Permeability level difference lower limit determination method, device and equipment

Abstract

The invention relates to the technical field of petroleum, in particular to a permeability level difference lower limit determination method, device and equipment. The permeability level difference lower limit determination method comprises the following steps: calculating a permeability level difference set of a target oil reservoir according to target oil reservoir data; the permeability grade difference set corresponds to a plurality of groups of rock cores; any group of rock cores in the plurality of groups of rock cores comprises a first rock core and a second rock core; the permeability of the first core is greater than that of the second core; obtaining the recovery degree of crude oil of the multiple groups of cores in the simulated target oil reservoir environment; and according to the crude oil recovery degree of the multiple groups of cores in the simulated target oil reservoir environment, determining the permeability grade difference lower limit of the target oil reservoir in the permeability grade difference set. According to the embodiment of the invention, the influence of the permeability level difference on the oil displacement effect of the target oil reservoir and the permeability level difference lower limit of the target oil reservoir can be determined under the simulated target oil reservoir environment, and the design of a heterogeneous oil reservoir development scheme can be guided, so that the heterogeneous oil reservoir can be developed more efficiently.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of petroleum technology, and specifically to a method, device and equipment for determining a lower limit of a permeability difference. Background Art

[0002] Tight oil is an important oil and gas resource and has received extensive attention in recent years. Increasing the development of unconventional tight oil reservoirs is an important means to increase oil and gas production and ensure energy security. However, unlike conventional oil reservoirs, tight oil reservoirs have extremely low porosity and permeability, and conventional water injection methods are difficult to implement in such reservoirs.

[0003] The successful development experience of many such reservoirs at home and abroad shows that CO2 injection / flooding can achieve efficient development of such reservoirs, mainly because CO2 is a gas with a small molecular size, which can enter the pores in tight oil reservoirs that water cannot enter, solving the problem of conventional water injection difficulties in such reservoirs and achieving effective use of reservoir crude oil. Therefore, injecting CO2 into tight oil reservoirs to increase oil recovery can not only achieve CO2 geological storage but also improve the recovery rate of such reservoirs, achieving a win-win effect of utilization and emission reduction.

[0004] However, the heterogeneity of the reservoir severely limits the effectiveness of existing CO2 displacement methods. Injected CO2 tends to flow along high-permeability channels and has limited impact on low-permeability areas. Therefore, how to provide a method for determining the lower limit of the permeability difference in heterogeneous reservoirs using CO2, so as to design a development plan before the development of heterogeneous reservoirs, and then develop tight reservoirs more efficiently is a key issue that needs to be solved urgently. Summary of the invention

[0005] The purpose of the embodiments of this specification is to provide a method, device and equipment for determining the lower limit of permeability difference, so as to clarify the influence of permeability difference on the oil displacement effect of target reservoir and the lower limit of permeability difference of target reservoir under the simulated target reservoir environment, so as to better involve the development plan of heterogeneous reservoir and develop heterogeneous reservoir more efficiently.

[0006] On the one hand, an embodiment of the present specification provides a method for determining a lower limit of a permeability difference, the method comprising: calculating a permeability difference set of a target oil reservoir according to target oil reservoir data; the permeability difference set corresponds to multiple groups of cores; any group of cores among the multiple groups of cores comprises a first core and a second core; the permeability of the first core is greater than the permeability of the second core; obtaining the degree of crude oil recovery of the multiple groups of cores under a simulated target oil reservoir environment; determining the lower limit of the permeability difference of the target oil reservoir in the permeability difference set according to the degree of crude oil recovery of the multiple groups of cores under a simulated target oil reservoir environment.

[0007] On the other hand, an embodiment of the present specification provides a device for determining a lower limit of a permeability difference, the device for determining a lower limit of a permeability difference comprising: a calculation module, for calculating a permeability difference set of a target oil reservoir based on target oil reservoir data; the permeability difference set corresponds to multiple groups of cores; any group of cores among the multiple groups of cores comprises a first core and a second core; the permeability of the first core is greater than the permeability of the second core; an acquisition module, for acquiring the degree of crude oil recovery of the multiple groups of cores under a simulated target oil reservoir environment; a determination module, for determining the lower limit of the permeability difference of the target oil reservoir in the permeability difference set based on the degree of crude oil recovery of the multiple groups of cores under a simulated target oil reservoir environment.

[0008] On the other hand, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the above-mentioned method for determining the lower limit of the permeability difference.

[0009] It can be seen from the technical solutions provided by the above embodiments of this specification that the embodiments of this specification can calculate the permeability difference set of the target reservoir according to the target reservoir data; the permeability difference set corresponds to multiple groups of cores; any group of cores in the multiple groups of cores includes a first core and a second core; the permeability of the first core is greater than the permeability of the second core; the degree of crude oil recovery of the multiple groups of cores under the simulated target reservoir environment is obtained; according to the degree of crude oil recovery of the multiple groups of cores under the simulated target reservoir environment, the lower limit of the permeability difference of the target reservoir in the permeability difference set is determined. Compared with the existing methods, the embodiments of this specification can clarify the influence of the permeability difference on the target reservoir displacement effect and the lower limit of the permeability difference of the target reservoir under the simulated target reservoir environment, which is helpful to guide the design of the heterogeneous reservoir development plan, and thus more efficiently develop the heterogeneous reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings required for use in the embodiments or the prior art description are briefly introduced below.

[0011] Figure 1 is a flow chart of a method for determining a lower limit of a permeability difference provided in an embodiment of this specification;

[0012] Figure 2 is a logical flow chart of core preparation provided in the embodiments of this specification;

[0013] Figure 3 It is a schematic diagram of the experimental process of core displacement oil provided in the embodiments of this specification;

[0014] Figure 4It is a well logging interpretation data map of the A oil reservoir provided in the embodiment of this specification;

[0015] Figure 5 is a histogram of effective porosity data of a group A core of an A oil reservoir provided in an embodiment of this specification;

[0016] Figure 6 is a bar graph of horizontal permeability data of a core of a group A of an oil reservoir A provided in an embodiment of this specification;

[0017] Figure 7 is a bar graph of effective porosity data of group B cores of reservoir A provided in the embodiments of this specification;

[0018] Figure 8 is a bar graph of horizontal permeability data of the core of Group B of the A oil reservoir provided in the embodiments of this specification;

[0019] Fig. 9 It is a schematic diagram of rock-forming mineral types and composition of oil reservoir A provided in the embodiments of this specification;

[0020] Fig.10 It is a schematic diagram of clay mineral types and compositions of oil reservoir A provided in the examples of this specification;

[0021] Fig.11 It is a data graph of CO2 injection volume and core recovery degree / gasoline ratio under the simulated A reservoir environment provided in the embodiments of this specification;

[0022] Fig.12 It is a schematic diagram of a comparison bar graph of the recovery degree of the first core and the second core under the simulated A reservoir environment provided in the embodiments of this specification and a fitting curve of the second core;

[0023] Fig.13 It is a schematic diagram of the structure of a device for determining the lower limit of permeability difference provided in an embodiment of this specification;

[0024] Fig.14 It is a schematic diagram of the structural composition of a computer device provided in an embodiment of this specification. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this specification.

[0026] Permeability refers to the ability of rock to allow fluid to pass under a certain pressure difference. It is a parameter that characterizes the ability of soil or rock itself to conduct liquid. The size of permeability is related to factors such as porosity, the geometry of the voids in the direction of liquid penetration, particle size and arrangement direction, but has nothing to do with the properties of the liquid moving in the medium. The unit of permeability is the square of length, which is the same as the unit of area, but in the field of petroleum technology, the commonly used unit is millidarcy (mD).

[0027] Permeability difference is an important parameter that reflects the amplitude of permeability change, indicating the distribution range and degree of difference of permeability. Its calculation formula is: Permeability difference = maximum permeability / minimum permeability. Specifically, the maximum permeability value in the reservoir can be selected as the maximum permeability and the minimum permeability value in the reservoir can be selected as the minimum permeability. Then, the maximum permeability can be divided by the minimum permeability to obtain the value of the permeability difference. The permeability difference is used to characterize the heterogeneity of the reservoir pore space. The larger the permeability difference, the stronger the heterogeneity of the reservoir pore space; conversely, the closer the permeability difference is to 1, the better the homogeneity of the reservoir pore space. The permeability difference is one of the important indicators for evaluating reservoir heterogeneity. In the development of oil and gas fields, the size of the permeability difference directly affects the production and development effect of oil and gas wells. The larger the permeability difference, the stronger the heterogeneity of the reservoir, and the worse the production and development effect of oil and gas wells may be. Therefore, in the process of oil and gas field exploration and development, it is necessary to conduct in-depth research and analysis on the permeability differential in order to formulate a reasonable development plan.

[0028] Figure 1 This is a flow chart of a method for determining the lower limit of permeability difference provided in an embodiment of this specification. In specific implementation, the method includes the following steps:

[0029] S101: Calculate a permeability difference set of a target oil reservoir according to target oil reservoir data; the permeability difference set corresponds to multiple groups of cores; any group of cores in the multiple groups of cores includes a first core and a second core; the permeability of the first core is greater than the permeability of the second core.

[0030] In some embodiments, the permeability interval of the target oil reservoir may be determined based on the target oil reservoir data; and a plurality of cores having permeabilities within the permeability interval may be obtained.

[0031] By generating multiple cores with permeabilities in the target reservoir permeability range based on the target reservoir data, a foundation is laid for oil displacement experiments based on cores with different permeabilities.

[0032] The target reservoir data covers various geological, fluid and reserve information related to the target reservoir. Geological information can specifically include structural data and sedimentary data. Structural data include information such as structural morphology, fault distribution, formation thickness, formation temperature and formation pressure of the target reservoir. Sedimentary data involves information such as sedimentary phase, sedimentary environment, sand body distribution, lithology, porosity, and permeability distribution. Fluid information can specifically include crude oil properties and formation water properties. Crude oil properties include temperature, viscosity, density, freezing point, wax content, gas content, sulfur content, initial distillation point, etc. of crude oil in the target reservoir. Formation water properties include information such as density, pH value, and total mineralization of formation water. Reserve information can specifically include oil-bearing area and reserves. The oil-bearing area refers to the area enclosed by the intersection of the oil-water contact surface and the top surface of the oil-bearing layer. Reserves include information such as geological reserves and recoverable reserves. Geological reserves refer to the total amount of oil and gas originally existing in the target reservoir, while recoverable reserves refer to the amount of oil and gas that can be recovered under existing technical and economic conditions. The permeability range of the target reservoir can be determined based on the lithology, porosity, and permeability distribution information of the formation in the target reservoir data. According to the mineral composition and permeability range of the target reservoir, the crushed gravel powder, sand and clay mineral components of the formation where the target reservoir is located with different mesh sizes can be selected and combined, and then multiple cores with permeabilities in the permeability range of the target reservoir can be generated.

[0033] In some embodiments, according to the permeability of the multiple cores, the multiple cores can be divided into multiple first cores and multiple second cores; according to the permeability of the multiple first cores and the permeability of the multiple second cores, a permeability difference set of the target oil reservoir can be combined to generate.

[0034] By dividing multiple cores into multiple first cores and multiple second cores and combining them to generate a permeability difference set of the target oil reservoir, a foundation is laid for conducting oil displacement experiments based on the multiple first cores and multiple second cores, and then the permeability difference lower limit of the permeability difference set is determined according to the degree of crude oil recovery from the multiple first cores and multiple second cores.

[0035] After determining the permeability interval of the target reservoir and generating multiple cores with permeabilities in the permeability interval of the target reservoir, a starting permeability can be selected based on the lithology, porosity, permeability distribution and other information in the target reservoir data. Specifically, the starting permeability can be determined based on the average permeability or typical permeability of the formation. In the absence of specific data, the permeability data of similar formations can be referenced or estimated based on experience. For example, for sandstone reservoirs, the starting permeability can be selected in the range of 1mD to 100mD, and the specific value depends on the permeabilities of the multiple cores generated. After determining the starting permeability, a permeability range within the permeability interval of the target reservoir can be set based on the permeabilities of the multiple cores generated. This permeability range covers the permeability changes that may occur in the formation, so that the fluid flow characteristics of the formation can be more fully understood in subsequent simulations or experiments. For example, if the starting permeability is selected at 10mD, the permeability interval can be set to 1mD to 100mD, or wider, such as 0.1mD to 1000mD. After determining the permeability range, different permeabilities can be uniformly selected within the permeability range to form a gradual permeability set. Each permeability in the permeability set corresponds to a generated core. This gradual permeability set can reflect the continuous change of permeability in the formation. The permeability values ​​can be selected in the permeability range in an approximate arithmetic progression or an approximate geometric progression according to the generated multiple cores. For example, if the permeability range is set to 0.1mD to 100mD, the following permeability values ​​can be selected to form a gradual permeability set: 0.5mD, 1mD, 2mD, 5mD, 10mD, 20mD, 50mD, 100mD. Each value corresponds to a generated core. These values ​​are evenly distributed within the permeability range and can better reflect the continuous change of permeability in the formation.

[0036] Multiple cores with permeabilities in a set permeability range can be divided to obtain multiple first cores and multiple second cores. The permeability of any first core is greater than the permeability of any second core. A permeability difference set of a target reservoir can be generated based on the permeabilities of multiple first cores and multiple second cores. For example, if the permeability range is set to 0.1mD to 100mD, and the permeabilities of multiple cores in this permeability range are 0.5mD, 1mD, 2mD, 5mD, 10mD, 20mD, 50mD, and 100mD, respectively. These cores can be divided according to the permeability to obtain multiple first cores with permeabilities of 10mD, 20mD, 50mD, and 100mD, respectively, and multiple second cores with permeabilities of 0.5mD, 1mD, 2mD, and 5mD, respectively. The first cores can be sorted in ascending order of permeability, and the second cores can be sorted in descending order of permeability. The sorted multiple first cores and multiple second cores are combined in pairs in order, and the permeability of the first core is divided by the permeability of the second core, and the permeability difference set obtained is {2, 10, 50, 200}.

[0037] In some embodiments, a mineral sample of the target oil reservoir may be obtained; the mineral sample of the target oil reservoir may be analyzed to determine the mineral composition of the target oil reservoir; and based on the mineral composition of the target oil reservoir, a plurality of cores having permeabilities in the permeability range may be obtained.

[0038] By analyzing the mineral samples of the target oil reservoir to determine the mineral composition of the target oil reservoir, the core permeability can be regulated as needed based on the mineral composition of the target oil reservoir, laying the foundation for oil displacement experiments based on cores with different permeabilities.

[0039] Reference Figure 2, the original clastic sandstone mineral sample that can reflect the geological characteristics of the target reservoir can be collected from the target reservoir. The collected mineral sample can be crushed to an appropriate size for mineral analysis. Further using X-ray diffraction (XRD), scanning electron microscopy (SEM) and other analytical techniques, the mineral composition and relative content in the mineral sample can be determined, which will not be repeated here. After determining the mineral composition of the target reservoir, the crushed gravel powder and sand can be screened using sieves of different meshes. The mesh number indicates how many holes per inch there are on the sieve. The larger the mesh number, the smaller the pore size. According to the mineral composition and permeability range of the target reservoir, crushed gravel powder, sand and clay mineral components of different mesh numbers can be selected and combined to generate multiple cores with permeabilities in the permeability range of the target reservoir. By adjusting the medium gravel particle size and the mesh number of quartz sand, the permeability of the core can be precisely controlled. Preferably, selecting a suitable mold can ensure that a core of a preset size can be formed. The combined mineral material can be placed in the mold. The core is filled according to the designed pressure to ensure that the mineral materials are tightly combined and form a core with a certain strength and permeability. After the filling is completed, the core can be removed from the mold. The core can be subjected to necessary post-processing, such as cleaning, drying, etc., to remove excess impurities and moisture.

[0040] In some embodiments, the multiple first cores and the multiple second cores can be combined to obtain multiple groups of cores; based on the ratio of the permeability of the first cores to the permeability of the second cores in each group of cores, the permeability difference corresponding to each group of cores can be determined; based on the permeability difference corresponding to each group of cores, a permeability difference set of the target oil reservoir can be generated.

[0041] By combining multiple first cores and multiple second cores to generate multiple groups of cores and permeability difference sets of target oil reservoirs, a foundation is laid for conducting oil displacement experiments based on multiple groups of cores, and then the permeability difference lower limit of the permeability difference set is determined according to the degree of crude oil recovery from multiple groups of cores.

[0042] The first cores are sorted in ascending order of permeability, and the second cores are sorted in descending order of permeability. The sorted multiple first cores and multiple second cores are combined in order to obtain multiple groups of cores. The permeability difference corresponding to each group of cores is determined by dividing the permeability of the first core in each group of cores by the permeability of the second core. According to the permeability difference corresponding to each group of cores, a permeability difference set of the target reservoir can be obtained. For example, for multiple first cores with permeabilities of 10mD, 20mD, 50mD, and 100mD, respectively, and multiple second cores with permeabilities of 0.5mD, 1mD, 2mD, and 5mD, respectively, after sorting them, a first core permeability set of {10mD, 20mD, 50mD, 100mD} and a second core permeability set of {5mD, 2mD, 1mD, 0.5mD} can be obtained. We can start from the first digit of the two sets and match them in pairs, and get four groups of cores: {10mD, 5mD}, {20mD, 2mD}, {50mD, 1mD}, and {100mD, 0.5mD}. Divide the permeability of the first core in each group of cores by the permeability of the second core, and get the permeability difference corresponding to each group of cores as 2, 10, 50, and 200, respectively. Based on the permeability difference corresponding to each group of cores, we can determine that the permeability difference set of the target reservoir is {2, 10, 50, 200}.

[0043] S102: Obtaining the crude oil recovery degree of the multiple groups of cores under the simulated target reservoir environment.

[0044] In some embodiments, the target oil reservoir data may include temperature data and pressure data of the target oil reservoir; the environment of the target oil reservoir may be simulated based on the temperature data and pressure data of the target oil reservoir formation; crude oil under the simulated target oil reservoir environment may be obtained; and the crude oil may be injected into the multiple groups of cores.

[0045] According to the target reservoir data, crude oil that meets the real environment of the target reservoir can be generated, and then the crude oil can be injected into the prepared multiple groups of cores to conduct oil displacement experiments on multiple groups of cores.

[0046] A device capable of simulating a high temperature and high pressure environment may be prepared, such as a high temperature and high pressure reactor or a simulated wellbore. The temperature and pressure parameters of the simulation device may be set according to the temperature data and pressure data of the target reservoir formation in the target reservoir data. Other geological conditions of the target reservoir, such as formation water content, salinity, etc., may also be simulated according to the target reservoir data. The simulation device may be started and allowed to run stably for a period of time at the set temperature and pressure to ensure that the environment reaches a stable state.

[0047] According to the crude oil characteristics (such as API gravity, sulfur content, wax content, etc.) in the target reservoir data, a suitable crude oil sample can be selected or prepared. The crude oil sample can be placed in a simulation device and subjected to heat treatment or chemical treatment at a set temperature and pressure to simulate the change process of the crude oil in the formation. After the simulation is completed, the crude oil sample can be analyzed for properties such as density, viscosity, component distribution, etc. to ensure that it meets the crude oil characteristics of the target reservoir. After the crude oil that meets the target reservoir is prepared, a device that can accurately control the injection pressure and flow rate, such as a high-pressure injection pump, can be prepared. The core and the crude oil injection device can be connected to ensure a good seal. According to the target reservoir data, the pressure and flow parameters of the injection device can be set to meet the actual conditions of the target reservoir. The injection device is started and the crude oil is injected into multiple groups of cores. After the injection is completed, the fluid distribution and property changes of the core can be observed. Appropriate analytical techniques (such as X-ray CT scanning, nuclear magnetic resonance, etc.) can be used to evaluate the flow behavior and retention of crude oil in the core to ensure that it meets the flow behavior characteristics and retention of the target reservoir.

[0048] In some embodiments, based on the target reservoir data, an oil-displacing medium under the simulated target reservoir environment can be generated; the oil-displacing medium can be injected into multiple groups of cores under the simulated target reservoir environment to obtain the degree of crude oil recovery of multiple first cores and multiple second cores in the multiple groups of cores under the simulated target reservoir environment.

[0049] By injecting oil displacement media into multiple groups of cores in a simulated target reservoir environment, the crude oil recovery levels of multiple first cores and multiple second cores in the multiple groups of cores in the simulated target reservoir environment can be obtained, laying a data foundation for determining the lower limit of the permeability difference based on the crude oil recovery levels of multiple second cores in the simulated target reservoir environment.

[0050] According to the target reservoir data, the component data of the oil recovery medium such as CO2 can be determined, including purity, impurity content (such as nitrogen, oxygen, carbon monoxide, sulfide, etc.) and other possible chemical components. Existing CO2 gas sources can be selected, such as associated gas from natural gas fields, CO2 recovery from industrial waste gas, etc. If the existing gas source does not meet the requirements, consider chemical preparation or physical separation to obtain CO2 of the required purity, which will not be repeated here. Appropriate purification technologies such as adsorption, membrane separation, and low-temperature separation can be used to purify the selected CO2 gas source to remove impurities that do not meet the requirements. After purification, analytical instruments such as gas chromatographs and mass spectrometers can be used to perform quality control analysis on the CO2 gas source to ensure that it meets the purity and other component requirements. The appropriate injection pressure can be determined based on the formation pressure and target injection depth in the target reservoir data, as well as the pressure difference between the production well and the production layer and the appropriate ambient temperature. Reference Figure 3, gas injection and oil recovery can be carried out in a pre-built experimental device including injection system, production system, data acquisition system and other equipment. Qualified CO2 gas source can be injected into multiple groups of cores. According to the target reservoir data, the injection pressure and flow rate are controlled, and the pressure and flow rate changes during the injection process are recorded. After CO2 is injected, the degree of crude oil recovery of multiple first cores and multiple second cores in multiple groups of cores under the simulated target reservoir environment can be observed and recorded.

[0051] S103: Determine the lower limit of the permeability difference of the target reservoir in the permeability difference set according to the crude oil recovery degree of the multiple groups of cores under the simulated target reservoir environment.

[0052] In some embodiments, the crude oil recovery rates of multiple second cores under simulated target reservoir environment may be fitted to generate a recovery curve; based on the recovery curve, the lower limit of the permeability difference of the target reservoir in the permeability difference set may be determined.

[0053] By fitting the crude oil recovery degree of multiple second cores in the simulated target reservoir environment, the changing relationship between the crude oil recovery degree and the permeability difference in the target reservoir environment can be accurately simulated, and then the lower limit of the permeability difference of the target reservoir can be determined based on this changing relationship.

[0054] After obtaining the crude oil recovery degree of multiple second cores under the simulated target reservoir environment, the second permeability and crude oil recovery degree corresponding to the multiple second cores can be fitted. The fitting model can be a linear regression, polynomial regression, exponential regression and other models. For example, a polynomial regression model can be used to fit the second permeability and crude oil recovery degree corresponding to the multiple second cores. Specifically, the second permeability and crude oil recovery degree corresponding to the multiple second cores can be checked to ensure that there are no missing values ​​or outliers. If there are, interpolation, deletion or replacement can be performed. The second permeability corresponding to the multiple second cores can be used as the x-axis and the recovery degree corresponding to the multiple second cores can be used as the y-axis to draw a scatter plot. By observing the scatter plot, it can be preliminarily determined whether there is a nonlinear relationship between the second permeability and the recovery degree. According to the trend of the scatter plot and the distribution of data points, a suitable polynomial order can be selected. The higher the order, the more complex the curve that the model can fit, but it may also lead to overfitting, which will not be described here. The polynomial regression function in statistical software (such as R, SAS) or programming language (such as Python) can be used for fitting. For example, in Python, you can use the polynomial regression function of libraries such as numpy and scikit-learn for fitting. After fitting the second permeability and crude oil recovery corresponding to multiple second cores, you can get the coefficients of the fitted recovery curve, which determine the shape of the recovery curve. The recovery curve fitting effect can be evaluated using indicators such as mean square error (MSE) and root mean square error (RMSE), which will not be described here.

[0055] The trend of the generated recovery curve can be observed to identify the point where the recovery begins to drop significantly. Based on the corresponding value of this point, the candidate value of the lower limit of the permeability difference can be determined. Specifically, on the recovery curve, a point that intersects with a preset recovery threshold (such as economically recoverable recovery) can be found. Based on the corresponding value of this point, the lower limit of the permeability difference can be determined. After determining the lower limit of the permeability difference, the determined lower limit of the permeability difference can be verified. The rationality of the determined lower limit of the permeability difference can be verified by comparing it with the actual reservoir data or by further simulation experiments. If the verification result shows that the lower limit value does not match the actual situation, corresponding adjustments need to be made, which will not be repeated here.

[0056] In some embodiments, based on the recovery degree curve, the second core corresponding to the preset recovery degree threshold can be determined; based on the second core corresponding to the preset recovery degree threshold, the corresponding permeability difference can be queried in the permeability difference set; based on the queried permeability difference, the lower limit of the permeability difference of the target oil reservoir can be determined.

[0057] By determining the second core corresponding to the preset recovery degree threshold when the recovery degree is reached, the lower limit of the permeability difference of the target oil reservoir can be accurately determined based on the permeability difference corresponding to the second core.

[0058] After determining the recovery degree curve, the preset recovery degree threshold can be substituted into the recovery degree curve to obtain the permeability corresponding to the preset recovery degree threshold. According to the permeability corresponding to the preset recovery degree threshold, the corresponding second core can be determined. According to the permeability of the second core, the corresponding permeability difference can be queried in the permeability difference set. The permeability difference obtained by the query can be used as the lower limit of the permeability difference of the target reservoir.

[0059] The method for determining the lower limit of permeability difference provided in the embodiment of this specification can calculate the permeability difference set of the target reservoir according to the target reservoir data; the permeability difference set corresponds to multiple groups of cores; any group of cores in the multiple groups of cores includes a first core and a second core; the permeability of the first core is greater than the permeability of the second core; the degree of crude oil recovery of the multiple groups of cores under the simulated target reservoir environment is obtained; the lower limit of the permeability difference of the target reservoir in the permeability difference set is determined according to the degree of crude oil recovery of the multiple groups of cores under the simulated target reservoir environment. The embodiment of this specification can clarify the influence of the permeability difference on the oil displacement effect of the target reservoir and the lower limit of the permeability difference of the target reservoir under the simulated target reservoir environment, and then guide the design of the heterogeneous reservoir development plan according to the lower limit of the permeability difference of the target reservoir.

[0060] The following introduces a specific scenario example of the embodiment of this specification.

[0061] 1.Reference Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Fig. 9 and Fig.10 The core data of the A and B reservoirs of Well A are shown. The dense sandstone cores with the size of 4.5 cm × 4.5 cm × 30 cm are prepared. The core preparation steps refer to Figure 2 :First, sample the original clastic sandstone of the target reservoir, crush it and analyze the mineral type and composition; second, select the crushed gravel powder of different meshes and sand of different meshes, mix the corresponding clay mineral components, adjust the medium gravel particle size and quartz sand mesh number, and realize the artificial core permeability regulation according to demand; finally, put it into the mold and press it according to the designed pressure to form the core of the target size / permeability. Reduce the instability of the core size to the experiment, and realize the production of artificial cores with a permeability of 0.01mD~400mD in the target reservoir.

[0062] 2. Use a high temperature and high pressure reactor to simulate the gas-bearing crude oil under the target reservoir formation temperature and pressure environment. The CO2 gas source is 99.99% pure gas source, and the CO2 viscosity is 0.07mPa·s under reservoir conditions. Figure 3 The experimental process combination is as follows, in which the core permeability difference adopts the gradual combination method, that is, the starting permeability is selected, and a range is set according to the formation characteristics. Different permeabilities are evenly selected within this range to form a gradual combination (the permeability difference set is 20.5, 9.6, 3.1, 2.6, 2.3, 2.0, 1.9).

[0063] 3. Carry out experimental research on gas injection to displace oil. Clarify important experimental parameters such as injection pressure, production and development pressure difference, ambient temperature, etc., and form an experimental chart of recovery degree / gasoline ratio, and refer to Fig.11 . Fig.11 This is a data chart about injection volume and recovery degree / gas-oil ratio. Fig.11 According to the gas situation, it is divided into initial gas stage, low gas stage and complete gas stage.

[0064] 4.Reference Fig.12 , the experimental data under different permeability differences were sorted out, and a comparison bar graph of the recovery degree of the first core / the second core was drawn. The recovery degree of the second core was fitted, and the recovery degree fitting curve of the second core y=-13.5ln(x)+24.715 was obtained. Through analysis, it can be considered that with the increase of the permeability difference, the recovery degree corresponding to the second core shows a logarithmic decrease. It can be calculated that when the permeability difference is 6, there is almost no produced liquid in the second core. It can be considered that the lower limit of the permeability difference for CO2 production is 6.

[0065] Based on the above-mentioned method for determining the lower limit of the permeability difference, this specification also proposes an embodiment of a device for determining the lower limit of the permeability difference. Fig.13 As shown, the permeability difference lower limit determining device 1300 may specifically include the following modules:

[0066] The calculation module 1301 can be used to calculate a permeability difference set of a target oil reservoir according to the target oil reservoir data; the permeability difference set corresponds to multiple groups of cores; any group of cores in the multiple groups of cores includes a first core and a second core; the permeability of the first core is greater than the permeability of the second core;

[0067] The acquisition module 1302 may be used to acquire the crude oil recovery degree of the plurality of core groups under the simulated target reservoir environment;

[0068] The determination module 1303 may be used to determine the lower limit of the permeability difference of the target reservoir in the permeability difference set according to the crude oil recovery degree of the multiple core groups under the simulated target reservoir environment.

[0069] In some embodiments, the above-mentioned calculation module 1301 can be specifically used to determine the permeability range of the target oil reservoir based on the target oil reservoir data; obtain multiple cores with permeabilities in the permeability range; divide the multiple cores into multiple first cores and multiple second cores based on the permeabilities of the multiple cores; and combine the permeabilities of the multiple first cores and the permeabilities of the multiple second cores to generate a permeability difference set of the target oil reservoir.

[0070] In some embodiments, the above-mentioned calculation module 1301 can also be specifically used to obtain mineral samples of the target oil reservoir; analyze the mineral samples of the target oil reservoir to determine the mineral composition of the target oil reservoir; and obtain multiple cores with permeabilities in the permeability range based on the mineral composition of the target oil reservoir.

[0071] In some embodiments, the above-mentioned calculation module 1301 can also be specifically used to combine the multiple first cores and the multiple second cores to obtain multiple groups of cores; the ratio of the permeability of the first cores and the permeability of the second cores in each group of cores is used to determine the permeability difference corresponding to each group of cores; based on the permeability difference corresponding to each group of cores, a permeability difference set of the target oil reservoir is generated.

[0072] In some embodiments, the acquisition module 1302 can be specifically used to simulate the environment of the target reservoir according to the temperature data and pressure data of the target reservoir formation; obtain crude oil under the simulated target reservoir environment; and inject the crude oil into multiple groups of cores under the simulated target reservoir environment.

[0073] In some embodiments, the acquisition module 1302 can also be used to generate an oil-displacing medium under the simulated target reservoir environment based on the target reservoir data; inject the oil-displacing medium into multiple groups of cores under the simulated target reservoir environment to obtain the degree of crude oil recovery of multiple first cores and multiple second cores in the multiple groups of cores under the simulated target reservoir environment.

[0074] In some embodiments, the above-mentioned determination module 1303 can be specifically used to fit the crude oil recovery degree of multiple second cores in a simulated target reservoir environment to generate a recovery degree curve; based on the recovery degree curve, determine the lower limit of the permeability difference of the target reservoir in the permeability difference set.

[0075] In some embodiments, the above-mentioned determination module 1303 can also be specifically used to determine, based on the recovery degree curve, a second core corresponding to a preset recovery degree threshold value; based on the second core corresponding to the preset recovery degree threshold value, query the corresponding permeability difference in the permeability difference set; and determine the lower limit of the permeability difference of the target oil reservoir based on the queried permeability difference.

[0076] It should be noted that the units, devices or modules described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. For the convenience of description, the above devices are described separately by functions divided into various modules. Of course, when implementing this specification, the functions of each module can be implemented in the same or more software and / or hardware, or the modules that implement the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0077] As can be seen from the above, based on the permeability difference lower limit determination device provided in the embodiment of this specification, the permeability difference set of the target oil reservoir can be calculated according to the target oil reservoir data; the permeability difference set corresponds to multiple groups of cores; any group of cores in the multiple groups of cores includes a first core and a second core; the permeability of the first core is greater than the permeability of the second core; the degree of crude oil recovery of the multiple groups of cores under the simulated target oil reservoir environment is obtained; according to the degree of crude oil recovery of the multiple groups of cores under the simulated target oil reservoir environment, the permeability difference lower limit of the target oil reservoir in the permeability difference set is determined. The embodiment of this specification can simulate the environment of the target oil reservoir to clarify the influence of the permeability difference on the oil displacement effect of the target oil reservoir and the permeability difference lower limit of the target oil reservoir under the simulated target oil reservoir environment, and then guide the design of the heterogeneous oil reservoir development plan according to the permeability difference lower limit of the target oil reservoir.

[0078] The embodiments of the present specification also provide a computer device for determining a lower limit of a permeability difference, comprising a processor and a memory for storing instructions executable by the processor, wherein the processor can perform the following steps according to the instructions when implemented: calculating a permeability difference set of a target reservoir according to target reservoir data; the permeability difference set corresponds to multiple groups of cores; any group of cores in the multiple groups of cores includes a first core and a second core; the permeability of the first core is greater than the permeability of the second core; obtaining the degree of crude oil recovery of the multiple groups of cores under a simulated target reservoir environment; and determining the lower limit of the permeability difference of the target reservoir in the permeability difference set according to the degree of crude oil recovery of the multiple groups of cores under a simulated target reservoir environment.

[0079] In order to complete the above instructions more accurately, refer to Fig.14As shown, the embodiment of this specification also provides another specific computer device 1400, wherein the computer device 1400 includes a network communication port 1401, a processor 1402 and a memory 1403, and the above structures are connected through internal cables so that each structure can perform specific data interaction.

[0080] The processor 1402 can be specifically used to calculate a permeability difference set of a target oil reservoir based on target oil reservoir data; the permeability difference set corresponds to multiple groups of cores; any group of cores in the multiple groups of cores includes a first core and a second core; the permeability of the first core is greater than the permeability of the second core; obtain the degree of crude oil recovery of the multiple groups of cores under a simulated target oil reservoir environment; determine the lower limit of the permeability difference of the target oil reservoir in the permeability difference set based on the degree of crude oil recovery of the multiple groups of cores under a simulated target oil reservoir environment.

[0081] The memory 1403 may be specifically used to store corresponding instruction programs.

[0082] In this embodiment, the network communication port 1401 can be a virtual port that is bound to different communication protocols so that different data can be sent or received. For example, the network communication port can be a port responsible for web data communication, a port responsible for FTP data communication, or a port responsible for email data communication. In addition, the network communication port can also be a physical communication interface or communication chip. For example, it can be a wireless mobile network communication chip, such as GSM, CDMA, etc.; it can also be a Wifi chip; it can also be a Bluetooth chip.

[0083] In this embodiment, the processor 1402 may be implemented in any appropriate manner. For example, the processor may take the form of a microprocessor or processor and a computer-readable medium storing a computer-readable program code (such as software or firmware) executable by the (micro)processor, a logic gate, a switch, an application specific integrated circuit (ASIC), a programmable logic controller, and an embedded microcontroller, etc. This specification does not limit this.

[0084] In this embodiment, the memory 1403 includes a volatile memory and a non-volatile memory. The memory 1403 may include multiple levels. In a digital system, anything that can store binary data can be a memory; in an integrated circuit, a circuit with a storage function without a physical form is also called a memory, such as RAM, FIFO, etc.; in a system, a storage device with a physical form is also called a memory, such as a memory stick, TF card, etc.

[0085] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0086] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0087] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0088] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0089] The specific embodiments 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 embodiment 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 method for determining the lower limit of permeability difference, characterized in that: include: Calculating a permeability difference set of the target reservoir according to the target reservoir data; the permeability difference set corresponds to multiple groups of cores; Any group of cores in the plurality of groups of cores includes a first core and a second core; the permeability of the first core is greater than the permeability of the second core; Obtaining the crude oil recovery degree of the plurality of core groups under a simulated target reservoir environment; According to the crude oil recovery degree of the plurality of core groups under the simulated target reservoir environment, the lower limit of the permeability difference of the target reservoir in the permeability difference set is determined.

2. The method according to claim 1, characterized in that: The step of calculating the permeability difference set of the target reservoir according to the target reservoir data includes: Determine the permeability range of the target reservoir based on the target reservoir data; Acquire a plurality of cores having permeabilities in the permeability range; Dividing the plurality of cores into a plurality of first cores and a plurality of second cores according to the permeability of the plurality of cores; A permeability difference set of the target oil reservoir is generated based on the permeabilities of the plurality of first cores and the permeabilities of the plurality of second cores.

3. The method according to claim 2, characterized in that: The obtaining of a plurality of cores having permeabilities in the permeability range includes: obtaining a mineral sample of the target oil reservoir; Analyzing a mineral sample of the target oil reservoir to determine the mineral composition of the target oil reservoir; According to the mineral composition of the target oil reservoir, a plurality of cores with permeabilities in the permeability range are obtained.

4. The method according to claim 2, characterized in that: The step of generating a permeability difference set of the target oil reservoir based on the permeabilities of the plurality of first cores and the permeabilities of the plurality of second cores comprises: Combining the plurality of first cores and the plurality of second cores to obtain a plurality of groups of cores; According to the ratio of the permeability of the first core to the permeability of the second core in each group of cores, the permeability difference corresponding to each group of cores is determined; According to the permeability differences corresponding to each group of cores, a permeability difference set of the target oil reservoir is generated.

5. The method according to claim 1, characterized in that: The target oil reservoir data includes temperature data and pressure data of the target oil reservoir; The method further comprises: Simulating the environment of the target oil reservoir according to the temperature data and pressure data of the target oil reservoir formation; Obtaining crude oil in the simulated target reservoir environment; The crude oil is injected into multiple groups of cores in the simulated target reservoir environment.

6. The method according to claim 1, characterized in that: The step of obtaining the crude oil recovery degree of the plurality of core groups under the simulated target reservoir environment includes: generating an oil displacement medium under the simulated target reservoir environment according to the target reservoir data; The oil displacement medium is injected into a plurality of groups of cores in a simulated target reservoir environment to obtain the crude oil recovery extent of a plurality of first cores and a plurality of second cores in the plurality of groups of cores in the simulated target reservoir environment.

7. The method according to claim 1, characterized in that: The step of determining the lower limit of the permeability difference of the target reservoir in the permeability difference set according to the crude oil recovery degree of the multiple core groups under the simulated target reservoir environment includes: Fitting the crude oil recovery rates of multiple second cores in a simulated target reservoir environment to generate a recovery rate curve; According to the recovery degree curve, the lower limit of the permeability difference of the target reservoir in the permeability difference set is determined.

8. The method according to claim 7, characterized in that: Determining the lower limit of the permeability difference of the target reservoir in the permeability difference set according to the recovery degree curve includes: According to the recovery degree curve, determining a second core corresponding to a recovery degree that is a preset recovery degree threshold; According to the second core corresponding to the recovery degree being a preset recovery degree threshold, querying the corresponding permeability difference in the permeability difference set; The lower limit of the permeability difference of the target reservoir is determined according to the queried permeability difference.

9. A device for determining a lower limit of a permeability difference, characterized in that: The device comprises: A calculation module, for calculating a permeability difference set of a target oil reservoir according to the target oil reservoir data; the permeability difference set corresponds to a plurality of groups of cores; any group of cores in the plurality of groups of cores includes a first core and a second core; the permeability of the first core is greater than the permeability of the second core; An acquisition module, used for acquiring the crude oil recovery degree of the plurality of core groups under a simulated target reservoir environment; The determination module is used to determine the lower limit of the permeability difference of the target reservoir in the permeability difference set according to the crude oil recovery degree of the multiple groups of cores under the simulated target reservoir environment.

10. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 8 is implemented.

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