Shale core high-temperature and high-pressure gas drive experiment method and experiment device
By employing a displacement method that gradually increases from low pressure and low speed to high pressure, along with a high-temperature and high-pressure gas drive experimental device, the problems of insufficient saturated oil volume and large metering errors in shale oil experiments were solved. This enabled effective experiments in shale oil gas drive and provided important basic data support.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DAQING OILFIELD CO LTD
- Filing Date
- 2025-01-13
- Publication Date
- 2026-07-14
AI Technical Summary
The lack of standardized experimental methods for high-temperature and high-pressure gas drive of shale oil in the existing technology leads to insufficient saturated oil volume, large measurement errors, and difficulty in establishing an effective drive system. Furthermore, the pores of shale cores close under high pressure, affecting the experimental results.
A method of low-pressure, low-speed displacement of saturated oil was adopted, combined with a gradual increase in high pressure, to ensure that the shale core was fully saturated with oil. The high-temperature, high-pressure gas drive experimental device was established by testing with a nuclear magnetic resonance device, including a core holder, an injection system, and metering equipment, to ensure that the experimental conditions closely approximate the formation conditions.
It significantly increased the saturated oil content of shale cores, reduced measurement errors, established an effective high-temperature and high-pressure gas drive experimental system, provided important basic data, and offered technical support for shale oil gas injection development.
Smart Images
Figure CN122383283A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of shale oil reservoir development technology, and in particular to a high-temperature and high-pressure gas drive experimental method and apparatus for shale core samples. Background Technology
[0002] The vast reserves and low primary recovery rate of shale oil leave significant room for improvement in enhanced oil recovery (EOR) technologies. Since 2009, domestic and international institutions have conducted laboratory experimental and numerical simulation studies, including field trials, on this topic. Gulong shale oil is rich in resources, but its primary recovery rate is low, necessitating the development of EOR technologies tailored to the characteristics of Gulong shale oil to provide technical support for the efficient development of the Gulong shale oilfield.
[0003] Studies have shown that CO2 injection is an effective means of enhancing oil recovery, but there is no standardized and feasible experimental method for high-temperature and high-pressure gas drive in shale oil production. Conventional gas drive experiments typically use vacuum extraction followed by self-absorption of saturated oil, but this method leads to insufficient saturation of shale cores. Conventional gas drive experiments use weighing methods for measurement, which can result in large measurement errors when applied to shale core gas drive experiments. Furthermore, shale cores have well-developed bedding, poor physical properties, and a strong pressure-sensitive effect; directly conducting displacement experiments under high pressure (≥30 MPa) can lead to pore closure, making it difficult to establish an effective drive system. Summary of the Invention
[0004] This invention addresses the lack of standardized experimental methods for high-temperature, high-pressure gas drive experiments in shale oil, providing a new method for such experiments using shale cores. This method, applied to gas drive experiments and evaluations of the Gulong shale oil, ensures sufficient saturation of oil in saturated shale cores, minimizes measurement errors in gas drive experiments, and facilitates the establishment of an effective drive system. It also reveals the enhanced oil recovery effect of shale oil gas drive, providing crucial foundational data for shale oil gas injection development. Furthermore, this invention provides a high-temperature, high-pressure gas drive experimental apparatus for shale cores.
[0005] The present invention solves its problems through the following technical solution:
[0006] The first aspect of this invention provides a high-temperature, high-pressure gas drive experimental method for shale cores, comprising the following steps:
[0007] Step 1: Displace saturated oil from shale cores and determine the amount of saturated oil;
[0008] Step 2: Assemble the experimental setup for shale core gas drive.
[0009] Step 3: Based on the saturated shale core, inject saturated medium to establish a shale core driving system;
[0010] Step 4: Conduct gas drive experiments on saturated shale cores;
[0011] Step 5: After the displacement experiment, calculate the oil yield from the shale core.
[0012] Furthermore, in step 1, the shale core is displaced to displace saturated oil, and the amount of saturated oil is determined. The specific methods include:
[0013] Shale cores are air-dried at low temperature until their weight remains constant, and then saturated. The shale cores are placed in a core holder and evacuated for more than 24 hours, followed by low-pressure, low-speed displacement of saturated oil. When the pressure of the low-pressure, low-speed displacement of saturated oil reaches 3 MPa, high-pressure displacement of saturated oil is carried out. The saturated cores are weighed and measured, and then the saturation of the mobile fluid is tested using a nuclear magnetic resonance device to determine the amount of saturated oil in the shale cores.
[0014] Furthermore, the saturated oil is displaced at low pressure and low speed. The low pressure and low speed displacement method is as follows: the internal pressure interval is 0.5MPa, which is increased from 1MPa to 3MPa.
[0015] High-pressure displacement of saturated oil is carried out. The high-pressure displacement method is as follows: the internal pressure is increased from 4MPa to 15MPa at 1MPa intervals, and each pressure point is stabilized for more than 1 hour.
[0016] Furthermore, in step 2, when assembling the shale core gas drive experimental process device, a process leak test must be performed. After the process leak test is qualified, the formation temperature is heated in a constant temperature chamber; the formation temperature is ≥90℃; and the saturated shale core is loaded into the core holder.
[0017] Furthermore, step 3 involves injecting a saturated medium into the saturated shale core to establish a shale core-driven system; the specific method includes:
[0018] The saturated medium is injected at a constant speed into the injection end of the core holder. The confining pressure is adjusted to be 3 MPa higher than the injection pressure. The back pressure valve is adjusted to raise the injection pressure of the displacement system to the experimental pressure. The changes at the injection end and the extraction end are observed. When the injection pressure remains constant for more than 4 hours and the displacement medium flows out stably from the outlet end, it indicates that the drive system has been established.
[0019] Furthermore, the injection rate of the saturated medium is between 0.05-0.1 ml / min; the injected saturated medium is saturated oil.
[0020] The experimental pressure is the formation pressure, and the experimental pressure is ≥30MPa.
[0021] Furthermore, the method for conducting gas drive experiments on saturated shale cores in step 4 is as follows:
[0022] Turn off the pump that injects saturated medium, adjust the pressure of the pump that injects displacing medium to the experimental pressure, and start the gas drive experiment. Record parameters such as injection pump pressure, flow rate, outlet pressure, flow rate, oil production, and gas production throughout the experiment. The gas drive experiment ends when almost no oil is produced at the outlet.
[0023] Furthermore, in step 5, the oil yield from the shale core is calculated using a combination of core weighing and nuclear magnetic resonance scanning to make the test results more accurate.
[0024] Another aspect of the present invention provides a high-temperature and high-pressure gas-driven experimental device for shale cores, including a core holder placed in a constant temperature chamber; the inlet end of the core holder is connected to an injection system for injecting displacement media; the outlet end is connected to a three-phase separator and a back pressure pump respectively through a back pressure valve; the top outlet of the three-phase separator is connected to a gas flow meter; and the confining pressure hole of the core holder is connected to a confining pressure pump.
[0025] Furthermore, the injection system is divided into an air injection pump and a liquid injection pump;
[0026] The gas injection pump is used to inject gas during gas-driven experiments;
[0027] The injection pump is used to inject saturated media;
[0028] The gas flow meter is used to measure the amount of gas produced; the core holder is used to hold the core.
[0029] The constant temperature chamber is heated to the formation temperature; the formation temperature is ≥90℃.
[0030] Compared with the above-mentioned background technology, the present invention has the following beneficial effects:
[0031] In the process of displacing saturated oil in shale cores to determine the amount of saturated oil, the shale core is placed in a core holder and evacuated for more than 24 hours. Then, a low-pressure, low-speed displacement of saturated oil is carried out using an injection pump. Due to the pressure-sensitive effect of shale, high pressure causes the shale pore space to close, while low pressure does not damage the shale pore structure. Crude oil can enter the core pores to saturate and support the shale pore structure. Finally, high-pressure displacement of saturated oil is carried out. The pressure is gradually increased to promote the full saturation of the shale core with oil. Under the same core size and physical properties, compared with the conventional vacuum self-aspiration saturation method, the amount of saturated oil in shale cores using this method can be increased by nearly 100%, which greatly improves the saturation of shale cores and makes them as close as possible to the oil saturation under the original formation conditions.
[0032] In determining the saturated oil volume, shale core displacement for saturated oil employs a low-pressure, low-rate displacement method. This involves increasing the internal pressure at 0.5 MPa intervals, from 1 MPa to 3 MPa. The purpose is to leverage the pressure-sensitive effect of shale; high pressure causes pore space closure, while low pressure does not damage the shale pore structure, allowing crude oil to fully enter the core pores and support the shale pore structure. High-pressure displacement is then performed at 1 MPa intervals, increasing from 4 MPa to 15 MPa, with each pressure point held for at least 1 hour. The aim is to gradually increase the pressure to promote full saturation of the shale core with oil. The resulting effect is that, under the same core size and physical properties, compared to the conventional vacuum self-aspiration saturation method, this method increases the saturated oil volume by nearly 100%, significantly improving the saturation degree of the shale core.
[0033] This invention establishes a high-temperature, high-pressure gas drive experimental technique and apparatus for shale oil. It conducts gas drive experimental evaluation studies on the Gulong shale oil, revealing the enhanced oil recovery effect of gas drive in shale oil and providing important basic data for shale oil gas injection development. This experimental technique fills a gap in gas drive experimental research in the shale field at Daqing Oilfield.
[0034] The experimental technique of this invention can be used for unconventional reservoir gas injection development experiments, especially suitable for core gas drive experiments in shale reservoirs with tight lithology, poor physical properties, well-developed laminae, and high stress sensitivity. It can also be used for core gas drive experiments in ultra-low permeability-tight reservoirs, which is of great significance for understanding the evaluation of gas drive development effectiveness in such reservoirs. It can be promoted throughout the industry, providing important technical support for the evaluation of gas drive development effectiveness in shale and tight reservoirs. Attached Figure Description
[0035] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0036] Figure 1 This is a flowchart of the high-temperature and high-pressure gas drive experimental method for shale cores according to the present invention;
[0037] Figure 2 This is a schematic diagram of the high-temperature and high-pressure gas-driven experimental device for shale cores according to the present invention.
[0038] In the diagram: 1. Air injection pump; 2. Liquid injection pump; 3. Confining pressure pump; 4. Back pressure pump; 5. Constant temperature chamber; 6. Core holder; 7. Back pressure valve; 8. Three-phase separator; 9. Gas flow meter. Detailed Implementation
[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.
[0040] like Figure 2 As shown, this invention discloses a high-temperature, high-pressure gas drive experimental device for shale cores, comprising a core holder 6 for holding shale cores, the core holder 6 being placed in the core holder 6; the core holder 6 is placed in a constant temperature chamber 5, the constant temperature chamber being heated to the formation temperature, the formation temperature being ≥90℃; the inlet end of the core holder 6 is connected to an injection system for injecting the displacement medium; the injection system is divided into a gas injection pump 1 and a liquid injection pump 2, the gas injection pump 1 being used to inject gas during the gas drive experiment; the liquid injection pump 2 being used to inject saturated medium; the outlet end of the core holder 6 is connected to a three-phase separator 8 and a back pressure pump 4 respectively through a back pressure valve 7; the top outlet of the three-phase separator 8 is connected to a gas flow meter 9; the gas flow meter 9 measures the produced gas volume; the confining pressure hole of the core holder 6 is connected to a confining pressure pump 3.
[0041] like Figure 1 As shown, this invention provides a high-temperature, high-pressure gas drive experimental method for shale cores, specifically including the following steps:
[0042] Step 1: Displace saturated oil from shale cores and determine the amount of saturated oil;
[0043] Shale cores were air-dried at low temperature until their weight remained constant. The shale cores were then saturated. The cores were placed in a core holder and evacuated for at least 24 hours. Low-pressure, low-speed displacement of the saturated oil was then performed (the internal pressure was increased from 1 MPa to 3 MPa at 0.5 MPa intervals). When the pressure of the low-pressure, low-speed displacement reached 3 MPa, high-pressure displacement of the saturated oil was performed (the internal pressure was increased from 4 MPa to 15 MPa at 1 MPa intervals, with each pressure point stabilized for at least 1 hour). The saturated cores were weighed and measured, and then the saturation of the mobile fluid was tested using an NMR spectrometer to determine the amount of saturated oil in the shale core.
[0044] Step 2: Assemble the experimental setup for shale core gas drive.
[0045] Assemble the shale core gas drive experimental process device, perform process leak testing, heat in a constant temperature chamber (formation temperature ≥90℃), and load the saturated shale core into the core holder.
[0046] Step 3: Based on the saturated shale core, inject saturated medium to establish a shale core driving system;
[0047] The saturated medium is injected at a constant rate (between 0.05-0.1 ml / min) into the injection end of the core holder 6. The confining pressure is adjusted to be 3 MPa higher than the injection pressure. The back pressure valve is adjusted to raise the injection pressure of the displacement system to the experimental pressure (formation pressure ≥ 30 MPa). The changes at the injection end and the production end are observed. When the injection pressure remains constant for more than 4 hours and the displacement medium is seen to flow out stably from the outlet end, it indicates that the drive system has been established.
[0048] Step 4: Conduct gas drive experiments on saturated shale cores.
[0049] Turn off the pump that injects saturated medium, adjust the pressure of the pump that injects displacing medium to the experimental pressure, and start the gas drive experiment. Record parameters such as injection pump pressure, flow rate, outlet pressure, flow rate, oil production, and gas production throughout the experiment. The gas drive experiment ends when almost no oil is produced at the outlet.
[0050] Step 5: Calculate the oil yield from shale cores.
[0051] After the displacement experiment, the shale core was removed from the core holder 6, the core weight was weighed, and the saturation of the movable fluid was tested again using a nuclear magnetic resonance device to calculate the oil production.
[0052] The amount of oil produced by gas drive is measured by a combination of core weighing and nuclear magnetic resonance scanning in order to make the test results more accurate.
[0053] The present invention will be further described in detail below using shale core samples from the Daqing Gulong shale oil reservoir as an example, in conjunction with the accompanying drawings.
[0054] Example 1
[0055] This embodiment takes a shale core from the Daqing Gulong shale oil reservoir as an example to specifically describe a high-temperature, high-pressure gas drive experimental method for shale cores, including the following steps:
[0056] Step 1: Displace saturated oil from shale cores and determine the amount of saturated oil;
[0057] Shale cores are loaded into core holder 6 and evacuated for more than 24 hours. Then, saturated oil is displaced at low pressure and low speed using injection pump 2 (internal pressure interval 0.5 MPa, increasing from 1 MPa to 3 MPa). Due to the pressure-sensitive effect of shale, high pressure will cause the shale pore space to close, while low pressure will not damage the shale pore structure. Crude oil can enter the core pores in a saturated manner and support the shale pore structure.
[0058] Finally, high-pressure displacement was performed to saturate the oil. The high-pressure displacement method was as follows: the internal pressure was increased at 1 MPa intervals, from 4 MPa to 15 MPa, and each pressure point was stabilized for more than 1 hour. This gradual increase in pressure promoted the full saturation of the shale core with oil. Under the same core size and physical properties, the volume of saturated oil obtained by the conventional vacuum self-aspiration saturation method accounted for only 43%-50% of the total pore volume of the core; while the volume of saturated oil in the shale core obtained by the method of this invention accounted for 80%-91% of the total pore volume of the core. It can be seen that the saturated oil volume after using the high-pressure displacement method of this invention was increased by nearly 100%, which greatly improved the oil saturation of the shale core, making it as close as possible to the oil saturation under the original formation conditions. The saturated core was weighed and measured, and then the movable fluid saturation was tested using an NMR device. Finally, the saturated oil volume was determined using the results of the NMR test.
[0059] Step 2: Assemble the experimental setup for shale core gas drive.
[0060] Assemble the shale core gas drive experimental process device and perform a leak test. After passing the test, heat the constant temperature chamber (formation temperature ≥ 90℃) and load the saturated shale core into the core holder. The purpose of heating at this time is to restore the formation temperature conditions and ensure that the core is under formation temperature conditions.
[0061] Step 3: Based on the saturated shale core, inject saturated medium (saturated medium is saturated oil) to establish a shale core driving system;
[0062] The saturated medium is injected at a constant rate using injection pump 2; the injection rate of the saturated medium is between 0.05-0.1 ml / min; the purpose of constant-rate injection is to allow the medium in the pores of the shale core to flow under low-pressure conditions.
[0063] The pressure of the confining pressure pump 3 is adjusted to be 3 MPa higher than that of the injection pump 2. The confining pressure is 3 MPa higher than the injection pressure so that the injected medium can form a displacement flow along the core end face and will not flow along the core surface. The pressure of the back pressure valve 4 is adjusted in real time to be slightly lower than the injection pressure so that the pressure of the injection pump 2 of the displacement system is raised to the experimental pressure (pressure ≥ 30 MPa). When the pressure of the injection pump 2 of the displacement system rises to the experimental pressure, the entire experimental system has been restored to the formation temperature and pressure conditions.
[0064] Observe the changes in injection pump 2 and three-phase separator 8 at the production end. When the pressure of injection pump 2 remains unchanged for more than 4 hours and the displacement medium flows out stably from the three-phase separator 8 at the production end, it indicates that the driving system has been established and subsequent gas drive experiments can be carried out.
[0065] Step 4: Conduct gas drive experiments on saturated shale cores;
[0066] Turn off the liquid injection pump 2, adjust the pressure of the gas injection pump 1 to the experimental pressure, and start the gas drive experiment. The gas drive experiment adopts constant pressure and near constant speed injection (the speed is between 0.05-0.1 ml / min). The purpose of constant pressure injection is to ensure that the injected gas volume can be accurately measured. The near constant speed injection of the gas injection pump 1 is achieved by adjusting the pressure of the back pressure valve 4. The purpose of near constant speed injection is to ensure the stable flow of the injected medium. During the entire experiment, the pressure and flow rate of the gas injection pump 1, the pressure of the back pressure pump 4 at the outlet, the amount of oil produced, and the amount of gas produced are recorded.
[0067] Step 5: Calculate the oil yield from shale cores;
[0068] After the displacement experiment, the shale core was removed from the core holder 6, the core weight was weighed, and the movable fluid saturation was tested again using a nuclear magnetic resonance (NMR) device. The oil production was calculated by measuring the difference in movable fluid saturation of the core before and after the gas drive experiment using the NMR device.
[0069] The oil production obtained by weighing is used to characterize the relationship between oil production and gas injection.
[0070] The output gas volume measured by the gas flow meter 9 is used to characterize the relationship between the output gas volume and the gas injection volume recorded by the gas injection pump 1, as well as the relationship between the output gas volume and the oil production volume.
[0071] By comparing and analyzing the above measurement parameters, we can clarify the oil displacement efficiency and production dynamics of gas-driven shale cores under formation temperature and pressure conditions, providing experimental data support and guidance for understanding the laws of shale oil gas-driven field tests.
[0072] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the implementation methods of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of the present invention.
Claims
1. A high-temperature, high-pressure gas drive experimental method for shale cores, characterized in that: Includes the following steps: Step 1: Displace saturated oil from shale cores and determine the amount of saturated oil; Step 2: Assemble the experimental setup for shale core gas drive. Step 3: Based on the saturated shale core, inject saturated medium to establish a shale core driving system; Step 4: Conduct gas drive experiments on saturated shale cores; Step 5: After the displacement experiment, calculate the oil yield from the shale core.
2. The high-temperature and high-pressure gas drive experimental method for shale cores according to claim 1, characterized in that: Step 1, displacing saturated oil in shale cores and determining the amount of saturated oil, includes the following specific methods: The shale cores are dried at low temperature until their weight remains constant, and then the shale cores are saturated. The shale cores are then placed in a core holder and vacuumed for at least 24 hours, and then the saturated oil is displaced at low pressure and low speed. When the pressure of the low-pressure, low-speed displacement saturated oil is increased to 3 MPa, high-pressure displacement of the saturated oil is carried out; the saturated core is weighed and measured, and then the saturation of the movable fluid is tested using a nuclear magnetic resonance device to determine the amount of saturated oil in the shale core.
3. The high-temperature and high-pressure gas drive experimental method for shale cores according to claim 2, characterized in that: The saturated oil was displaced at low pressure and low speed. The low pressure and low speed displacement method was as follows: the internal pressure was increased from 1 MPa to 3 MPa at intervals of 0.5 MPa; each pressure point was stabilized for more than 1 hour. High-pressure displacement of saturated oil is carried out. The high-pressure displacement method is as follows: the internal pressure is increased from 4MPa to 15MPa at 1MPa intervals, and each pressure point is stabilized for more than 1 hour.
4. The high-temperature and high-pressure gas drive experimental method for shale cores according to claim 1, characterized in that: When assembling the shale core gas drive experimental process device in step 2, a process leak test must be performed. After the process leak test is qualified, the constant temperature chamber is heated to the formation temperature; the formation temperature is ≥90℃; the saturated shale core is then loaded into the core holder.
5. The high-temperature and high-pressure gas drive experimental method for shale cores according to claim 1, characterized in that: Step 3 involves injecting a saturated medium into the saturated shale core to establish a shale core-driven system; specific methods include: The saturated medium is injected at a constant speed into the injection end of the core holder. The confining pressure is adjusted to be 3 MPa higher than the injection pressure. The back pressure valve is adjusted to raise the injection pressure of the displacement system to the experimental pressure. The changes at the injection end and the extraction end are observed. When the injection pressure remains constant for more than 4 hours and the displacement medium flows out stably from the outlet end, it indicates that the drive system has been established.
6. The high-temperature and high-pressure gas drive experimental method for shale cores according to claim 5, characterized in that: The injection rate of the saturated medium is between 0.05 and 0.1 ml / min; the saturated medium is saturated oil. The experimental pressure is the formation pressure, and the experimental pressure is ≥30MPa.
7. The high-temperature and high-pressure gas drive experimental method for shale cores according to claim 1, characterized in that: The method for conducting gas drive experiments on saturated shale cores in step 4 is as follows: Turn off the pump that injects saturated medium, adjust the pressure of the pump that injects displacing medium to the experimental pressure, and start the gas drive experiment. Record the injection pump pressure and flow rate, outlet pressure and flow rate, oil production and gas production, and other parameters throughout the experiment. When there is almost no oil at the outlet, the gas drive experiment ends.
8. The high-temperature and high-pressure gas drive experimental method for shale cores according to claim 1, characterized in that: Step 5 calculates the oil production from shale cores using a combination of core weighing and nuclear magnetic resonance scanning to make the test results more accurate.
9. The experimental apparatus used in the method according to any one of claims 1-8, characterized in that: The system includes a core holder (6), which is placed in a constant temperature chamber (5); the inlet end of the core holder (6) is connected to an injection system for injecting displacement media; the outlet end is connected to a three-phase separator (8) and a back pressure pump (4) respectively through a back pressure valve (7); the top outlet of the three-phase separator (8) is connected to a gas flow meter (9); and the confining pressure hole of the core holder (6) is connected to a confining pressure pump (3).
10. The experimental apparatus according to claim 9, characterized in that: The injection system is divided into an air injection pump (1) and a liquid injection pump (2); The gas injection pump (1) is used to inject gas during gas drive experiments; The injection pump (2) is used to inject saturated medium; The gas flow meter (9) is used to measure the output gas volume; The core holder is used to hold shale cores; The constant temperature chamber is heated to the formation temperature; the formation temperature is ≥90℃.