Reservoir pore structure corrosion simulation experiment method, device and system

Abstract

The invention provides a reservoir pore structure corrosion simulation experiment method, device and system, and the method comprises the steps: determining the generation parameters of organic acid of hydrocarbon source rock in a target research area according to a typical hydrocarbon source rock sample in the target research area; the method comprises the following steps: placing a reservoir sample of a target research area into a sample corrosion assembly, and setting an experimental confining pressure and an experimental temperature interval for the reservoir sample according to a formation pressure and formation temperature interval; starting a nuclear magnetic resonance device of the sample corrosion assembly to test pore throat radius distribution in the reservoir sample, and injecting organic acid into the reservoir sample; according to test data of the nuclear magnetic resonance device, the change rule of the pore structure in the organic acid corrosion process is obtained. Based on the technical scheme of the invention, the continuous flow corrosion experiment of organic acid on the tight reservoir under the actual temperature and pressure condition can be carried out, the real-time pore structure change can be detected, the real-time change rule of the pore structure of the tight reservoir can be quantitatively represented through nuclear magnetic on-line detection, and a basis is provided for the prediction of a petroleum favorable enrichment area.

Description

Technical Field

[0001] This invention relates to the field of unconventional oil and gas reservoir pore structure research technology, and particularly to a reservoir pore structure dissolution simulation experimental method, apparatus and system. Background Technology

[0002] Tight oil is widely distributed in oil and gas basins in my country and is an important area for increasing oil and gas production. Tight oil reservoirs widely develop micro- and nano-pore throat systems, and the microscopic pore structure is a crucial factor influencing oil and gas migration and accumulation. During the thermal evolution of organic matter in source rocks, a large amount of organic acids are released, which dissolve carbonate and silicate minerals in adjacent reservoirs, thereby forming large-scale secondary pores, altering the pore structure of tight reservoirs, and affecting oil migration and accumulation.

[0003] Currently, there is some research on the dissolving effect of organic acids both domestically and internationally. In the field of petroleum geology, related devices and technical solutions for organic acid dissolution or diagenesis have been developed. For example, some researchers have proposed experimental schemes for the dissolution effect of organic acids on tight oil reservoirs, using a reaction vessel as the experimental container to explore the thermodynamic model of organic acid decarboxylation reaction through static dissolution experiments. Other researchers have proposed simulation experimental schemes for reservoir dissolution, using a continuous flow dissolution method under high temperature and high pressure conditions, and analyzing the reaction solution, reservoir minerals, sample mass and volume after dissolution to study the impact of dissolution on the reservoir. Still other researchers have proposed analytical schemes for the dissolution effect of carbonate rocks, using CT scanning to compare the reservoir pore structure before and after organic acid dissolution to explore the impact of dissolution on the reservoir pore structure.

[0004] However, most current research, including the existing schemes mentioned above, focuses on the study of organic acid dissolution mechanism, changes in solution ion content, and characterization of static pore structure before and after dissolution. It does not involve changes in pore structure during dissolution, and in particular, it cannot achieve real-time detection and analysis of pore structure in tight reservoirs under the action of organic acid dissolution. Consequently, it is impossible to effectively determine the real-time change law of pore structure in tight reservoirs during organic acid dissolution. Summary of the Invention

[0005] To address the problem that existing technologies cannot achieve real-time detection and analysis of the pore structure of tight reservoirs under the action of organic acid dissolution, and cannot determine the real-time change law of the pore structure of tight reservoirs during the organic acid dissolution process, this invention proposes a reservoir pore structure dissolution simulation experimental method, device and system.

[0006] In a first aspect, the present invention proposes a method for simulating the dissolution of reservoir pore structures, which includes the following steps:

[0007] Based on typical source rock samples from the target study area, determine the organic acid generation parameters of the source rocks in the target study area. The generation parameters include at least the type of organic acid, the concentration of organic acid, and the formation pressure and formation temperature range.

[0008] The reservoir sample of the target study area is placed in the sample dissolution assembly, and the experimental confining pressure and experimental temperature range for the reservoir sample are set according to the formation pressure and formation temperature range.

[0009] The nuclear magnetic resonance device of the sample dissolution component is activated to test the pore throat radius distribution in the reservoir sample. Organic acid is injected into the reservoir sample to gradually increase the experimental temperature from the lower limit of the experimental temperature range to the upper limit of the range.

[0010] When the experimental temperature reaches the upper limit of the range, the change law of pore structure during the organic acid dissolution process is obtained based on the test data of the nuclear magnetic resonance device.

[0011] In one implementation, the formation parameters of organic acids in the source rocks of the target study area are determined based on typical source rock samples from the target study area, including the following sub-steps:

[0012] Hydrogen generation simulation experiments were conducted using the typical source rock samples, and the type and concentration of organic acids, as well as the formation temperature range, were determined based on the experimental results.

[0013] Based on the geological background of the target study area, basin simulation is performed to determine the formation pressure at which organic acids are generated in the generation parameters.

[0014] In one embodiment, injecting an organic acid into the reservoir sample includes the following sub-steps:

[0015] Based on the type and concentration of organic acid in the generation parameters, select the corresponding type and concentration of organic acid;

[0016] An organic acid at a predetermined temperature is pumped into the reservoir sample, the predetermined temperature being determined based on the current specific temperature value of the reservoir sample.

[0017] In one embodiment, a reservoir sample from the target study area is placed in a sample dissolution assembly, and an experimental confining pressure and temperature range for the reservoir sample are set according to the formation pressure and formation temperature range, including the following sub-steps:

[0018] The reservoir sample is placed in a sample chamber corresponding to the nuclear magnetic resonance device of the sample dissolution assembly;

[0019] A confining pressure medium is pumped into the interlayer of the sample chamber using the first confining pressure maintenance unit. The pumping pressure of the confining pressure medium is matched with the formation pressure, and the pumping temperature is matched with the lower limit of the formation temperature range.

[0020] The confining pressure medium output from the interlayer is received by the second confining pressure maintaining unit.

[0021] In one embodiment, the confining pressure medium output from the interlayer is received by the second confining pressure maintaining unit, and the method further includes:

[0022] The pressure of the second confining pressure maintaining unit is lower than the pumping pressure of the first confining pressure maintaining unit on the confining pressure medium.

[0023] In one embodiment, gradually increasing the experimental temperature from the lower limit of the experimental temperature range to its upper limit includes the following sub-steps:

[0024] The temperature of the confining pressure medium pumped into the first confining pressure maintenance unit is changed so that the experimental temperature gradually increases from the lower limit of the experimental temperature range to the upper limit of the range.

[0025] In one embodiment, the experimental temperature gradually increases from the lower limit of the experimental temperature range to the upper limit of the range at a rate of 10°C / h.

[0026] In one embodiment, based on the test data from the nuclear magnetic resonance device, the change pattern of pore structure during the organic acid dissolution process is determined, including:

[0027] Based on the test data from the nuclear magnetic resonance device, the distribution and changes of pores in the reservoir sample corresponding to the relaxation time T2 during the dissolution process are determined, and the change law of pore structure during organic acid dissolution is obtained.

[0028] Secondly, the present invention provides a reservoir pore structure dissolution simulation experimental device, which includes:

[0029] A sample dissolution assembly includes a nuclear magnetic resonance device and a sample chamber configured to correspond to the nuclear magnetic resonance device, the sample chamber being used to hold a reservoir sample;

[0030] An environmental simulation component, connected via piping to the interlayer of the sample chamber, is used to inject confining pressure media at corresponding temperatures and pressures into the interlayer to simulate formation pressure and temperature; and

[0031] An organic acid injection assembly, which is connected to the interior of the sample chamber via a pipe, is used to inject organic acid into the sample chamber to dissolve the reservoir sample.

[0032] In one embodiment, the sample chamber includes a cylindrical confining device, which is erected and has clamps inserted at its top and bottom ends to form the internal space of the sample chamber. The confining device is made of an elastic material and the interlayer is constructed inside the confining device.

[0033] The organic acid injection assembly is connected to the clamp at the top via a pipe, so as to communicate with the interior of the sample chamber through a channel constructed in the clamp at the top.

[0034] In one embodiment, a solution collection assembly is also included, which is connected via a conduit to the clamp at the bottom end to communicate with the interior of the sample chamber through a channel constructed within the clamp at the bottom end.

[0035] In one embodiment, the environmental simulation component includes a first confining pressure maintaining unit and a second confining pressure maintaining unit with identical structures. The confining pressure maintaining unit includes a confining pressure medium container and a confining pressure pump connected by a pipeline.

[0036] The two confining pressure medium containers are respectively connected to the interlayer through pipelines, and the pumping pressure of the confining pressure pump of the first confining pressure maintaining unit is greater than that of the confining pressure pump of the second confining pressure maintaining unit. The confining pressure medium container of the first confining pressure maintaining unit is placed in a constant temperature chamber.

[0037] In one embodiment, the organic acid injection assembly includes an organic acid container placed in a constant temperature chamber and an injection pump connected to the organic acid container via a pipe, the organic acid container being connected to the sample chamber via the pipe.

[0038] Thirdly, the present invention proposes a reservoir pore structure dissolution simulation experimental system, which includes the above-mentioned reservoir pore structure dissolution simulation experimental device and a data acquisition device electrically connected to the experimental device. The data acquisition device is used to collect various temperature and pressure data of the experimental device and test data of the nuclear magnetic resonance device.

[0039] The above-mentioned technical features can be combined in various suitable ways or replaced by equivalent technical features, as long as the purpose of the present invention can be achieved.

[0040] The present invention provides a method, apparatus, and system for simulating reservoir pore structure dissolution, which, compared with the prior art, has at least the following advantages:

[0041] This invention provides a method, apparatus, and system for simulating reservoir pore structure dissolution. It can conduct continuous flow dissolution experiments of tight reservoirs by organic acids under actual temperature and pressure conditions and detect real-time changes in pore structure. Online NMR detection can provide a detailed description of the modification process and patterns of the tight reservoir pore structure by organic acids, thereby quantitatively characterizing the real-time changes in the pore structure of tight reservoirs during organic acid dissolution. This provides a basis for predicting favorable oil enrichment areas. Attached Figure Description

[0042] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0043] Figure 1 The main flowchart of the reservoir pore structure dissolution simulation experimental method of the present invention is shown;

[0044] Figure 2 This invention shows a schematic diagram of the principle structure of the reservoir pore structure dissolution simulation experimental device and system of the present invention;

[0045] Figure 3 The nuclear magnetic resonance (NMR) results of the reservoir pore structure dissolution simulation experiment method of the present invention are shown in the T2 spectrum distribution of the pore structure.

[0046] In the accompanying drawings, the same parts use the same reference numerals. The drawings are not to scale.

[0047] Figure label:

[0048] 1-Data acquisition device, 2-Organic acid injection assembly, 3-Sample dissolution assembly, 4-Environmental simulation assembly, 5-Solution collection assembly, 6-Nuclear magnetic resonance device;

[0049] 7-Seal, 8-Clamper, 9-Containing pressure device;

[0050] 10-First confining pressure medium container, 11-First confining pressure pump, 12-First constant temperature chamber, 13-First valve, 14-Second valve;

[0051] 15-Third thermostatic chamber, 16-Organic acid container, 17-Injection pump, 18-Third valve, 19-Check valve;

[0052] 20-Fourth valve, 21-Fifth valve, 22-Collection container, 23-Waste liquid container;

[0053] 24-First pressure gauge, 25-Second pressure gauge, 26-Computer, 27-Second confining pressure medium container, 28-Second confining pressure pump, 29-Second constant temperature chamber;

[0054] 30 - Reservoir sample. Detailed Implementation

[0055] The invention will now be further described with reference to the accompanying drawings.

[0056] Example 1

[0057] An embodiment of the present invention provides a method for simulating the dissolution of reservoir pore structure, which includes the following steps:

[0058] S100: Based on typical source rock samples from the target study area, determine the organic acid generation parameters of the source rocks in the target study area. The generation parameters should include at least the type of organic acid, the concentration of organic acid, and the formation pressure and temperature range during the generation of organic acid.

[0059] S110: Hydrogen generation simulation experiments were conducted using typical source rock samples. Based on the experimental results, the type of organic acid, concentration of organic acid, and formation temperature range in the generation parameters were determined.

[0060] Specifically, based on the geological background and conditions of the target study area, typical source rock samples and reservoir samples are selected. Hydrogen generation thermal simulation experiments of organic acid formation are conducted on typical source rock samples, or previous data are collected to determine the type, concentration, generation temperature, and hydrocarbon generation threshold of organic acids in the target study area. The organic acid generation temperature and hydrocarbon generation threshold are respectively the lower and upper limits of the formation temperature range.

[0061] S120: Based on the geological background of the target study area, basin simulation is performed to determine the formation pressure at which organic acids are generated in the generation parameters.

[0062] Specifically, basin simulation technology was used to reconstruct the formation pressure evolution history of the target study area, determine the formation pressure when the source rocks produced organic acids, and set the experimental pressure with reference to this formation pressure.

[0063] S200: Place the reservoir sample from the target study area into the sample dissolution assembly, and set the experimental confining pressure and experimental temperature range for the reservoir sample according to the formation pressure and formation temperature range.

[0064] S210: Place the reservoir sample in the sample chamber of the sample dissolution assembly (the sample chamber corresponds to the nuclear magnetic resonance device of the sample dissolution assembly).

[0065] Specifically, based on the size of the sample chamber, the reservoir sample is prepared to match the shape and size of the sample chamber and then placed inside the sample chamber. The sample chamber has a sandwich structure with an expandable inner frame cavity inside. This cavity is used to expand the inner wall of the sandwich to fit the reservoir sample and apply pressure to the reservoir sample by injecting a confining medium with a certain pressure into the sandwich, thereby simulating the formation confining pressure.

[0066] S220: The first confining pressure maintenance unit pumps confining pressure medium into the interlayer of the sample chamber. The pumping pressure of the confining pressure medium is matched with the formation pressure, and the pumping temperature is matched with the lower limit of the formation temperature range.

[0067] Specifically, based on the design of the sample chamber interlayer, a confining pressure pump is used to pump the confining pressure medium into the interlayer. By setting the pumping pressure of the confining pressure pump, the confining pressure medium in the interlayer has a corresponding pressure to simulate the formation pressure. At the same time, the confining pressure medium has a certain temperature when pumped in (which can be achieved by setting a corresponding heater). The confining pressure medium with a certain temperature is used to transfer heat to the sample chamber, simulating the actual formation temperature.

[0068] S230: Make the pressure of the second confining pressure maintaining unit less than the pumping pressure of the first confining pressure maintaining unit for the confining pressure medium, and use the second confining pressure maintaining unit to receive the confining pressure medium output from the interlayer.

[0069] Specifically, since this invention uses the pressure and temperature of the confining medium to simulate formation pressure and temperature, in order to ensure the reliability of the simulated pressure and temperature, especially the stability of the temperature, the confining medium in the sample chamber needs to be constantly renewed. This is because only in this way can the confining medium in the sample chamber be kept at the corresponding temperature, maintain the stability of the experimental temperature, and prevent the temperature of the confining medium in the sample chamber from dropping due to natural heat dissipation.

[0070] Therefore, the sample chamber has two confining pressure maintenance units. These two units jointly apply pressure to the confining pressure medium in the sample chamber's interlayer. Since the pressure in the first confining pressure maintenance unit is greater than that in the second, the confining pressure medium input from the first unit will spontaneously flow to the second. This allows for a continuous flow of the confining pressure medium through the sample chamber's interlayer, ensuring constant renewal of the confining pressure medium within the interlayer. Preferably, the pressure in the second confining pressure maintenance unit is lower than the pumping pressure of the confining pressure medium from the first unit. This pressure difference allows the confining pressure medium to flow more quickly and smoothly within the interlayer of the confining pressure chamber, ensuring that the heat from the confining pressure medium reaches the reservoir sample as quickly as possible. This prevents the confining pressure medium from flowing into the sample chamber too slowly, thus avoiding the problem of excessive heat dissipation and temperature drop before entering the sample chamber.

[0071] It should be noted that this embodiment simulates both formation pressure and formation temperature simultaneously using a continuously flowing confining pressure medium. Structurally, there is no need for a heating structure in the sample chamber, thus simplifying its structure and making it fully adaptable to the limited internal space of the NMR device. It also avoids introducing factors that could easily affect NMR results, such as the presence of metal components in heating structures. Therefore, the entire sample chamber is made of non-metallic materials.

[0072] S300: Start the nuclear magnetic resonance device of the sample dissolution component to test the pore throat radius distribution in the reservoir sample, inject organic acid into the reservoir sample, and gradually increase the experimental temperature from the lower limit of the experimental temperature range to the upper limit of the range.

[0073] Specifically, the nuclear magnetic resonance (NMR) device can be activated before the organic acid injection to test the pore structure of the reservoir sample before dissolution. Furthermore, it should be noted that this invention studies the effect of dissolution on the reservoir pore structure by injecting organic acid. To control variables, the reservoir sample is preferably a rock sample from the target study area reservoir, i.e., a non-source rock, to avoid introducing other variables due to the sample's own hydrocarbon generation and acid production.

[0074] S310: Select the appropriate type and concentration of organic acid based on the type and concentration of organic acid in the generation parameters.

[0075] S320: Pump organic acid at a predetermined temperature into the reservoir sample. The predetermined temperature is determined based on the current specific temperature value of the reservoir sample.

[0076] Specifically, when organic acids are injected into reservoir samples, they will obviously affect the temperature of the reservoir samples themselves. Therefore, in order to ensure that the temperature of the reservoir samples is closer to the actual formation temperature, the organic acids can be heated in advance (at a temperature lower than the decomposition temperature of the organic acids) so that their temperature matches the temperature of the confining medium injected into the sample chamber interlayer (i.e., the specific temperature of the reservoir sample in the experimental temperature range).

[0077] S330: Change the temperature of the confining pressure medium pumped into the first confining pressure maintenance unit so that the experimental temperature gradually increases from the lower limit of the experimental temperature range to the upper limit of the range; wherein, the rate of temperature change from the lower limit of the experimental temperature range to its upper limit is 10℃ / h.

[0078] Specifically, the confining pressure medium pumped into the first confining pressure maintenance unit mainly forms a temperature environment that simulates the formation temperature. By gradually changing the temperature of the confining pressure medium pumped into the first confining pressure maintenance unit, the experimental temperature for the reservoir sample can be changed, thereby simulating various temperatures during hydrocarbon generation and acid production in actual reservoir source rocks.

[0079] S400: When the experimental temperature reaches the upper limit of the range, the change law of pore structure during the organic acid dissolution process is obtained based on the test data of the nuclear magnetic resonance device.

[0080] S410: Based on the test data from the nuclear magnetic resonance device, determine the distribution and changes of pores in the reservoir sample corresponding to the relaxation time T2 during the dissolution process, and derive the change law of pore structure during organic acid dissolution.

[0081] Specifically, during the experimental temperature range, nuclear magnetic resonance (NMR) tests can be performed on the samples at set time intervals. Based on the T2 spectrum data obtained from the NMR device, the distribution and changes in the number of pores at different time points during the dissolution process can be determined. This allows for the determination of the impact of organic acid dissolution on the pore structure of the reservoir samples, revealing its variation patterns, and achieving continuous quantitative characterization of the pore structure during organic acid dissolution. Tight reservoir oil accumulation is mainly characterized by near-source charging, and its enrichment degree is influenced by the pore structure. Therefore, the obtained variation patterns and quantitative characterization of the pore structure can provide a basis for predicting favorable oil enrichment areas.

[0082] Based on the experimental method proposed in this invention, continuous flow dissolution experiments of organic acids on tight reservoirs under actual temperature and pressure conditions can be carried out and real-time changes in pore structure can be detected. Through online nuclear magnetic resonance detection, the process and law of organic acid modification of tight reservoir pore structure can be described in detail, thereby quantitatively characterizing the real-time change law of tight reservoir pore structure during organic acid dissolution, providing a basis for the prediction of favorable oil enrichment areas.

[0083] Example 2

[0084] An embodiment of the present invention provides a method for simulating the dissolution of reservoir pore structure, which includes the following steps:

[0085] S100: Based on typical source rock samples from the target study area, determine the organic acid generation parameters of the source rocks in the target study area. The generation parameters should include at least the type of organic acid, the concentration of organic acid, and the formation pressure and temperature range.

[0086] S110: Hydrogen generation simulation experiments were conducted using typical source rock samples. Based on the experimental results, the type of organic acid, concentration of organic acid, and formation temperature range in the generation parameters were determined.

[0087] Specifically, based on the geological background and conditions of the target study area, typical source rock samples and reservoir samples are selected. Hydrogen generation thermal simulation experiments of organic acid formation are conducted on typical source rock samples, or previous data are collected to determine the type, concentration, generation temperature, and hydrocarbon generation threshold of organic acids in the target study area. The organic acid generation temperature and hydrocarbon generation threshold are respectively the lower and upper limits of the formation temperature range.

[0088] S120: Based on the geological background of the target study area, basin simulation is performed to determine the formation pressure at which organic acids are generated in the generation parameters.

[0089] Specifically, basin simulation technology was used to reconstruct the formation pressure evolution history of the target study area, determine the formation pressure when the source rocks produced organic acids, and set the experimental pressure with reference to this formation pressure.

[0090] S200: Place the reservoir sample from the target study area into the sample dissolution assembly, and set the experimental confining pressure and experimental temperature range for the reservoir sample according to the formation pressure and formation temperature range.

[0091] S210: Place the reservoir sample in the sample chamber of the sample dissolution assembly, seal the sample chamber, inject water to test the seal, and then drain the excess water to ensure that the reservoir sample contains water; the specific composition of the water injected into the sample chamber is configured according to the composition of the formation water in the target study area.

[0092] Specifically, based on the size of the sample chamber, the reservoir sample is prepared to match the shape and size of the sample chamber and then placed inside. The sample chamber has a sandwich structure with an expandable inner frame cavity. This cavity is used to inject a confining medium at a certain pressure into the sandwich, causing the inner wall of the sandwich to expand until it adheres to the reservoir sample, thus applying pressure to the sample and simulating formation confining pressure. While testing the sealing performance with water injection, the reservoir sample can also be infused with water, simulating the actual state of the reservoir sample in the formation.

[0093] S220: The first confining pressure maintenance unit pumps confining pressure medium into the interlayer of the sample chamber. The pumping pressure of the confining pressure medium is matched with the formation pressure, and the pumping temperature is matched with the lower limit of the formation temperature range.

[0094] Specifically, based on the design of the sample chamber interlayer, a confining pressure pump is used to pump the confining pressure medium into the interlayer. By setting the pumping pressure of the confining pressure pump, the confining pressure medium in the interlayer has a corresponding pressure to simulate the formation pressure. At the same time, the confining pressure medium has a certain temperature when pumped in (which can be achieved by setting a corresponding heater). The confining pressure medium with a certain temperature is used to transfer heat to the sample chamber, simulating the actual formation temperature.

[0095] S230: Make the pressure of the second confining pressure maintaining unit less than the pumping pressure of the first confining pressure maintaining unit for the confining pressure medium, and use the second confining pressure maintaining unit to receive the confining pressure medium output from the interlayer.

[0096] Specifically, since this invention uses the pressure and temperature of the confining medium to simulate formation pressure and temperature, in order to ensure the reliability of the simulated pressure and temperature, especially the stability of the temperature, the confining medium in the sample chamber needs to be constantly renewed. This is because only in this way can the confining medium in the sample chamber be kept at the corresponding temperature, maintain the stability of the experimental temperature, and prevent the temperature of the confining medium in the sample chamber from dropping due to natural heat dissipation.

[0097] Therefore, the sample chamber has two confining pressure maintenance units. These two units jointly apply pressure to the confining pressure medium in the sample chamber's interlayer. Since the pressure in the first confining pressure maintenance unit is greater than that in the second, the confining pressure medium input from the first unit will spontaneously flow to the second. This allows for a continuous flow of the confining pressure medium through the sample chamber's interlayer, ensuring constant renewal of the confining pressure medium within the interlayer. Preferably, the pressure in the second confining pressure maintenance unit is lower than the pumping pressure of the confining pressure medium from the first unit. This pressure difference allows the confining pressure medium to flow more quickly and smoothly within the interlayer of the confining pressure chamber, ensuring that the heat from the confining pressure medium reaches the reservoir sample as quickly as possible. This prevents the confining pressure medium from flowing into the sample chamber too slowly, thus avoiding the problem of excessive heat dissipation and temperature drop before entering the sample chamber.

[0098] It should be noted that this embodiment simulates both formation pressure and formation temperature simultaneously using a continuously flowing confining pressure medium. Structurally, there is no need for a heating structure in the sample chamber, thus simplifying its structure and making it fully adaptable to the limited internal space of the NMR device. It also avoids introducing factors that could easily affect NMR results, such as the presence of metal components in heating structures. Therefore, the entire sample chamber is made of non-metallic materials.

[0099] S300: Start the nuclear magnetic resonance device of the sample dissolution component to test the pore throat radius distribution in the reservoir sample, inject organic acid into the reservoir sample, and gradually increase the experimental temperature from the lower limit of the experimental temperature range to the upper limit of the range.

[0100] Specifically, the nuclear magnetic resonance (NMR) device can be activated before organic acid injection to test the pore structure of the reservoir sample before dissolution. Furthermore, it should be noted that this invention studies the impact of dissolution on reservoir pore structure by injecting organic acid. To control variables, the reservoir sample is preferably a rock sample from the target study area, i.e., a non-source rock, to avoid introducing other variables due to the sample's own hydrocarbon generation and acid production. The organic acid injection rate can also be specifically controlled; for example, the organic acid generation rate and amount in the S110 experimental results can be referenced to control the injection rate and amount, thereby simulating the actual situation in the formation as closely as possible.

[0101] S310: Select the appropriate type and concentration of organic acid based on the type and concentration of organic acid in the generation parameters.

[0102] S320: Pump an organic acid at a predetermined temperature into the top region of the reservoir sample, and collect the solution after the dissolution reaction through a pipe connected to the bottom region of the reservoir sample. The predetermined temperature is determined based on the current specific temperature value of the reservoir sample.

[0103] Specifically, when organic acids are injected into reservoir samples, they obviously affect the temperature of the reservoir samples themselves. Therefore, to ensure that the temperature of the reservoir samples more closely matches the actual formation temperature, the organic acids can be preheated (to a temperature lower than their decomposition temperature) to match the temperature of the confining medium injected into the sample chamber interlayer (i.e., the specific temperature of the reservoir samples within the experimental temperature range). Further collection of the solution after the organic acid and reservoir sample dissolution reaction allows for the determination of the dissolution reaction mechanism by comparing the composition and content of the organic acid and the solution.

[0104] S330: Change the temperature and pressure of the confining pressure medium pumped into the first confining pressure maintaining unit, while ensuring that the pressure difference between the first confining pressure maintaining unit and the second pressure maintaining unit remains constant, so that the experimental temperature gradually increases from the lower limit of the experimental temperature range to the upper limit of the range and the experimental pressure continuously increases; wherein, the rate of temperature change from the lower limit of the experimental temperature range to its upper limit is 10℃ / h.

[0105] Specifically, the confining pressure medium pumped into the first confining pressure maintenance unit mainly creates a temperature environment simulating formation temperature. By gradually changing the temperature of the confining pressure medium pumped into the first confining pressure maintenance unit, the experimental temperature for the reservoir sample can be changed, thereby simulating various temperatures during hydrocarbon generation and acid production in actual reservoir source rocks. Simultaneously, while maintaining a constant pressure difference between the first and second confining pressure maintenance units and ensuring a constant flow rate of the confining pressure medium in the sample chamber, the pressure in both units is increased synchronously. This increases the pressure exerted on the reservoir sample by the confining pressure medium, thereby changing the experimental pressure and enabling further research on the dissolution of the reservoir sample's pore structure by organic acids under different formation pressures and temperatures.

[0106] S400: When the experimental temperature reaches the upper limit of the range, the change law of pore structure during the organic acid dissolution process is obtained based on the test data of the nuclear magnetic resonance device.

[0107] S410: Based on the test data from the nuclear magnetic resonance device, determine the distribution and changes of pores in the reservoir sample corresponding to the relaxation time T2 during the dissolution process, and derive the change law of pore structure during organic acid dissolution.

[0108] Specifically, during the experimental temperature range, nuclear magnetic resonance (NMR) tests can be performed on the samples at set time intervals. Based on the T2 spectrum data obtained from the NMR device, the distribution and changes in the number of pores at different time points during the dissolution process can be determined. This allows for the determination of the impact of organic acid dissolution on the pore structure of the reservoir samples, revealing its variation patterns, and achieving continuous quantitative characterization of the pore structure during organic acid dissolution. Tight reservoir oil accumulation is mainly characterized by near-source charging, and its enrichment degree is influenced by the pore structure. Therefore, the obtained variation patterns and quantitative characterization of the pore structure can provide a basis for predicting favorable oil enrichment areas.

[0109] Based on the experimental method proposed in this invention, continuous flow dissolution experiments of organic acids on tight reservoirs under actual temperature and pressure conditions can be carried out and real-time changes in pore structure can be detected. Through online nuclear magnetic resonance detection, the process and law of organic acid modification of tight reservoir pore structure can be described in detail, thereby quantitatively characterizing the real-time change law of tight reservoir pore structure during organic acid dissolution, providing a basis for the prediction of favorable oil enrichment areas.

[0110] Example 3

[0111] Taking typical source rock and reservoir samples from a target study area as examples, embodiments of the present invention provide an experimental method for simulating the dissolution of reservoir pore structure, which includes the following steps:

[0112] S100: Based on typical source rock samples from the target study area, determine the organic acid generation parameters of the source rocks in the target study area. The generation parameters should include at least the type of organic acid, the concentration of organic acid, and the formation pressure and temperature range.

[0113] S110: Hydrogen generation simulation experiments were conducted using typical source rock samples. Based on the experimental results, the type of organic acid, concentration of organic acid, and formation temperature range in the generation parameters were determined.

[0114] Specifically, based on the geological background and conditions of the target study area, typical source rock samples and reservoir samples were selected. Thermal simulation experiments and hydrocarbon generation experiments were conducted on the typical source rock samples to generate organic acids. The experimental results showed that the main types of organic acids in the study area were formic acid and acetic acid, with an average organic acid concentration of 0.2 mol / L, an organic acid generation temperature of approximately 40℃, and a hydrocarbon generation threshold of approximately 120℃.

[0115] S120: Based on the geological background of the target study area, basin simulation is performed to determine the formation pressure at which organic acids are generated in the generation parameters.

[0116] Specifically, basin simulation technology was used to reconstruct the formation pressure evolution history of the target study area. The simulation results showed that when organic acids were produced in the formation, the formation pressure was about 30 MPa.

[0117] S200: Place the reservoir sample from the target study area into the sample dissolution assembly, and set the experimental confining pressure and experimental temperature range for the reservoir sample according to the formation pressure and formation temperature range.

[0118] S210: Place the reservoir sample in the sample chamber of the sample dissolution assembly, seal the sample chamber, inject water to test the seal, and then drain the excess water to ensure that the reservoir sample contains water; the specific composition of the water injected into the sample chamber is configured according to the composition of the formation water in the target study area.

[0119] Specifically, the reservoir sample is prepared as a plunger sample with a diameter of 2 cm and a length of 5 cm. The reservoir sample is placed in the sample chamber, and water is injected into the sample chamber to test the sealing performance and saturate the reservoir sample with formation water.

[0120] S220: The first confining pressure maintenance unit pumps confining pressure medium into the interlayer of the sample chamber. The pumping pressure of the confining pressure medium is matched with the formation pressure, and the pumping temperature is matched with the lower limit of the formation temperature range.

[0121] Specifically, a fluoride liquid is injected into the first confining pressure maintenance unit as the confining pressure medium. A corresponding heater is used to heat the confining pressure medium, maintaining its temperature at a predetermined experimental temperature. In this embodiment, based on the organic acid formation temperature of approximately 40°C, the confining pressure medium is heated to its initial temperature of 40°C. The first confining pressure maintenance unit is then activated, pumping the confining pressure medium into the sample chamber's interlayer. The pumping pressure of the first confining pressure maintenance unit is controlled so that the pressure gauge displayed on the pipe communicating with the sample chamber's interlayer matches the experimental pressure, i.e., 30 MPa.

[0122] S230: Make the pressure of the second confining pressure maintaining unit less than the pumping pressure of the first confining pressure maintaining unit for the confining pressure medium, and use the second confining pressure maintaining unit to receive the confining pressure medium output from the interlayer.

[0123] Specifically, since this invention uses the pressure and temperature of the confining medium to simulate formation pressure and temperature, in order to ensure the reliability of the simulated pressure and temperature, especially the stability of the temperature, the confining medium in the sample chamber needs to be constantly renewed. This is because only in this way can the confining medium in the sample chamber be kept at the corresponding temperature, maintain the stability of the experimental temperature, and prevent the temperature of the confining medium in the sample chamber from dropping due to natural heat dissipation.

[0124] Therefore, the sample chamber has two confining pressure maintenance units. These two units jointly apply pressure to the confining pressure medium in the sample chamber's interlayer. Since the pressure in the first confining pressure maintenance unit is greater than that in the second, the confining pressure medium input from the first unit will spontaneously flow to the second. This allows for a continuous flow of the confining pressure medium through the sample chamber's interlayer, ensuring constant renewal of the confining pressure medium within the interlayer. Preferably, the pressure in the second confining pressure maintenance unit is lower than the pumping pressure of the confining pressure medium from the first unit. This pressure difference allows the confining pressure medium to flow more quickly and smoothly within the interlayer of the confining pressure chamber, ensuring that the heat from the confining pressure medium reaches the reservoir sample as quickly as possible. This prevents the confining pressure medium from flowing into the sample chamber too slowly, thus avoiding the problem of excessive heat dissipation and temperature drop before entering the sample chamber.

[0125] It should be noted that this embodiment simulates both formation pressure and formation temperature simultaneously using a continuously flowing confining pressure medium. Structurally, there is no need for a heating structure in the sample chamber, thus simplifying its structure and making it fully adaptable to the limited internal space of the NMR device. It also avoids introducing factors that could easily affect NMR results, such as the presence of metal components in heating structures. Therefore, the entire sample chamber is made of non-metallic materials.

[0126] S300: Start the nuclear magnetic resonance device of the sample dissolution component to test the pore throat radius distribution in the reservoir sample, inject organic acid into the reservoir sample, and gradually increase the experimental temperature from the lower limit of the experimental temperature range to the upper limit of the range.

[0127] S310: Select the appropriate type and concentration of organic acid based on the type and concentration of organic acid in the generation parameters.

[0128] S320: Pump an organic acid at a predetermined temperature into the top region of the reservoir sample, and collect the solution after the dissolution reaction through a pipe connected to the bottom region of the reservoir sample. The predetermined temperature is determined based on the current specific temperature value of the reservoir sample.

[0129] Specifically, when organic acids are injected into reservoir samples, they obviously affect the temperature of the reservoir samples themselves. Therefore, to ensure that the temperature of the reservoir samples more closely matches the actual formation temperature, the organic acids can be preheated (to a temperature lower than their decomposition temperature) to match the temperature of the confining medium injected into the sample chamber interlayer (i.e., the specific temperature of the reservoir samples within the experimental temperature range). Further collection of the solution after the organic acid and reservoir sample dissolution reaction allows for the determination of the dissolution reaction mechanism by comparing the composition and content of the organic acid and the solution.

[0130] In this embodiment, considering the safety of the experiment, acetic acid was selected as the organic acid used in the experiment, with a concentration of 0.2 mol / L. After opening the valve on the corresponding pipeline, the organic acid was pumped into the sample chamber.

[0131] S330: Change the temperature and pressure of the confining pressure medium pumped into the first confining pressure maintaining unit, while ensuring that the pressure difference between the first confining pressure maintaining unit and the second pressure maintaining unit remains constant, so that the experimental temperature gradually increases from the lower limit of the experimental temperature range to the upper limit of the range and the experimental pressure continuously increases; wherein, the rate of temperature change from the lower limit of the experimental temperature range to its upper limit is 10℃ / h.

[0132] Specifically, the confining pressure medium pumped into the first confining pressure maintenance unit mainly creates a temperature environment simulating formation temperature. By gradually changing the temperature of the confining pressure medium pumped into the first confining pressure maintenance unit, the experimental temperature for the reservoir sample can be changed, thereby simulating various temperatures during hydrocarbon generation and acid production in actual reservoir source rocks. Simultaneously, while maintaining a constant pressure difference between the first and second confining pressure maintenance units and ensuring a constant flow rate of the confining pressure medium in the sample chamber, the pressure in both units is increased synchronously. This increases the pressure exerted on the reservoir sample by the confining pressure medium, thereby changing the experimental pressure and enabling further research on the dissolution of the reservoir sample's pore structure by organic acids under different formation pressures and temperatures.

[0133] S400: When the experimental temperature reaches the upper limit of 120℃, the change law of pore structure during the organic acid dissolution process is obtained based on the test data of the nuclear magnetic resonance device.

[0134] S410: Based on the test data from the nuclear magnetic resonance device, determine the distribution and changes of pores in the reservoir sample corresponding to the relaxation time T2 during the dissolution process, and derive the change law of pore structure during organic acid dissolution.

[0135] Specifically, the T2 spectrum distribution diagram of the pore structure corresponding to the test data is shown in the attached figure. Figure 3 As shown in the figure, the results indicate that after the dissolution reaction begins, the number of pores with a T2 relaxation time greater than 8 ms increases, while the number of pores with a T2 relaxation time between 1 and 8 ms decreases. Simultaneously, as the experiment progresses, the organic acid dissolution effect slows down, and the rates of pore increase and decrease become slower. Furthermore, the pore distribution of the reservoir sample before dissolution exhibits a peak with a T2 relaxation time of 3 ms; the pore distribution after organic acid dissolution shows two peaks with T2 relaxation times of 40 ms and 2 ms, respectively, while the number of pores with a T2 relaxation time between 0.1 and 1 ms decreases.

[0136] The above results indicate that after organic acid dissolution, the radius of medium- and large-scale pores in the reservoir increases due to the dissolution process. However, the water-rock products generated by the dissolution reaction may precipitate in small pores, blocking some of them. Therefore, it can be concluded that after reservoir dissolution, the pore distribution will be concentrated in the area where the original medium- and large-scale pores were located, and consequently, the oil-rich areas of tight reservoirs will also be concentrated in the corresponding regions.

[0137] Example 4

[0138] An embodiment of the present invention provides a reservoir pore structure dissolution simulation experimental device, which includes a sample dissolution component 3, an environmental simulation component 4, and an organic acid injection component 2. The sample dissolution component 3 includes a nuclear magnetic resonance device 6 and a sample chamber configured to correspond to the nuclear magnetic resonance device 6, the sample chamber being used to hold a reservoir sample 30; the environmental simulation component 4 is connected to the interlayer of the sample chamber through a pipe, and is used to inject a confining pressure medium with corresponding temperature and pressure into the interlayer to simulate formation pressure and formation temperature; the organic acid injection component 2 is connected to the interior of the sample chamber through a pipe, and is used to inject organic acid into the sample chamber to dissolve the reservoir sample 30.

[0139] Specifically, as shown in the attached diagram. Figure 2As shown, the simulation experimental device mainly comprises three parts: a sample dissolution component 3, an environmental simulation component 4, and an organic acid injection component 2. The sample dissolution component 3 is used to load the reservoir sample 30, and includes a nuclear magnetic resonance (NMR) device 6 and a sample chamber corresponding to the NMR device 6. Based on the aforementioned embodiment, metal components may affect the test results of the NMR device 6; therefore, the sample chamber is preferably made of non-metallic materials. The environmental simulation component 4 is mainly used to simulate formation pressure and temperature for the sample chamber. This simulation is achieved by introducing a fluid medium with corresponding temperature and pressure into the interlayer of the sample chamber. The organic acid injection component 2 is mainly used to hold organic acid and inject it into the sample chamber to dissolve the reservoir sample 30.

[0140] Furthermore, the sample chamber includes a cylindrical confining device 9, which is erected and has clamps 8 inserted at its top and bottom to form the internal space of the sample chamber. The confining device 9 is made of elastic material and has a sandwich structure inside it. The organic acid injection component 2 is connected to the clamps 8 at the top through a pipe to connect to the interior of the sample chamber through a channel constructed in the clamps 8 at the top.

[0141] The solution collection assembly 5 is connected to the clamp 8 at the bottom via a pipe, so as to communicate with the interior of the sample chamber through a channel constructed in the clamp 8 at the bottom.

[0142] Specifically, as shown in the attached diagram. Figure 2 As shown, the cylindrical confining pressure device 9 is erected (i.e., its axis is vertical). Two clamps 8 are partially embedded in the openings at the top and bottom of the confining pressure device 9, respectively. The top and bottom of the confining pressure device 9 are also provided with sealing elements 7 to enclose the embedded portions, which improve the sealing of the enclosed sample chamber and ensure a stable fit between the clamps 8 and the confining pressure device 9. A channel connecting the middle of the clamps 8 to the interior of the sample chamber is provided for connecting corresponding components via pipes. The clamps 8 are preferably made of non-metallic material; for example, in this embodiment, the clamps 8 are made of polyetheretherketone resin. The confining pressure device 9 is made of non-metallic plastic material, which makes its internal interlayer space expandable, thereby allowing the pressure of the confining medium to be fully applied to the reservoir sample 30.

[0143] The organic acid injection assembly 2 is connected to the upper clamp 8 via a pipe for injecting organic acid into the sample chamber. The solution collection assembly 5 is connected to the lower clamp 8 via a pipe for collecting the solution generated after the organic acid injected from above reacts with the reservoir sample 30, facilitating the determination of the reaction mechanism between the organic acid and the reservoir sample 30 by analyzing the composition and content of the solution.

[0144] Furthermore, as shown in the attached figure Figure 2As shown, the solution collection assembly 5 includes a collection container 22 and a waste liquid container 23 connected in parallel. A fourth valve 20 and a fifth valve 21 are respectively installed on the corresponding pipe branches of the collection container 22 and the waste liquid container 23. When solution needs to be collected, the fourth valve 20 is opened and the fifth valve 21 is closed, allowing the solution to enter the collection container 22 for collection; when solution collection is not needed, the fourth valve 20 is closed and the fifth valve 21 is opened, allowing the solution to enter the waste liquid container 23 for collection.

[0145] Furthermore, the environmental simulation component 4 includes a first confining pressure maintaining unit and a second confining pressure maintaining unit with identical structures. The confining pressure maintaining unit includes a confining pressure medium container and a confining pressure pump connected by a pipeline. The two confining pressure medium containers are respectively connected to the interlayer by pipelines, and the pumping pressure of the confining pressure pump of the first confining pressure maintaining unit is greater than that of the confining pressure pump of the second confining pressure maintaining unit. The confining pressure medium container of the first confining pressure maintaining unit is placed in a constant temperature chamber.

[0146] Specifically, as shown in the attached diagram. Figure 2 As shown, the environmental simulation component 4 includes a first confining pressure maintenance unit (above) and a second confining pressure maintenance unit (below) with the same structure. Both are composed of a confining pressure medium container and a confining pressure pump. A partition is provided in the confining pressure medium container. The confining pressure pump pushes the partition by pumping water or other liquids into the confining pressure medium container, thereby driving the confining pressure medium into the interlayer of the sample chamber.

[0147] In practical use, the first confining pressure medium container 10 is filled with confining pressure medium, while the second confining pressure medium container 27 is empty. The first confining pressure pump 11 injects the confining pressure medium from the first confining pressure medium container 10 into the upper part of the sample chamber interlayer (a first pressure gauge 24 is installed on the pumping pipeline). Under the action of pumping power and gravity, the confining pressure medium reaches the bottom of the sample chamber and enters the second confining pressure medium container 27. The second confining pressure pump 28 also maintains a pumping pressure no greater than that of the first confining pressure pump 11. Therefore, the two confining pressure pumps can jointly maintain the pressure in the sample chamber interlayer. The first confining pressure medium container 10 is placed in the first constant temperature chamber 12, so the confining pressure medium has a certain temperature when pumped in, which is used to simulate the formation temperature through heat transfer with the reservoir. A first valve 13 and a second valve 14 are respectively installed on the pipelines connecting the two confining pressure medium containers to the sample chamber interlayer.

[0148] In addition, the pumping pressure of the second confining pressure pump 28 is lower than that of the first confining pressure pump 11. This allows the confining pressure medium to flow more smoothly and quickly from the first confining pressure maintaining unit to the second confining pressure maintaining unit under the action of the pressure difference. This avoids the confining pressure medium from flowing for too long and experiencing a temperature drop due to natural heat dissipation, thereby preventing the formation temperature simulation from being distorted due to a drop in the temperature of the confining pressure medium.

[0149] Preferably, the second confining pressure medium container 27 is placed in the second constant temperature chamber 29, which, together with the first constant temperature chamber 12, maintains the temperature of the confining pressure medium stably and prevents heat dissipation from affecting the temperature of the confining pressure medium. The temperature of the second constant temperature chamber 29 is consistent with that of the first constant temperature chamber 12 and changes synchronously.

[0150] Furthermore, the organic acid injection assembly 2 includes an organic acid container 16 placed in a constant temperature chamber and an injection pump 17 connected to the organic acid container 16 via a pipe. The organic acid container 16 is connected to the sample chamber via a pipe.

[0151] Specifically, as shown in the attached diagram. Figure 2 As shown, the organic acid container 16 is placed in the third constant temperature chamber 15 to maintain the organic acid at a certain temperature. When the organic acid is injected into the sample chamber, the temperature environment in the sample chamber is made to better match the actual formation (the organic acid in the actual formation is generated at a certain temperature). The structure of the organic acid container 16 is the same as that of the aforementioned confining pressure medium container, both of which are equipped with baffles. One end of the organic acid container 16 is connected to the upper clamp 8 through a pipe, and the other end is connected to the injection pump 17 through a pipe. The output pipe of the organic acid container 16 is equipped with a third valve 18 and a one-way valve 19 in sequence. A second pressure gauge 25 is installed on the pipe connecting the organic acid container 16 and the clamp 8.

[0152] The experimental procedure based on the experimental apparatus in this embodiment is as follows:

[0153] S100: Based on typical source rock samples from the target study area, determine the organic acid generation parameters of the source rocks in the target study area. The generation parameters should include at least the type of organic acid, the concentration of organic acid, and the formation pressure and temperature range.

[0154] S110: Hydrogen generation simulation experiments were conducted using typical source rock samples. Based on the experimental results, the type of organic acid, concentration of organic acid, and formation temperature range in the generation parameters were determined.

[0155] S120: Based on the geological background of the target study area, basin simulation is performed to determine the formation pressure at which organic acids are generated in the generation parameters.

[0156] S200: Place the reservoir sample 30 of the target study area into the sample dissolution assembly 3, and set the experimental confining pressure and experimental temperature range for the reservoir sample 30 according to the formation pressure and formation temperature range.

[0157] S210: Place the reservoir sample 30 in the sample chamber corresponding to the nuclear magnetic resonance device 6 of the sample dissolution component 3, seal the sample chamber, inject water to test the sealing performance, and then drain the excess water to make the reservoir sample 30 saturated with water; the specific composition of the water injected into the sample chamber is configured according to the composition of the formation water in the target study area.

[0158] S220: Fill the first confining pressure medium container 10 with confining pressure medium (fluoride liquid in this embodiment), set the first constant temperature chamber 12 according to the experimental temperature conditions, open the first valve 13, use the first confining pressure pump 11 to pump the confining pressure medium into the jacket of the sample chamber, and make the pressure displayed by the first pressure gauge 24 match the experimental pressure.

[0159] S230: While keeping the value of the first pressure gauge 24 unchanged, make the pressure of the second confining pressure maintaining unit less than the pumping pressure of the first confining pressure maintaining unit on the confining pressure medium, so that there is a pressure difference ΔP between the two, and use the second confining pressure maintaining unit to receive the confining pressure medium output from the interlayer.

[0160] S300: Start the nuclear magnetic resonance device 6 to test the pore throat radius distribution in the reservoir sample 30, inject organic acid into the reservoir sample 30, and gradually increase the experimental temperature from the lower limit of the experimental temperature range to the upper limit of the range.

[0161] S310: Select the appropriate type and concentration of organic acid based on the type and concentration of organic acid in the generation parameters.

[0162] S320: Set the temperature of the third thermostat 15, open the third valve 18, and use the injection pump 17 to pump the organic acid from the organic acid container 16, allowing the organic acid to enter the sample chamber through the one-way valve 19; simultaneously open the third valve 18 and close the fourth valve 20, using the collection container 22 to collect the solution after the dissolution reaction; when solution collection is no longer needed, close the third valve 18 and open the fourth valve 20, allowing the solution to enter the waste liquid container 23. Record the data from the second pressure gauge 25. After starting the nuclear magnetic resonance instrument, record the pore throat radius distribution in the column reservoir sample 30.

[0163] S330: During the organic acid dissolution process, open the second valve 14 to allow the confining pressure medium to enter the second confining pressure maintenance unit. Adjust the temperature of the first constant temperature chamber 12 to gradually increase the experimental temperature from the lower limit of the experimental temperature range to the upper limit of the range; at the same time, the temperature of the third constant temperature chamber 15 can be adjusted to make the temperature of the organic acid closer to the actual formation conditions.

[0164] During the dissolution process, the pressure of the first and second confining pressure pumps can be increased while keeping ΔP constant, thereby increasing the experimental pressure.

[0165] S400: When the experimental temperature reaches the upper limit of the range, the change law of pore structure during the organic acid dissolution process is obtained based on the test data of the nuclear magnetic resonance device.

[0166] S410: Based on the test data from the nuclear magnetic resonance device 6, determine the distribution and changes of pores in the reservoir sample 30 corresponding to the relaxation time T2 during the dissolution process, and derive the change law of pore structure during organic acid dissolution.

[0167] Based on the experimental apparatus proposed in this invention, continuous flow dissolution experiments of organic acids on tight reservoirs under actual temperature and pressure conditions can be carried out and real-time changes in pore structure can be detected. Through online nuclear magnetic resonance detection, the process and law of organic acid modification of tight reservoir pore structure can be described in detail, thereby quantitatively characterizing the real-time change law of tight reservoir pore structure during organic acid dissolution, providing a basis for the prediction of favorable oil enrichment areas.

[0168] Example 5

[0169] An embodiment of the present invention provides a reservoir pore structure dissolution simulation experimental system, which includes a reservoir pore structure dissolution simulation experimental device and a data acquisition device 1 electrically connected to the experimental device. The data acquisition device 1 is used to collect various temperature and pressure data of the experimental device and test data of the nuclear magnetic resonance device 6.

[0170] The reservoir pore structure dissolution simulation experimental device includes a sample dissolution component 3, an environmental simulation component 4, and an organic acid injection component 2. The sample dissolution component 3 includes a nuclear magnetic resonance device 6 and a sample chamber configured to correspond to the nuclear magnetic resonance device 6. The sample chamber is used to hold the reservoir sample 30. The environmental simulation component 4 is connected to the interlayer of the sample chamber through a pipe and is used to inject a confining pressure medium with corresponding temperature and pressure into the interlayer to simulate formation pressure and formation temperature. The organic acid injection component 2 is connected to the interior of the sample chamber through a pipe and is used to inject organic acid into the sample chamber to dissolve the reservoir sample 30.

[0171] Furthermore, the sample chamber includes a cylindrical confining device 9, which is erected and has clamps 8 inserted at its top and bottom to enclose the internal space of the sample chamber. The confining device 9 is made of an elastic material and has a sandwich structure inside. The organic acid injection assembly 2 is connected to the clamps 8 at the top via a pipe, allowing it to communicate with the interior of the sample chamber through a channel within the clamps 8. The solution collection assembly 5 is connected to the clamps 8 at the bottom via a pipe, allowing it to communicate with the interior of the sample chamber through a channel within the clamps 8.

[0172] Furthermore, as shown in the attached figure Figure 2 As shown, the solution collection assembly 5 includes a collection container 22 and a waste liquid container 23 connected in parallel. A fourth valve 20 and a fifth valve 21 are respectively installed on the corresponding pipe branches of the collection container 22 and the waste liquid container 23. When solution needs to be collected, the fourth valve 20 is opened and the fifth valve 21 is closed, allowing the solution to enter the collection container 22 for collection; when solution collection is not needed, the fourth valve 20 is closed and the fifth valve 21 is opened, allowing the solution to enter the waste liquid container 23 for collection.

[0173] Furthermore, the environmental simulation component 4 includes a first confining pressure maintaining unit and a second confining pressure maintaining unit with identical structures. The confining pressure maintaining unit includes a confining pressure medium container and a confining pressure pump connected by a pipeline. The two confining pressure medium containers are respectively connected to the interlayer by pipelines, and the pumping pressure of the confining pressure pump of the first confining pressure maintaining unit is greater than that of the confining pressure pump of the second confining pressure maintaining unit. The confining pressure medium container of the first confining pressure maintaining unit is placed in a constant temperature chamber.

[0174] Preferably, the second confining pressure medium container 27 is placed in the second constant temperature chamber 29, which, together with the first constant temperature chamber 12, maintains the temperature of the confining pressure medium stably and prevents heat dissipation from affecting the temperature of the confining pressure medium. The temperature of the second constant temperature chamber 29 is consistent with that of the first constant temperature chamber 12 and changes synchronously.

[0175] Furthermore, the organic acid injection assembly 2 includes an organic acid container 16 placed in a constant temperature chamber and an injection pump 17 connected to the organic acid container 16 via a pipe. The organic acid container 16 is connected to the sample chamber via a pipe.

[0176] In the description of this invention, it should be understood that the terms "upper", "lower", "bottom", "top", "front", "rear", "inner", "outer", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element 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 this invention.

[0177] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method for simulating the dissolution of reservoir pore structure, characterized in that, Includes the following steps: Based on typical source rock samples from the target study area, determine the organic acid generation parameters of the source rocks in the target study area. The generation parameters include at least the type of organic acid, the concentration of organic acid, and the formation pressure and formation temperature range. The reservoir sample of the target study area is placed in the sample dissolution assembly, and the experimental confining pressure and experimental temperature range for the reservoir sample are set according to the formation pressure and formation temperature range. The nuclear magnetic resonance device of the sample dissolution component is activated to test the pore throat radius distribution in the reservoir sample. Organic acid is injected into the reservoir sample to gradually increase the experimental temperature from the lower limit of the experimental temperature range to the upper limit of the range. When the experimental temperature reaches the upper limit of the range, the change law of pore structure during the organic acid dissolution process is obtained based on the test data of the nuclear magnetic resonance device.

2. The reservoir pore structure dissolution simulation experimental method according to claim 1, characterized in that, Based on typical source rock samples from the target study area, the formation parameters of organic acids in the source rocks of the target study area are determined, including the following sub-steps: Hydrogen generation simulation experiments were conducted using the typical source rock samples, and the type and concentration of organic acids, as well as the formation temperature range, were determined based on the experimental results. Based on the geological background of the target study area, basin simulation is performed to determine the formation pressure at which organic acids are generated in the generation parameters.

3. The reservoir pore structure dissolution simulation experimental method according to claim 1 or 2, characterized in that, Injecting organic acids into the reservoir sample includes the following sub-steps: Based on the type and concentration of organic acid in the generation parameters, select the corresponding type and concentration of organic acid; An organic acid at a predetermined temperature is pumped into the reservoir sample, the predetermined temperature being determined based on the current specific temperature value of the reservoir sample.

4. The reservoir pore structure dissolution simulation experimental method according to claim 1, characterized in that, The reservoir sample from the target study area is placed in the sample dissolution assembly. The experimental confining pressure and temperature range for the reservoir sample are set according to the formation pressure and temperature range, including the following sub-steps: The reservoir sample is placed in a sample chamber corresponding to the nuclear magnetic resonance device of the sample dissolution assembly; A confining pressure medium is pumped into the interlayer of the sample chamber using the first confining pressure maintenance unit. The pumping pressure of the confining pressure medium is matched with the formation pressure, and the pumping temperature is matched with the lower limit of the formation temperature range. The confining pressure medium output from the interlayer is received by the second confining pressure maintaining unit.

5. The reservoir pore structure dissolution simulation experimental method according to claim 4, characterized in that, The second confining pressure maintaining unit receives the confining pressure medium output from the interlayer, and further includes: The pressure of the second confining pressure maintaining unit is lower than the pumping pressure of the first confining pressure maintaining unit on the confining pressure medium.

6. The reservoir pore structure dissolution simulation experimental method according to claim 4, characterized in that, The process of gradually increasing the experimental temperature from the lower limit of the experimental temperature range to its upper limit includes the following sub-steps: The temperature of the confining pressure medium pumped into the first confining pressure maintenance unit is changed so that the experimental temperature gradually increases from the lower limit of the experimental temperature range to the upper limit of the range.

7. The reservoir pore structure dissolution simulation experimental method according to claim 1 or 6, characterized in that, The experimental temperature gradually increases from the lower limit of the experimental temperature range to the upper limit of the range at a rate of 10℃ / h.

8. The reservoir pore structure dissolution simulation experimental method according to claim 1, characterized in that, Based on the test data from the nuclear magnetic resonance device, the changes in pore structure during the organic acid dissolution process were determined, including: Based on the test data from the nuclear magnetic resonance device, the distribution and changes of pores in the reservoir sample corresponding to the relaxation time T2 during the dissolution process are determined, and the change law of pore structure during organic acid dissolution is obtained.

9. An experimental apparatus for simulating the dissolution of reservoir pore structures, characterized in that, include: A sample dissolution assembly includes a nuclear magnetic resonance device and a sample chamber disposed within the nuclear magnetic resonance device, the sample chamber being used to hold a reservoir sample; An environmental simulation component, which is connected to the interlayer of the sample chamber via a pipeline, is used to inject a confining pressure medium with corresponding temperature and pressure into the interlayer to simulate formation pressure and formation temperature. as well as An organic acid injection assembly, which is connected to the interior of the sample chamber via a pipe, is used to inject organic acid into the sample chamber to dissolve the reservoir sample.

10. The reservoir pore structure dissolution simulation experimental apparatus according to claim 9, characterized in that, The sample chamber includes a cylindrical confining device, which is erected and has clamps inserted at its top and bottom to form the internal space of the sample chamber. The confining device is made of elastic material and the sandwich structure is inside the confining device. The organic acid injection assembly is connected to the clamp at the top via a pipe, so as to communicate with the interior of the sample chamber through a channel constructed in the clamp at the top.

11. The reservoir pore structure dissolution simulation experimental apparatus according to claim 10, characterized in that, It also includes a solution collection assembly connected via a pipe to the clamp at the bottom end to communicate with the interior of the sample chamber through a channel constructed within the clamp at the bottom end.

12. The reservoir pore structure dissolution simulation experimental apparatus according to claim 9, characterized in that, The environmental simulation component includes a first confining pressure maintaining unit and a second confining pressure maintaining unit with identical structures. The confining pressure maintaining unit includes a confining pressure medium container and a confining pressure pump connected by a pipeline. The two confining pressure medium containers are respectively connected to the interlayer through pipelines, and the pumping pressure of the confining pressure pump of the first confining pressure maintaining unit is greater than that of the confining pressure pump of the second confining pressure maintaining unit. The confining pressure medium container of the first confining pressure maintaining unit is placed in a constant temperature chamber.

13. The reservoir pore structure dissolution simulation experimental apparatus according to claim 9, characterized in that, The organic acid injection assembly includes an organic acid container placed in a constant temperature chamber and an injection pump connected to the organic acid container via a pipe. The organic acid container is connected to the sample chamber via a pipe.

14. A reservoir pore structure dissolution simulation experimental system, characterized in that, The apparatus includes a reservoir pore structure dissolution simulation experimental device as described in any one of claims 9 to 13, and a data acquisition device electrically connected to the experimental device, wherein the data acquisition device is used to acquire various temperature and pressure data of the experimental device and test data of the nuclear magnetic resonance device.

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