Device and method for testing stress sensitivity of high-temperature and high-pressure rock core

Abstract

The invention provides a high-temperature and high-pressure rock core stress sensitivity testing device and method, and relates to the technical field of geological prospecting, the high-temperature and high-pressure rock core stress sensitivity testing device comprises a rock core holder, a confining pressure pump connected to the middle side surface of the rock core holder, a high-pressure gas cylinder connected to the inlet end of the rock core holder, and a fluid heater connected in series between the high-pressure gas cylinder and the rock core holder, a resistance wire is arranged on the inner wall of the core holder, and the outlet end of the core holder is sequentially connected with a needle throttle valve and a soap film flowmeter; the pipeline between the high-pressure gas cylinder and the fluid heater is also connected with an internal pressure pump through a multi-way valve I; and pressure gauges are connected between the core holder and the confining pressure pump, between the core holder and the fluid heater and between the core holder and the needle throttle valve. The needle throttle valve is used for replacing a back-pressure valve in the prior art, so that the high-temperature and high-pressure rock core stress sensitivity test is realized at low cost while a good back-pressure stabilizing effect is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of geological exploration, and in particular to a core stress sensitivity testing device and a method thereof. Background Art

[0002] In the effective development process of low-permeability reservoirs, permeability is one of the important rock physical parameters that affect the development of oil and gas fields. As the effective stress gradually increases, the pore space of the reservoir continues to decrease, and the permeability also decreases. This phenomenon is called reservoir stress sensitivity. In the process of oil and gas reservoir exploitation, changes in formation pressure cause stress sensitivity effects in the oil and gas reservoir, affecting the flow of oil and gas reservoir fluids. Especially in the exploitation of deep oil and gas reservoirs, changes in reservoir effective stress under high temperature and high pressure will have an important impact on oil and gas well production. Therefore, conducting indoor experiments to evaluate the stress sensitivity of cores under high temperature and high pressure can provide technical and theoretical support for the efficient development of deep oil and gas reservoirs.

[0003] At present, the methods commonly used in domestic and foreign laboratories to determine reservoir stress sensitivity mainly include variable confining pressure (simulating the overburden pressure of the reservoir), constant internal pressure (simulating the formation pressure of the reservoir), and constant confining pressure and variable internal pressure. Combined with the actual mining conditions, the experimental method of constant confining pressure and variable internal pressure is scientific and reasonable, but the existing experimental devices have large errors in the actual operation of changing the internal pressure, and the pressure is not easy to control, which cannot achieve the effect of truly simulating the formation pressure, and cannot meet the requirements of high temperature and high pressure formation environment.

[0004] The relevant research on the stress sensitivity evaluation of cores under high temperature and high pressure conditions mainly focuses on the following two aspects: ① The entire set of measuring devices is placed under high temperature conditions, and then the core permeability is calculated directly by collecting the flow at the outlet of the core holder through Darcy's law. ② The core holder is placed under high temperature and high pressure in the reservoir, and a precision instrument resistant to high temperature and high pressure is used to first heat the fluid, and then cool it down after passing through the core holder to measure the flow of the fluid. In order to truly reflect the permeability and its changing law under formation conditions, a back pressure valve is usually added to the outlet of the core to simulate the production pressure difference in actual production to achieve a higher pore fluid pressure. The main principle of the back pressure valve is to set a back pressure value through the back pressure valve. When the pressure at the outlet of the core is higher than the set back pressure value, the back pressure valve opens to allow the fluid to flow through the core; controlling the back pressure change can achieve a high pore fluid pressure. However, the back pressure valves currently used generally have problems such as high starting pressure, difficult deformation recovery, and low control accuracy, resulting in poor reliability. In addition, its price is relatively expensive and the cost of use is high. Summary of the invention

[0005] The purpose of the present invention is to provide a high-temperature and high-pressure core stress sensitivity testing device and method, by using a needle-type throttle valve to replace the back pressure valve in the prior art, while ensuring good back pressure stability, high-temperature and high-pressure core stress sensitivity testing can be achieved at a low cost.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A high-temperature and high-pressure core stress sensitivity testing device comprises a core holder, a confining pressure pump connected to the middle side of the core holder, and a high-pressure gas cylinder connected to the inlet end of the core holder, a fluid heater is connected in series between the high-pressure gas cylinder and the core holder, a resistance wire is arranged on the inner wall of the core holder, and a needle-type throttle valve and a soap film flowmeter are connected to the outlet end of the core holder in sequence; an internal pressure pump is also connected to the pipeline between the high-pressure gas cylinder and the fluid heater through a multi-way valve; and a pressure gauge is connected between the core holder and the confining pressure pump, the fluid heater, and the needle-type throttle valve.

[0008] Furthermore: an intermediate container is connected in series between the internal pressure pump and the multi-way valve 1.

[0009] Furthermore, it also includes a data monitoring and display device, the confining pressure pump and the core clamp are connected through the multi-way valve 2, and the data monitoring and display device is connected to the multi-way valve 1, the multi-way valve 2, and the needle throttle valve. The data monitoring and display device can monitor the change curve relationship between different pore fluid pressures and rock permeability in real time, and more accurately detect the permeability of rocks under different cores and different pore fluid pressures.

[0010] Furthermore: the fluid heater comprises a shell and a resistance wire installed in the shell through a bracket, the shell is provided with an inlet and an outlet, the inlet is connected to the high-pressure gas cylinder, and the outlet is connected to the core holder; the resistance wire is evenly arranged in the shell.

[0011] Furthermore: baffles are installed on the mounting plate, a tortuous flow channel from the inlet to the outlet is formed between the baffles, and the resistance wire is arranged on the baffles.

[0012] Furthermore: the confining pressure pump and the internal pressure pump are both constant pressure and constant speed pumps, and an electronic control system is provided in the constant pressure and constant speed pump.

[0013] The present invention also provides a high temperature and high pressure core stress sensitivity testing method, comprising the following steps:

[0014] S1: Core preparation: prepare the plunger sample core and keep all valves in the device closed;

[0015] S2: calibrate the volume contained in the pipeline, then put the plunger sample core into the core holder, and gradually pressurize the core holder with the confining pressure pump to make the simulated overburden pressure of the formation stable;

[0016] S3: The high-pressure gas is completely heated to the reservoir temperature through the fluid heater, and then the multi-way valve 1 is opened to adjust the pressure of the internal pressure pump, and the high-pressure gas is passed into the high-temperature core for measurement;

[0017] S4: Adjust the needle throttle valve to adjust the back pressure step by step; adjust the pressure difference between the two ends of the core holder to the designed pressure difference, so that the pressure difference between the two ends of the core holder remains constant;

[0018] S5: Open the needle throttle valve and measure the flow rate of soap bubbles per unit time through the soap film flowmeter;

[0019] S6: repeat the above steps S2-S5, and adjust the pressure of the internal pressure pump in S3 step by step each time, and use the soap film flowmeter to measure the flow rate per unit time of the soap film flowmeter under different pressure differences at both ends of the core holder, and calculate the permeability under each pressure according to the flow rate;

[0020] S7: The sensitivity of the core is obtained according to the above permeability and the corresponding confining pressure and internal pressure;

[0021] S8: After the experiment is over, the confining pressure and internal pressure are released, and the multi-way valve is opened to release the fluid in the pipeline.

[0022] Further: the specific steps of preparing the plunger sample core in S1 include: extracting, cleaning, drying the selected core, and then measuring the dry weight, diameter, and length.

[0023] Further: in S5, the flow rate of soap bubbles per unit time is measured 3-5 times under different temperature and pressure difference conditions.

[0024] Compared with the original technology, the present invention has the following beneficial effects:

[0025] 1. The present invention replaces the back pressure valve in the prior art with a needle throttle valve to adjust the fluid pressure under different pores to which the core in the core holder is subjected, and has a good back pressure stabilization effect. At the same time, the throttle valve processing and production technology is mature, low-cost, and highly adaptable.

[0026] Second, by setting up an electronic control system in the constant pressure and constant speed pump, the confining pressure and back pressure are gradually controlled with a preset pressure step to achieve stable pressure increase.

[0027] Third, by connecting an intermediate container between the internal pressure pump and the core holder, it is easy to control the internal pressure leading to the core to change steadily step by step, making the pressurization effect more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the present invention;

[0029] Figure 2is a structural schematic diagram of a fluid heater;

[0030] In the figure:

[0031] 1. Core holder; 2. Confining pressure pump; 3. High-pressure gas cylinder; 4. Fluid heater; 5. Resistance wire; 6. Needle throttle valve; 7. Soap film flowmeter; 8. Multi-way valve 1; 9. Internal pressure pump; 10. Intermediate container; 11. Flowmeter; 12. Data monitoring and display device; 13. Multi-way valve 2; 14. Thermometer. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. 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.

[0033] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0034] like Figure 1 As shown: a high-temperature and high-pressure core stress sensitivity test device, including a core holder 1, a confining pressure pump 2 connected to the middle side of the core holder 1, and a high-pressure gas cylinder 3 connected to the inlet end of the core holder 1. A fluid heater 4 is connected in series between the high-pressure gas cylinder 3 and the core holder 1. A resistance wire 5 is arranged on the inner wall of the core holder 1. The resistance wire 5 is close to the core and is used to heat the core; the outlet end of the core holder 1 is connected in sequence with a needle-type throttle valve 6 and a soap film flowmeter 11; the pipeline between the high-pressure gas cylinder 3 and the fluid heater 4 is also connected to an internal pressure pump 9 through a multi-way valve 8; a pressure gauge is connected between the core holder 1 and the confining pressure pump 2, the fluid heater 4, and the needle-type throttle valve 6; an intermediate container 10 is connected in series between the internal pressure pump 9 and the multi-way valve 8. The confining pressure pump 2 and the internal pressure pump 9 are both constant pressure and constant speed pumps.

[0035] The data monitoring and display device 12 is also included. The confining pressure pump 2 is connected to the core holder 1 through a multi-way valve 2 13. The data monitoring and display device 12 is connected to the multi-way valve 1 8, the multi-way valve 2 13, and the needle throttle valve 6. The data monitoring and display device 12 can monitor the relationship between the change curves of different pore fluid pressures and rock permeability in real time, and more accurately detect the permeability of rocks under different cores and different pore fluid pressures.

[0036] The fluid heater 4 includes a shell and a resistance wire 5 installed in the shell through a bracket. The shell is provided with an inlet and an outlet, the inlet is connected to the high-pressure gas cylinder 3, and the outlet is connected to the core holder 1; the resistance wire 5 is evenly arranged in the shell. A baffle is installed on the mounting plate, and a tortuous flow channel from the inlet to the outlet is formed between the baffles. The resistance wire 5 is arranged on the baffle. A thermometer 14 is installed on the fluid heater 4 and the core holder 1, and the thermometer 14 and the resistance wire 5 are connected to the data monitoring and display device 12. When the gas passes through the fluid heater 4, the resistance wire 5 can fully heat the gas to the target temperature, ensuring that the fluid temperature is consistent with the core during measurement, the state is stable, and the permeability error measured is small.

[0037] The present invention also provides a high temperature and high pressure core stress sensitivity testing method, comprising the following steps:

[0038] S1: Core preparation: prepare plunger sample cores, extract, clean, dry the selected cores, measure dry weight, diameter, and length, and keep all valves in the device closed;

[0039] S2: calibrate the volume contained in the pipeline, then put the plunger sample core into the core holder, and gradually pressurize the core holder with the confining pressure pump to make the simulated overburden pressure of the formation stable;

[0040] S3: The high-pressure gas is completely heated to the reservoir temperature through the fluid heater, and then the multi-way valve 8 is opened to adjust the pressure of the internal pressure pump 9, and the high-pressure gas is passed into the high-temperature core for measurement;

[0041] S4: Adjust the needle throttle valve to adjust the back pressure step by step; adjust the pressure difference between the two ends of the core holder to the designed pressure difference, so that the pressure difference between the two ends of the core holder remains constant;

[0042] S5: Open the needle throttle valve, and measure the flow rate of soap bubbles per unit time 3-5 times under different temperature and pressure difference conditions through the needle throttle valve 6;

[0043] S6: repeat the above steps S2-S5, and adjust the pressure of the internal pressure pump 9 in S3 step by step each time, and use the needle throttle valve 6 to measure the flow rate per unit time of the soap mold flowmeter 11 under different pressure differences at both ends of the core holder, and calculate the permeability under each pressure according to the flowmeter 11;

[0044] S7: The sensitivity of the core is obtained according to the above permeability and the corresponding confining pressure and internal pressure;

[0045] S8: After the experiment is over, the confining pressure and internal pressure are released, and the multi-way valve 8 is opened to release the fluid in the pipeline.

[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-temperature and high-pressure core stress sensitivity testing device, comprising a core holder, a confining pressure pump connected to the middle side of the core holder, a high-pressure gas cylinder connected to the inlet end of the core holder, a fluid heater connected in series between the high-pressure gas cylinder and the core holder, and a resistance wire provided on the inner wall of the core holder, characterized in that: The outlet end of the core holder is connected with a needle throttle valve and a soap film flowmeter in sequence; the pipeline between the high-pressure gas cylinder and the fluid heater is also connected with an internal pressure pump through a multi-way valve; a pressure gauge is connected between the core holder and the confining pressure pump, the fluid heater and the needle throttle valve.

2. A high temperature and high pressure core stress sensitivity testing device according to claim 1, characterized in that: An intermediate container is connected in series between the internal pressure pump and the multi-way valve 1.

3. A high temperature and high pressure core stress sensitivity testing device according to claim 1, characterized in that: It also includes a data monitoring and display device. The confining pressure pump and the core clamp are connected through a multi-way valve 2. The data monitoring and display device is connected to the multi-way valve 1, the multi-way valve 2, and the needle throttle valve.

4. A high temperature and high pressure core stress sensitivity testing device according to claim 1, characterized in that: The fluid heater comprises a shell and a resistance wire installed in the shell through a bracket. The shell is provided with an inlet and an outlet, the inlet is connected to the high-pressure gas cylinder, and the outlet is connected to the core holder; the resistance wire is evenly arranged in the shell.

5. A high temperature and high pressure core stress sensitivity testing device according to claim 4, characterized in that: The mounting plate is provided with baffles, a zigzag flow path from the inlet to the outlet is formed between the baffles, and the resistance wire is arranged on the baffles.

6. A high temperature and high pressure core stress sensitivity testing device according to claim 1, characterized in that: The confining pressure pump and the internal pressure pump are both constant pressure and constant speed pumps, and an electronic control system is arranged in the constant pressure and constant speed pump.

7. A method for testing high temperature and high pressure core stress sensitivity using any one of the high temperature and high pressure core stress sensitivity testing devices as claimed in claims 1 to 6, characterized in that: S1: Core preparation: prepare the plunger sample core and keep all valves in the device closed; S2: calibrate the volume contained in the pipeline, then put the plunger sample core into the core holder, and gradually pressurize the core holder with the confining pressure pump to make the simulated overburden pressure of the formation stable; S3: The high-pressure gas is completely heated to the reservoir temperature through the fluid heater, and then the multi-way valve 1 is opened to adjust the pressure of the internal pressure pump, and the high-pressure gas is passed into the high-temperature core for measurement; S4: Adjust the needle throttle valve to adjust the back pressure step by step; adjust the pressure difference between the two ends of the core holder to the designed pressure difference, so that the pressure difference between the two ends of the core holder remains constant; S5: Open the needle throttle valve and measure the flow rate of soap bubbles per unit time through the soap film flowmeter; S6: repeating steps S2-S5, adjusting the pressure of the internal pressure pump in S3 step by step each time, respectively measuring the flow rate per unit time of the soap film flowmeter under different pressure differences at both ends of the core holder, and calculating the permeability under each pressure according to the flow rate; S7: The sensitivity is obtained according to the above permeability and the corresponding confining pressure and internal pressure; S8: After the experiment is over, the confining pressure and internal pressure are released, and the multi-way valve 1 is opened to release the fluid in the pipeline.

8. A high temperature and high pressure core stress sensitivity testing method according to claim 7, characterized in that: The specific steps of preparing the plunger sample core in S1 include: extracting, cleaning, and drying the selected core and then measuring the dry weight, diameter, and length.

9. A high temperature and high pressure core stress sensitivity testing method according to claim 7, characterized in that: In S5, the flow rate of soap bubbles per unit time is measured 3-5 times under different temperature and pressure difference conditions.

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