Device and method for evaluating tight core imbibition and ion diffusion

Abstract

The invention discloses a device and a method for evaluating tight core imbibition and ion diffusion, and relates to the technical field of oil-gas field development. The nuclear magnetic tester can perform nuclear magnetic detection on a rock core, the nuclear magnetic tester and the holder are both arranged in the first heating box, and the first heating box is provided with a medium inlet pressure gauge, a medium outlet pressure gauge, a ring pressure gauge, a first reversing valve, a second reversing valve and a flow meter. The first temporary storage container stores fluorocarbon oil, the second temporary storage container and the first temporary storage container are connected in parallel to store an imbibition solution, and the sample container and the second temporary storage container are connected in parallel to perform drying, vacuum diffusion and constant-pressure imbibition treatment on a to-be-detected rock core; the submersible driving pump can pump media in the first temporary storage container and the second temporary storage container into the first heating box, actual high-temperature and high-pressure oil and gas reservoir conditions can be simulated, nuclear magnetic detection is conducted on a rock core at the same time, and therefore the permeability damage characteristics in the imbibition process and the occurrence and migration law of fluid in a rock sample are accurately analyzed.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a device and method for evaluating dense core imbibition and ion diffusion. Background Art

[0002] The development scale of unconventional oil and gas resources such as tight oil and gas reservoirs is expanding day by day, and its efficient development technology is a hot topic in current research. Due to the tight reservoir and low matrix permeability, the conventional mining technology has poor adaptability to this type of reservoir. At the same time, this type of reservoir has small pore throats and strong capillary force. Therefore, using capillary force to replace oil and water through imbibition is an important mechanism and means for this type of reservoir. For this type of gas reservoir, there is no unified understanding of the mechanism of low return rate and high mineralization return fluid at home and abroad. At the same time, the impact of fracturing fluid imbibed into the tight gas reservoir on the project has not been mastered.

[0003] Among them, imbibition is the process of spontaneous absorption of a certain wetting fluid by a porous medium. When a porous medium saturated with fluid is immersed in or contacts another liquid with stronger wetting ability, spontaneous imbibition can also occur. This liquid will replace the original non-wetting fluid in the process of wetting and absorbing the porous medium. The imbibition phenomenon is an objective phenomenon in the development of oil and gas fields, and it is an indispensable driving force for water-wet rock media. For the spontaneous imbibition phenomenon of gas-water two-phase in porous media, Hand (1960) first proposed a corresponding descriptive expression (i.e., the Hand formula) and demonstrated it through experiments. The results show that the square of the volume of the imbibed fluid is linearly related to time. The Hand formula laid an important foundation for the subsequent study of spontaneous imbibition.

[0004] Commonly used indoor imbibition laboratory methods include volumetric method and mass method, which mainly measure the changes in the mass of the output fluid or core, and then quantitatively obtain the core imbibition efficiency. The volumetric method is suitable for rock samples with high porosity and high permeability. For dense samples with poor porosity and permeability, the total pore volume of the rock sample is small, the amount of water absorbed is small, and the imbibition time is long. The temperature change causes the wetting liquid to evaporate, which brings errors to the experiment, thus limiting its application. In order to overcome the errors caused by the above experiments, the weighing method is adopted. The current electronic fully automatic imbibition instrument has simple testing and extremely high accuracy. The existing devices for measuring rock imbibition characteristics are all carried out at normal temperature and pressure. Not only can the final test results be obtained, but also the dynamics of imbibition can be observed; but it cannot measure the imbibition characteristics of rocks under high temperature and high pressure environments. Summary of the invention

[0005] In view of the fact that existing devices for measuring rock imbibition characteristics are unable to measure the imbibition characteristics of rocks under high temperature and high pressure environments, the present invention provides a device and method for evaluating dense core imbibition and ion diffusion, which can simulate actual high temperature and high pressure oil and gas reservoir conditions, and perform nuclear magnetic resonance detection on the core while conducting permeability tests at set pressure and temperature, so as to accurately analyze the permeability damage characteristics during the imbibition process and the occurrence and migration laws of fluids in rock samples.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a device for evaluating the imbibition and ion diffusion of dense cores, comprising: a clamp for clamping the core to be tested; a nuclear magnetic tester for performing nuclear magnetic detection on the core to be tested clamped by the clamp; a first heating box for accommodating and heating the clamp and the detection magnet of the nuclear magnetic tester, adapted to be equipped with a medium inlet pressure gauge, a medium outlet pressure gauge, an annular pressure gauge, a first reversing valve, a second reversing valve and a flow meter, wherein the first reversing valve and the second reversing valve are used to switch the flow direction of the imbibition solution flowing through the first heating box, and the flow meter is used to detect the flow of the imbibition solution from the first heating box. The flow rate of the imbibition solution flowing out of the first heating box; an annular pressure pump, used to input a medium of a set pressure into the first heating box; a first temporary storage container, used to store fluorocarbon oil; a second temporary storage container, connected in parallel with the first temporary storage container, used to store the imbibition solution; a sample container, connected in parallel with the second temporary storage container, used to dry, vacuum diffuse, and perform constant pressure imbibition treatment on the core to be tested; a submersible pump, used to pump the medium in the first temporary storage container and the second temporary storage container into the first heating box; wherein the medium in the second temporary storage container can be input into the sample container.

[0008] The present invention provides a device for evaluating the imbibition and ion diffusion of dense cores. The nuclear magnetic tester can perform nuclear magnetic detection on the core clamped by the clamp, and the nuclear magnetic tester and the clamp are both arranged in a first heating box. The first heating box is adapted to be equipped with a medium inlet pressure gauge, a medium outlet pressure gauge, an annular pressure gauge, a first reversing valve, a second reversing valve and a flow meter. The first temporary storage container stores fluorocarbon oil, the second temporary storage container is connected in parallel with the first temporary storage container to store the imbibition solution, and the sample container is connected in parallel with the second temporary storage container to dry, vacuum diffuse, and perform constant pressure imbibition treatment on the core to be tested. The submersible pump can pump the medium in the first temporary storage container and the second temporary storage container into the first heating box. Therefore, the present invention can simulate actual high-temperature and high-pressure oil and gas reservoir conditions, and perform nuclear magnetic detection on the core while performing permeability testing at set pressure and temperature, so as to accurately analyze the permeability damage characteristics during the imbibition process and the occurrence and migration laws of the fluid in the rock sample.

[0009] In an optional embodiment, a second heating box is further included, and the first temporary storage container, the second temporary storage container and the sample container are all placed in the second heating box to directly heat the substances in the first temporary storage container, the second temporary storage container and the sample container.

[0010] In an optional embodiment, the sample container is equipped with a hygrometer, a first weighing device, and a constant pressure liquid driving device; the hygrometer is used to detect the humidity in the sample container, the first weighing device is used to measure the weight of the sample to be tested in the sample container, and the constant pressure liquid driving device is used to drive the medium in the sample container into the first heating box at a constant pressure, so as to directly perform a pressurized absorption test on the sample.

[0011] In an optional embodiment, the constant pressure liquid expelling device is a gas storage bottle equipped with a pressure reducing valve to prevent the medium output by the constant pressure liquid expelling device from contaminating the medium in the sample container.

[0012] In an optional embodiment, the sample container is connected to a vacuum pump to facilitate direct vacuuming of the sample container.

[0013] In an optional embodiment, it also includes: a data collector, which is electrically connected to the outlet pressure gauge, the medium outlet pressure gauge, the annular pressure gauge, the annular pressure pump and the submersible pump respectively; a controller, which is electrically connected to the data collector and is used to analyze and process the data fed back by the data collector, so as to automatically collect and process the data of the electronic devices in the system, and control the start and stop of the corresponding equipment according to the corresponding data, and obtain the mathematical relationship of the corresponding data.

[0014] In an optional embodiment, it also includes a first imbibition container, which is adapted to be equipped with a second weighing device, a first heater and a first conductivity meter, and the medium in the first temporary storage container can be input into the first imbibition container; the first imbibition container is used to accommodate the core to be tested, the first conductivity meter is used to monitor the conductivity of the medium in the first imbibition container, the second weighing device is electrically connected to the data collector, and the second weighing device is used to measure the weight of the core to be tested in the first imbibition container, so as to perform normal pressure imbibition test on the core at a set temperature, so as to monitor the mass change and conductivity change in the process of ion diffusion of imbibition oil drive in real time online.

[0015] In an optional embodiment, it also includes a second imbibition container, which is equipped with a third weighing device, a second heater and a second conductivity meter, and the medium in the second temporary storage container can be input into the second imbibition container; the second imbibition container is used to accommodate the core to be tested, and the second conductivity meter is used to monitor the conductivity of the medium in the second imbibition container, and the third weighing device is electrically connected to the data collector, and the third weighing device is used to measure the weight of the core to be tested in the second imbibition container, so as to perform a normal pressure imbibition test on another core at another set temperature, so as to monitor the mass change and conductivity change in the spontaneous imbibition ion diffusion process in real time online.

[0016] In an optional embodiment, both the first imbibition container and the second imbibition container are transparent containers to facilitate intuitive observation of the core imbibition process at different temperatures.

[0017] In a second aspect, the present invention provides a method for evaluating dense core imbibition and ion diffusion, based on the above-mentioned device for evaluating dense core imbibition and ion diffusion, comprising the following steps:

[0018] S10, clamping the weighed dense core in a clamp, and performing a permeability test and a nuclear magnetic resonance test on the dense core clamped by the clamp under a set confining pressure to obtain a damage rate of the tested rock and a nuclear magnetic resonance T2 spectrum before and after damage;

[0019] S20, placing another core sample of a set size in a sample container, imbibing an imbibition solution in the sample container at a set pressure and temperature, and detecting the weight of the core sample in the sample container in real time;

[0020] S30, measuring at different temperatures to measure the imbibition and ion diffusion curves of the corresponding core samples;

[0021] S40, clamping the samples in S20 and S30 in the clamps respectively, measuring the irreducible water saturation of the corresponding core samples, and calculating the corresponding water lock damage rates under normal pressure and pressurized conditions based on the irreducible water saturation;

[0022] S50. A multivariate nonlinear regression model was used to establish a quantitative prediction model for water lock damage rate.

[0023] The method for evaluating dense core imbibition and ion diffusion provided by the present invention comprises the following steps: firstly clamping the weighed dense core in a clamper, and performing a permeability test and a nuclear magnetic resonance test on the dense core clamped by the clamper under a set confining pressure to obtain the damage rate of the rock to be tested and the nuclear magnetic resonance T2 spectrum before and after damage; then placing another core sample of a set size in a sample container, imbibing the imbibition solution in the sample container under a set pressure and temperature, and detecting the weight of the core sample in the sample container in real time; and measuring at different temperatures to measure the imbibition and ion diffusion curves of the corresponding core sample; then measuring the bound water saturation of the corresponding core sample, and calculating the corresponding water lock damage rate under normal pressure and pressurized state based on the bound water saturation; finally, using a multivariate nonlinear regression model to establish a quantitative prediction model for the water lock damage rate, which can accurately reflect the water lock damage evaluated by imbibition.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] 1. The device for evaluating the imbibition and ion diffusion of dense cores provided by the present invention, the nuclear magnetic tester can perform nuclear magnetic detection on the core clamped by the clamp, and the nuclear magnetic tester and the clamp are both arranged in the first heating box, the first heating box is adapted to be equipped with a medium inlet pressure gauge, a medium outlet pressure gauge, an annular pressure gauge, a first reversing valve, a second reversing valve and a flow meter, and the first temporary storage container stores fluorocarbon oil, the second temporary storage container is connected in parallel with the first temporary storage container to store the imbibition solution, and the sample container is connected in parallel with the second temporary storage container to dry, vacuum diffuse, and perform constant pressure imbibition treatment on the core to be tested, and the submersible pump can pump the medium in the first temporary storage container and the second temporary storage container into the first heating box. Therefore, the present invention can simulate the actual high-temperature and high-pressure oil and gas reservoir conditions, and perform nuclear magnetic detection on the core while performing permeability testing at set pressure and temperature, so as to accurately analyze the permeability damage characteristics during the imbibition process and the occurrence and migration laws of the fluid in the rock sample.

[0026] 2. The method for evaluating the imbibition and ion diffusion of dense cores provided by the present invention comprises the following steps: firstly clamping the weighed dense core in a clamp, and performing a permeability test and a nuclear magnetic resonance test on the dense core clamped by the clamp under a set confining pressure to obtain the damage rate of the rock to be tested and the nuclear magnetic resonance T2 spectrum before and after damage; then placing another core sample of a set size in a sample container, imbibing the imbibition solution in the sample container at a set pressure and temperature, and detecting the weight of the core sample in the sample container in real time; and measuring at different temperatures to measure the imbibition and ion diffusion curves of the corresponding core sample; then measuring the bound water saturation of the corresponding core sample, and calculating the corresponding water lock damage rate under normal pressure and pressurized conditions based on the bound water saturation; finally, a multivariate nonlinear regression model is used to establish a quantitative prediction model for the water lock damage rate, which can accurately reflect the water lock damage evaluated by imbibition. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0028] In the attached picture:

[0029] Figure 1 It is a schematic diagram of the structure of a device for evaluating dense core imbibition and ion diffusion according to an embodiment of the present invention.

[0030] Figure 2 Schematic diagram of the structure of the nuclear magnetic resonance module of this embodiment;

[0031] Figure 3 Schematic diagram of rock sample permeability damage test results in this embodiment;

[0032] Figure 4 It is the T2 spectrum of nuclear magnetic resonance test before and after the rock sample experiment in this embodiment.

[0033] Marks and corresponding parts names in the attached drawings:

[0034] 1- holder, 2- nuclear magnetic tester, 2a- detection magnet, 2b- radio frequency transmitter, 3- first heating box, 4- medium inlet pressure gauge, 5- medium outlet pressure gauge, 6- annular pressure gauge, 7- first reversing valve, 8- second reversing valve, 9- flow meter, 10- annular pressure pump, 11- first temporary storage container, 12- second temporary storage container, 13- sample container, 14- submersible pump, 15- second heating box, 16- hygrometer, 17- first weighing device, 18- constant pressure liquid driving device, 19- vacuum pump, 20- data acquisition device, 21- controller, 22- first imbibition container, 23- second weighing device, 24- first heater, 25- first conductivity meter, 26- second imbibition container, 27- third weighing device, 28- second heater, 29- second conductivity meter, 30- core. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0036] In the description of the embodiments of the present application, the indicated orientation or position relationship is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the application is conventionally placed when in use, or is the orientation or position relationship conventionally understood by those skilled in the art. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0037] At the same time, the terms "disposed", "opened", "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] Example 1

[0039] Combination Figure 1 , this embodiment provides a device for evaluating the imbibition and ion diffusion of a dense core, comprising: a clamp 1 for clamping a core to be tested; a nuclear magnetic tester 2 for performing nuclear magnetic detection on the core to be tested clamped by the clamp 1; a first heating box 3 for accommodating and heating the clamp 1 and the detection magnet 2a of the nuclear magnetic tester 2, adapted to be equipped with a medium inlet pressure gauge 4, a medium outlet pressure gauge 5, an annular pressure gauge 6, a first reversing valve 7, a second reversing valve 8 and a flow meter 9, wherein the first reversing valve 7 and the second reversing valve 8 are used to switch the flow direction of the imbibition solution flowing through the first heating box 3, and the flow meter 9 is used to detect the flow rate of the imbibition solution flowing out of the first heating box 3 ( A high-precision electronic balance is used to record the mass of the outlet effluent per unit time); an annular pressure pump 10 is used to input a medium of set pressure into the first heating box 3; a first temporary storage container 11 is used to store fluorocarbon oil; a second temporary storage container 12 is connected in parallel with the first temporary storage container 11 and is used to store an imbibition solution; a sample container 13 is connected in parallel with the second temporary storage container 12 and is used to dry, vacuum diffuse, and perform constant pressure imbibition treatment on the core to be tested; a submersible pump 14 is used to pump the medium in the first temporary storage container 11 and the second temporary storage container 12 into the first heating box 3; wherein the medium in the second temporary storage container 12 can be input into the sample container 13.

[0040] Specifically, the sample container 13 is equipped with a hygrometer 16, a first weighing device 17, and a constant pressure liquid displacing device 18; the hygrometer 16 is used to detect the humidity in the sample container 13, the first weighing device 17 is used to measure the weight of the sample to be tested in the sample container 13, and the constant pressure liquid displacing device 18 is used to drive the medium in the sample container 13 into the first heating box 3 at a constant pressure, so as to directly perform a pressurized imbibition test on the sample, thereby quantitatively and in real time evaluating the imbibition effect and adsorption-diffusion effect of the core.

[0041] Preferably, the constant pressure liquid displacing device 18 is a gas storage bottle equipped with a pressure reducing valve to prevent the medium output by the constant pressure liquid displacing device 18 from contaminating the medium in the sample container 13 .

[0042] Meanwhile, the sample container 13 is connected to a vacuum pump 19 to facilitate direct evacuation of the sample container 13 .

[0043] In this embodiment, a second heating box 15 is further included. The first temporary storage container 11, the second temporary storage container 12 and the sample container 13 are all placed in the second heating box 15 to directly heat the substances in the first temporary storage container 11, the second temporary storage container 12 and the sample container 13.

[0044] Generally speaking, the operation of the brake control device is usually controlled by a controller 21, which in this embodiment also includes: a data collector 20, which is electrically connected to the outlet pressure gauge, the medium outlet pressure gauge 5, the annular pressure gauge 6, the annular pressure pump 10 and the submersible pump 14; a controller 21, which is electrically connected to the data collector 20, is used to analyze and process the data fed back by the data collector 20, so as to automatically collect and process the data of the electronic devices in the system, and control the start and stop of the corresponding equipment according to the corresponding data, and obtain the mathematical relationship of the corresponding data. In other words, the controller 21 system can record the core mass changes in the process of imbibition and ion diffusion in real time through the data collector 20 and the recording software, and automatically draw the imbibition time curve and the ion diffusion time curve.

[0045] On this basis, it also includes a first imbibition container 22, which is adapted to be equipped with a second weighing device 23, a first heater 24 and a first conductivity meter 25, and the medium in the first temporary storage container 11 can be input into the first imbibition container 22; the first imbibition container 22 is used to accommodate the core to be tested, the first conductivity meter 25 is used to monitor the conductivity of the medium in the first imbibition container 22, the second weighing device 23 is electrically connected to the data acquisition device 20, and the second weighing device 23 is used to measure the weight of the core to be tested in the first imbibition container 22, so as to perform normal pressure imbibition test on the core at a set temperature, so as to monitor the mass change and conductivity change in the process of imbibition oil diffusion in real time online.

[0046] Furthermore, it also includes a second imbibition container 26, which is equipped with a third weighing device 27, a second heater 28 and a second conductivity meter 29, and the medium in the second temporary storage container 12 can be input into the second imbibition container 26; the second imbibition container 26 is used to accommodate the core to be tested, and the second conductivity meter 29 is used to monitor the conductivity of the medium in the second imbibition container 26, and the third weighing device 27 is electrically connected to the data acquisition device 20, and the third weighing device 27 is used to measure the weight of the core to be tested in the second imbibition container 26, so as to facilitate the normal pressure imbibition test of another core at another set temperature, so as to monitor the mass change and conductivity change in the process of spontaneous imbibition ion diffusion in real time online. The use of two sets of parallel imbibition and ion diffusion metering modules can not only realize spontaneous imbibition oil recovery, but also realize spontaneous imbibition of different fluids.

[0047] Preferably, the first imbibition container 22 and the second imbibition container 26 are both transparent containers, such as made of organic glass, so as to visually observe the core imbibition process at different temperatures. Accordingly, each heater and heating box is provided with a visual window.

[0048] It should be understood that the weight change of core imbibition is small, so a high-precision electronic balance is usually used as a weighing device, such as an electronic balance with a resolution of 0.0001g. The heating temperature of each heater can be adjusted to achieve imbibition and ion diffusion tests of dense cores at different temperatures. The medium in the first temporary storage container 11 is usually fluorocarbon oil, so that the imbibition oil recovery has no hydrogen signal and does not generate interference signals for the nuclear magnetic resonance test; the imbibition solution in the second temporary storage container 12 can be any one of pure water, surfactant aqueous solution, clay stabilizer aqueous solution, drag reducing agent aqueous solution, fracturing fluid, and fracturing return fluid.

[0049] In addition, each pipeline node is connected in series with a switch valve, such as the inlet and outlet of each container, the outlet of the pump, etc., are connected with a switch valve to control the on-off of the flow path; the height of the sample container 13, the first imbibition container 22 and the second imbibition container 26 are all lower than the first temporary storage container 11 and the second temporary storage container 12, so that the medium in the temporary storage container can input the corresponding medium into the corresponding reaction container under the action of gravity.

[0050] It should be noted that a large number of theoretical models and indoor experiments have been conducted in this field to study the self-imbibition characteristics of water-gas-rock or water-oil-rock systems at the core scale, such as the influence of microstructure, physical properties, boundary conditions, rock mineralogy, initial water saturation, temperature, wettability and immersion time. The CT and NMR methods are to analyze the generated images and spectra by computer, and finally obtain the imbibition efficiency of the experimental core qualitatively. It is an effective and non-destructive technology to describe the imbibition phenomenon to characterize the fluid distribution in tight sandstone. In addition, due to the low porosity and low imbibition amount of the matrix core of the tight oil and gas reservoir, the conventional CT, NMR and volume methods cannot accurately and quantitatively obtain the imbibition efficiency of the core. Therefore, the city has established a mass method combined with the NMR method to conduct an imbibition experiment on the matrix core of the tight oil and gas reservoir, which is an effective and accurate method to explore the imbibition mechanism of oil and gas reservoirs.

[0051] It is understandable that the device for evaluating dense core imbibition and ion diffusion provided in this embodiment is only used when the dynamic imbibition module (i.e., displacement system, attached Figure 1 When the sample container 13 is not included, the inlet and outlet pressures and outlet flow rates of the first heating box 3 can be recorded, and the permeability can be calculated using the Darcy formula to complete the test of the effect of the fluid on the permeability of the tight reservoir. The forward displacement and reverse displacement (based on the Figure 1 The thermostat can heat the sample and fluid in the core holder 1 to simulate the reservoir temperature and conduct dynamic imbibition experiments.

[0052] When the pipeline adapted to the sample container 13 is started, after the air interference is eliminated by the vacuum pump 19, the constant pressure liquid drive device 18 maintains the pressure in the sample container 13 stable. By testing the contact and non-contact of the injected liquid with the rock sample, the mass changes of the rock sample during infiltration and diffusion adsorption can be recorded respectively.

[0053] Therefore, this embodiment can simulate actual high-temperature and high-pressure oil and gas reservoir conditions, and perform nuclear magnetic resonance detection on the core while conducting permeability tests at set pressure and temperature, so as to accurately analyze the permeability damage characteristics during the infiltration process and the distribution and migration laws of the fluid in the rock sample.

[0054] In summary, this embodiment can simulate the whole process of "fracturing-shut-in-flowback" by regulating temperature and pressure, and can obtain the permeability influence law and nuclear magnetic resonance T2 spectrum experimental data in the dynamic pressurized imbibition process through displacement nuclear magnetic simulation, and analyze the permeability damage characteristics in the imbibition process and the occurrence and migration law of fluid in the rock sample. It solves the problems of low precision of traditional imbibition devices, inability to realize core imbibition and ion diffusion tests at the same time, inability to fully perform static and dynamic imbibition under different temperature and pressure conditions, and inability to quantitatively describe the fluid distribution in the imbibition process.

[0055] Example 2

[0056] This embodiment provides a method for evaluating dense core imbibition and ion diffusion according to the present invention, based on the device for evaluating dense core imbibition and ion diffusion described in Example 1, comprising the following steps:

[0057] S10, clamping the weighed dense core in the clamp 1, and performing a permeability test and a nuclear magnetic resonance test on the dense core clamped by the clamp 1 under a set confining pressure to obtain the damage rate of the rock to be tested and the nuclear magnetic resonance T2 spectra before and after damage.

[0058] That is, the dense core to be tested is weighed, with an initial mass m0, placed in the holder 1 and subjected to a nuclear magnetic resonance test; specifically:

[0059] Apply an initial confining pressure (2.0-3.0 MPa in this embodiment) to the core in the holder 1 through the annular pressure pump 10, and keep the confining pressure 2.0-5.0 MPa greater than the inlet pressure;

[0060] Add standard saline to the second temporary storage container 12, open the corresponding valve, start the displacement pump, and the displacement speed is 0.1-0.2 ml / min, so as to measure the initial permeability K0;

[0061] Determination of the permeability K of tight cores damaged by fracturing fluids i and mass m1, thereby calculating the damage rate D1 of the core and conducting nuclear magnetic resonance testing at the same time;

[0062] The experimental data are stored and plotted through the controller 21 to obtain the core damage rate and the nuclear magnetic resonance T2 spectra before and after damage.

[0063] Among them, the rock sample permeability damage test results are as follows Figure 3 , the T2 spectrum of NMR test before and after the experiment is as follows Figure 4 .

[0064] As can be seen from the figure, in this embodiment, the penetration damage rate of distilled water to the core is 31.46%, and the nuclear magnetic resonance T2 spectrum curve mainly shows a bimodal morphology, with peak values ​​distributed around 0.6ms and 4.7ms, and the corresponding pore sizes are mainly distributed in the range of 0.01-0.1μm and 0.1-1μm. When pressurized infiltration saturated distilled water is used, the fluid saturation is 87.61%.

[0065] S20, placing another core sample of a set size in the sample container 13, imbibing the imbibition solution in the sample container 13 at a set pressure and temperature, and detecting the weight of the core sample in the sample container 13 in real time.

[0066] Specifically, in this embodiment, a column-packed core sample with a diameter of 2.5 cm and a length of 5 cm is placed in a second heating box 15 at 110°C and dried for 24 hours until constant weight is achieved, and its dry weight is recorded as m0 by an electronic balance; then the temperature of the second heating box 15 is adjusted to the experimental temperature, the sample is suspended under the first weighing device 17 in the sample container 13, and when the air tightness of the pipeline of the sample container 13 meets the requirements, it is vacuumed for 0.5 hours.

[0067] The core sample is saturated with methane gas to reach the saturation pressure P0. After stabilization for 2 hours, the displacement pump and the inlet valve at the lower end of the second temporary storage container 12 are opened to inject the liquid in the sample container 13 until the core sample is completely immersed, and then the inlet valve of the sample container 13 is closed; the pressure regulating valve is adjusted to maintain a constant pressure P0 in the sample container 13, so that the core sample is subjected to constant temperature and constant pressure infiltration, and then the sample mass mi is recorded at different times. In this embodiment, the infiltration capacity of the core sample under a pressure of 10MPa for 24 hours is 92.54%.

[0068] S30. Measure at different temperatures to determine the imbibition and ion diffusion curves of the corresponding core samples.

[0069] Specifically, the oil displacement and ion diffusion are carried out in the first absorption container 22, and the natural absorption of the aqueous solution and the ion diffusion are carried out in the second absorption container 26. The absorption oil is fluorocarbon oil and is stored in the first temporary storage container 11, which will not generate interference signals for the nuclear magnetic resonance test. The aqueous solution can be any one of pure water, surfactant aqueous solution, clay stabilizer aqueous solution, drag reducing agent aqueous solution, fracturing fluid, and fracturing flowback fluid, and is stored in the second temporary storage container 12.

[0070] According to the experimental needs, the corresponding weighing device and conductivity meter are turned on, and the temperature of the corresponding heater is adjusted to measure the imbibition and ion diffusion curves at different temperatures, and the data is monitored and plotted in real time through the controller 21.

[0071] In this embodiment, the imbibition capacity of the core sample after imbibing distilled water for 24 hours under natural conditions is 54.64%.

[0072] S40, clamping the samples in S20 and S30 in the clamp 1 respectively, measuring the irreducible water saturation of the corresponding core samples, and calculating the corresponding water lock damage rate under normal pressure and pressurized state based on the irreducible water saturation.

[0073] Specifically, the core after S20 pressure imbibition is placed in the clamp 1, the constant pressure liquid drive device 18 is turned on, and the core sample is subjected to constant pressure gas drive until no liquid flows out of the outlet of the first heating box 3, and its permeability remains stable and reaches the state of bound water saturation, and then the core sample is weighed, and the mass of the dry rock sample is subtracted. The bound water saturation of the core sample after S20 treatment calculated in this embodiment is 35.24%. Similarly, after S30 normal pressure imbibition, the bound water saturation of the core sample is 34.54%.

[0074] In the imbibition flooding, before and after the core imbibition, only the core is 100% saturated with oil and saturated with oil after imbibition, and the imbibition is partially saturated with water. The volume of saturated water is V, the weighing device data difference is M, and the saturated oil density is ρ. 油 , saturated water density ρ 水 The weight change data is the difference between the mass of the same volume of imbibed water and the mass of the same volume of saturated oil displaced. From this, it can be deduced that: V = M / (ρ 水 -ρ 油 )

[0075] In natural imbibition, first calibrate the ratio of the liquid area to the cross-sectional area of ​​the weighing object (i.e., the volume ratio V 渗 / V 排 ), the volume of imbibed liquid V 渗 , weighing device data difference M, liquid density ρ 液 , the buoyancy force (M×g=ρ 液 ×g×V 排 ). Where g is a constant. From this we can deduce:

[0076] M=ρ 液 ×V 排

[0077] V 渗 =A×(M / ρ 液 )

[0078] Among them, the pressure imbibition water lock damage rate calculated by the gas permeability under the irreducible water saturation state and the initial gas permeability is 45.25%, and the corresponding normal pressure imbibition water lock damage rate is 44.45%. Eight groups of pressure imbibition and normal pressure imbibition tests were conducted respectively, and the imbibition capacity after 24 hours of imbibition, the irreducible water saturation when the constant pressure gas drive reaches the irreducible water saturation state, and the water lock damage rate were recorded. The results are shown in Table 1:

[0079] Table 1

[0080]

[0081] S50. A multivariate nonlinear regression model was used to establish a quantitative prediction model for water lock damage rate.

[0082] Specifically, in this embodiment, let y be the water lock damage rate D, x1 be the bound water saturation W, and x2 be the maximum imbibition capacity C. The nonlinear model established for y is: y=a0+a1x1+a2x2+x1x2. This model can reflect the influence of bound water saturation and maximum imbibition capacity on the water lock damage rate.

[0083] At the same time, under pressure imbibition, the nonlinear relationship between the permeability damage rate caused by water lock and various factors is: D = -29.32 + 3.776W + 0.3688C - 0.04177 * W * C, R 2 =0.9893.

[0084] Under normal pressure imbibition, the nonlinear equation is: D = -532.7 + 27.88W + 5.712C - 0.2866*W*C, R 2 =0.9829. The results show that the quantitative prediction model of water lock damage rate can accurately reflect the water lock damage evaluated by imbibition.

[0085] In summary, the method for evaluating the imbibition and ion diffusion of dense cores provided in this embodiment is to first clamp the weighed dense core in the clamp 1, and perform permeability test and nuclear magnetic resonance test on the dense core clamped by the clamp 1 under a set confining pressure to obtain the damage rate of the rock to be tested and the nuclear magnetic resonance T2 spectrum before and after damage; then, another core sample of a set size is placed in a sample container 13, and the imbibition solution in the sample container 13 is imbibed at a set pressure and temperature, and the weight of the core sample in the sample container 13 is detected in real time; and the imbibition and ion diffusion curves of the corresponding core samples are measured at different temperatures; then, the bound water saturation of the corresponding core sample is measured, and the corresponding water lock damage rate under normal pressure and pressurized conditions is calculated based on the bound water saturation; finally, a multivariate nonlinear regression model is used to establish a quantitative prediction model for the water lock damage rate, which can accurately reflect the water lock damage evaluated by imbibition.

[0086] This embodiment has the characteristics of high precision and can realize continuous online measurement of the imbibition and ion diffusion processes. At the same time, it can realize imbibition under static and dynamic conditions and under different temperature and pressure conditions, and can simulate actual high-temperature and high-pressure oil and gas reservoir conditions.

[0087] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for evaluating dense core imbibition and ion diffusion, characterized in that: include: A clamp (1), used for clamping the core to be tested; A nuclear magnetic tester (2), used for performing nuclear magnetic testing on the rock core to be tested clamped by the clamp (1); a first heating box (3), used for accommodating and heating the holder (1) and the detection magnet (2a) of the nuclear magnetic tester (2), and adapted to be equipped with a medium inlet pressure gauge (4), a medium outlet pressure gauge (5), an annular pressure gauge (6), a first reversing valve (7), a second reversing valve (8) and a flow meter (9), wherein the first reversing valve (7) and the second reversing valve (8) are used to switch the flow direction of the imbibition solution flowing through the first heating box (3), and the flow meter (9) is used to detect the flow rate of the imbibition solution flowing out of the first heating box (3); An annular pressure pump (10), used for inputting a medium of a set pressure into the first heating box (3); A first temporary storage container (11) for storing fluorocarbon oil; A second temporary storage container (12), connected in parallel with the first temporary storage container (11), for storing the imbibition solution; A sample container (13) is connected in parallel with the second temporary storage container (12) and is used to perform drying, vacuum diffusion, and constant pressure imbibition treatment on the core to be tested; a submersible pump (14) for pumping the medium in the first temporary storage container (11) and the second temporary storage container (12) into the first heating box (3); The medium in the second temporary storage container (12) can be input into the sample container (13).

2. The device for evaluating dense core imbibition and ion diffusion according to claim 1, characterized in that: The invention also comprises a second heating box (15), wherein the first temporary storage container (11), the second temporary storage container (12) and the sample container (13) are all placed in the second heating box (15).

3. The device for evaluating dense core imbibition and ion diffusion according to claim 1, characterized in that: The sample container (13) is equipped with a hygrometer (16), a first weighing device (17), and a constant pressure liquid displacing device (18); The hygrometer (16) is used to detect the humidity in the sample container (13), the first weighing device (17) is used to measure the weight of the sample to be tested in the sample container (13), and the constant pressure liquid driving device (18) is used to drive the medium in the sample container (13) into the first heating box (3) at a constant pressure.

4. The device for evaluating dense core imbibition and ion diffusion according to claim 3, characterized in that: The constant pressure liquid displacing device (18) is a gas storage bottle equipped with a pressure reducing valve.

5. The device for evaluating dense core imbibition and ion diffusion according to claim 3, characterized in that: The sample container (13) is connected to a vacuum pump (19).

6. The device for evaluating dense core imbibition and ion diffusion according to claim 1, characterized in that: Also includes: A data collector (20), wherein the data collector (20) is electrically connected to the outlet pressure gauge, the medium outlet pressure gauge (5), the annular pressure gauge (6), the annular pressure pump (10) and the submersible pump (14) respectively; The controller (21) is electrically connected to the data collector (20) and is used to analyze and process the data fed back by the data collector (20).

7. The device for evaluating dense core imbibition and ion diffusion according to claim 6, characterized in that: It also includes a first imbibition container (22), wherein the first imbibition container (22) is equipped with a second weighing device (23), a first heater (24) and a first conductivity meter (25), and the medium in the first temporary storage container (11) can be input into the first imbibition container (22); The first imbibition container (22) is used to accommodate the rock core to be tested, the first conductivity meter (25) is used to monitor the conductivity of the medium in the first imbibition container (22), the second weighing device (23) is electrically connected to the data acquisition device (20), and the second weighing device (23) is used to measure the weight of the rock core to be tested in the first imbibition container (22).

8. The device for evaluating dense core imbibition and ion diffusion according to claim 7, characterized in that: It also includes a second imbibition container (26), wherein the second imbibition container (26) is equipped with a third weighing device (27), a second heater (28) and a second conductivity meter (29), and the medium in the second temporary storage container (12) can be input into the second imbibition container (26); The second imbibition container (26) is used to accommodate the core to be tested, the second conductivity meter (29) is used to monitor the conductivity of the medium in the second imbibition container (26), and the third weighing device (27) is electrically connected to the data acquisition device (20), and the third weighing device (27) is used to measure the weight of the core to be tested in the second imbibition container (26).

9. The device for evaluating dense core imbibition and ion diffusion according to claim 8, characterized in that: The first imbibition container (22) and the second imbibition container (26) are both transparent containers.

10. A method for evaluating dense core imbibition and ion diffusion, characterized in that: The device for evaluating dense core imbibition and ion diffusion according to any one of claims 1 to 9 comprises the following steps: S10, clamping the weighed dense rock core in a clamp (1), and performing a permeability test and a nuclear magnetic resonance test on the dense rock core clamped by the clamp (1) under a set confining pressure to obtain a damage rate of the rock to be tested and a nuclear magnetic resonance T2 spectrum before and after damage; S20, placing another core sample of a set size in a sample container (13), imbibing the imbibition solution in the sample container (13) at a set pressure and temperature, and detecting the weight of the core sample in the sample container (13) in real time; S30, measuring at different temperatures to measure the imbibition and ion diffusion curves of the corresponding core samples; S40, clamping the samples in S20 and S30 in the clamp (1) respectively, and measuring the irreducible water saturation of the corresponding core samples, and calculating the corresponding water lock damage rate under normal pressure and pressurized state based on the irreducible water saturation; S50. A multivariate nonlinear regression model was used to establish a quantitative prediction model for water lock damage rate.

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