Gas reservoir sensitivity experimental evaluation method and device

Abstract

The invention discloses a gas reservoir sensitivity experimental evaluation method and device, and relates to the technical field of oil-gas field development. The device simulates the states of rock and fluid at the formation temperature; before and after the rock core is damaged, establishing water saturation consistent with the original water saturation of the stratum; a nitrogen test permeability is adopted to simulate reservoir seepage conditions; the core controls the pressure at the outlet end and simulates stratum seepage conditions; evaluating the damage degree of the rock core according to the change rate of the moving speed of the liquid film in the soap film flowmeter. The method solves the problems of salting-out crystallization of experimental fluid, inconsistency between reflected temperature and pressure and formation conditions, large liquid measurement permeability error, sensitivity of stress generated by experimental pressure difference and the like in the process of evaluating the sensitivity of the volcanic gas reservoir at present. According to the method, the stratum seepage conditions are fully simulated, the experimental core pressure and the permeability before and after gas logging sensitivity are controlled, the reservoir sensitivity evaluation of the volcanic gas reservoir is more accurate, and a basis is provided for reasonable development of the volcanic gas reservoir.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and more specifically to a method and device for evaluating gas reservoir reservoir sensitivity damage experiment. Background Art

[0002] After a hundred years of oil and gas exploration and development practice, volcanic rocks have gradually become an important oil and gas exploration target after clastic rocks and carbonate rocks, instead of being an exploration "forbidden zone". At present, igneous oil and gas reservoirs or oil and gas shows have been found in igneous rock sections in more than 300 basins / blocks around the world, among which industrial oil and gas flows and large-scale reserves have been obtained from volcanic rocks in 40 basins in 13 countries.

[0003] Different from conventional sedimentary oil and gas reservoirs, the formation and evolution of volcanic reservoirs have undergone multiple processes, including volcanic eruption, hydrothermal alteration after the magmatic period, weathering and leaching transformation during the interval of volcanic eruption, burial diagenesis transformation, uplift and denudation transformation, and structural fault transformation. Volcanic oil and gas reservoirs generally have the characteristics of diverse reservoir mineral components, low porosity and low permeability of matrix, development of primary pore fractures, and high clay mineral content. Its special mineral components and pore structures lead to many types of potential reservoir sensitivity damage. It is necessary to carry out reservoir sensitivity damage evaluation to reduce the degree of reservoir sensitivity damage.

[0004] However, there are few reports on the systematic evaluation of volcanic reservoir sensitivity. The main operating procedures for gas reservoir fluid sensitivity evaluation refer to the petroleum industry standard "SY / T 5358-2010 Reservoir Sensitivity Flow Experiment Evaluation Method". This standard is mainly for clastic reservoirs with air permeability greater than 1mD, while clastic reservoirs or other lithological reservoirs with air permeability less than 1mD can refer to this standard for reservoir sensitivity evaluation.

[0005] However, for clay-rich, low-permeability and ultra-low-permeability volcanic gas reservoirs, their seepage laws are different from those of conventional oil and gas reservoirs. Therefore, conventional reservoir sensitivity evaluation methods are inappropriate: ① The mineralization of formation water in gas reservoirs is high, and salts in formation water are easy to crystallize and precipitate at room temperature, blocking pore throats and reducing permeability; ② The original water saturation of gas layers is generally lower than <40%, and the current evaluation method has not been established with the original water saturation of gas layers, and the initial permeability tested by the recommended method lacks reference significance; ③ The seepage of gas layers is mainly gas phase, and the gas phase seepage capacity is the main focus. The current method recommends the use of liquid phase to test permeability, which lacks representativeness; ④ In conventional displacement experiments, the pressure difference between the inlet and outlet of the low-permeability core is large, and the outlet is usually atmospheric pressure. The pressure difference between the confining pressure and the pore pressure is large, which is easy to produce additional stress-sensitive damage.

[0006] Reservoir sensitivity evaluation is the basis of reservoir protection and a key link in ensuring the development effect of oil and gas reservoirs. However, the current evaluation method cannot fully adapt to the development needs of volcanic gas reservoirs. Volcanic gas reservoirs are an important area of ​​oil and gas exploration and development in my country. Therefore, forming a sensitivity evaluation method for volcanic gas reservoirs is of great significance to the protection and efficient development of volcanic gas reservoirs. Summary of the invention

[0007] In order to overcome the defects and deficiencies in the above-mentioned prior art, the present invention provides a method and device for evaluating the sensitivity of gas reservoir reservoirs. The purpose of the present invention is to solve the problem that the evaluation methods in the prior art cannot fully adapt to the development needs of volcanic gas reservoirs. The present invention simulates the state of rock and fluid at formation temperature; establishes a water saturation consistent with the original water saturation of the formation before and after core damage; uses nitrogen to test permeability to simulate reservoir seepage conditions; controls the outlet pressure of the core to simulate formation seepage conditions; and evaluates the degree of core damage according to the rate of change of the liquid film moving speed in the soap film flowmeter. The present invention solves the problems of salting out and crystallization of experimental fluids, inconsistency between the reflected temperature and pressure and formation conditions, large error in liquid permeability, and stress sensitivity caused by experimental pressure difference in the current evaluation process of reservoir sensitivity of volcanic gas reservoirs. The present invention fully simulates the formation seepage conditions, controls the experimental core pressure, and the permeability before and after gas sensitivity testing, so as to achieve a more accurate evaluation of the sensitivity of volcanic gas reservoir reservoirs and provide a basis for the rational development of volcanic gas reservoirs.

[0008] In order to solve the above problems existing in the prior art, the present invention is implemented through the following technical solutions.

[0009] The first aspect of the present invention provides a gas reservoir reservoir sensitivity experimental evaluation method, the method comprising the following steps: S1, drilling a plunger core, treating it and testing the core porosity and pore volume; S2, preparing simulated formation water, evacuating the plunger core and saturating it with simulated formation water; S3, placing the saturated core plug in the displacement system, setting the temperature to the formation temperature, and setting the system pressure to be consistent with the formation pressure; S4. Use the displacement medium to displace the plunger core and measure the initial water saturation S of the plunger core. w1 and initial seepage capacity parameters; S5, displacing the plunger core treated in step S4 using the fluid to be evaluated; S6, using the displacement medium to displace the plunger core treated in step S5, so that the water saturation S of the plunger core after displacement is w2 With S w1 then measure the post-damage seepage capacity parameters of the plug core after the fluid to be evaluated is displaced; S7. Evaluate the core damage rate based on the initial seepage capacity parameters measured when the displacement medium displaces the plunger core and the post-damage seepage capacity parameters of the plunger core after the displacement of the fluid to be evaluated.

[0010] Further preferably, in step S4 and step S6, the displacement medium is nitrogen.

[0011] More preferably, in step S4, nitrogen is used to displace the plunger core after vacuum saturation treatment, and the initial core water saturation S is established by detecting the amount of liquid discharged from the core outlet, which is consistent with the original formation water saturation. w1 .

[0012] More preferably, in step S4, when nitrogen is used to displace the plunger core after vacuum saturation treatment, the liquid film velocity V1 of the soap film flowmeter is tested as the initial seepage capacity parameter.

[0013] More preferably, in step S5, when the plug core treated in step S4 is displaced with the fluid to be evaluated, 10-15 times the pore volume of the sample is displaced.

[0014] More preferably, in step S6, when nitrogen is used to displace the plunger core treated in step S5, the water saturation S of the core is established by detecting the amount of liquid discharged from the core outlet. w2 , and keep S w2 =S w1 .

[0015] More preferably, in the step S6, when nitrogen is used to displace the plunger core treated in the step S5, the liquid film velocity V2 of the soap film flowmeter is tested as the post-damage seepage capacity parameter.

[0016] More preferably, in step S7, the core damage rate is evaluated as follows: , where Rd indicates core damage, V1 indicates the gas flow rate of the core under initial conditions, in mm / s; V2 indicates the gas flow rate of the core after displacement by the fluid to be evaluated, in mm / s.

[0017] Further preferably, in step S1, after the plunger core is drilled, the processing thereof specifically refers to washing the drilled plunger core with oil, washing with salt and drying it.

[0018] Further preferably, the simulated formation water is configured according to regional formation water data.

[0019] The second aspect of the present invention provides a gas reservoir sensitivity experimental evaluation device, which includes a constant temperature box for constant temperature simulation of formation temperature, a core holder for placing a plunger core is arranged in the constant temperature box, and the core holder is connected to a displacement pump, a confining pressure pump, a back pressure pump, a back pressure valve and a soap film flowmeter; by controlling the confining pressure pump and the back pressure pump, the formation pressure is maintained inside the core holder; the core holder is also connected to a data acquisition device for collecting pressure changes on the core holder, and the soap film flowmeter is data-connected to the data acquisition device; the core holder is connected to a first container, a second container and a nitrogen bottle through a pipeline, and the displacement pump is used to drive the medium in the first container and the second container to displace the plunger core in the core holder.

[0020] Further preferably, the first container and the second container are both placed in a constant temperature box.

[0021] Further preferably, the displacement pump is connected to the first container and the second container respectively through a six-way valve; the nitrogen bottle, the first container and the second container are connected to the core holder through a six-way valve.

[0022] More preferably, the first container is used to place simulated formation water, and the second container is used to place fluid to be evaluated.

[0023] Compared with the prior art, the beneficial technical effects brought by the present invention are as follows: 1. The present invention simulates the state of rock and fluid at formation temperature; establishes a water saturation consistent with the initial water saturation of the formation before and after core damage; uses nitrogen to test permeability to simulate reservoir seepage conditions; controls the outlet pressure of the core to simulate formation seepage conditions; and evaluates the degree of core damage based on the rate of change of the liquid film movement velocity in the soap film flowmeter. The present invention solves the problems of salting out and crystallization of experimental fluids, inconsistency between reflected temperature and pressure and formation conditions, large errors in liquid-measured permeability, and stress sensitivity caused by experimental pressure differences in the current evaluation of reservoir sensitivity of volcanic gas reservoirs. The present invention fully simulates formation seepage conditions, controls the experimental core pressure, and the liquid film velocity before and after gas-measured sensitivity, thereby achieving a more accurate evaluation of reservoir sensitivity of volcanic gas reservoirs and providing a basis for the rational development of volcanic gas reservoirs.

[0024] 2. The displacement experiment of the present invention is carried out in a constant temperature environment, and the test temperature condition is ensured to be consistent with the formation temperature. Before the experiment, the experimental pressure consistent with the formation pressure is established. During the experiment, the core controls the outlet pressure to ensure that the pressure of the whole experiment is consistent with the formation pressure. Before the core permeability test, nitrogen is used to displace the saturated fluid core to establish a water saturation consistent with the original water saturation of the formation. The experimental process can better simulate the actual formation seepage conditions.

[0025] 3. The experimental evaluation device of the present invention is configured with formation water and test fluid sealed in an intermediate container and stored at the formation temperature to prevent fluid salting out and crystallization. The experimental device is placed in a constant temperature box, and the experimental process is carried out in the constant temperature box to ensure that the test temperature conditions are consistent with the formation temperature to avoid salting out and crystallization during the experiment. The back pressure is controlled at the core outlet to keep the pressure difference between the outlet and the inlet small, avoiding additional stress-sensitive damage caused by excessive experimental pressure difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of the experimental evaluation method of the present invention; Figure 2 is a structural diagram of the experimental evaluation device of the present invention; Figure 3 is a diagram of experimental evaluation results in an embodiment of the present invention; Figure numerals: 1. constant temperature box, 2. core clamp, 3. displacement pump, 4. confining pressure pump, 5. back pressure pump, 6. back pressure valve, 7. soap film flowmeter, 8. data acquisition equipment, 9. first container, 10. second container, 11. nitrogen bottle, 12. six-way valve. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings of the present invention specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1 As a preferred embodiment of the present invention, refer to the attached specification Figure 1 As shown, this embodiment discloses a gas reservoir reservoir sensitivity experimental evaluation method, which includes the following steps: S1, drilling a plunger core, treating it and testing the core porosity and pore volume; S2, preparing simulated formation water, evacuating the plunger core and saturating it with simulated formation water; S3, placing the plunger core after vacuum saturation treatment in the displacement system, and setting the temperature to the formation temperature, and setting the system pressure to be consistent with the formation pressure; S4. Use the displacement medium to displace the plunger core and measure the initial water saturation S of the plunger core. w1 and initial seepage capacity parameters; S5, displacing the plunger core treated in step S4 using the fluid to be evaluated; S6, using the displacement medium to displace the plunger core treated in step S5, so that the water saturation S of the plunger core after displacement is w2 With S w1 then measure the post-damage seepage capacity parameters of the plug core after the fluid to be evaluated is displaced; S7. Evaluate the core damage rate based on the initial seepage capacity parameters measured when the displacement medium displaces the plunger core and the post-damage seepage capacity parameters of the plunger core after the displacement of the fluid to be evaluated.

[0029] Example 2 As another preferred embodiment of the present invention, this embodiment is a further detailed description and supplement of the basic scheme of the present invention based on the above-mentioned embodiment 1. In this embodiment, in step S4 and step S6, the displacement medium is nitrogen. In step S4, nitrogen is used to displace the plunger core after vacuum saturation treatment, and the core water saturation S is established by detecting the amount of liquid discharged from the core outlet, which is consistent with the original formation water saturation. w1 In step S4, when nitrogen is used to displace the plunger core after vacuum saturation treatment, the liquid film velocity V1 of the soap film flowmeter is tested as the initial seepage capacity parameter. In step S5, when the plunger core treated in step S4 is displaced with the fluid to be evaluated, 10-15 times the pore volume of the sample is displaced. In step S6, when nitrogen is used to displace the plunger core treated in step S5, the water saturation S of the core is established by detecting the amount of liquid discharged from the core outlet. w2 , and keep S w2 =S w1 In step S6, when nitrogen is used to displace the plunger core treated in step S5, the liquid film velocity V2 of the soap film flowmeter is tested as the post-damage seepage capacity parameter. In step S7, the core damage rate is evaluated as follows: , where Rd indicates core damage, V1 indicates the gas flow rate of the core under initial conditions, in mm / s; V2 indicates the gas flow rate of the core after displacement by the fluid to be evaluated, in mm / s.

[0030] Example 3 As another preferred embodiment of the present invention, this embodiment is a further detailed supplement and elaboration of the technical solution of the present invention based on the above-mentioned embodiment 1 or embodiment 2. In this embodiment, a method for evaluating the sensitivity of a gas reservoir is provided. The method simulates the state of rock and fluid at the formation temperature; establishes a water saturation consistent with the original water saturation of the formation before and after core damage; uses nitrogen to test permeability to simulate reservoir seepage conditions; controls the outlet pressure of the core to simulate the formation seepage conditions; and evaluates the degree of core damage based on the rate of change of the liquid film movement velocity in the soap film flowmeter.

[0031] The purpose of this embodiment is achieved through the following technical solutions: (1) Drilling plunger cores, washing the oil and salt, and drying the cores, and testing the core porosity φ and pore volume V; (2) Prepare simulated formation water according to regional formation water data, place the plunger core into the core saturation device, and vacuum the core to saturate it for 24 hours; (3) Prepare the intermediate fluid to be tested for sensitivity evaluation and place it into the intermediate container in the constant temperature box; (4) The temperature in the thermostat is set to the formation temperature, and the confining pressure pump, displacement pump, and back pressure valve are controlled to keep the pressure in the displacement system consistent with the formation pressure; (5) Place the core in a thermostatic chamber and use nitrogen to displace the core. By detecting the amount of liquid discharged from the core outlet, establish the core water saturation S that is consistent with the original formation water saturation. w1 ; (6) Using nitrogen to displace the core, test the soap film flowmeter liquid film velocity V1 as the initial seepage capacity parameter of the core; (7) Displace the core with the fluid to be evaluated, displacing 10 to 15 times the pore volume of the sample; (8) Use nitrogen to displace the core and establish the core water saturation S by detecting the amount of liquid discharged from the core outlet. w2 , keep S w1 With S w2 Consistency; (9) Using nitrogen to displace the core, test the soap film flowmeter liquid film velocity V2 as the initial seepage capacity parameter of the core; (10) Evaluation of core damage rate: , where V1 is the gas flow rate of the core under initial conditions, mm / s; V2 is the gas flow rate of the core after sensitive reaction, mm / s.

[0032] Example 4 As another preferred embodiment of the present invention, refer to the attached specification Figure 2As shown, this embodiment provides a gas reservoir reservoir sensitivity experimental evaluation device, which includes a constant temperature box 1 for constant temperature simulation of formation temperature, a core holder 2 for placing a plunger core is arranged in the constant temperature box 1, and the core holder 2 is connected to a displacement pump 3, a confining pressure pump 4, a back pressure pump 5, a back pressure valve 6 and a soap film flowmeter 7; by controlling the confining pressure pump 4 and the back pressure pump 5, the formation pressure inside the core holder 2 is maintained; the core holder 2 is also connected to a data acquisition device 8 for collecting pressure changes on the core holder 2, and the soap film flowmeter 7 is data-connected to the data acquisition device 8; the core holder 2 is connected to a first container 9, a second container 10 and a nitrogen bottle 11 through a pipeline, and the displacement pump 3 is used to drive the medium in the first container 9 and the second container 10 to displace the plunger core in the core holder.

[0033] Further preferably, the first container 9 and the second container 10 are both placed in a thermostatic box. The displacement pump 3 is connected to the first container 9 and the second container 10 respectively through a six-way valve 12; the nitrogen bottle 11, the first container 9 and the second container 10 are connected to the core holder 2 through the six-way valve 12. The first container 9 is used to place simulated formation water, and the second container 10 is used to place the fluid to be evaluated.

[0034] Example 5 As an example of the present invention, taking the Permian volcanic rock reservoir core in Jianyang area of ​​Sichuan Basin as an example, two volcanic rock cores with similar lithology and physical properties were selected to evaluate the degree of water-sensitive damage using the invented method. The gas permeability of core B-1 is 0.016mD, and the gas permeability of core B-2 is 0.060mD. The mineralization of formation water in the area is 60000mg / L.

[0035] The experimental evaluation was carried out according to the method described in the above-mentioned Example 1, Example 2 or Example 3, and the Permian volcanic rocks in Jianyang area were selected. The degree of water-sensitive damage was evaluated by the method of the invention, and the soap film flow test experimental pressure was 0.5 MPa. Figure 3 is the flow ratio obtained in the experiment. The experimental results show that: The gas permeability of core B-1 is 0.016mD. After the core was saturated with formation water mineralization, 1 / 2 formation water mineralization, and distilled water for 24 hours, the liquid film velocities of the gas-measured soap film flowmeter were measured to be 19.12mm / s, 14.77mm / s, and 8.72mm / s, respectively. The degree of salt-sensitive damage was 54.38%, and the degree of water-sensitive damage was medium to strong.

[0036] The gas permeability of core B-2 is 0.060mD. After the core was saturated with formation water mineralization, 1 / 2 formation water mineralization, and distilled water for 24 hours, the liquid film velocities of the gas-measured soap film flowmeter were measured to be 16.31 mm / s, 13.73 mm / s, and mmμL / s, respectively. The degree of salt-sensitive damage was 40.82%, and the degree of water-sensitive damage was medium to weak.

Claims

1. A gas reservoir reservoir sensitivity experimental evaluation method, characterized in that: The method comprises the following steps, S1, drilling a plunger core, treating it and testing the core porosity and pore volume; S2, preparing simulated formation water, evacuating the plunger core and saturating it with simulated formation water; S3, placing the plunger core after vacuum saturation treatment in the displacement system, and setting the temperature to the formation temperature, and setting the system pressure to be consistent with the formation pressure; S4. Use the displacement medium to displace the plunger core and measure the initial water saturation S of the plunger core. w1 and initial seepage capacity parameters; S5, displacing the plunger core treated in step S4 using the fluid to be evaluated; S6, using the displacement medium to displace the plunger core treated in step S5, so that the water saturation S of the plunger core after displacement is w2 With S w1 then measure the post-damage seepage capacity parameters of the plug core after the fluid to be evaluated is displaced; S7. Evaluate the core damage rate based on the initial seepage capacity parameters measured when the displacement medium displaces the plunger core and the post-damage seepage capacity parameters of the plunger core after the displacement of the fluid to be evaluated.

2. A gas reservoir reservoir sensitivity experimental evaluation method according to claim 1, characterized in that: In steps S4 and S6, the displacement medium is nitrogen.

3. A gas reservoir reservoir sensitivity evaluation experimental method according to claim 1, characterized in that: In step S4, nitrogen is used to displace the plunger core after vacuum saturation treatment, and the core water saturation S is established by detecting the amount of liquid discharged from the core outlet, which is consistent with the original formation water saturation. w1 .

4. A gas reservoir reservoir sensitivity experimental evaluation method as claimed in claim 3, characterized in that: In step S4, when nitrogen is used to displace the plunger core after vacuum saturation treatment, the liquid film velocity V1 of the soap film flowmeter is tested as the initial seepage capacity parameter.

5. A gas reservoir reservoir sensitivity experimental evaluation method according to any one of claims 1 to 4, characterized in that: In step S5, when the plug core treated in step S4 is displaced with the fluid to be evaluated, 10-15 times the pore volume of the sample is displaced.

6. A gas reservoir reservoir sensitivity experimental evaluation method according to any one of claims 1 to 4, characterized in that: In step S6, when nitrogen is used to displace the plunger core treated in step S5, the water saturation S of the core is established by detecting the amount of liquid discharged from the core outlet. w2 , and keep S w2 =S w1 .

7. A gas reservoir reservoir sensitivity experimental evaluation method as claimed in claim 4, characterized in that: In the step S6, when nitrogen is used to displace the plunger core treated in the step S5, the liquid film velocity V2 of the soap film flowmeter is tested as the post-damage seepage capacity parameter.

8. A gas reservoir reservoir sensitivity experimental evaluation method according to claim 7, characterized in that: In step S7, the core damage rate is evaluated as follows: , where Rd indicates core damage, V1 indicates the gas flow rate of the core under initial conditions, in mm / s; V2 indicates the gas flow rate of the core after displacement by the fluid to be evaluated, in mm / s.

9. A gas reservoir formation sensitivity test evaluation method according to any one of claims 1 to 4 or 7 or 8, characterized in that: In step S1, after the plunger core is drilled, the plunger core is processed, specifically, the drilled plunger core is washed with oil, washed with salt and dried.

10. A gas reservoir formation sensitivity experimental evaluation method according to any one of claims 1 to 4 or 7 or 8, characterized in that: The simulated formation water is configured according to regional formation water data.

11. A device suitable for the gas reservoir reservoir sensitivity experimental evaluation method according to any one of claims 1 to 10, characterized in that: The invention comprises a thermostatic box (1) for simulating formation temperature at a constant temperature, wherein a core holder (2) for placing a plunger core is arranged in the thermostatic box (1), and the core holder (2) is connected to a displacement pump (3), a confining pressure pump (4), a back pressure pump (5), a back pressure valve (6) and a soap film flow meter (7); the confining pressure pump (4) and the back pressure pump (5) are controlled so that the formation pressure is maintained inside the core holder (2); the core holder (2) is also connected to a data acquisition device (8) for acquiring pressure changes inside the core holder (2), and the soap film flow meter (7) is data-connected to the data acquisition device (8); the core holder (2) is connected to a first container (9), a second container (10) and a nitrogen bottle (11) through a pipeline, and the displacement pump (3) is used to drive the medium in the first container (9) and the second container (10) to displace the plunger core in the core holder (2).

12. A gas reservoir reservoir sensitivity test and evaluation device according to claim 11, characterized in that: The first container (9) and the second container (10) are both placed in a constant temperature box.

13. A gas reservoir reservoir sensitivity test and evaluation device according to claim 11 or 12, characterized in that: The displacement pump (3) is connected to the first container (9) and the second container (10) respectively through a six-way valve (12); the nitrogen bottle (11), the first container (9) and the second container (10) are connected to the core holder (2) through the six-way valve (12).

14. A gas reservoir reservoir sensitivity test and evaluation device according to claim 11 or 12, characterized in that: The first container (9) is used to place simulated formation water, and the second container (10) is used to place fluid to be evaluated.

Images