure sensor 27, a back pressure valve 28, a gas-liquid separator 29, a second beaker 30, a second balance 31, a dryer 32, a sixth cutoff valve 33, a first mass flow meter 34, a seventh cutoff valve 35, a second mass flow meter 36, a gas tank 37; the backpressure valve 28 is used for adjusting the pressure of the crack diversion chamber 20 and simulating the hydrate depressurization exploitation process; the first mass flow meter 34 and the second mass flow meter 36 are flow meters with different measuring ranges, and a proper measuring range can be selected according to the actual flow; the gas tank 37 is used to collect gas.
In an embodiment of the present invention, there is also provided a method for testing conductivity of a natural gas hydrate stimulation joint, the method including:
preparing a sample from the deposit: filling the in-situ hydrate reservoir sediment mixed with a certain mass of water or configured sediment into a mold, applying load in layers to compress the sediment, and pressing to obtain a lower sediment 42;
filling a sample: the prepared sediment sample is put into a crack diversion chamber 20 to be flattened, a certain amount of proppant filling layer 44 is poured into the upper part of the sediment sample, the proppant filling layer 44 is scraped by a scraper, and then another upper sediment 43 is filled above the proppant filling layer 44.
Connecting equipment: filling an upper piston 41 in the crack guide chamber 20, and connecting joints of the crack guide chamber 20; applying a closing pressure of 1.0MPa by a closing pressure hydraulic loader 21 to tightly attach the lower sediment 42 and the upper sediment 43, the proppant filling layer 44, the upper piston 41 and the lower piston 40, injecting CH4 gas, and checking the air tightness of the system;
hydrate synthesis: quantitatively injecting CH4 gas through a CH4 gas cylinder 1, a pressure reducing valve 3 and a gas mass flow controller 5, stopping injecting the gas when the pressure reaches a set value, closing all valves, starting a low-temperature water bath device 15 and an injection fluid precooling circulating pump 16, and cooling the crack flow guide chamber 20 until the crack flow guide chamber 20 reaches the set temperature; monitoring the temperature and pressure change of the crack diversion chamber 20 in real time, and when the temperature and pressure change of the crack diversion chamber 20 does not exceed a preset value, determining that the generation of the hydrate is finished;
and (3) testing the flow conductivity: the conductivity test comprises gas conductivity measurement, liquid conductivity measurement and gas conductivity measurement in the hydrate decomposition process;
disassembling and cleaning the instrument: after the experiment was completed, the instrument was disassembled and all vessels and lines were cleaned, keeping the equipment clean.
In this embodiment, the process of the conductivity test specifically includes:
gas measurement of flow conductivity: setting a back pressure valve 28 to enable the back pressure to be the pressure after hydrate synthesis, controlling a closed pressure hydraulic loader 21, setting different closed pressures, quantitatively injecting CH4 gas refrigerated by an injection fluid precooler 18 into a crack flow guide chamber 20, detecting the flow rate of outlet gas by using a first mass flow meter 34 and a second mass flow meter 36, detecting the pressure change of a differential pressure sensor 23 and the displacement change of a displacement sensor 22 in real time, and calculating the flow guide capacity of a support crack layer according to a gas Darcy formula;
the permeability of the supporting fracture layer is calculated according to the formula (1):
in the formula:
permeability of k-supporting fracture layer in mum2；
L-sample length in cm;
mu-experimental gas viscosity under the experimental temperature condition, wherein the unit is mPa & s;
Q0flow at atmospheric pressure in cm3·s；
P0-atmospheric pressure in 0.1 MPa;
a-permeation channel area in cm2；
P1-upstream pressure in 0.1 MPa;
P2downstream pressure, in units of 0.1 MPa.
The flow conductivity of the propped fracture is calculated according to the formula (2)
In the formula:
Wf-proppant pack thickness in cm.
Liquid measurement of flow conductivity: setting a backpressure valve 28 to enable backpressure to be pressure after hydrate synthesis, injecting distilled water into the crack diversion chamber 20 by using a constant-pressure constant-flow pump 9 to enable a sediment sample to be saturated, controlling a closed-pressure hydraulic loading machine 21, setting different closed pressures, quantitatively injecting liquid refrigerated by an injection fluid precooler 18 into the crack diversion chamber 20 by using the constant-pressure constant-flow pump 9 and a stirring piston tank 12, detecting outlet flow until the flow is stable, detecting pressure change of a differential pressure sensor 23 and displacement change of a displacement sensor 22 in real time, and calculating diversion capacity of a supporting crack layer according to a liquid Darcy formula.
And (3) calculating the permeability of the support fracture layer according to the formula:
in the formula:
permeability of k-supporting fracture layer in mum2；
L-sample length in cm;
mu-experimental gas viscosity under the experimental temperature condition, wherein the unit is mPa & s;
q-flow in cm3·s；
A-permeation channel area in cm2；
Δ p-differential pressure (upstream pressure minus downstream pressure) in kPa.
The flow conductivity of the propped fracture is calculated according to the formula (4):
in the formula:
Wf-proppant pack thickness in cm.
Gas measurement conductivity during hydrate decomposition: the back pressure valve 28 is arranged to enable the back pressure to be lower than the hydrate phase equilibrium pressure, the closing pressure hydraulic loader 21 is controlled, the closing pressure is kept not changed, CH4 gas which is cooled by the injection fluid precooler 18 is injected into the crack flow guide chamber 20 in a fixed quantity, the gas flow rate of an outlet is detected by the first mass flow meter 34 and the second mass flow meter 36, the output quantity change of the gas is measured, the hydrate decomposition quantity is calculated by a mass balance formula, the pressure change of the differential pressure sensor 23 and the displacement change of the displacement sensor 22 are detected in real time, and the flow guide capacity in the hydrate decomposition process is calculated according to a gas Darcy formula.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (8)
1. The utility model provides a natural gas hydrate stimulation seam water conservancy diversion ability testing arrangement which characterized in that, the device includes: the gas injection unit and the liquid injection unit are connected with the crack flow guide instrument, the gas injection unit is used for injecting CH4 gas required by hydrate synthesis into the crack flow guide instrument and controlling the flow and pressure of the injected CH4 gas, the liquid injection unit is used for injecting water and saturated sediments for hydrate synthesis into the crack flow guide instrument and controlling the flow and pressure of injected liquid, the crack flow guide instrument is arranged in the temperature control unit, the temperature control unit is used for controlling the temperature of the crack flow guide instrument and injected fluid, the crack flow guide instrument is a linear flow guide chamber and is used for simulating the support crack parameters of a modified hydrate reservoir stratum, the outlet control unit is connected with the crack flow guide instrument and is used for collecting produced gas and detecting the gas flow, the liquid flow and the corresponding output pressure of the gas and the liquid, the data processing unit is connected with the gas injection unit, the liquid injection unit, the temperature control unit, the crack flow guide instrument and the outlet control unit and is used for data acquisition and data processing.
2. The gas hydrate stimulation fracture conductivity testing device of claim 1, wherein the gas injection unit comprises a CH4 gas cylinder, a first stop valve, a pressure reducing valve, a first pressure sensor, a gas mass flow controller and a second stop valve, and the CH4 gas cylinder, the first stop valve, the pressure reducing valve, the first pressure sensor, the gas mass flow controller and the second stop valve are sequentially connected in series.
3. The natural gas hydrate production increasing seam flow guiding capability testing device of claim 1, wherein the liquid injection unit comprises a first balance, a first beaker, a constant-pressure constant-flow pump, a third stop valve, a second pressure sensor, a stirring piston tank, a fourth stop valve and a fifth stop valve, the first beaker is arranged on the first balance, the constant-pressure constant-flow pump is connected with the first beaker through a pipeline, the constant-pressure constant-flow pump, the third stop valve, the second pressure sensor and the fifth stop valve are connected in series, and the stirring piston tank is connected with the fifth stop valve in parallel after being connected with the fourth stop valve in series.
4. The natural gas hydrate production increasing crack flow conductivity testing device according to claim 1, wherein the crack flow conductivity tester comprises an injection fluid precooler, a first temperature sensor, a crack flow conductivity chamber, a closed pressure hydraulic loader, a displacement sensor, a differential pressure sensor, a second temperature sensor, a third pressure sensor and a fourth pressure sensor, the injection fluid precooler, the first temperature sensor, the closed pressure hydraulic loader, the displacement sensor, the differential pressure sensor, the second temperature sensor, the third pressure sensor and the fourth pressure sensor are all connected with the crack flow conductivity chamber, and the closed pressure hydraulic loader is used for pressurizing the crack flow conductivity chamber.
5. A natural gas hydrate production stimulation fracture conductivity testing device as claimed in claim 4, wherein a refrigeration cavity and a flow guide chamber cavity are arranged in the fracture flow guide chamber, an upper piston and a lower piston are respectively arranged at two ends of the flow guide chamber cavity in a sliding manner, the closed pressure hydraulic loading machine is arranged on one side, away from each other, of the upper piston and the lower piston, a proppant filling layer is arranged between the upper piston and the lower piston, an upper sediment is arranged between the proppant filling layer and the upper piston, and a lower sediment is arranged between the proppant filling layer and the lower piston.
6. The natural gas hydrate production increasing crack flow conductivity testing device of claim 1, wherein the outlet control unit comprises a fifth pressure sensor, a back pressure valve, a gas-liquid separator, a second beaker, a second balance, a dryer, a sixth stop valve, a first mass flowmeter, a seventh stop valve, a second mass flowmeter and a gas storage tank, the gas storage tank is connected with the first mass flowmeter and the second mass flowmeter, the first mass flowmeter and the second mass flowmeter are respectively connected with the dryer through the sixth stop valve and the seventh stop valve, the dryer is connected with the crack flow conductivity meter through the back pressure valve and the gas-liquid separator in sequence, the second beaker is placed on the second balance, and the gas-liquid separator is connected with the second beaker through a pipeline.
7. A method for testing the conductivity of a natural gas hydrate stimulation joint is characterized by comprising the following steps:
preparing a sample from the deposit: filling the in-situ hydrate reservoir sediment mixed with a certain mass of water or configured sediment into a mold, applying load in layers to compress the sediment, and pressing to obtain a lower sediment;
filling a sample: and placing the prepared sediment sample into a crack diversion chamber to flatten the sediment sample, pouring a certain amount of proppant filling layer into the upper part of the sediment sample, scraping the proppant filling layer by using a scraper, and then filling another upper sediment above the proppant filling layer.
Connecting equipment: filling an upper piston in the crack diversion chamber, and connecting joints of the crack diversion chamber; applying a closing pressure of 1.0MPa by a closing pressure hydraulic loader to ensure that the lower sediment and the upper sediment, the proppant filling layer, the upper piston and the lower piston are tightly attached, injecting CH4 gas, and checking the air tightness of the system;
hydrate synthesis: quantitatively injecting CH4 gas through a CH4 gas cylinder, a pressure reducing valve and a gas mass flow controller, stopping injecting the gas when the pressure reaches a set value, closing all valves, starting low-temperature water bath equipment and an injection fluid precooling circulating pump, and cooling a crack flow guide chamber until the crack flow guide chamber reaches the set temperature; monitoring the temperature and pressure change of the crack diversion chamber in real time, and when the temperature and pressure change of the crack diversion chamber does not exceed a preset value, determining that the generation of the hydrate is finished;
and (3) testing the flow conductivity: the conductivity test comprises gas conductivity measurement, liquid conductivity measurement and gas conductivity measurement in the hydrate decomposition process;
disassembling and cleaning the instrument: after the experiment was completed, the instrument was disassembled and all vessels and lines were cleaned, keeping the equipment clean.
8. The method for testing the flow conductivity of the gas hydrate stimulation joint according to claim 7, wherein the process of testing the flow conductivity specifically comprises the following steps:
gas measurement of flow conductivity: setting a backpressure valve to enable backpressure to be pressure after hydrate synthesis, controlling a closed pressure hydraulic loader, setting different closed pressures, quantitatively injecting CH4 gas refrigerated by an injection fluid precooler into a crack diversion chamber, detecting outlet gas flow by using a first mass flowmeter and a second mass flowmeter, detecting pressure change of a differential pressure sensor and displacement change of a displacement sensor in real time, and calculating diversion capacity of a supporting crack layer according to a gas Darcy formula;
liquid measurement of flow conductivity: setting a back pressure valve to enable the back pressure to be the pressure after hydrate synthesis, injecting distilled water into a crack flow guiding chamber by using a constant-pressure constant-flow pump to enable a sediment sample to be saturated, controlling a closed-pressure hydraulic loading machine, setting different closed pressures, quantitatively injecting the liquid refrigerated by an injection fluid precooler into the crack flow guiding chamber by using the constant-pressure constant-flow pump and a stirring piston tank, detecting the flow rate of an outlet until the flow rate is stable, detecting the pressure change of a differential pressure sensor and the displacement change of a displacement sensor in real time, and calculating the flow guiding capacity of a supporting crack layer according to a liquid Darcy formula;
gas measurement conductivity during hydrate decomposition: setting a back pressure valve to enable the back pressure to be lower than the hydrate phase equilibrium pressure, controlling a closed pressure hydraulic loader, keeping the closed pressure not to inject CH4 gas which is refrigerated by an injection fluid precooler into a crack flow guide chamber in a fixed quantity, detecting the flow of gas at an outlet by using a first mass flow meter and a second mass flow meter, measuring the output change of the gas, calculating the hydrate decomposition amount by using a mass balance formula, detecting the pressure change of a differential pressure sensor and the displacement change of a displacement sensor in real time, and calculating the flow guide capacity in the hydrate decomposition process according to a gas Darcy formula.
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