Experimental device for evaluating shale gas reservoir pressure control production and evaluation method thereof
By designing an experimental device for shale gas reservoirs, we can detect the stress sensitivity effect of shale cores in real time and set up different pressure-controlled production systems, which solves the problem that traditional methods cannot effectively verify the pressure-controlled production system, and improves the procurement of shale gas reservoirs Yield and productivity benefits.
Patent Information
- Application Number
- CN202310740415.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-21
- Publication Date
- 2024-12-24
AI Technical Summary
The traditional shale gas reservoir pressure-controlled production evaluation method cannot observe the shale stress-sensitive effect in real time, resulting in a lack of effective verification when formulating the pressure-controlled production system, which affects the shale gas recovery rate.
Design an experimental device, including a formation fluid saturation system, a real-time detection system for shale stress sensitivity effects, a confining pressure control unit, a gas-liquid separation and metering device and a backpressure control system, and a real-time detection page by installing oil nozzles of different diameters in the production well The stress sensitivity effect of rock cores, and different pressure-controlled production systems are set up to optimize the optimal production mode.
Real-time detection and verification of the pressure-controlled production method of shale gas reservoirs has been achieved, the recovery rate and production efficiency of shale gas reservoirs have been improved, and the negative impact of fracture closure caused by stress sensitivity on recovery rate is delayed.
Smart Images
Figure CN119177842A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of unconventional oil and gas resources, and in particular to an experimental device for evaluating shale gas reservoir pressure-controlled production and an evaluation method thereof, and belongs to the technical field of oil and gas production experimental equipment. Background Art
[0002] The traditional shale gas reservoir pressure control production evaluation method is mainly based on the shale stress sensitivity parameters measured in the laboratory, which are substituted into the numerical simulation software to select the optimal pressure control production system for the gas reservoir by setting different pressure control production systems. The traditional method cannot reflect the shale core stress sensitivity effect in real time, and the pressure control production system obtained by numerical simulation has not been effectively verified.
[0003] In view of the above problems, the present invention aims to provide an experimental device and method for evaluating the pressure-controlled production of shale gas reservoirs, so as to solve the shortcomings of the prior art that the shale stress sensitivity effect cannot be observed in real time, thereby formulating a qualified pressure-controlled production system, and provide an experimental basis for the efficient production of shale gas. Summary of the invention
[0004] The purpose of the present invention is to provide an experimental device for evaluating the controlled pressure production of shale gas reservoirs and an evaluation method thereof, through which the stress sensitivity effect and the controlled pressure production mode of the block shale gas reservoir can be preliminarily determined. Based on the experimental results, different controlled pressure production modes can be realized on site by installing nozzles of different diameters in the production wells, preventing the damage of the permeability of the shale gas reservoir caused by the pressure release production, delaying the influence of the crack closure caused by stress sensitivity on the recovery rate of the shale gas reservoir, thereby increasing the gas production of the production wells and effectively improving the benefits of shale gas reservoir exploitation.
[0005] The objective of the present invention is achieved through the following technical solutions: An experimental device for evaluating the controlled pressure production of shale gas reservoirs comprises a formation fluid saturation system, wherein the formation fluid saturation system is respectively connected to a shale gas controlled pressure production control unit I and a shale gas controlled pressure production control unit II, wherein the shale gas controlled pressure production control unit I is respectively connected to a shale stress sensitive effect real-time detection system, a confining pressure control unit, a gas-liquid separation and gas-liquid metering device II and a back pressure control system II, wherein the shale gas controlled pressure production control unit II is respectively connected to a shale stress sensitive effect real-time detection system, a confining pressure control unit, a back pressure control system I and a gas-liquid separation and gas-liquid metering device I.
[0006] Preferably, the formation fluid saturation system includes a high-pressure displacement device I and a three-way valve I connected in sequence, the three-way valve I is respectively connected to a one-way valve I and a one-way valve II, the one-way valve I is connected in sequence to an intermediate container containing fracturing fluid, a one-way valve IV, a three-way valve III and a shale gas pressure-controlled production control unit II, and the one-way valve II is connected in sequence to an intermediate container containing shale gas, a one-way valve III, a three-way valve II and a shale gas pressure-controlled production control unit I.
[0007] Preferably, the shale gas pressure-controlled production control unit I includes a one-way valve V, which is respectively connected to a three-way valve II and a high-temperature and high-pressure pressure gauge I, and the high-temperature and high-pressure pressure gauge I is sequentially connected to a long core holder I, a high-temperature and high-pressure pressure gauge II and a three-way valve IV, and the long core holder I is also connected to a confining pressure control unit, and the three-way valve IV is respectively connected to a gas-liquid separation and gas-liquid metering device II and a back pressure control system II.
[0008] Preferably, the gas-liquid separation and gas-liquid metering device II comprises a gas-liquid separator II, and the gas-liquid separator II is respectively connected to the three-way valve IV, the liquid metering device II and the gas rotor flowmeter II.
[0009] Preferably, the back pressure control system II comprises a high-precision back pressure valve II, and the high-precision back pressure valve II is connected to the high-pressure displacement device III and the three-way valve IV respectively.
[0010] Preferably, the shale gas pressure-controlled production control unit II includes a one-way valve VI, which is respectively connected to a high-temperature and high-pressure pressure gauge III and a three-way valve III, and the high-temperature and high-pressure pressure gauge III is sequentially connected to a long core holder II, a high-temperature and high-pressure pressure gauge IV and a three-way valve V, and the long core holder II is also connected to a confining pressure control unit, and the three-way valve V is respectively connected to a back pressure control system I and a gas-liquid separation and gas-liquid metering device I.
[0011] Preferably, the back pressure control system I comprises a high-precision back pressure valve I, and the high-precision back pressure valve I is connected to the high-pressure displacement device II and the three-way valve V respectively.
[0012] Preferably, the gas-liquid separation and gas-liquid metering device I comprises a gas-liquid separator I, and the gas-liquid separator I is respectively connected to the three-way valve V, the liquid metering device I and the gas rotor flowmeter I.
[0013] Preferably, the real-time detection system for shale stress sensitive effect comprises an X-ray detection device, and the X-ray detection device is respectively connected to the long core holder I, the long core holder II and the computer.
[0014] Preferably, the confining pressure control unit includes a three-way valve VI, which is respectively connected to the long core holder I, the long core holder II and the high temperature and high pressure pressure gauge V, and the high temperature and high pressure pressure gauge V is also connected to the high pressure displacement device IV.
[0015] A method for evaluating controlled pressure production of shale gas reservoirs comprises the following steps: Step 1: Saturation of formation fluid and injection of fracturing fluid; Step 2: Start the real-time detection system for shale stress sensitivity effect, and record the stress sensitivity effect of shale core under different pressure-controlled production conditions in real time; upload the experimental and X-ray detection data to the computer to obtain the shale stress sensitivity of the area under different production conditions; Step 3: Set up different pressure control production systems; Step 4: Collect formation fluids and calculate gas recovery rates under different production systems.
[0016] Preferably, in the step one, the high-pressure displacement device I, the one-way valve II, and the one-way valve III are opened to displace the formation fluid into the shale gas pressure-controlled production control unit I and the shale gas pressure-controlled production control unit II. After the long core is completely saturated with the formation fluid, the one-way valve II and the one-way valve III are closed, and the one-way valve I and the one-way valve IV are opened to displace the fracturing fluid into the shale gas pressure-controlled production control unit I and the shale gas pressure-controlled production control unit II, simulating the retention of the fracturing fluid in the formation after the fracturing is completed.
[0017] Preferably, in step three, the one-way valve V and the one-way valve VI are closed, and based on the established original formation temperature and pressure conditions, different pressures of the high-pressure displacement device III and the high-pressure displacement device II are reasonably set, and the high-precision back pressure valve II and the high-precision back pressure valve I are used to respectively realize the setting of different pressure controlled production systems of the shale gas pressure controlled production control unit I and the shale gas pressure controlled production control unit II; at the same time, the pressure of the high-pressure displacement device III is set to 0.1 MPa to simulate the depressurization production of the shale gas reservoir, and finally the depressurization production results are compared with the pressure controlled production results.
[0018] Preferably, in step four, the formation fluid collected from the shale gas pressure-controlled production control unit I and the shale gas pressure-controlled production control unit II is separated from the shale gas by passing through the gas-liquid separator II and the gas-liquid separator I, and the volume of the produced shale gas is measured by the gas rotor flowmeter II and the gas rotor flowmeter I to calculate the gas production degree under different production systems.
[0019] The beneficial effects of this technical solution are as follows: 1. The present invention provides an experimental device for evaluating the controlled pressure production of shale gas reservoirs, which can effectively detect the degree of closure of shale core fractures in the shale gas controlled pressure production control unit under different controlled pressure production conditions in real time, and can record the stress sensitivity effect of shale core under different controlled pressure production conditions in real time; the optimal controlled pressure production system for the shale gas reservoir block is determined by setting different controlled pressure production systems for the shale gas controlled pressure production control unit I and the shale gas controlled pressure production control unit II, and based on the shale gas recovery degree and fracture closure obtained in the experiment, the optimal controlled pressure production system for the block is selected to improve the economic benefits of shale gas reservoir production.
[0020] 2. The present invention provides an experimental device for evaluating the controlled pressure production of shale gas reservoirs, wherein the high-pressure displacement device I provides injection pressure for the intermediate container containing shale gas and the intermediate container containing fracturing fluid, and displays the injection pressure in real time on the screen of the high-pressure displacement device; the inlet pressure change of the long core holder I can be monitored by the high-temperature and high-pressure pressure gauge I, and the outlet pressure change of the long core holder I can be monitored by the high-temperature and high-pressure pressure gauge II; the inlet pressure change of the long core holder II can be monitored by the high-temperature and high-pressure pressure gauge III, and the outlet pressure change of the long core holder II can be monitored by the high-temperature and high-pressure pressure gauge IV; by setting different controlled pressure production modes for the shale gas controlled pressure production control unit I and the shale gas controlled pressure production control unit II, the effects of pressure release production and controlled pressure production on the production of shale gas reservoirs or the effects of different controlled pressure production systems on the production of shale gas reservoirs can be compared and analyzed in one experiment.
[0021] 3. The present invention provides an experimental device for evaluating the pressure-controlled production of shale gas reservoirs, wherein different pressures are set in a high-pressure displacement device III, and the back pressure of a long core holder I is controlled by a high-precision back-pressure valve II, and then a shale gas pressure-controlled production control unit I is set to release pressure or different pressure-controlled production systems; the fluid collected from the shale gas pressure-controlled production control unit I is separated into gas and liquid by a gas-liquid separator II, the volume of the produced fracturing fluid is measured by a liquid metering device II, and the volume of the produced shale gas is measured by a gas rotor flowmeter II.
[0022] 4. The present invention provides an experimental device for evaluating the pressure-controlled production of shale gas reservoirs, wherein different pressures are set in the high-pressure displacement device II, and the back pressure of the long core clamp II is controlled by a high-precision back-pressure valve II, and then the shale gas pressure-controlled production control unit II is set to release the pressure or different pressure-controlled production systems; the fluid collected from the shale gas pressure-controlled production control unit II is separated by gas-liquid separator I, the volume of the produced fracturing fluid is measured by the liquid metering device I, and the volume of the produced shale gas is measured by the gas rotor flowmeter I.
[0023] 5. The present invention provides an experimental device for evaluating the controlled pressure production of shale gas reservoirs. During the experiment of setting different controlled pressure production modes for shale gas controlled pressure production control unit I and shale gas controlled pressure production control unit II, an X-ray detection device is used to detect in real time the degree of closure of shale core fractures in the shale gas controlled pressure production control unit under different controlled pressure production conditions, so as to record in real time the stress sensitivity effect of shale core under different controlled pressure production conditions; the experimental and X-ray detection data are uploaded to a computer to obtain the stress sensitivity of shale in the area under different production conditions, and the optimal controlled pressure production system for the block is selected based on the shale gas recovery degree and fracture closure obtained in the experiment. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is a schematic diagram of the structure of the wellhead device and the pipe string in the present invention; Figure 2This is a diagram of the mechanism of crack closure caused by shale stress sensitivity in the invention; Figure 3 is a graph showing the relationship between the permeability of the shale core and the effective stress in the present invention; Figure 4 It is the extraction degree of different production systems in the present invention; Among them: 100, formation fluid saturation system; 101, high pressure displacement device I; 102, three-way valve I; 103, single-way valve I; 104, single-way valve II; 105, intermediate container for shale gas; 106, intermediate container for fracturing fluid; 107, single-way valve III; 108, single-way valve IV; 109, three-way valve II; 110, three-way valve III; 200, real-time detection system for shale stress sensitivity effect; 201, X-ray detection device; 202, computer; 300, back pressure control system I; 301, high-precision back pressure valve I; 302, high pressure displacement device II; 400, gas-liquid separation and gas-liquid metering device I; 401, gas-liquid separator I; 402, liquid metering device I; 403, gas rotor flowmeter I; 500, gas-liquid separation and gas-liquid metering device II; 5 01. Gas-liquid separator II; 502. Liquid metering device II; 503. Gas rotor flowmeter II; 600. Back pressure control system II; 601. High-precision back pressure valve II; 602. High-pressure displacement device III; 700. Shale gas pressure control production control unit I; 701. One-way valve V; 702. High-temperature and high-pressure pressure gauge I; 703. Long core holder I; 704. High-temperature and high-pressure pressure gauge II; 705. Three-way valve IV; 800. Shale gas pressure control production control unit II; 801. One-way valve VI; 802. High-temperature and high-pressure pressure gauge III; 803. Long core holder II; 804. High-temperature and high-pressure pressure gauge IV; 805. Three-way valve V; 900. Confining pressure control unit; 901. Three-way valve VI; 902. High-temperature and high-pressure pressure gauge V; 903. High-pressure displacement device IV. DETAILED DESCRIPTION
[0025] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.
[0026] It should be noted that when a component is referred to as being "mounted on", "fixed on" or "disposed on" another component, it may be directly on the other component or there may be a central component at the same time. When a component is referred to as being "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time.
[0027] It should also be noted that the directional terms such as left, right, up, and down in the embodiments of the present invention are merely relative concepts or are based on the normal use status of the product and should not be considered as restrictive.
[0028] Example 1 like Figure 1 As shown, an experimental device for evaluating the controlled pressure production of shale gas reservoirs comprises a formation fluid saturation system 100, wherein the formation fluid saturation system 100 is respectively connected to a shale gas controlled pressure production control unit Ⅰ700 and a shale gas controlled pressure production control unit Ⅱ800, wherein the shale gas controlled pressure production control unit Ⅰ700 is respectively connected to a shale stress sensitive effect real-time detection system 200, a confining pressure control unit 900, a gas-liquid separation and gas-liquid metering device Ⅱ500 and a back pressure control system Ⅱ600, wherein the shale gas controlled pressure production control unit Ⅱ800 is respectively connected to a shale stress sensitive effect real-time detection system 200, a confining pressure control unit 900, a back pressure control system Ⅰ300 and a gas-liquid separation and gas-liquid metering device Ⅰ400. The method can effectively detect the degree of closure of shale core fractures in the shale gas pressure-controlled production control unit under different pressure-controlled production systems in real time, and can record the stress sensitivity effect of shale core under different pressure-controlled production systems in real time; the optimal pressure-controlled production system for the shale gas reservoir block is selected based on the shale gas recovery degree and fracture closure obtained in the experiment, by setting different pressure-controlled production systems for the shale gas pressure-controlled production control unit I700 and the shale gas pressure-controlled production control unit II800, and improving the economic benefits of shale gas reservoir production.
[0029] Example 2 The difference between this embodiment and embodiment 1 is that the formation fluid saturation system 100 includes a high-pressure displacement device Ⅰ101 and a three-way valve Ⅰ102 connected in sequence, the three-way valve Ⅰ102 is connected to a one-way valve Ⅰ103 and a one-way valve Ⅱ104 respectively, the one-way valve Ⅰ103 is connected to an intermediate container 106 for containing fracturing fluid, a one-way valve Ⅳ108, a three-way valve Ⅲ110 and a shale gas pressure-controlled production control unit Ⅱ800 in sequence, and the one-way valve Ⅱ104 is connected to an intermediate container 105 for containing shale gas, a one-way valve Ⅲ107, a three-way valve Ⅱ109 and a shale gas pressure-controlled production control unit Ⅰ700 in sequence.
[0030] Among them, the shale gas pressure-controlled production control unit I700 includes a one-way valve V701, and the one-way valve V701 is respectively connected to the three-way valve II109 and the high-temperature and high-pressure pressure gauge I702, and the high-temperature and high-pressure pressure gauge I702 is connected to the long core holder I703, the high-temperature and high-pressure pressure gauge II704 and the three-way valve IV705 in sequence, and the long core holder I703 is also connected to the confining pressure control unit 900, and the three-way valve IV705 is respectively connected to the gas-liquid separation and gas-liquid metering device II500 and the back pressure control system II600.
[0031] The gas-liquid separation and gas-liquid metering device II500 comprises a gas-liquid separator II501, and the gas-liquid separator II501 is respectively connected to a three-way valve IV705, a liquid metering device II502 and a gas rotor flowmeter II503.
[0032] The back pressure control system II600 includes a high-precision back pressure valve II601, which is respectively connected to the high-pressure displacement device III602 and the three-way valve IV705. The high-pressure displacement device III602 is set to different pressures, and the back pressure of the long core holder I703 is controlled by the high-precision back pressure valve II601, and then the shale gas pressure control production control unit I700 is set to release pressure or different pressure control production systems; the fluid collected from the shale gas pressure control production control unit I700 is separated into gas and liquid by the gas-liquid separator II501, and the volume of the produced fracturing fluid is measured by the liquid metering device II502, and the volume of the produced shale gas is measured by the gas rotor flowmeter II503.
[0033] Among them, the shale gas pressure-controlled production control unit II800 includes a one-way valve VI801, and the one-way valve VI801 is respectively connected to a high-temperature and high-pressure pressure gauge III802 and a three-way valve III110, and the high-temperature and high-pressure pressure gauge III802 is connected to a long core holder II803, a high-temperature and high-pressure pressure gauge IV804 and a three-way valve V805 in sequence, and the long core holder II803 is also connected to a confining pressure control unit 900, and the three-way valve V805 is respectively connected to a back pressure control system I300 and a gas-liquid separation and gas-liquid metering device I400. The high-pressure displacement device Ⅰ101 provides injection pressure for the intermediate container 105 containing shale gas and the intermediate container 106 containing fracturing fluid, and displays it in real time on the screen of the high-pressure displacement device; the inlet pressure change of the long core holder Ⅰ703 can be monitored by the high-temperature and high-pressure pressure gauge Ⅰ702, and the outlet pressure change of the long core holder Ⅰ703 can be monitored by the high-temperature and high-pressure pressure gauge Ⅱ704; the inlet pressure change of the long core holder Ⅱ803 can be monitored by the high-temperature and high-pressure pressure gauge Ⅲ802, and the outlet pressure change of the long core holder Ⅱ803 can be monitored by the high-temperature and high-pressure pressure gauge Ⅳ804; by setting different pressure control production modes for the shale gas pressure control production control unit Ⅰ700 and the shale gas pressure control production control unit Ⅱ800, the effects of pressure release production and pressure control production on the production of shale gas reservoirs or the effects of different pressure control production systems on the production of shale gas reservoirs can be compared and analyzed in one experiment.
[0034] The back pressure control system I300 includes a high-precision back pressure valve I301, which is respectively connected to the high-pressure displacement device II302 and the three-way valve V805. The high-pressure displacement device II302 is set to different pressures, and the back pressure of the long core holder II803 is controlled by the high-precision back pressure valve II601, and then the shale gas pressure control production control unit II800 is set to release pressure or different pressure control production systems; the fluid collected from the shale gas pressure control production control unit II800 is separated into gas and liquid by the gas-liquid separator I401, and the volume of the produced fracturing fluid is measured by the liquid metering device I402, and the volume of the produced shale gas is measured by the gas rotor flowmeter I403.
[0035] The gas-liquid separation and gas-liquid metering device I400 comprises a gas-liquid separator I401, and the gas-liquid separator I401 is respectively connected to the three-way valve V805, the liquid metering device I402 and the gas rotor flowmeter I403.
[0036] The real-time detection system 200 for shale stress sensitivity effect includes an X-ray detection device 201, which is respectively connected to the long core holder I703, the long core holder II803 and the computer 202. During the experiment of setting different controlled pressure production modes for the shale gas controlled pressure production control unit I700 and the shale gas controlled pressure production control unit II800, the X-ray detection device 201 is used to detect the degree of closure of shale core fractures in the shale gas controlled pressure production control unit under different controlled pressure production conditions in real time, so as to record the stress sensitivity effect of shale core under different controlled pressure production conditions in real time; the experimental and X-ray detection data are uploaded to the computer 202, so as to obtain the shale stress sensitivity of the region under different production conditions, and the optimal controlled pressure production system of the block is selected based on the shale gas recovery degree and fracture closure obtained in the experiment.
[0037] The confining pressure control unit 900 includes a three-way valve VI 901, which is respectively connected to the long core holder I 703, the long core holder II 803 and the high temperature and high pressure pressure gauge V 902, and the high temperature and high pressure pressure gauge V 902 is also connected to the high pressure displacement device IV 903.
[0038] A method for evaluating controlled pressure production of shale gas reservoirs comprises the following steps: Step 1, saturation of formation fluid and injection of fracturing fluid stage; open the high-pressure displacement device Ⅰ101, the one-way valve Ⅱ104, and the one-way valve Ⅲ107, displace the formation fluid into the shale gas pressure-controlled production control unit Ⅰ700 and the shale gas pressure-controlled production control unit Ⅱ800, and after the long core is completely saturated with the formation fluid, close the one-way valve Ⅱ104 and the one-way valve Ⅲ107, open the one-way valve Ⅰ103 and the one-way valve Ⅳ108, and displace the fracturing fluid into the shale gas pressure-controlled production control unit Ⅰ700 and the shale gas pressure-controlled production control unit Ⅱ800, to simulate the retention of the fracturing fluid in the formation after the fracturing is completed; Step 2: Start the real-time detection system 200 for shale stress sensitivity effect, and record the stress sensitivity effect of shale core under different pressure-controlled production conditions in real time; upload the experimental and X-ray detection data to the computer 202, and obtain the shale stress sensitivity of the region under different production conditions; Step 3, set different pressure control production systems; close the one-way valve V701 and the one-way valve VI801, and reasonably set different pressures of the high-pressure displacement device III602 and the high-pressure displacement device II302 based on the established original formation temperature and pressure conditions (the lower part of the piston of the high-pressure displacement device III602 and the high-pressure displacement device II302 is high-performance hydraulic oil, and the upper part of the piston is nitrogen. High-performance hydraulic oil is continuously injected into the high-pressure displacement device III602, and the piston moves upward to compress the nitrogen on the upper part of the piston. The nitrogen acts on the back pressure valve through the pipeline to achieve pressure transmission; at the same time, a pressure detection device is installed inside the high-pressure displacement device III602, which can reflect the internal pressure of the back pressure valve in real time and display it on the external display screen of the high-pressure displacement device III602. In the pressure control production experiment, according to the experimental plan, the working mode of the high-pressure displacement device III602 is set to pressure control and fixed liquid, and the high-performance hydraulic oil pumping speed is controlled to 0.01 ml / min, set the pressure of high-pressure displacement device III602 to the required production pressure, and the pressure of high-pressure displacement device III and high-pressure displacement device II can be evenly and slowly decreased), and the setting of different pressure control production systems of shale gas pressure control production control unit I700 and shale gas pressure control production control unit II800 can be realized through high-precision back pressure valve II601 and high-precision back pressure valve I301 respectively; at the same time, the pressure of high-pressure displacement device III602 can also be set to 0.1MPa to simulate the pressure release production of shale gas reservoirs, and finally the pressure release production results can be compared with the pressure control production results; Step 4: Collect formation fluid and calculate the gas production degree under different production systems; the formation fluid collected from the shale gas pressure-controlled production control unit I700 and the shale gas pressure-controlled production control unit II800 is separated from the shale gas and liquid by the gas-liquid separator II501 and the gas-liquid separator I401. The volume of produced shale gas is measured by the gas rotor flowmeter II503 and the gas rotor flowmeter I403 to calculate the gas production degree under different production systems.
[0039] Example 3 The difference between this embodiment and embodiment 2 is that the formation pressure is set to 48MPa and the temperature is set to 104°C. In view of the strong stress sensitivity of shale reservoir fractures and the unclear pressure control production system, 6 groups of fracturing transformation shale pressure control production long core experiments are designed. The specific experimental scheme is shown in Table 1. Different back pressures are set by high-precision back pressure valve II601 and high-precision back pressure valve I301 to achieve different pressure control production systems.
[0040] Table 1 Experimental scheme for long cores in shale pressure control production by fracturing The shale stress sensitivity effect real-time detection system 200 and the shale gas production degree measured by the gas rotor flowmeter are as follows: Figure 3 and Figure 4 As shown: A. Rock reservoir fractures are more sensitive to stress (e.g. Figure 2 As shown in the figure, depressurization production can easily cause reservoir damage and affect the final cumulative gas production of the gas well.
[0041] B. The stress sensitivity effect has a significant impact on the shale test results. When the effective stress is set at 6.9 MPa (the stress sensitivity effect is low), the final recovery rate reaches 92%, while when the confining pressure is set at 60 MPa (the effective stress continues to increase), the recovery rate is 82%.
[0042] C. Shale gas reservoirs should be properly pressure controlled during production. When the pressure is released to the abandoned pressure (5MPa), the recovery rate is only 68.9%, and the pressure difference between the inlet and outlet reaches 5MPa; while the back pressure is controlled to decrease by 1MPa every 15min, the recovery rate is increased to 82%, and the pressure difference between the inlet and outlet is 4.1MPa, indicating that pressure-controlled production of shale gas reservoirs can effectively reduce the impact of stress sensitivity on production.
[0043] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.
Claims
1. An experimental device for evaluating pressure-controlled production of shale gas reservoirs, characterized in that: The invention comprises the following steps: comprising a formation fluid saturation system (100), wherein the formation fluid saturation system (100) is respectively connected to a shale gas pressure-controlled production control unit I (700) and a shale gas pressure-controlled production control unit II (800), wherein the shale gas pressure-controlled production control unit I (700) is respectively connected to a shale stress sensitive effect real-time detection system (200), a confining pressure control unit (900), a gas-liquid separation and gas-liquid metering device II (500) and a back pressure control system II (600), and wherein the shale gas pressure-controlled production control unit II (800) is respectively connected to a shale stress sensitive effect real-time detection system (200), a confining pressure control unit (900), a back pressure control system I (300) and a gas-liquid separation and gas-liquid metering device I (400).
2. The experimental device for evaluating the controlled pressure production of shale gas reservoirs according to claim 1, characterized in that: The formation fluid saturation system (100) comprises a high-pressure displacement device I (101) and a three-way valve I (102) connected in sequence, wherein the three-way valve I (102) is connected to a one-way valve I (103) and a one-way valve II (104) respectively, wherein the one-way valve I (103) is connected to an intermediate container (106) containing fracturing fluid, a one-way valve IV (108), a three-way valve III (110) and a shale gas pressure-controlled production control unit II (800) in sequence, and the one-way valve II (104) is connected to an intermediate container (105) containing shale gas, a one-way valve III (107), a three-way valve II (109) and a shale gas pressure-controlled production control unit I (700) in sequence.
3. The experimental device for evaluating the controlled pressure production of shale gas reservoirs according to claim 2, characterized in that: The shale gas pressure-controlled production control unit I (700) comprises a one-way valve V (701), wherein the one-way valve V (701) is respectively connected to a three-way valve II (109) and a high-temperature and high-pressure pressure gauge I (702), wherein the high-temperature and high-pressure pressure gauge I (702) is sequentially connected to a long core holder I (703), a high-temperature and high-pressure pressure gauge II (704) and a three-way valve IV (705), wherein the long core holder I (703) is also connected to a confining pressure control unit (900), and wherein the three-way valve IV (705) is respectively connected to a gas-liquid separation and gas-liquid metering device II (500) and a back pressure control system II (600).
4. The experimental device for evaluating the controlled pressure production of shale gas reservoirs according to claim 3, characterized in that: The gas-liquid separation and gas-liquid metering device II (500) comprises a gas-liquid separator II (501), and the gas-liquid separator II (501) is respectively connected to a three-way valve IV (705), a liquid metering device II (502) and a gas rotor flowmeter II (503).
5. The experimental device for evaluating the controlled pressure production of shale gas reservoirs according to claim 4, characterized in that: The back pressure control system II (600) comprises a high-precision back pressure valve II (601), and the high-precision back pressure valve II (601) is connected to the high-pressure displacement device III (602) and the three-way valve IV (705) respectively.
6. The experimental device for evaluating the controlled pressure production of shale gas reservoirs according to claim 5, characterized in that: The shale gas pressure-controlled production control unit II (800) comprises a one-way valve VI (801), wherein the one-way valve VI (801) is respectively connected to a high-temperature and high-pressure pressure gauge III (802) and a three-way valve III (110), wherein the high-temperature and high-pressure pressure gauge III (802) is sequentially connected to a long core holder II (803), a high-temperature and high-pressure pressure gauge IV (804) and a three-way valve V (805), wherein the long core holder II (803) is also connected to a confining pressure control unit (900), and wherein the three-way valve V (805) is respectively connected to a back pressure control system I (300) and a gas-liquid separation and gas-liquid metering device I (400).
7. The experimental device for evaluating the controlled pressure production of shale gas reservoirs according to claim 6, characterized in that: The back pressure control system I (300) comprises a high-precision back pressure valve I (301), and the high-precision back pressure valve I (301) is connected to the high-pressure displacement device II (302) and the three-way valve V (805) respectively.
8. The experimental device for evaluating the controlled pressure production of shale gas reservoirs according to claim 7, characterized in that: The gas-liquid separation and gas-liquid metering device I (400) comprises a gas-liquid separator I (401), and the gas-liquid separator I (401) is respectively connected to a three-way valve V (805), a liquid metering device I (402) and a gas rotor flowmeter I (403).
9. The experimental device for evaluating the controlled pressure production of shale gas reservoirs according to claim 8, characterized in that: The shale stress sensitive effect real-time detection system (200) comprises an X-ray detection device (201), wherein the X-ray detection device (201) is respectively connected to a long core holder I (703), a long core holder II (803) and a computer (202).
10. The experimental device for evaluating the controlled pressure production of shale gas reservoirs according to claim 9, characterized in that: The confining pressure control unit (900) comprises a three-way valve VI (901), wherein the three-way valve VI (901) is respectively connected to the long core holder I (703), the long core holder II (803) and the high temperature and high pressure pressure gauge V (902), and the high temperature and high pressure pressure gauge V (902) is also connected to the high pressure displacement device IV (903).
11. A method for evaluating pressure-controlled production of shale gas reservoirs, characterized in that: The following steps are involved: Step 1: Saturation of formation fluid and injection of fracturing fluid; Step 2: start the real-time detection system for shale stress sensitivity effect (200) to record the shale core stress sensitivity effect under different controlled pressure production conditions in real time; By uploading the experimental and X-ray detection data to a computer (202), the stress sensitivity of shale in the region under different production conditions can be obtained; Step 3: Set up different pressure control production systems; Step 4: Collect formation fluids and calculate gas recovery rates under different production systems.
12. The method for evaluating controlled pressure production of shale gas reservoirs according to claim 11, characterized in that: In the step 1, the high-pressure displacement device I (101), the one-way valve II (104), and the one-way valve III (107) are opened to displace the formation fluid into the shale gas pressure-controlled production control unit I (700) and the shale gas pressure-controlled production control unit II (800). After the long core is completely saturated with the formation fluid, the one-way valve II (104) and the one-way valve III (107) are closed, and the one-way valve I (103) and the one-way valve IV (108) are opened to displace the fracturing fluid into the shale gas pressure-controlled production control unit I (700) and the shale gas pressure-controlled production control unit II (800), thereby simulating the retention of the fracturing fluid in the formation after the fracturing is completed.
13. The method for evaluating controlled pressure production of shale gas reservoirs according to claim 12, characterized in that: In the step three, the one-way valve V (701) and the one-way valve VI (801) are closed, and based on the established original formation temperature and pressure conditions, different pressures of the high-pressure displacement device III (602) and the high-pressure displacement device II (302) are reasonably set, and different pressure control production systems of the shale gas pressure control production control unit I (700) and the shale gas pressure control production control unit II (800) are set through the high-precision back pressure valve II (601) and the high-precision back pressure valve I (301), respectively; at the same time, the pressure of the high-pressure displacement device III (602) is set to 0.1 MPa to simulate the depressurization production of the shale gas reservoir, and finally the depressurization production result is compared with the pressure control production result.
14. The method for evaluating controlled pressure production of shale gas reservoirs according to claim 13, characterized in that: In step 4, the formation fluid collected from the shale gas pressure-controlled production control unit I (700) and the shale gas pressure-controlled production control unit II (800) is separated from the shale gas and the liquid by passing through the gas-liquid separator II (501) and the gas-liquid separator I (401), and the volume of the produced shale gas is measured by the gas rotor flowmeter II (503) and the gas rotor flowmeter I (403) to calculate the gas production degree under different production systems.