Method and holder for preventing degassing of formation crude oil in displacement experiments

Abstract

This invention provides a displacement experiment method and support device for preventing formation crude oil degassing. The support device includes a base, a lower fixed frame, and an upper fixed frame. A connecting shaft is fixedly installed on the top of the base. The lower fixed frame is hinged to the base via the connecting shaft. The upper fixed frame is correspondingly connected to the lower fixed frame. An intermediate container is fixed between the upper and lower fixed frames. The base has several fixing holes, and the bottom of the lower fixed frame has several slots. Corresponding slots are connected to the fixing holes by fixing pins to fix the position of the intermediate container. The intermediate container has a valve at each of its front and rear ends and a stirring slider inside. When a power outage, temperature loss, or pressure drop occurs during a long core displacement experiment, the gas released from the intermediate container can be easily redissolved into the crude oil, avoiding secondary degassing or leakage of the sample.

Description

Technical Field

[0001] This invention belongs to the field of CO2 flooding and storage technology in the development technology of low-permeability oil and gas reservoirs, specifically involving a displacement experimental method and support device to prevent formation crude oil degassing. Background Technology

[0002] CO2-driven long core displacement experiments are one of the important experiments for evaluating the feasibility of CO2 enhanced oil recovery technology. These experiments can obtain characteristic parameters such as the recovery rate and displacement patterns of natural core CO2-driven oil recovery under formation temperature and pressure conditions. The fluids used in the experiments are typically formation oil and formation water. The formation oil is usually formation oil obtained from high-pressure physical property sampling or simulated formation oil (i.e., simulated formation oil compounded according to the original gas-oil ratio and saturation pressure). Only by using this type of gas-containing formation oil can the displacement patterns of formation oil after CO2-driven long core displacement be realistically simulated.

[0003] In experiments, intermediate containers are typically used to hold experimental fluids such as formation crude oil and CO2 gas. Due to the long cycle of long core displacement experiments, if the core length reaches 100cm, the time for one set of experiments is usually about one month. During the experiment, sometimes there are situations where the temperature of the constant temperature chamber or the pressure of the intermediate container drops due to reasons such as sudden power outages or pipeline leaks. This can lead to a decrease in the temperature and pressure inside the intermediate container holding the formation crude oil, causing the formation crude oil to degas.

[0004] If the formation crude oil is degassed, it will distort the entire experimental data, making it impossible to obtain accurate data. Therefore, in this case, it is necessary to thoroughly stir and mix the formation oil in the intermediate container to allow the extracted natural gas to re-integrate into the crude oil.

[0005] Typically, the intermediate container in a constant temperature chamber is fixed by a circular support at the bottom or by hooks on the chamber wall. This means the intermediate container can only be placed vertically, making it impossible to mix and stir the degassed crude oil inside.

[0006] The usual experimental procedure is to remove the intermediate container from the constant temperature chamber, and use a pump to inject the formation oil and degassing gas in the intermediate container into the formation oil mixing unit. In the mixing unit, the sample is heated and pressurized and thoroughly stirred to compress it into a single phase. Then, the sample is pumped back into the intermediate container and sent back to the constant temperature chamber for use.

[0007] Applying the above method requires transferring the fluid to different containers multiple times, which is quite inconvenient and can easily cause secondary degassing or leakage of the sample. For example, if there is a power outage or damage to the pipes or valves during the container transfer process, the formation oil can easily undergo secondary degassing. When the pipes or valves are damaged, the fluid can easily leak, which may cause the extracted natural gas to leak out, resulting in a sharp reduction in the gas-oil ratio of the formation crude oil in the entire container, thus requiring the re-preparation of the simulated formation oil. Summary of the Invention

[0008] In order to overcome the defects in the existing technology, the present invention provides a displacement experiment method and support device to prevent formation crude oil degassing. When problems such as power failure, temperature loss or pressure loss occur suddenly during the long core displacement experiment, the gas released from the intermediate container can be easily re-dissolved into the crude oil, avoiding secondary degassing or leakage of the sample.

[0009] The technical solution adopted by this invention to solve its technical problem is: a displacement experimental support device for preventing formation crude oil degassing, comprising a base, a lower fixed frame, and an upper fixed frame. A connecting shaft is fixedly installed on the top of the base. The lower fixed frame is hinged to the base via the connecting shaft. The upper fixed frame is correspondingly connected to the lower fixed frame. An intermediate container is fixed between the upper and lower fixed frames. The base has several fixing holes, and the bottom of the lower fixed frame has several slots. The corresponding slots are connected to the fixing holes via fixing pins to fix the position of the intermediate container. The intermediate container has a valve at each of its front and rear ends, and a stirring slider is installed inside.

[0010] Furthermore, the lower fixed frame includes two side wall plates arranged at intervals and symmetrically, with several arc-shaped support plates connected between the two side wall plates to support the intermediate container; each of the two side wall plates is provided with an outwardly extending roller for rotatably connecting with a connecting shaft; the bottom of the multiple support plates is connected to a vertically arranged bottom beam, with several holes and slots opened on the bottom beam.

[0011] Furthermore, the base includes a horizontally arranged rectangular frame and trapezoidal frames vertically connected to both sides of the rectangular frame. A connecting shaft is fixedly installed on the top trapezoidal surface of the trapezoidal frame. Each of the two trapezoidal frames has a crossbeam at its upper part, and each of the two crossbeams has several fixing holes. The fixing holes on the two crossbeams are in corresponding positions.

[0012] Furthermore, the upper fixing frame includes several arc-shaped buckles and a connecting plate connected between the buckles.

[0013] A displacement experiment method for preventing formation crude oil degassing, using the aforementioned support device, includes the following steps:

[0014] Step 1: In the experimental preparation stage, place the support device into the constant temperature chamber, place the formation oil intermediate container horizontally into the lower fixed frame, and fix the formation oil intermediate container with the upper fixed frame. Connect the valves and pipelines at the inlet and outlet ends of the formation oil intermediate container, and start the experiment.

[0015] Step 2: When degassing occurs in the formation oil intermediate container, first stop the formation oil intermediate container from losing pressure and temperature;

[0016] Step 3: Wait for the temperature in the constant temperature chamber to rise back to the experimental temperature, so that the formation fluid in the intermediate container of formation oil can be restored to the formation pressure;

[0017] Step 4: Pull out the fixing pin of the support device to put the formation oil intermediate container in a movable state. Rotate the formation oil intermediate container up and down repeatedly to make the stirring slider in the formation oil intermediate container move repeatedly to stir the fluid in the formation oil intermediate container, so that the gas and liquid two phases become a single phase. After the pressure at the inlet end of the formation oil intermediate container no longer fluctuates, tilt the inlet end of the formation oil intermediate container up and insert the fixing pin into the fixing hole with the corresponding tilt angle to fix the position of the formation oil intermediate container.

[0018] Step 5: Restart saturating the formation oil;

[0019] Step 6: After saturating the formation with oil, conduct displacement experiments.

[0020] Furthermore, step 2 specifically involves: when the formation oil in the intermediate container degasses, immediately open the constant temperature chamber, close the inlet and outlet of the intermediate container to prevent further depressurization, and then use a heated enclosure to prevent further temperature loss.

[0021] Furthermore, step 3 specifically involves: waiting for the temperature in the constant temperature chamber to rise back to the experimental temperature, turning on the injection pump and adjusting the pump pressure to the formation pressure, and then opening the inlet valve of the intermediate formation oil container to restore the formation fluid in the intermediate formation oil container to the formation pressure.

[0022] Furthermore, in step 4, the inlet angle of the formation oil intermediate container is 30 degrees or 60 degrees.

[0023] The beneficial effects of this invention include: by improving the experimental method and modifying the traditional intermediate container support, a novel intermediate container support device and experimental method are invented. This overcomes the limitations of traditional experimental methods and solves the problem of degassing formation crude oil after cooling or depressurization. By adding a novel rotatable support and valves at the front and rear ends of the intermediate container, the crude oil and degassing gas inside the container are fully mixed and dissolved, thereby improving experimental efficiency and accuracy. This invention can be used in various long core displacement experiments, long thin tube displacement experiments, and other displacement experiments. Through multi-angle fixation and rotational stirring of the intermediate container, the crude oil and degassing gas inside the container are fully mixed and dissolved. The improved experimental method greatly enhances experimental efficiency and accuracy, and has broad application prospects.

[0024] The experimental method provided by this invention is simple in principle and easy to implement during the experimental process. It can effectively reduce the workload of the experimenter, reduce operating costs, help improve experimental accuracy, and make experimental data more reliable and accurate.

[0025] This invention is mainly applied in the CO2-driven core displacement experiment, which can better ensure that the saturated formation oil is closer to the actual underground conditions of the mining site throughout the entire experimental process, and truly restore the migration and seepage state of formation fluids in the core. Attached Figure Description

[0026] Figure 1 This is a flowchart of the CO2-driven core displacement experiment.

[0027] Figure 2 This is a schematic diagram of the overall structure of the intermediate container support device;

[0028] Figure 3 This is a schematic diagram of the lower fixed frame structure;

[0029] Figure 4 This is a schematic diagram of the upper fixed frame structure;

[0030] Figure 5 This is a side view of the intermediate container support assembly.

[0031] The following are the labels in the attached diagram: 1-base, 2-lower fixing bracket, 3-upper fixing bracket, 4-middle container, 5-fixing pin, 6-connecting shaft, 7-fixing hole, 8-fixing bolt, 9-fixing bolts for upper and lower brackets;

[0032] 2-1. Side wall panel; 2-2. Support plate; 2-3. Roller; 2-4. Bottom beam; 3-1. Buckle plate; 3-2. Connecting plate. Detailed Implementation

[0033] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] In the description of this invention, it should be noted that the terms "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used only to distinguish components and should not be construed as indicating or implying relative importance.

[0035] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] This invention primarily addresses the issue that during long core displacement experiments, sudden power outages, temperature drops, or pressure reductions can lead to the crude oil in the intermediate container potentially becoming degassed, causing the simulated formation oil's gas-oil ratio and other parameters to fail to meet experimental requirements. The original long core displacement experiment process and method have been redesigned. The fixed intermediate container has been replaced with one equipped with valves at both ends. A stirring slider is placed inside the intermediate container and housed in a novel support device that can rotate vertically at a fixed angle. This solves the problem that traditional supports only provide support and fixation, failing to perform the necessary rotation and stirring to ensure thorough mixing and dissolution of oil and gas. In the event of a power outage or pressure reduction, the valves at both ends of the intermediate container are closed, and the container automatically rotates vertically, allowing the degassed gas to redissolve back into the crude oil.

[0037] Example 1

[0038] The equipment typically used in a CO2-driven core displacement experiment includes: one injection pump, three intermediate containers, one core holder, one backpressure valve, one backpressure pump, one annular pressure pump, and one metering system. (See the flowchart for reference.) Figure 1 .

[0039] During experiments, the intermediate container for formation oil is typically fixed in a constant-temperature chamber and cannot be moved. Due to the long experimental period, if a power outage or valve leakage occurs midway, the pressure in the intermediate container for formation oil will decrease, causing the single-phase formation oil to degas and become a two-phase gas-liquid mixture. The experiment must then be stopped, requiring the replacement of the formation oil with fresh oil or the degassed oil to be transferred to a mixing tank, reheated, pressurized, and stirred to form a single phase before the experiment can continue.

[0040] To overcome the above problems, this embodiment provides a displacement test support device to prevent formation crude oil degassing. During the CO2 displacement experiment of long core, when the experimental equipment is powered off or the pipe valves leak, leading to system cooling or depressurization, the intermediate container support device provided in this embodiment can be used to ensure that the formation oil does not degas.

[0041] Specifically, such as Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown, the support device includes a base 1, a lower fixed frame 2, and an upper fixed frame 3. The base 1 includes a horizontally arranged rectangular frame and trapezoidal frames that are vertically connected to both sides of the rectangular frame. The top trapezoidal surface of the trapezoidal frame is fixedly mounted with a connecting shaft 6 by fixing bolts 8. The lower fixed frame 2 is hinged to the base 1 by the connecting shaft 6. The upper fixed frame 3 is correspondingly connected to the lower fixed frame 2 by upper and lower support fixing bolts 9. The intermediate container 4 is fixed between the upper fixed frame 3 and the lower fixed frame 2. That is, after the upper fixed frame 3 and the lower fixed frame 2 are connected, the upper and lower support fixing bolts 9 are tightened to fix the body of the intermediate container 4.

[0042] Each of the two trapezoidal frames has a crossbeam at its top, and each crossbeam has three fixing holes 7, with the fixing holes 7 on the two crossbeams being positioned correspondingly.

[0043] The lower fixing frame 2 includes two side wall plates 2-1 arranged at intervals and symmetrically. Several arc-shaped support plates 2-2 are connected between the two side wall plates 2-1 to support the intermediate container 4. In this embodiment, three support plates 2-2 are used as an example. The two ends of the support plates 2-2 on both sides are provided with horizontally outward extending connecting parts a. Each of the two side wall plates 2-1 is provided with an outward extending roller 2-3 for rotatably connecting with the connecting shaft 6. The bottom of the three support plates 2-2 is connected to a vertically arranged bottom beam 2-4, and the bottom beam 2-4 is provided with three holes and slots.

[0044] The corresponding slots and fixing holes 7 are connected by fixing pins 5. By connecting different slots and fixing holes 7, the intermediate container 4 can be fixed at three different angles.

[0045] The upper fixing frame 3 includes several arc-shaped buckle plates 3-1 and connecting plates 3-2 connected between the buckle plates 3-1. In this embodiment, two buckle plates 3-1 are used as an example. Both ends of the two buckle plates 3-1 are provided with horizontally outward extending connecting parts b, which are used to cooperate with the support plate 2-2 with connecting parts a, and are fastened by upper and lower bracket fixing bolts 9.

[0046] The intermediate container 4 has a valve at each of its front and rear ends, and a stirring slider inside.

[0047] In the above embodiment, all components of the base 1 are made of CO2-resistant 316 stainless steel. The upper fixing frame 3 and the lower fixing frame 2 are fixed together by four upper and lower bracket fixing bolts 9. The connecting shaft 6 is fixed to the upper trapezoidal surface of the base 1 by four fixing bolts 8. On the upper part of the base 1, there are three fixing holes 7 at different angles, which can fix the inlet or outlet end of the intermediate container 4 at three angles: +60 degrees, 0 degrees, or -60 degrees. It should be noted that more fixing holes 7 at different angles can be provided, and more corresponding holes and slots can be provided on the bottom beams 2-4 to achieve fixing of the intermediate container 4 at more angles.

[0048] Example 2

[0049] Example 1 mainly presents an improved support device for the CO2-driven core displacement experiment. This device is an intermediate container support that can be tilted and rotated. By adding this device, an experimental method for preventing formation oil degassing during the CO2-driven core displacement process is formed in this example.

[0050] Since saturated natural gas-simulated formation oil is typically only needed in CO2 injection experiments, this embodiment is mainly applied in CO2-driven elongation core displacement experiments. The typical experimental procedure in a CO2-driven elongation core displacement experiment is as follows:

[0051] 1. Place the core sample in a saturated water device to saturate it with formation water, measure its dry and wet weights, and calculate the pore volume;

[0052] 2. Place the core into the long core holder, apply ring pressure, and then saturate with water until the flow rate of the produced fluid stabilizes.

[0053] 3. After saturation with water, apply back pressure to the formation pressure at the outlet end of the long core holder, then open the intermediate container for formation oil and inject it with a pump to saturate the formation oil in the core, establish bound water, and calculate the oil saturation.

[0054] 4. Then, experiments such as water drive, CO2 drive, and alternating water-gas drive were carried out.

[0055] This embodiment mainly focuses on the experiment in step 3, and establishes a new experimental method using the support device described in embodiment 1:

[0056] Step 1: In the preparation stage of the experiment, place the intermediate container support device in the appropriate position in the constant temperature chamber, unscrew the upper and lower support fixing bolts 9 at the four corners of the upper fixed frame 3, remove the upper fixed frame 3, then place the formation oil intermediate container horizontally into the lower fixed frame 2, and after it is stable, cover it with the upper fixed frame 3, then tighten the upper and lower support fixing bolts 9 at the four corners of the upper fixed frame 3, connect the valves and pipelines at the inlet and outlet of the intermediate container 4, and start the experiment.

[0057] Once the core sample is saturated with water, during the process of saturating formation oil, a sudden power outage or pipeline leak can lead to temperature loss in the thermostat or pressure loss in the intermediate container. If the temperature or pressure suddenly drops, the formation oil in intermediate container 4 will degas, turning the single-phase fluid into a two-phase fluid, which will affect the accuracy of the experiment.

[0058] Step 2: In case of an unexpected situation, the equipment pressure and temperature system will alarm. At this time, immediately open the constant temperature chamber, close the inlet and outlet of the formation oil intermediate container, keep the intermediate container from continuing to lose pressure, and then wrap the intermediate container with a heating element to prevent it from continuing to lose temperature.

[0059] Step 3: After the laboratory power is restored, wait for the temperature in the constant temperature chamber to rise back to the experimental temperature, turn on and adjust the injection pump pressure to the formation pressure, and then open the inlet valve of the intermediate formation oil container to restore the formation fluid in the intermediate container to the formation pressure.

[0060] Step 4: Pull out the fixing pin 5 of the intermediate container support device. At this time, the intermediate container is in a movable state. Rotate the intermediate container up and down, and the maximum angle can reach ±60 degrees. At this time, the micro stirring slider in the intermediate container will start to move up and down repeatedly to fully stir the fluid in the intermediate container, so that the gas and liquid two phases become a single phase. After stirring for a period of time, observe whether the pressure at the inlet end of the intermediate container is stable. If the pressure fluctuates, continue stirring until the pressure at the inlet end no longer fluctuates. After the pressure is stable, usually tilt the inlet end up 30 degrees or 60 degrees and insert the fixing pin 5 into the fixing hole 7 of the corresponding tilt angle to fix the position of the intermediate container.

[0061] Step 5: Open the outlet end of the intermediate formation oil container, and the injection pump continues to inject, restarting the saturation of formation oil.

[0062] Step 6: After saturating the formation with oil, conduct experiments such as water flooding, CO2 flooding, and alternating water-gas displacement.

[0063] Step 7: If a power outage or leakage occurs during the water drive or gas drive experiment, and the experiment is stopped, repeat steps 2-6 when the core needs to be resaturated.

[0064] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A displacement experimental support device for preventing formation crude oil degassing, characterized in that, The device includes a base (1), a lower fixing frame (2), and an upper fixing frame (3). A connecting shaft (6) is fixedly installed on the top of the base (1). The lower fixing frame (2) is hinged to the base (1) through the connecting shaft (6). The upper fixing frame (3) is connected to the lower fixing frame (2). The intermediate container (4) is fixed between the upper fixing frame (3) and the lower fixing frame (2). The base (1) has several fixing holes (7). The bottom of the lower fixing frame (2) has several slots. The corresponding slots are connected to the fixing holes (7) through fixing pins (5) to fix the position of the intermediate container (4). The intermediate container (4) has a valve at each end of its body and a stirring slider inside.

2. The displacement experimental support device for preventing formation crude oil degassing according to claim 1, characterized in that, The lower fixing frame (2) includes two side wall plates (2-1) arranged at intervals and symmetrically. Several arc-shaped support plates (2-2) are connected between the two side wall plates (2-1) to support the intermediate container (4). Each of the two side wall plates (2-1) is provided with a roller (2-3) extending outward to cooperate with the connecting shaft (6) for rotational connection. The bottom of the multiple support plates (2-2) is connected to a vertically arranged bottom beam (2-4), and several holes and slots are opened on the bottom beam (2-4).

3. The displacement experimental support device for preventing formation crude oil degassing according to claim 1, characterized in that, The base (1) includes a horizontally arranged rectangular frame and trapezoidal frames that are vertically connected to both sides of the rectangular frame. A connecting shaft (6) is fixedly installed on the top trapezoidal surface of the trapezoidal frame. Each of the two trapezoidal frames has a crossbeam at its upper part, and each of the two crossbeams has several fixing holes (7). The fixing holes (7) on the two crossbeams are in corresponding positions.

4. The displacement experimental support device for preventing formation crude oil degassing according to claim 1, characterized in that, The upper fixing frame (3) includes several arc-shaped buckle plates (3-1) and a connecting plate (3-2) connecting the several buckle plates (3-1).

5. A displacement test method for preventing formation crude oil degassing, using the support device according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: In the experimental preparation stage, place the support device into the constant temperature chamber, place the intermediate formation oil container horizontally into the lower fixed frame (2), and fix the intermediate formation oil container through the upper fixed frame (3). Connect the valves and pipelines at the inlet and outlet ends of the intermediate formation oil container and start the experiment. Step 2: When degassing occurs in the formation oil intermediate container, first stop the formation oil intermediate container from losing pressure and temperature; Step 3: Wait for the temperature in the constant temperature chamber to rise back to the experimental temperature, so that the formation fluid in the intermediate container of formation oil can be restored to the formation pressure; Step 4: Pull out the fixing pin (5) of the support device to make the formation oil intermediate container in an active state. Rotate the formation oil intermediate container up and down repeatedly to make the stirring slider in the formation oil intermediate container move repeatedly to stir the fluid in the formation oil intermediate container, so that the gas and liquid two phases become a single phase. After the pressure at the inlet end of the formation oil intermediate container no longer fluctuates, lift up the inlet end of the formation oil intermediate container and insert the fixing pin (5) into the fixing hole (7) of the corresponding tilt angle to fix the position of the formation oil intermediate container. Step 5: Restart saturating the formation oil; Step 6: After saturating the formation with oil, conduct displacement experiments.

6. The displacement test method for preventing formation crude oil degassing according to claim 5, characterized in that, Step 2 specifically involves: when the formation oil in the intermediate container degasses, immediately open the constant temperature chamber, close the inlet and outlet of the intermediate container to prevent further depressurization, and then use a heated enclosure to prevent further temperature loss.

7. The displacement test method for preventing formation crude oil degassing according to claim 5, characterized in that, Step 3 specifically involves: waiting for the temperature in the constant temperature chamber to rise back to the experimental temperature, turning on the injection pump and adjusting the pump pressure to the formation pressure, and then opening the inlet valve of the intermediate formation oil container to restore the formation fluid in the intermediate formation oil container to the formation pressure.

8. The displacement test method for preventing formation crude oil degassing according to claim 5, characterized in that, The angle at the inlet end of the formation oil intermediate container in step 4 is 30 degrees or 60 degrees.

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