Heterogeneous core miscible displacement experimental device and method based on layered nuclear magnetism T2 test

Abstract

The invention discloses a heterogeneous rock core miscible flooding experimental device and method based on layered nuclear magnetism T2 test, and belongs to the technical field of low-permeability heterogeneous oil reservoir miscible flooding development, the device comprises a liquid supply system, a temperature control system, a 1.5-inch online nuclear magnetism rock core holder, a pressure loading system, a 1.5-inch rock core barrel, a nuclear magnetic resonance spectrometer and a metering device; a 1.5-inch rock core sample is spliced to simulate the heterogeneous condition of rocks in a reservoir, T2 spectrum distribution conditions of regions with different permeability in the heterogeneous stratum are obtained through layered T2 scanning in the experiment process, accurate simulation of the effect of improving the recovery efficiency of heterogeneous oil reservoirs and miscible flooding is achieved, and the method has the advantages of being high in practicability and easy to popularize and apply. The method is favorable for researching the distribution condition of residual oil in the rock in the miscible-phase flooding process, and provides a basis for improving the final recovery efficiency of an oil reservoir and improving the productivity and recovery efficiency of an oil well.

Description

Technical Field

[0001] The invention belongs to the technical field of miscible flooding development of low-permeability heterogeneous oil reservoirs, and specifically relates to a heterogeneous core miscible flooding experimental device and method based on layered nuclear magnetic resonance T2 testing. Background Art

[0002] CO2 miscible flooding technology can not only increase oil production, but also achieve geological storage of greenhouse gas CO2, which has both economic and environmental benefits and is an effective way to ensure energy security and mitigate the greenhouse effect. However, the rock structural properties of reservoirs formed under different sedimentation are different, resulting in reservoir heterogeneity, affecting the distribution and migration of fluids, thereby affecting the development effect. The miscible flooding effect of CO2 in porous media is controlled by the complex pore structure. At present, there is a lack of understanding of the miscible displacement mechanism in heterogeneous porous media. Therefore, in-depth research on the impact of reservoir heterogeneity on oilfield exploitation is of great significance for improving recovery and CO2 flooding and storage efficiency.

[0003] When studying the miscible flooding process of heterogeneous cores, current indoor physical simulation experiments usually use parallel core holders or sand-filled small core column models to simulate the intra-layer heterogeneous system. These methods can basically reproduce the heterogeneity of rocks, but there are still significant problems: the parallel holder will affect the CO2 miscible effect during the experiment, and the various parameters of each permeable layer of the sand-filled small core column model cannot be accurately measured and cannot accurately simulate the intra-layer heterogeneity of thick oil layers. In addition, these methods are only suitable for measuring the final recovery rate of miscible flooding and cannot be used to study the miscible displacement mechanism in heterogeneous porous media. Therefore, it is urgent to propose a heterogeneous core miscible flooding experimental process and method based on layered nuclear magnetic resonance T2 testing to accurately obtain the specific distribution of residual oil at each stage in the heterogeneous core CO2 miscible flooding process and study the miscible displacement mechanism in heterogeneous cores. Summary of the invention

[0004] In view of the above-mentioned problems existing in the prior art, the present invention proposes a heterogeneous core miscible drive experimental device and method based on layered nuclear magnetic resonance T2 testing, which realizes the true simulation of the miscible development process of heterogeneous reservoirs in oil fields, provides technical support for studying the specific distribution of oil and water in each stage of the CO2 miscible drive process, is conducive to studying the miscible drive mechanism in heterogeneous cores, has a reasonable design, solves the shortcomings of the prior art, and has good effects.

[0005] A heterogeneous core miscible flooding experimental device based on layered nuclear magnetic resonance T2 testing, comprising a fluid supply system, a temperature control system, a 1.5-inch online nuclear magnetic resonance core holder, a pressure loading system, a 1.5-inch core barrel, a nuclear magnetic resonance instrument and a metering device;

[0006] The fluid supply system includes a constant speed and constant pressure pump and three intermediate containers, wherein the three intermediate containers are a manganese water intermediate container, a formation oil intermediate container and a CO2 intermediate container, and are used to inject fluid into the 1.5-inch online nuclear magnetic core holder;

[0007] The 1.5-inch online nuclear magnetic core holder is used to hold the core sample and is matched with the nuclear magnetic resonance instrument to monitor the specific T2 spectrum of the core sample in real time during the pressure drive process;

[0008] The pressure loading system includes a confining pressure circulation pump and a manual high-pressure pump, wherein the confining pressure circulation pump is used to apply confining pressure to the core sample in the 1.5-inch online nuclear magnetic core holder, obtain the confining pressure value in real time, and circulate and keep warm;

[0009] The temperature control system is used to control the temperature of the fluid injected into the core sample;

[0010] The metering device is used to measure the water output from the outflow end of the 1.5-inch online nuclear magnetic core holder.

[0011] Furthermore, the constant speed and constant pressure pump is respectively connected to the high-pressure injection pipelines of the manganese water intermediate container, the formation oil intermediate container and the CO2 intermediate container through a four-way valve; the outflow ends of the manganese water intermediate container, the formation oil intermediate container and the CO2 intermediate container are all connected to high-pressure liquid outlet pipelines, and each high-pressure liquid outlet pipeline is connected to the injection pipeline arranged at the injection end of the 1.5-inch online nuclear magnetic core clamp through a six-way valve, and the outflow end of the 1.5-inch online nuclear magnetic core clamp is connected to the metering device through a discharge pipeline, and a back pressure valve and an outlet control valve are arranged on the discharge pipeline.

[0012] Furthermore, an injection pressure gauge is provided on the six-way valve for obtaining the injection pressure of the fluid in the core sample in real time.

[0013] Furthermore, the confining pressure pump circulates through the pressure injection pipeline and the fluorine oil intermediate container and then connects to the 1.5-inch online nuclear magnetic core holder, using fluorine oil to avoid the influence of the confining pressure liquid on the nuclear magnetic signal; the manual high-pressure pump is connected to the back pressure valve through the pressure injection pipeline.

[0014] Furthermore, the 1.5-inch online nuclear magnetic core holder includes a cylinder, a sealing cover and an external coil. The cylinder has a core sample built in it, and both ends of the cylinder are sealed with sealing covers; the core sample is covered with a rubber sleeve, and a radio frequency coil is arranged outside the sealing cover to measure the internal core T2 signal.

[0015] Furthermore, the temperature control system is configured to provide an electric heating insulation sleeve on the outer walls of the manganese water intermediate container, the formation oil intermediate container, the CO2 intermediate container and the fluorine oil intermediate container, and an electric heater is provided in the clamp to adjust the internal temperature of the clamp.

[0016] A heterogeneous core miscible flooding experimental method based on layered nuclear magnetic T2 testing, using a heterogeneous core miscible flooding experimental device based on layered nuclear magnetic T2 testing as described above, comprises the following steps:

[0017] Step 1: Prepare core samples. The core samples are divided into heterogeneous artificial core cementation and natural heterogeneous core splicing cementation;

[0018] Step 2: injecting manganese water, formation oil and CO2 into the manganese water intermediate container, the formation oil intermediate container and the CO2 intermediate container respectively, and injecting fluorine oil into the fluorine oil intermediate container;

[0019] Step 3: Control the confining pressure circulation pump to apply an initial confining pressure to the cavity of the 1.5-inch online nuclear magnetic core holder. The initial confining pressure ranges from 2 to 5 MPa. At the same time, the temperature of the fluid in each intermediate container and the temperature of the core sample in the 1.5-inch online nuclear magnetic core holder are kept consistent with the formation temperature of the reservoir to be simulated. After the temperature is constant at the formation temperature, adjust the four-way valve and use a constant speed and constant pressure pump to increase the pressure of the formation oil intermediate container and the CO2 intermediate container to the formation pressure and stabilize it;

[0020] Step 4: Adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, use the manganese water to displace the core sample, obtain the manganese water injection pressure according to the reading of the injection pressure gauge, and use the metering device to measure the water flow rate of the discharge pipe. After the formation water injection pressure and the water flow rate are stable, calculate the initial water permeability of the core;

[0021] Step 5: Control the manual high-pressure pump to slowly apply back pressure to the back pressure valve to the formation pressure, observe the injection pressure gauge, and control the confining pressure circulation pump to ensure that the confining pressure is always higher than the injection pressure; after the injection pressure indicator is stable, adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject the formation oil in the formation oil intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, and close the inlet and outlet switches of the holder after the outflow end stops emitting water. After the formation oil has aged for a period of time, test the initial core T2 signal in layers;

[0022] Step 6: Adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, use the manganese water to displace the core sample, and test the core T2 signal in layers every time a certain pore volume of manganese water is injected; when the metering device just appears manganese water, adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject a certain pore volume of CO2 at a preset flow rate, during which the core T2 signal is continuously tested in layers, and the metering device is used to measure the oil output of the discharge pipeline to obtain the injection pressure and recovery rate change curve over time;

[0023] Step 7: Adjust the four-way valve and the six-way valve, control the constant speed and pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, and test the core T2 signal in layers every time a certain pore volume of manganese water is injected; and use a metering device to measure the oil output of the discharge pipeline to obtain the injection pressure and recovery rate change curve over time. When the outlet stops producing oil, stop the experiment; according to the obtained layered test core T2 signal, analyze the oil distribution in the heterogeneous core formation at different displacement stages, and study the miscible displacement mechanism in the heterogeneous core.

[0024] Furthermore, in step 1, the heterogeneous artificial core cementation preparation process is as follows: inject different purpose sands into two beakers respectively, then add 5% epoxy resin respectively and stir them fully to obtain two different mixed sands; put a semi-cylindrical pad into a 1.5-inch core barrel, fill a small amount of one mixed sand that is stirred evenly into the 1.5-inch core barrel multiple times, take out the pad and fill a small amount of another mixed sand into the 1.5-inch core barrel multiple times, fully compact with a press, put it in a constant temperature box for drying, and then measure the specific porosity and permeability of the core sample;

[0025] The natural heterogeneous core splicing and cementing process is as follows: the existing natural cores are cut and spliced ​​together, and the specific porosity and permeability of the spliced ​​core samples are measured; the spliced ​​core samples are vacuumed, saturated with formation water, and placed in a 1.5-inch online nuclear magnetic core holder;

[0026] If the gravity effect is not considered, the core joint surface is made perpendicular to the length direction of the core;

[0027] If the effect of gravity is considered, the core joint surface is made parallel to the length direction of the core. For the positive rhythm study, the core with low permeability is placed on the top, and for the negative rhythm study, the core with low permeability is placed on the bottom.

[0028] Furthermore, in steps 5 to 7, if the effect of gravity is not considered, the core T2 signal is tested in layers perpendicular to the length direction of the core; if the effect of gravity is considered, the core T2 signal is tested in layers parallel to the length direction of the core.

[0029] Beneficial technical effects brought by the present invention:

[0030] The present invention proposes a 1.5-inch multi-layer spliced ​​core test method, which avoids the influence of the CO2 miscibility effect during the parallel clamp test and the inability to accurately measure the various parameters of each permeable layer of the sand-filled small core column model and accurately simulate the intra-layer heterogeneity of the thick oil layer, and truly restores the heterogeneity of the rock in the reservoir.

[0031] The present invention proposes a heterogeneous core miscible flooding experimental process and method based on layered nuclear magnetic resonance T2 testing, which uses spliced ​​1.5-inch core samples to simulate the rock heterogeneity in the reservoir. During the experiment, the T2 spectrum distribution of different permeability areas in the heterogeneous formation is obtained through layered T2 scanning, which realizes the accurate simulation of the heterogeneous oil reservoir and the effect of miscible flooding on improving the recovery rate, is conducive to studying the distribution of residual oil in the rock during the miscible flooding process, and provides a basis for improving the ultimate recovery rate of the oil reservoir and improving the production capacity and recovery rate of the oil well. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a heterogeneous core miscible flooding experimental device based on layered nuclear magnetic resonance T2 test in the present invention;

[0033] Figure 2 This is a top view of the 1.5-inch core barrel used during the experiment;

[0034] In the figure, 1-constant speed constant pressure pump; 2-four-way valve; 3-manganese water intermediate container; 4-formation oil intermediate container; 5-CO2 intermediate container; 6-six-way valve; 7-injection pressure gauge; 8-circulating confining pressure pump; 9-fluorine oil intermediate container; 10-1.5-inch online nuclear magnetic core holder; 11-nuclear magnetic resonance instrument; 12-manual high-pressure pump; 13-back pressure valve; 14-outlet control valve; 15-metering device; 16-temperature control system. DETAILED DESCRIPTION

[0035] The specific implementation of the present invention is further described below in conjunction with specific embodiments:

[0036] A heterogeneous core miscible flooding experimental device based on layered nuclear magnetic resonance T2 testing, such as Figure 1 As shown, it includes a fluid supply system, a temperature control system 16, a 1.5-inch online nuclear magnetic core holder, a pressure loading system, a 1.5-inch core barrel, a nuclear magnetic resonance instrument 11 and a metering device 15;

[0037] The fluid supply system includes a constant speed and constant pressure pump 1 and three intermediate containers, wherein the three intermediate containers are a manganese water intermediate container 3, a formation oil intermediate container 4 and a CO2 intermediate container 5, and are used to inject fluid into a 1.5-inch online nuclear magnetic core holder 10;

[0038] The constant speed constant pressure pump 1 is connected to the high pressure injection pipelines of the manganese water intermediate container 3, the formation oil intermediate container 4 and the CO2 intermediate container 5 respectively through the four-way valve 2; the outflow ends of the manganese water intermediate container 3, the formation oil intermediate container 4 and the CO2 intermediate container 5 are all connected with high pressure liquid outlet pipelines, and each high pressure liquid outlet pipeline is connected to the injection pipeline arranged at the injection end of the 1.5-inch online nuclear magnetic core clamp 10 through the six-way valve 6, and the outflow end of the 1.5-inch online nuclear magnetic core clamp 10 is connected to the metering device 15 through the discharge pipeline, and the back pressure valve 13 and the outlet control valve 14 are arranged on the discharge pipeline. The six-way valve 6 is provided with an injection pressure gauge 7 for obtaining the injection pressure of the fluid in the core sample in real time.

[0039] The 1.5-inch online nuclear magnetic core holder 10 is used to clamp the core sample and is matched with the nuclear magnetic resonance instrument 11 to monitor the specific T2 spectrum of the core sample in the pressure-driving process in real time; the 1.5-inch online nuclear magnetic core holder 10 includes a cylinder, a sealing cover and an external coil. The cylinder has the core sample built in, and the two ends of the cylinder are sealed with sealing covers; the core sample is covered with a rubber sleeve on the outside, and a coil is arranged on the outside of the sealing cover to measure the internal core T2 signal.

[0040] The pressure loading system includes a confining pressure circulation pump and a manual high-pressure pump 12. The confining pressure circulation pump is used to apply confining pressure to the core sample in the 1.5-inch online nuclear magnetic core holder 10, obtain the confining pressure value in real time, and circulate and keep warm; the confining pressure pump circulates through the pressure injection pipeline and the fluorine oil intermediate container 9 and then connects to the 1.5-inch online nuclear magnetic core holder 10, using fluorine oil to avoid the influence of the confining pressure liquid on the nuclear magnetic signal; the manual high-pressure pump 12 is connected to the back pressure valve 13 through the pressure injection pipeline.

[0041] The temperature control system 16 is used to control the temperature of the fluid injected into the core sample; the temperature control system 16 is configured to provide an electric heating insulation sleeve on the outer walls of the manganese water intermediate container 3, the formation oil intermediate container 4, the CO2 intermediate container 5 and the fluorine oil intermediate container 9, and a temperature controller is provided in the cylinder body for monitoring and adjusting the internal temperature of the cylinder body.

[0042] The metering device 15 is used to measure the water output from the outflow end of the 1.5-inch online nuclear magnetic core holder 10 .

[0043] A heterogeneous core miscible flooding experimental method based on layered nuclear magnetic T2 testing, using a heterogeneous core miscible flooding experimental device based on layered nuclear magnetic T2 testing as described above, comprises the following steps:

[0044] Step 1: Prepare core samples. The core samples are divided into heterogeneous artificial core cementation and natural heterogeneous core splicing cementation;

[0045] The preparation process of the heterogeneous artificial core cementation is as follows: inject a certain mesh sand and 5% epoxy resin into two beakers and stir them thoroughly to obtain two different mixed sands; put a semi-cylindrical spacer into a 1.5-inch core barrel, such as Figure 2 As shown, the 1.5-inch core barrel is composed of two semi-hollow cylindrical structures. A mixed sand of a kind of uniformly stirred is filled into the 1.5-inch core barrel in small amounts and multiple times. The pad is taken out and another mixed sand is filled into the 1.5-inch core barrel in small amounts and multiple times. The core sample is fully compacted by a press and placed in a constant temperature box for drying. The specific porosity and permeability of the core sample is measured to preset the fluid flow rate and calculate the pore volume. It can also be used to analyze and compare the displacement effects of cores with different porosity and permeability.

[0046] The natural heterogeneous core splicing and cementing process is as follows: the existing natural cores are cut and spliced ​​together, and the specific porosity and permeability of the spliced ​​core samples are measured; the spliced ​​core samples are vacuumed, saturated with formation water, and placed in a 1.5-inch online nuclear magnetic core holder;

[0047] If the gravity effect is not considered, the core joint surface is made perpendicular to the length direction of the core;

[0048] If the effect of gravity is considered, the core joint surface is made parallel to the length direction of the core. For the positive rhythm study, the core with low permeability is placed on the top, and for the negative rhythm study, the core with low permeability is placed on the bottom.

[0049] Step 2: injecting manganese water, formation oil and CO2 into the manganese water intermediate container, the formation oil intermediate container and the CO2 intermediate container respectively, and injecting fluorine oil into the fluorine oil intermediate container;

[0050] Step 3: Control the confining pressure circulation pump to apply an initial confining pressure to the cavity of the 1.5-inch online nuclear magnetic core holder. The initial confining pressure ranges from 2 to 5 MPa. At the same time, the temperature of the fluid in each intermediate container and the temperature of the core sample in the 1.5-inch online nuclear magnetic core holder are kept consistent with the formation temperature of the reservoir to be simulated. After the temperature is constant at the formation temperature, adjust the four-way valve and use a constant speed and constant pressure pump to increase the pressure of the formation oil intermediate container and the CO2 intermediate container to the formation pressure and stabilize it;

[0051] Step 4: Adjust the four-way valve and the six-way valve, and control the constant speed and pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at the preset flow rate. For cores with worse porosity and permeability, use a smaller flow rate to avoid pressure build-up due to excessive inlet flow. Use manganese water to displace the core sample, obtain the injection pressure of manganese water according to the indication of the injection pressure gauge, and use a metering device to measure the outlet flow rate of the discharge pipe. After the formation water injection pressure and outlet flow rate are stable, calculate the initial water permeability of the core;

[0052] Step 5: Control the manual high-pressure pump to slowly apply back pressure to the back pressure valve to the formation pressure, observe the injection pressure gauge, and control the confining pressure circulation pump to ensure that the confining pressure is always higher than the injection pressure; after the injection pressure indicator is stable, adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject the formation oil in the formation oil intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, and close the inlet and outlet switches of the holder after the outflow end stops emitting water. After the formation oil has aged for a period of time, test the initial core T2 signal in layers;

[0053] Step 6: Adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, use the manganese water to displace the core sample, and test the core T2 signal in layers every time a certain pore volume of manganese water is injected; when the metering device just appears manganese water, adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject a certain pore volume of CO2 at a preset flow rate, during which the core T2 signal is continuously tested in layers, and the metering device is used to measure the oil output of the discharge pipeline to obtain the injection pressure and recovery rate change curve over time;

[0054] Step 7: Adjust the four-way valve and the six-way valve, control the constant speed and pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, and test the core T2 signal in layers every time a certain pore volume of manganese water is injected; and use a metering device to measure the oil output of the discharge pipeline to obtain the injection pressure and recovery rate change curve over time. When the outlet stops producing oil, stop the experiment; according to the obtained layered test core T2 signal, analyze the oil distribution in the heterogeneous core formation at different displacement stages, and study the miscible displacement mechanism in the heterogeneous core.

[0055] In steps 5 to 7, if the gravity effect is not considered, the core T2 signal is tested layer by layer perpendicular to the length direction of the core; if the gravity effect is considered, the core T2 signal is tested layer by layer parallel to the length direction of the core.

[0056] Example 1

[0057] In this embodiment, a heterogeneous core miscible flooding experimental method based on layered nuclear magnetic resonance T2 testing is proposed. The device described above is used to measure the specific distribution of residual oil at each stage of the miscible flooding process under heterogeneous different rhythm conditions, taking into account the gravity effect, including the following steps:

[0058] Step 1: Prepare core samples. The core samples are divided into heterogeneous artificial core cementation and natural heterogeneous core splicing cementation;

[0059] The preparation process of heterogeneous artificial core cementation is as follows: Sample 1: inject 200 mesh quartz sand and 5% epoxy resin by mass into a beaker and mix them thoroughly; Sample 2: inject 40 mesh quartz sand and 5% epoxy resin by mass into a beaker and mix them thoroughly to obtain two different mixed sands. Put a semi-cylindrical pad into a 1.5-inch core barrel, and fill a small amount of one mixed sand that has been stirred evenly into the 1.5-inch core barrel multiple times. Take out the pad and fill a small amount of another mixed sand into the 1.5-inch core barrel multiple times. Use a press to fully compact it and put it into a constant temperature box for drying for 24 hours, then measure the specific porosity and permeability of the core sample;

[0060] The natural heterogeneous core splicing and cementing process is as follows: the existing natural cores are cut and spliced ​​together, and the specific porosity and permeability of the spliced ​​core samples are measured; the spliced ​​core samples are vacuumed, saturated with formation water, and placed in a 1.5-inch online nuclear magnetic core holder;

[0061] Let the core joint surface be parallel to the length direction of the core. For the positive rhythm study, the core with low permeability is placed on the top, and for the reverse rhythm study, the core with low permeability is placed on the bottom.

[0062] Step 2: injecting manganese water, formation oil and CO2 into the manganese water intermediate container, the formation oil intermediate container and the CO2 intermediate container respectively, and injecting fluorine oil into the fluorine oil intermediate container;

[0063] Step 3: Control the confining pressure circulation pump to apply an initial confining pressure of 5 MPa to the cavity of the 1.5-inch online nuclear magnetic core holder. At the same time, keep the fluid temperature in each intermediate container and the temperature of the core sample in the 1.5-inch online nuclear magnetic core holder consistent with the formation temperature of the reservoir to be simulated. After the temperature is constant at the formation temperature, adjust the four-way valve and use a constant speed and constant pressure pump to increase the pressure of the formation oil intermediate container and the CO2 intermediate container to the formation pressure and stabilize it;

[0064] Step 4: Adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a flow rate of 1 ml / min, use the manganese water to displace the core sample, obtain the manganese water injection pressure according to the indication of the injection pressure gauge, and use the metering device to measure the water output of the discharge pipe. After the formation water injection pressure and water output are stable, calculate the initial water permeability of the core;

[0065] Step 5: Control the manual high-pressure pump to slowly apply back pressure to the back pressure valve to the formation pressure, observe the injection pressure gauge, and control the confining pressure circulation pump to ensure that the confining pressure is always 3MPa higher than the injection pressure; after the injection pressure indicator is stable, adjust the four-way valve and the six-way valve, and control the constant speed and constant pressure pump to inject the formation oil in the formation oil intermediate container into the 1.5-inch online nuclear magnetic core holder at a flow rate of 0.08ml / min. After the outflow end stops emitting water, close the inlet and outlet switches of the holder. After the formation oil is aged for 24h, use the layered test parallel to the core length direction to test the initial core T2 signal;

[0066] Step 6: Adjust the four-way valve and the six-way valve, control the constant speed and pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a flow rate of 0.08 ml / min, use the manganese water to displace the core sample, and test the core T2 signal in layers parallel to the length direction of the core every time 0.1 PV of manganese water is injected; when the metering device just appears manganese water, adjust the four-way valve and the six-way valve, control the constant speed and pressure pump to inject 0.3 PV of CO2 at a flow rate of 0.08 ml / min, and test the core T2 signal in layers parallel to the length direction of the core every time 0.1 PV is injected, and use the metering device to measure the oil output of the discharge pipeline to obtain the injection pressure and recovery rate change curve over time;

[0067] Step 7: Adjust the four-way valve and the six-way valve, control the constant speed and pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a flow rate of 0.08 ml / min, and test the core T2 signal in layers parallel to the length direction of the core for every 0.1 PV of manganese water injected; and use a metering device to measure the oil output of the discharge pipeline to obtain the injection pressure and recovery rate change curve with time. When the outlet stops producing oil, stop the experiment; according to the obtained core T2 signal tested in layers parallel to the length direction of the core, analyze the oil distribution in the heterogeneous core formation at different displacement stages, and study the miscible displacement mechanism in the heterogeneous core.

[0068] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A heterogeneous core miscible flooding experimental device based on layered nuclear magnetic resonance T2 testing, characterized in that: It includes a fluid supply system, a temperature control system, a 1.5-inch online nuclear magnetic core holder, a pressure loading system, a 1.5-inch core barrel, a nuclear magnetic resonance instrument and a metering device; The fluid supply system includes a constant speed and constant pressure pump and three intermediate containers, wherein the three intermediate containers are a manganese water intermediate container, a formation oil intermediate container and a CO2 intermediate container, and are used to inject fluid into the 1.5-inch online nuclear magnetic core holder; The 1.5-inch online nuclear magnetic core holder is used to hold the core sample and is matched with the nuclear magnetic resonance instrument to monitor the specific T2 spectrum of the core sample in real time during the pressure drive process; The pressure loading system includes a confining pressure circulation pump and a manual high-pressure pump, wherein the confining pressure circulation pump is used to apply confining pressure to the core sample in the 1.5-inch online nuclear magnetic core holder, obtain the confining pressure value in real time, and circulate and keep warm; The temperature control system is used to control the temperature of the fluid injected into the core sample; The metering device is used to measure the water output from the outflow end of the 1.5-inch online nuclear magnetic core holder.

2. The heterogeneous core miscible flooding experimental device based on layered nuclear magnetic resonance T2 testing according to claim 1 is characterized in that: The constant speed and constant pressure pump is connected to the high-pressure injection pipelines of the manganese water intermediate container, the formation oil intermediate container and the CO2 intermediate container respectively through a four-way valve; the outflow ends of the manganese water intermediate container, the formation oil intermediate container and the CO2 intermediate container are all connected with high-pressure liquid outlet pipelines, and each high-pressure liquid outlet pipeline is connected to the injection pipeline arranged at the injection end of the 1.5-inch online nuclear magnetic core clamp through a six-way valve, and the outflow end of the 1.5-inch online nuclear magnetic core clamp is connected to the metering device through a discharge pipeline, and a back pressure valve and an outlet control valve are arranged on the discharge pipeline.

3. The heterogeneous core miscible flooding experimental device based on layered nuclear magnetic resonance T2 test according to claim 2 is characterized in that: The six-way valve is provided with an injection pressure gauge for obtaining the injection pressure of the fluid in the core sample in real time.

4. The heterogeneous core miscible flooding experimental device based on layered nuclear magnetic resonance T2 testing according to claim 3 is characterized in that: The confining pressure pump circulates through the pressure injection pipeline and the fluorine oil intermediate container and then connects to the 1.5-inch online nuclear magnetic core holder, using fluorine oil to avoid the influence of the confining pressure liquid on the nuclear magnetic signal; the manual high-pressure pump is connected to the back pressure valve through the pressure injection pipeline.

5. The heterogeneous core miscible flooding experimental device based on layered nuclear magnetic resonance T2 testing according to claim 4 is characterized in that: The 1.5-inch online nuclear magnetic core holder includes a cylinder, a sealing cover and an external coil. The cylinder has a core sample built in it, and both ends of the cylinder are sealed with sealing covers. The core sample is covered with a rubber sleeve, and a radio frequency coil is arranged outside the sealing cover to measure the internal core T2 signal.

6. The heterogeneous core miscible flooding experimental device based on layered nuclear magnetic resonance T2 testing according to claim 5 is characterized in that: The temperature control system is configured such that an electric heating insulation sleeve is provided on the outer walls of the manganese water intermediate container, the formation oil intermediate container, the CO2 intermediate container and the fluorine oil intermediate container, and an electric heater is provided in the clamp to adjust the internal temperature of the clamp.

7. A heterogeneous core miscible flooding experimental method based on layered nuclear magnetic resonance T2 testing, characterized in that: A heterogeneous core miscible flooding experimental device based on layered nuclear magnetic resonance T2 testing as described in any one of claims 1 to 6 is used, comprising the following steps: Step 1: Prepare core samples. The core samples are divided into heterogeneous artificial core cementation and natural heterogeneous core splicing cementation; Step 2: injecting manganese water, formation oil and CO2 into the manganese water intermediate container, the formation oil intermediate container and the CO2 intermediate container respectively, and injecting fluorine oil into the fluorine oil intermediate container; Step 3: Control the confining pressure circulation pump to apply an initial confining pressure to the cavity of the 1.5-inch online nuclear magnetic core holder. The initial confining pressure ranges from 2 to 5 MPa. At the same time, the temperature of the fluid in each intermediate container and the temperature of the core sample in the 1.5-inch online nuclear magnetic core holder are kept consistent with the formation temperature of the reservoir to be simulated. After the temperature is constant at the formation temperature, adjust the four-way valve and use a constant speed and constant pressure pump to increase the pressure of the formation oil intermediate container and the CO2 intermediate container to the formation pressure and stabilize it; Step 4: Adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, use the manganese water to displace the core sample, obtain the manganese water injection pressure according to the reading of the injection pressure gauge, and use the metering device to measure the water flow rate of the discharge pipe. After the formation water injection pressure and the water flow rate are stable, calculate the initial water permeability of the core; Step 5: Control the manual high-pressure pump to slowly apply back pressure to the back pressure valve to the formation pressure, observe the injection pressure gauge, and control the confining pressure circulation pump to ensure that the confining pressure is always higher than the injection pressure; after the injection pressure indicator is stable, adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject the formation oil in the formation oil intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, and close the inlet and outlet switches of the holder after the outflow end stops emitting water. After the formation oil has aged for a period of time, test the initial core T2 signal in layers; Step 6: Adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, use the manganese water to displace the core sample, and test the core T2 signal in layers every time a certain pore volume of manganese water is injected; when the metering device just appears manganese water, adjust the four-way valve and the six-way valve, control the constant speed and constant pressure pump to inject a certain pore volume of CO2 at a preset flow rate, during which the core T2 signal is continuously tested in layers, and the metering device is used to measure the oil output of the discharge pipeline to obtain the injection pressure and recovery rate change curve over time; Step 7: Adjust the four-way valve and the six-way valve, control the constant speed and pressure pump to inject the manganese water in the manganese water intermediate container into the 1.5-inch online nuclear magnetic core holder at a preset flow rate, and test the core T2 signal in layers every time a certain pore volume of manganese water is injected; and use a metering device to measure the oil output of the discharge pipeline to obtain the injection pressure and recovery rate change curve over time. When the outlet stops producing oil, stop the experiment; according to the obtained layered test core T2 signal, analyze the oil distribution in the heterogeneous core formation at different displacement stages, and study the miscible displacement mechanism in the heterogeneous core.

8. The heterogeneous core miscible flooding experimental method based on layered nuclear magnetic resonance T2 testing according to claim 7 is characterized in that: In step 1, the preparation process of the heterogeneous artificial core cementation is as follows: inject different purpose sands into two beakers respectively, then add 5% epoxy resin respectively and stir them fully to obtain two different mixed sands; put a semi-cylindrical pad into a 1.5-inch core barrel, fill a small amount of one mixed sand that is stirred evenly into the 1.5-inch core barrel multiple times, take out the pad and fill a small amount of another mixed sand into the 1.5-inch core barrel multiple times, fully compact with a press, put it in a constant temperature box for drying, and then measure the specific porosity and permeability of the core sample; The natural heterogeneous core splicing and cementing process is as follows: the existing natural cores are cut and spliced ​​together, and the specific porosity and permeability of the spliced ​​core samples are measured; the spliced ​​core samples are vacuumed, saturated with formation water, and placed in a 1.5-inch online nuclear magnetic core holder; If the gravity effect is not considered, the core joint surface is made perpendicular to the length direction of the core; If the effect of gravity is considered, the core joint surface is made parallel to the length direction of the core. For the positive rhythm study, the core with low permeability is placed on the top, and for the negative rhythm study, the core with low permeability is placed on the bottom.

9. The heterogeneous core miscible flooding experimental method based on layered nuclear magnetic resonance T2 testing according to claim 7 is characterized in that: In the steps 5 to 7, if the gravity effect is not considered, the core T2 signal is tested layer by layer perpendicular to the length direction of the core; if the gravity effect is considered, the core T2 signal is tested layer by layer parallel to the length direction of the core.

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