Microcosmic remaining oil occurrence state testing device and method

Abstract

The invention discloses a microscopic remaining oil occurrence state testing device and method, and belongs to the technical field of oil exploitation. The testing device comprises a plunger pump, a crude oil displacement tank, an underground water displacement tank, a chemical agent displacement tank, a first multi-way valve, a second multi-way valve, a data acquisition system, a CT scanner, a rock core holder, a freezing bin, a temperature control system, a back-pressure valve and a measuring cup. The crude oil displacement tank, the underground water displacement tank and the chemical agent displacement tank are connected with the plunger pump and the rock core holder through the first multi-way valve and the second multi-way valve respectively, the rock core holder is arranged in the freezing bin, and the temperature control system is used for adjusting the temperature in the freezing bin and freezing fluid in a rock core in the rock core holder into a solid state; the CT scanner is arranged at the top of the freezing bin and used for scanning the fluid state in the rock core frozen into the solid state and transmitting a scanning result to the data acquisition system. The rock core can be frozen and solidified at any moment in the displacement process accurately, and the real fluid distribution form at any moment is captured.

Description

Technical Field

[0001] The present invention relates to the technical field of oil production, and in particular to a device and method for testing the microscopic residual oil occurrence state. Background Art

[0002] In enhanced oil recovery (EOR) research, the microscopic state of remaining oil plays a crucial role in enhancing oil recovery. It reveals the distribution patterns and occurrence mechanisms of remaining oil during the extraction process and is key to understanding recovery bottlenecks, selecting appropriate EOR methods, optimizing implementation plans, and ultimately significantly improving the ultimate recovery of an oilfield.

[0003] CT scanning technology is one of the main testing methods for the microscopic state of remaining oil. Because it is applicable to a variety of fluids and rock types, and has the characteristics of non-destructiveness, high resolution, three-dimensional visualization, dynamic monitoring, and quantitative analysis, it has become an indispensable means for studying microscopic remaining oil and optimizing enhanced oil recovery (EOR) in modern petroleum engineering.

[0004] For example, Chinese patent CN106770377A discloses an experimental device and method for monitoring the distribution of residual oil in a core during carbon dioxide displacement. This device uses a core holder with a sealing packer and a CT scanner to study the spatial distribution of microscopic residual oil in the core under liquid and supercritical carbon dioxide and different carbon dioxide injection parameters. This patent has the following drawbacks: ① During the displacement process, since CT imaging requires a certain amount of time, it is impossible to capture the true fluid distribution pattern at a specific moment; ② When the displacement pump is stopped or the equipment is adjusted, pressure fluctuations occur, causing the observed state to deviate from the actual displacement equilibrium state; ③ During the scanning process, resolution often needs to be sacrificed or scanning time must be shortened to reduce dynamic blur, resulting in the inability to output high-resolution images, making it difficult to meet the requirements for studying the true microscopic distribution pattern of residual oil.

[0005] Therefore, there is an urgent need to develop an experimental device and testing method that can achieve continuous, high-precision dynamic imaging of microscopic residual oil in rocks, providing a reliable basis for oil displacement mechanism research and scheme design. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a device and method for testing the microscopic residual oil occurrence state.

[0007] The technical solution adopted in the present invention is:

[0008] A device for testing the microscopic residual oil occurrence state comprises a plunger pump, a crude oil displacement tank, a groundwater displacement tank, a chemical displacement tank, a first multi-way valve, a second multi-way valve, a data acquisition system, a CT scanner, a core holder, a freezing chamber, a temperature control system, a back pressure valve, and a measuring cup. The plunger pump is connected to the crude oil displacement tank, the groundwater displacement tank, and the chemical displacement tank respectively through the first multi-way valve. The crude oil displacement tank, the groundwater displacement tank, and the chemical displacement tank are respectively connected to the core holder through the second multi-way valve. The core holder is connected to the measuring cup through the back pressure valve. The core holder is arranged in the freezing chamber. The temperature control system is used to adjust the temperature in the freezing chamber to freeze the fluid in the core in the core holder into a solid state. The CT scanner is arranged on the top of the freezing chamber and is used to scan the fluid state in the frozen solid core and transmit the scanning result to the data acquisition system.

[0009] Furthermore, the freezing chamber is made of double-layer plexiglass, a hatch is provided on the front side of the freezing chamber, pipe holes are provided on the left and right sides respectively, a nitrogen inlet and a nitrogen outlet are provided on the front and back sides respectively, and a liquid nitrogen inlet control valve and a liquid nitrogen outlet control valve are provided on the nitrogen inlet and the nitrogen outlet respectively.

[0010] Furthermore, a temperature sensor is provided in the freezing chamber.

[0011] Furthermore, the temperature control system includes a liquid nitrogen tank, a liquid nitrogen inlet control valve, a liquid nitrogen outlet control valve, a temperature sensor and a temperature controller. The liquid nitrogen tank is connected to the liquid nitrogen inlet control valve through a pipeline, and the temperature controller is connected to the liquid nitrogen outlet control valve, the liquid nitrogen inlet control valve and the temperature sensor.

[0012] Furthermore, a first pressure gauge is provided on the inlet pipe of the core holder.

[0013] Furthermore, a second pressure gauge is provided on the outlet pipe of the core holder.

[0014] Furthermore, the plunger pump is an ISCO piston pump.

[0015] Further, the core holder is a CT core holder.

[0016] The method for testing the microscopic residual oil occurrence state using any of the above-mentioned microscopic residual oil occurrence state testing devices comprises the following steps:

[0017] (1) Prepare a core sample with a length of 8 cm and a diameter of 2.5 cm and evacuate the sample using a vacuum pump;

[0018] (2) Clamp the core sample with a core holder, open the hatch, place the core holder and the core sample in the freezing chamber, and connect the core holder through a pipe;

[0019] (3) Open the water valves in the first and second multi-way valves and inject groundwater into the core sample at a rate of 0.1 mL / min. After the saturated water pretreatment process is completed, close the water valves.

[0020] (4) Open the oil valve and start saturating the simulated formation oil, maintaining the oil injection rate at 1 mL / min;

[0021] (5) After the saturated oil pretreatment process is completed, the freezing chamber is kept at room temperature, the piston pump is turned on, the oil valve of the first multi-way valve is closed, and the water valve is opened to perform core water displacement; during this process, the pressure in the core holder is controlled by the back pressure valve to simulate the formation pressure;

[0022] (6) After the displacement is completed, the piston pump, the first multi-way valve and the second multi-way valve are turned off, and the temperature control system is started to adjust the temperature in the freezing chamber to below -10°C to freeze the oil and water phases in the core sample;

[0023] (7) After the oil and water phases are fixed, the CT scanner is turned on for scanning, and the scanning results are transmitted to the data acquisition system for analysis.

[0024] Furthermore, step (5.1) is included between step (5) and step (6). Step (5.1) is: after the water displacement is completed, the chemical valve is opened and the chemical agent is injected into the core sample to perform chemical displacement.

[0025] Beneficial effects of the present invention:

[0026] 1. By using a freezing chamber to freeze and solidify the test core after displacement, CT imaging can capture the true fluid distribution pattern; the object of scanning and analysis is a static solid without motion blur, which can accurately capture the microscopic residual oil occurrence state and improve the accuracy of microscopic residual oil occurrence state monitoring.

[0027] 2. By adopting a multiphase fluid collaborative injection system in a freezing chamber and installing a CT scanning device above the freezing chamber, the pressure conditions between formations can be precisely controlled, supporting oil, water and chemical displacement experiments in the core to simulate the environmental conditions of complex underground displacement scenarios such as formation water flooding and chemical flooding. It can also continuously scan and image the occurrence state of microscopic residual oil in the rock, accurately select the core to be frozen and solidified at any moment in the displacement process, and capture the true fluid distribution pattern at any moment.

[0028] 3. By injecting water through the injection unit ISCO constant pressure and constant speed pump, the pore pressure of the core in the core holder is increased, which can realize the measurement and dynamic tracking of the microscopic remaining oil state of the core under different pore pressures, with strong adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a structural schematic diagram of the microscopic residual oil occurrence state testing device of the present invention.

[0030] In the figure, 1 is a plunger pump; 2 is a crude oil displacement tank; 3 is a groundwater displacement tank; 4 is a chemical agent displacement tank; 5 is a first six-way valve; 6 is a second six-way valve; 7 is a first pressure gauge; 8 is a data acquisition system; 9 is a CT scanner; 10 is a temperature sensor; 11 is a core holder; 12 is a freezing chamber; 13 is a temperature control system; 14 is a second pressure gauge; 15 is a back pressure valve; 16 is a measuring cup. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and preferred embodiments.

[0032] See Figure 1 A device for testing the microscopic residual oil occurrence state includes a plunger pump 1, a crude oil displacement tank 2, a groundwater displacement tank 3, a chemical agent displacement tank 4, a first six-way valve 5, a second six-way valve 6, a first pressure gauge 7, a data acquisition system 8, a CT scanner 9, a temperature sensor 10, a core holder 11, a freezing chamber 12, a temperature control system 13, a second pressure gauge 14, a back pressure valve 15, and a measuring cup 16.

[0033] The plunger pump 1 is connected to the inlet of a first six-way valve 5 via a pipeline. The three outlets of the first six-way valve 5 are connected to the inlets of a crude oil displacement tank 2, a groundwater displacement tank 3, and a chemical displacement tank 4 via pipelines. The outlets of the crude oil displacement tank 2, the groundwater displacement tank 3, and the chemical displacement tank 4 are connected to the three inlet ends of a second six-way valve 6 via pipelines. The outlet of the second six-way valve 6 is connected to the inlet end of a core holder 11 via a pipeline. The core holder 11 is located inside a freezing chamber 12. The outlet end of the core holder 11 is connected to a measuring cup 16 via a pipeline. The inlet pipeline of the core holder 11 is provided with a first pressure gauge 7, and the outlet pipeline of the core holder 11 is provided with a second pressure gauge 14 and a back-pressure valve 15.

[0034] The first pressure gauge 7 is used to detect the fluid pressure at the inlet of the core holder 11, the second pressure gauge 14 is used to detect the fluid pressure at the outlet of the core holder 11, and the back pressure valve 14 is used to adjust the fluid pressure in the core holder 11 to simulate the formation pressure.

[0035] The core clamp 11 can adopt the CT core clamp in patent CN202020670858.X.

[0036] A CT scanner 9 is provided above the freezing chamber 12 , and is used to scan and image the core in the core holder 11 in the freezing chamber.

[0037] The freezing chamber 12 is made of double-layer organic glass, which can pass X-rays well without affecting the detection accuracy and can be easily observed. The double-layer organic glass can achieve the heat preservation of the freezing chamber and prevent the loss of cold.

[0038] The freezing chamber 12 has a hatch on its side, with corresponding pipe holes on the left and right sides. After the core holder 11 is placed into the freezing chamber through the hatch, the pipes pass through the pipe holes and connect to the core holder 11. Nitrogen inlets and outlets are located on the front and back sides of the freezing chamber 12 (not shown).

[0039] A temperature sensor 10 is provided in the freezing chamber 12. The temperature sensor is provided in the freezing chamber for detecting the temperature in the freezing chamber.

[0040] The temperature control system 13 includes a liquid nitrogen tank (not shown in the figure), a liquid nitrogen inlet control valve, a liquid nitrogen outlet control valve and a temperature controller. The liquid nitrogen tank is connected to the nitrogen inlet of the freezing chamber 12 through a liquid nitrogen inlet pipe. The liquid nitrogen inlet control valve is arranged on the nitrogen inlet for controlling the rapid opening and closing of the nitrogen inlet; the liquid nitrogen outlet control valve is arranged on the nitrogen outlet for controlling the rapid opening and closing of the nitrogen outlet; the temperature controller is connected to the liquid nitrogen outlet control valve, the liquid nitrogen inlet control valve and the temperature sensor 10.

[0041] The low-temperature liquid nitrogen in the liquid nitrogen tank is transported to the freezing chamber through the liquid nitrogen inlet pipeline. When the liquid nitrogen inlet control valve and the liquid nitrogen outlet control valve are opened, the liquid nitrogen quickly rushes out of the liquid nitrogen inlet control valve, vaporizes and absorbs heat, and instantly freezes the fluid in the core into a solid state.

[0042] The CT scanner 9 is connected to the data acquisition system 8 via a wire.

[0043] Example 2

[0044] The method for testing the microscopic residual oil occurrence state using the testing device of Example 1 comprises:

[0045] Step 1: Prepare a core sample with a length of 8 cm and a diameter of 2.5 cm, and use a vacuum pump to evacuate the sample for 24 hours.

[0046] Step 2: Hold the core sample with the core holder 11, open the hatch, place the core holder 9 and the core sample into the freezing chamber 12, and connect the core holder 11 via a pipe;

[0047] Step 3: Open the water valves in the first six-way valve 5 and the second six-way valve 6, and inject water into the core sample at a rate of 0.1 mL / min. When the injection rate and the output rate are consistent, the saturated water pretreatment process is completed, and the water valve of the first six-way valve is closed.

[0048] Step 4: Open the oil valve and start saturating the simulated formation oil. The oil injection rate is maintained at 1 mL / min. When the pressure is stable and the injection rate is consistent with the oil production rate at the outlet, the saturated oil pretreatment process is completed.

[0049] Step 5: Maintain the freezing chamber at room temperature, turn on the ISCO piston pump, close the oil valve of the first six-way valve, open the water valve, and perform core water displacement. During this process, the pressure in the core holder is controlled by the back pressure valve to simulate the formation pressure.

[0050] Step 6: After the displacement is completed, the ISCO piston pump, the first six-way valve 5, and the second six-way valve 6 are closed, and the temperature control system 13 is started to input liquid nitrogen into the freezing chamber to adjust the temperature in the freezing chamber to -10°C to quickly freeze the oil and water phases in the core sample;

[0051] Step 7: After the oil-water phases are fixed, the CT scanner 9 is turned on for scanning, and the scanning results are transmitted to the data acquisition system 8 for analysis.

[0052] Example 3

[0053] Example 3 is basically the same as Example 2, except that step 5.1 is included between step 5 and step 6.

[0054] Step 5.1 is: after the water displacement is completed, the chemical valve is opened and the chemical agent is injected into the core sample to perform chemical displacement.

[0055] Through Example 3, the environmental condition simulation of complex underground flooding scenarios such as formation water flooding and chemical flooding can be realized.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also within the scope of protection of the present invention.

Claims

1. A device for testing the microscopic residual oil occurrence state, characterized in that: The invention comprises a plunger pump (1), a crude oil displacement tank (2), a groundwater displacement tank (3), a chemical agent displacement tank (4), a first multi-way valve, a second multi-way valve, a data acquisition system (8), a CT scanner (9), a core holder (11), a freezing chamber (12), a temperature control system (13), a back pressure valve (15) and a measuring cup (16); the plunger pump (1) is connected to the crude oil displacement tank (2), the groundwater displacement tank (3) and the chemical agent displacement tank (4) respectively through the first multi-way valve, and the crude oil displacement tank (2), the groundwater displacement tank (3) and the chemical agent displacement tank (4) are connected to the groundwater displacement tank (3) and the chemical agent displacement tank (4). The replacement tank (4) is connected to the core holder (11) through a second multi-way valve, and the core holder (11) is connected to the measuring cup (16) through a back pressure valve (15); the core holder (11) is arranged in a freezing chamber (12), and the temperature control system (13) is used to adjust the temperature in the freezing chamber (12) to freeze the fluid in the core in the core holder (11) into a solid state; the CT scanner (9) is arranged on the top of the freezing chamber (12) and is used to scan the state of the fluid in the frozen solid core and transmit the scanning result to the data acquisition system (8).

2. A microscopic residual oil occurrence state testing device according to claim 1, characterized in that: The freezing chamber (12) is made of double-layer organic glass, the front side of the freezing chamber is provided with a hatch, the left and right sides are provided with pipeline holes, the front and rear sides are provided with a nitrogen inlet and a nitrogen outlet respectively, and the nitrogen inlet and the nitrogen outlet are provided with a liquid nitrogen inlet control valve and a liquid nitrogen outlet control valve respectively.

3. A microscopic residual oil occurrence state testing device according to claim 2, characterized in that: A temperature sensor (10) is provided in the freezing chamber (12).

4. A microscopic residual oil occurrence state testing device according to claim 3, characterized in that: The temperature control system (13) comprises a liquid nitrogen tank, a liquid nitrogen inlet control valve, a liquid nitrogen outlet control valve, a temperature sensor (10) and a temperature controller. The liquid nitrogen tank is connected to the liquid nitrogen inlet control valve via a pipeline, and the temperature controller is connected to the liquid nitrogen outlet control valve, the liquid nitrogen inlet control valve and the temperature sensor (10).

5. The device for testing the microscopic residual oil occurrence state according to claim 1, characterized in that: A first pressure gauge (7) is provided on the inlet pipe of the core holder (11).

6. The device for testing the microscopic residual oil occurrence state according to claim 1, characterized in that: A second pressure gauge (14) is provided on the outlet pipe of the core holder (11).

7. The device for testing the microscopic residual oil occurrence state according to claim 1, characterized in that: The plunger pump (1) is an ISCO piston pump.

8. The device for testing the microscopic residual oil occurrence state according to claim 1, characterized in that: The core holder (11) is a CT core holder.

9. A method for testing the microscopic residual oil occurrence state using the microscopic residual oil occurrence state testing device according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Prepare a core sample with a length of 8 cm and a diameter of 2.5 cm and evacuate the sample using a vacuum pump; (2) Clamp the core sample with a core holder, open the hatch, place the core holder and the core sample into the freezing chamber 2, and connect the core holder through a pipe; (3) Open the water valves in the first and second multi-way valves and inject groundwater into the core sample at a rate of 0.1 mL / min. After the saturated water pretreatment process is completed, close the water valves. (4) Open the oil valve and start saturating the simulated formation oil, maintaining the oil injection rate at 1 mL / min; (5) After the saturated oil pretreatment process is completed, the freezing chamber is kept at room temperature, the piston pump is turned on, the oil valve of the first multi-way valve is closed, and the water valve is opened to perform core water displacement; during this process, the pressure in the core holder is controlled by the back pressure valve to simulate the formation pressure; (6) After the displacement is completed, the piston pump, the first multi-way valve and the second multi-way valve are turned off, and the temperature control system is started to adjust the temperature in the freezing chamber to below -10°C to freeze the oil and water phases in the core sample; (7) After the oil and water phases are fixed, the CT scanner is turned on for scanning, and the scanning results are transmitted to the data acquisition system for analysis.

10. The method according to claim 9, characterized in that Between step (5) and step (6), step (5.1) is also included. Step (5.1) is: after the water displacement is completed, the chemical valve is opened and the chemical agent is injected into the core sample to perform chemical displacement.

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