Rock core permeability measuring method and device

Abstract

The invention provides a rock core permeability measuring method and device, and the method comprises the steps: controlling an injection pump to inject a preset fluid in a first intermediate container into an upstream container of a rock core slice until the pressure in the upstream container of the rock core slice is equal to a first preset pressure; wherein the preset fluid is any one of formation water, drilling fluid, fracturing fluid and an oil displacement agent; controlling an injection pump to inject the crude oil sample in the second intermediate container into a downstream container of the core slice until the pressure in the downstream container of the core slice is equal to a second preset pressure; wherein the second preset pressure is smaller than the first preset pressure; monitoring the change of the pressure in the downstream container of the rock core slice, and determining a change curve of the pressure in the downstream container of the rock core slice along with the passing time; in the monitoring process, the pressure in the upstream container of the rock core slice is controlled to be kept unchanged at the first preset pressure all the time; and determining the rock core permeability according to the change curve of the pressure in the downstream container of the rock core slice along with the passing time.

Description

Technical Field

[0001] The present invention relates to the field of oil exploration, and particularly to a method and device for measuring core permeability. Background Art

[0002] This section aims to provide background or context for the embodiments of the present invention described in the claims. The description herein is not admitted to be prior art merely by virtue of being included in this section.

[0003] Heterogeneous tight reservoirs such as tight sandstone and carbonate rock are widely distributed, and the proportion of tight sandstone and carbonate rock in the proven geological reserves is increasing. Compared with medium-high permeability oil reservoirs, low-permeability reservoirs are more compact and have lower permeability, resulting in the reservoir being more sensitive to the influence of external fluids. External fluids in the exploration and production process, such as fracturing fluid, drilling fluid or oil displacement agent, will all affect the reservoir permeability. For example, the solid-phase damage of fracturing fluid and drilling fluid will cause an instantaneous drop in permeability, leading to a sharp decline in productivity. Therefore, how to accurately measure the permeability of downhole rock samples in the reservoir when applying different external fluids, and then provide an optimization direction for the liquid system in oilfield development, has become the basis and key for the development of tight sandstone reservoirs.

[0004] Conventional steady-state methods in the prior art include: water measurement method and gas measurement method. There are great uncertainties in the conventional steady-state method testing methods. Among them, the displacement efficiency of the water measurement method is low, and the displacement fluid may not be able to displace through the entire core sample, resulting in too high a leading-edge displacement pressure and unable to quickly and accurately measure the permeability of the core sample; the slippage effect of the gas measurement method will cause a large difference between the gas-measured permeability and the true permeability of the core, making the permeability measurement result inaccurate. Summary of the Invention

[0005] In an embodiment of the present invention, a method for measuring core permeability is proposed to improve the accuracy of core permeability measurement, improve the measurement efficiency of core permeability, and provide data support for oilfield exploration and development, including:

[0006] Controlling an injection pump to inject a preset fluid in a first intermediate container into an upstream container of a core slice until the pressure in the upstream container of the core slice is equal to a first preset pressure; wherein, the preset fluid is any one of formation water, drilling fluid, fracturing fluid, and oil displacement agent; the core slice is placed at a preset position of a core holder, and the core slice divides the internal space of the core holder into a sealed space at the top of the core slice and a sealed space at the bottom of the core slice; the upstream container of the core slice is the sealed space at the top of the core slice; the first intermediate container is communicated with the upstream container of the core slice through the injection pump;

[0007] Control the injection pump to inject the crude oil sample in the second intermediate container into the downstream container of the core slice until the pressure in the downstream container of the core slice is equal to the second preset pressure; wherein, the second preset pressure is less than the first preset pressure; the downstream container of the core slice is the sealed space at the bottom of the core slice; the second intermediate container is connected to the downstream container of the core slice through the injection pump;

[0008] Monitor the change of the pressure in the downstream container of the core slice, and determine the change curve of the pressure in the downstream container of the core slice with the elapsed time; during the monitoring process, control the pressure in the upstream container of the core slice to always remain unchanged at the first preset pressure;

[0009] Determine the core permeability according to the change curve of the pressure in the downstream container of the core slice with the elapsed time.

[0010] In the embodiment of the present invention, a core permeability measuring device is proposed to improve the accuracy of core permeability measurement, improve the measurement efficiency of core permeability, and provide data support for oilfield exploration and development, including:

[0011] The first control module is used to control the injection pump to inject the preset fluid in the first intermediate container into the upstream container of the core slice until the pressure in the upstream container of the core slice is equal to the first preset pressure; wherein, the preset fluid is any one of formation water, drilling fluid, fracturing fluid, and oil displacement agent; the core slice is placed at a preset position of the core holder, and the core slice divides the internal space of the core holder into a sealed space at the top of the core slice and a sealed space at the bottom of the core slice; the upstream container of the core slice is the sealed space at the top of the core slice; the first intermediate container is connected to the upstream container of the core slice through the injection pump;

[0012] The second control module is used to control the injection pump to inject the crude oil sample in the second intermediate container into the downstream container of the core slice until the pressure in the downstream container of the core slice is equal to the second preset pressure; wherein, the second preset pressure is less than the first preset pressure; the downstream container of the core slice is the sealed space at the bottom of the core slice; the second intermediate container is connected to the downstream container of the core slice through the injection pump;

[0013] The pressure monitoring module is used to monitor the change of the pressure in the downstream container of the core slice, and determine the change curve of the pressure in the downstream container of the core slice with the elapsed time; during the monitoring process, control the pressure in the upstream container of the core slice to always remain unchanged at the first preset pressure;

[0014] The permeability determination module is used to determine the core permeability according to the change curve of the pressure in the downstream container of the core slice with the elapsed time.

[0015] In an embodiment of the present invention, a computer device is provided, which includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, a core permeability measurement method is implemented.

[0016] In an embodiment of the present invention, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, a core permeability measurement method is implemented.

[0017] In an embodiment of the present invention, a computer program product is provided. The computer program product includes a computer program, and when the computer program is executed by a processor, a core permeability measurement method is implemented.

[0018] The core permeability measurement method and device proposed in the embodiments of the present invention can solve the problem of low accuracy and efficiency in core permeability measurement in the prior art. In the embodiments of the present invention, a preset fluid in a first intermediate container is injected into the upstream container of the core slice by controlling an injection pump until the pressure in the upstream container of the core slice is equal to a first preset pressure. Wherein, the preset fluid is any one of formation water, drilling fluid, fracturing fluid, and oil displacement agent. The core slice is placed at a preset position of a core holder, and the core slice divides the internal space of the core holder into a sealed space at the top of the core slice and a sealed space at the bottom of the core slice. The upstream container of the core slice is the sealed space at the top of the core slice. The first intermediate container is connected to the upstream container of the core slice through an injection pump. The crude oil sample in a second intermediate container is injected into the downstream container of the core slice by controlling the injection pump until the pressure in the downstream container of the core slice is equal to a second preset pressure. Wherein, the second preset pressure is less than the first preset pressure. The downstream container of the core slice is the sealed space at the bottom of the core slice. The second intermediate container is connected to the downstream container of the core slice through an injection pump. The change in the pressure in the downstream container of the core slice is monitored to determine the change curve of the pressure in the downstream container of the core slice with the elapsed time. During the monitoring process, the pressure in the upstream container of the core slice is controlled to always remain unchanged at the first preset pressure. The core permeability is determined according to the change curve of the pressure in the downstream container of the core slice with the elapsed time. The embodiments of the present invention can improve the accuracy of core permeability measurement, improve the measurement efficiency of core permeability, and provide data support for oilfield exploration and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a schematic flow diagram of the core permeability measurement method according to an embodiment of the present invention;

[0021] Figure 2 It is a schematic diagram of the core permeability test experimental device according to an embodiment of the present invention;

[0022] Figure 3 It is a schematic structural diagram of a core slice according to an embodiment of the present invention;

[0023] Figure 4 It is a specific example diagram of the core permeability measurement method according to an embodiment of the present invention;

[0024] Figure 5 It is a specific example diagram of the core permeability measurement method according to an embodiment of the present invention;

[0025] Figure 6 It is a specific example diagram of the core permeability measurement method according to an embodiment of the present invention;

[0026] Figure 7 It is a specific example diagram of the core permeability measurement method according to an embodiment of the present invention;

[0027] Figure 8 It is a specific example diagram of the core permeability measurement method according to an embodiment of the present invention;

[0028] Figure 9 It is a specific example diagram of the core permeability measurement method according to an embodiment of the present invention;

[0029] Figure 10 It is a schematic diagram of the core permeability measurement device according to an embodiment of the present invention;

[0030] Figure 11 It is a schematic diagram of a computer device in an embodiment of the present invention. Detailed implementation manners

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer and more understandable, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but not to limit the present invention.

[0032] The term "and / or" in this article only describes an associated relationship and indicates that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the term "at least one" in this article means any one of a plurality or any combination of at least two of a plurality. For example, including at least one of A, B, and C can represent any one or more elements selected from the set composed of A, B, and C.

[0033] In the description of this specification, the terms "comprising", "including", "having", "containing", etc. are all open-ended terms, meaning including but not limited to. The description with reference to terms such as "one embodiment", "one specific embodiment", "some embodiments", "for example", etc. means that the specific features, structures or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. The order of steps involved in each embodiment is used to schematically illustrate the implementation of the present application, and the order of steps is not limited and can be adjusted appropriately as needed.

[0034] The principles and spirit of the present invention will be explained in detail below with reference to several representative embodiments of the present invention.

[0035] Figure 1 is a schematic flow chart of the core permeability measurement method according to an embodiment of the present invention. As Figure 1 shown, the method includes:

[0036] Step 101, controlling an injection pump to inject a preset fluid in a first intermediate container into the upstream container of the core slice until the pressure in the upstream container of the core slice is equal to a first preset pressure; wherein, the preset fluid is any one of formation water, drilling fluid, fracturing fluid, oil displacement agent; the core slice is placed at a preset position of a core holder, and the core slice divides the internal space of the core holder into a sealed space at the top of the core slice and a sealed space at the bottom of the core slice; the upstream container of the core slice is the sealed space at the top of the core slice; the first intermediate container is connected to the upstream container of the core slice through the injection pump; the core slice is obtained from a tight reservoir;

[0037] Step 102, controlling the injection pump to inject a crude oil sample in a second intermediate container into the downstream container of the core slice until the pressure in the downstream container of the core slice is equal to a second preset pressure; wherein, the second preset pressure is less than the first preset pressure; the downstream container of the core slice is the sealed space at the bottom of the core slice; the second intermediate container is connected to the downstream container of the core slice through the injection pump;

[0038] Step 103, monitoring the change in the pressure in the downstream container of the core slice, and determining the change curve of the pressure in the downstream container of the core slice with the elapsed time; during the monitoring process, controlling the pressure in the upstream container of the core slice to always remain unchanged at the first preset pressure;

[0039] Step 104, determining the core permeability according to the change curve of the pressure in the downstream container of the core slice with the elapsed time.

[0040] ByFigure 1 As can be seen from the shown process, in the embodiment of the present invention, a preset fluid in a first intermediate container is injected into an upstream container of a core slice by controlling an injection pump until the pressure in the upstream container of the core slice is equal to a first preset pressure; wherein, the preset fluid is any one of formation water, drilling fluid, fracturing fluid, and oil displacement agent; the core slice is placed at a preset position of a core holder, and the core slice divides the internal space of the core holder into a sealed space at the top of the core slice and a sealed space at the bottom of the core slice; the upstream container of the core slice is the sealed space at the top of the core slice; the first intermediate container is communicated with the upstream container of the core slice through the injection pump; the injection pump is controlled to inject a crude oil sample in a second intermediate container into a downstream container of the core slice until the pressure in the downstream container of the core slice is equal to a second preset pressure; wherein, the second preset pressure is less than the first preset pressure; the downstream container of the core slice is the sealed space at the bottom of the core slice; the second intermediate container is communicated with the downstream container of the core slice through the injection pump; the change in the pressure in the downstream container of the core slice is monitored to determine a change curve of the pressure in the downstream container of the core slice with the elapsed time; during the monitoring process, the pressure in the upstream container of the core slice is controlled to always remain unchanged at the first preset pressure; the core permeability is determined according to the change curve of the pressure in the downstream container of the core slice with the elapsed time. The embodiment of the present invention can accurately measure the core permeability under different external fluids, improve the measurement efficiency of the core permeability, and provide data support for oilfield exploration and development.

[0041] In the embodiment of the present invention, by maintaining a constant pressure in the upstream container and measuring the change in the pressure in the downstream container, and by measuring the pressure transient decay instead of testing the flow of the fluid through the core. This method greatly reduces the test time and improves the measurement of permeability under different order-of-magnitude conditions (the lowest measurable permeability order of magnitude is 10-6 mD), and can quickly and efficiently evaluate the influence of drilling fluid, fracturing fluid or oil displacement agent on the core permeability.

[0042] Next, with reference to several representative embodiments of the present invention, the principles and spirits of the present invention will be elaborated in detail.

[0043] Figure 2 It is a schematic diagram of a core permeability test experimental device according to an embodiment of the present invention.

[0044] In an embodiment of the present invention, by using the unsteady-state pressure conduction theory and method, an unsteady-state pressure conduction instrument experiment (i.e., a core permeability test experimental device) is built; refer to Figure 2, the experimental system consists of an injection pump, a first intermediate container, a second intermediate container, a core holder, a pressure sensor, a data acquisition system, a nitrogen cylinder, and a graduated cylinder. The core slice is placed at a preset position in the core holder, and the core slice divides the internal space of the core holder into a sealed space at the top of the core slice and a sealed space at the bottom of the core slice; the upstream container of the core slice is the sealed space at the top of the core slice, and the downstream container of the core slice is the sealed space at the bottom of the core slice; the first intermediate container is connected to the upstream container of the core slice through the injection pump; the second intermediate container is connected to the downstream container of the core slice through the injection pump; control the injection pump to inject a preset fluid in the first intermediate container into the upstream container of the core slice, and the preset fluid is one of formation (salt) water, drilling fluid, fracturing fluid, and oil displacement agent; use the pressure sensor to monitor the pressures in the downstream container of the core slice and the upstream container of the core slice, and conduct subsequent permeability tests through the data acquisition system. When testing the permeability, control the nitrogen cylinder to fill nitrogen into the upstream container of the core slice to keep the pressure in the upstream container of the core slice unchanged; the core slice is obtained from a tight reservoir to evaluate the effect of external fluid on the permeability change of the tight reservoir. Finally, when the measurement experiment is over, the external fluid in the upstream container and the crude oil sample in the downstream container may be miscible or enter the core and be contaminated, and cannot flow back to the first intermediate container and the second intermediate container for reuse, and the graduated cylinder is used to recycle it here.

[0045] In one embodiment of the present invention, the thickness of the core slice is a preset thickness value, and epoxy resin surrounds the core slice; wherein, the epoxy resin is used to increase the tightness of the upstream container of the core slice and the downstream container of the core slice.

[0046] Figure 3 It is a schematic structural diagram of the core slice in the embodiment of the present invention.

[0047] In one embodiment of the present invention, before measuring the core permeability, it is necessary to construct a downhole rock sample thin slice (i.e., a core slice with a preset thickness) for unsteady-state method measurement. Place the standard core to be measured (for example: with a diameter of 2.5 cm and a length of 5.0 cm) at the center position of a circular plastic container, and then pour epoxy resin into the plastic cylinder (for example: with a diameter of 5.0 cm and a length of 7.5 cm) so that the epoxy resin evenly wraps the core to be measured. After the core wrapped with epoxy resin is left standing at room temperature for a preset time (for example: one week) to ensure that the epoxy resin is completely hardened, then cut the core wrapped with epoxy resin into core slices with a preset thickness (for example: 1 cm), so that the core slice has the core in the center and epoxy resin around it. Refer to Figure 3 , the epoxy resin is to ensure the tightness around the core and ensure that the external fluid to be measured can only transmit the pressures of the upstream container and the downstream container of the core slice through the core.

[0048] In one embodiment of the present invention, the core slice is a core slice that has been pre-saturated with crude oil or n-dodecane.

[0049] During specific implementation, the core slice is saturated with crude oil. The core slice to be measured is saturated with crude oil or n-dodecane through a vacuum pump. After the pressure stabilizes, it is considered completely saturated to restore the true oil sample saturation environment in the downhole reservoir.

[0050] In one embodiment of the present invention, an external fluid and a crude oil sample are respectively placed in a first intermediate container and a second intermediate container. The pipeline of the first intermediate container is connected to the inlet of the upstream container of the core slice, and the second intermediate container is connected to the inlet of the downstream container of the core slice; then the core thin slice is placed in a core holder, and the pipelines in the experimental device are evacuated to ensure that there is no other liquid in the pipelines, providing a single fluid source for the measurement of the external fluid, so as to accurately measure the core permeability under different external fluids.

[0051] In one embodiment of the present invention, controlling the pressure in the upstream container of the core slice to always remain at a first preset pressure includes:

[0052] Controlling a nitrogen cylinder to fill nitrogen into the upstream container of the core slice so that the pressure in the upstream container of the core slice always remains at the first preset pressure, wherein the nitrogen cylinder is connected to the upstream container of the core slice.

[0053] In one embodiment of the present invention, controlling an injection pump to inject a preset fluid in the first intermediate container into the upstream container of the core slice until the pressure in the upstream container of the core slice is equal to the first preset pressure; specifically, injecting the fluid to be measured (formation water or external fluid to be measured) into the upstream container of the core slice at a displacement pressure of the first preset pressure P0 through the constant pressure mode of the injection pump. After the initial pressure in the upstream container of the core slice is P0, use a nitrogen cylinder to stabilize this pressure at P0. The external fluid to be measured can be fluids such as drilling fluid, fracturing fluid, or oil displacement agent.

[0054] In one embodiment of the present invention, controlling an injection pump to inject the crude oil sample in the second intermediate container into the downstream container of the core slice until the pressure in the downstream container of the core slice is equal to the second preset pressure, monitoring the change in the pressure in the downstream container of the core slice, and determining the change curve of the pressure in the downstream container of the core slice with the elapsed time; specifically, injecting the crude oil sample into the downstream container of the core slice at a displacement pressure of the second preset pressure P m through the constant pressure mode of the injection pump. After the initial pressure of the downstream container of the core slice is P mAfter that, stop the constant pressure mode of the injection pump. Use a pressure sensor in the downstream container of the core slice to record the curve of pressure change with elapsed time, that is, P(t) (P(t) can also be expressed as P(L,t), where L represents the core height). To ensure that the external fluid flows from the upstream container to the downstream container, the second preset pressure P m of the downstream container should be less than the second preset pressure P0 of the upstream container.

[0055] In one embodiment of the present invention, determining the core permeability according to the curve of pressure change with elapsed time in the downstream container of the core slice includes:

[0056] Determine the functional relationship between and t; where, The functional relationship between and t is expressed as follows:

[0057]

[0058] According to the functional relationship between and t, determine the slope of and t;

[0059] According to the slope of and t, determine the core permeability according to the following formula:

[0060]

[0061] where, P(t) represents the curve of pressure change with elapsed time in the downstream container of the core slice, t represents the elapsed time; P m represents the second preset pressure; P0 represents the first preset pressure; γ represents the slope of and t; k represents the core permeability; μ represents the viscosity of the crude oil sample; C represents the compressibility of the crude oil sample; V represents the volume of the downstream container of the core slice; L represents the height of the core slice; A represents the cross-sectional area of the core slice.

[0062] During specific implementation, monitor the pressure change in the downstream container of the core slice until the pressures in the downstream container and the upstream container of the core slice are balanced, and plot the relationship chart between and the elapsed time t, and determine the straight line slope of the chart. The permeability of the core slice can be calculated according to the straight line slope of the chart.

[0063] In one embodiment of the present invention, based on the unsteady-state method pressure conduction theory involved in the core permeability measurement experimental device of the present invention, calculate the one-dimensional seepage diffusion equation as follows:

[0064]

[0065]

[0066] The initial conditions are as follows:

[0067] P(x,0)=p0 0<x<L

[0068] The boundary conditions are as follows:

[0069] P(0,t)=p m t≥0

[0070]

[0071] The analytical solution of the infinite series of the pulse method mathematical model is as follows:

[0072]

[0073] Combining the above equations, we can get:

[0074]

[0075] Among them, γ represents The slope with t, after calculating the slope, the core permeability is determined according to the following formula:

[0076]

[0077] Where P, also known as P(x, t), represents the pressure in the downstream container of a core slice with a thickness of x as a function of the time t; P(t), also known as P(L, t), represents the pressure in the downstream container of a core slice with a thickness of L as a function of the time t, where t represents the time, s; x represents the core thickness, and the maximum core thickness is L, cm; η represents the pressure conductivity of the core slice, cm 2 / s;P m represents the second preset pressure, MPa; P0 represents the first preset pressure, MPa; k represents the core permeability, mD; μ represents the viscosity of the crude oil sample, mPa·s; C represents the compressibility coefficient of the crude oil sample, MPa -1 ; V is the volume of the downstream container of the core slice, cm 3 ; L is the height of the core slice; A is the cross-sectional area of ​​the core slice, cm 2 ; φ represents the porosity of the core slice; n represents the number of pulses corresponding to the developed phase; φ n Represents the porosity of the core slice measured at the nth time.

[0078] In specific implementation, in order to ensure that the external fluid flows from the upstream container to the downstream container, the initial pressure (i.e., the second preset pressure) of the downstream container is P mIt should be less than the initial pressure (i.e., the first preset pressure) P0 of the upstream container. At this time, the pressure in the downstream container will gradually rise as the pressure of the upstream container is transmitted, and will eventually rise to the same as the initial pressure P0 of the upstream container. According to the relative magnitudes of the physical properties and permeability of the tight reservoir, when the core permeability is relatively large, the pressure in the downstream container will rise to the initial pressure (i.e., the first preset pressure) in the upstream container relatively quickly. When the permeability of the core to be measured is relatively small, the pressure in the downstream container will rise to the initial pressure (i.e., the first preset pressure) in the upstream container relatively slowly. The permeability of the core to be measured can be determined according to the pressure rise rate in the downstream container.

[0079] Figures 4 - 9 It is a specific example diagram of the core permeability measurement method of the embodiment of the present invention.

[0080] In an embodiment of the present invention, the following experiment is carried out according to the core permeability measurement method of the present invention. Three ultra-low permeability tight shale cores with permeabilities all lower than 0.005 mD and porosities less than 10% are used. It is impossible to measure the cores with such a low order of magnitude permeability by the conventional steady-state method. The fluid to be measured is shown in Table 1. The wt% in Table 1 represents the percentage by weight content, and the KCl solution represents formation brine;

[0081] Table 1

[0082]

[0083] Slice the core and saturate it with crude oil. Keep the upstream and downstream containers in a vacuum state for 60 min at the same time. Saturate the core slice to be measured with n-dodecane through a vacuum pump, and the saturation pressure is 15 MPa. After the pressure is stable, it is considered that the saturation is complete;

[0084] Place the fluid to be measured outside and the crude oil sample in the first intermediate container and the second intermediate container respectively. In order to conduct a more comprehensive study on the core permeability, the embodiments of the present invention respectively design formation brine (2 wt% KCl solution), 3 wt% displacing agent, 2 wt% displacing agent, and 1 wt% displacing agent solution as the external fluid, and respectively compare the permeability enhancement effects of not using a displacing agent and using displacing agents with different concentrations;

[0085] Inject the fluid to be measured (formation water or the external fluid to be measured) into the upstream container of the core slice at a displacement pressure of the first preset pressure P0 (for example: 0.5 MPa) in the constant pressure mode of the injection pump. After the pressure in the upstream container (upstream pressure) is P0, keep the pressure in the upstream container of the core slice at P0;

[0086] Inject the crude oil sample into the downstream container of the core slice at a displacement pressure of the second preset pressure P m (for example: 0.1 MPa) in the constant pressure mode of the injection pump. After the pressure in the downstream container (downstream pressure) is Pm After that, stop the constant pressure mode of the injection pump. Use a pressure sensor in the downstream container of the core slice to record the change curve of the downstream pressure over time (i.e., elapsed time), which is P(t); refer to Figure 4 Part (a) of [reference] shows the relationship between the downstream pressure and the upstream pressure over time when the injected fluid is 2wt% KCl solution for the core numbered S-1; refer to Figure 4 Part (b) of [reference] shows the dimensionless pressure change when the core numbered S-1 is displaced with 2wt% KCl solution; refer to Figure 5 Part (a) of [reference] shows the relationship between the downstream pressure and the upstream pressure over time when the injected fluid is 2wt% KCl solution for the core numbered S-2; refer to Figure 5 Part (b) of [reference] shows the dimensionless pressure change when the core numbered S-2 is displaced with 2wt% KCl solution; refer to Figure 6 Part (a) of [reference] shows the relationship between the downstream pressure and the upstream pressure over time when the injected fluid is 2wt% KCl solution for the core numbered S-3; refer to Figure 6 Part (b) of [reference] shows the dimensionless pressure change when the core numbered S-3 is displaced with 2wt% KCl solution; Table 2 shows the permeability test results under conventional formation brine. The liquid permeability distribution range of the 3 cores is less than 0.002 mD, and the average permeability is 0.001837 mD;

[0087] Table 2

[0088] Serial number Core number Conductivity coefficient Liquid permeability / mD 1 S-1 -0.0032 0.00198 2 S-2 -0.0030 0.00186 3 S-3 -0.0027 0.00167

[0089] Refer to Figure 7 Part (a) of [reference] shows the relationship between the downstream pressure and the upstream pressure over time when the injected fluid is 3wt% oil displacement agent for the core numbered S-1; refer to Figure 7 Part (b) of [reference] shows the dimensionless pressure change when the core numbered S-1 is displaced with 3wt% oil displacement agent; refer to Figure 8 Part (a) of [reference] shows the relationship between the downstream pressure and the upstream pressure over time when the injected fluid is 2wt% oil displacement agent for the core numbered S-2; refer to Figure 8 Part (b) of [reference] shows the dimensionless pressure change when the core numbered S-2 is displaced with 2wt% oil displacement agent; refer to Figure 9 Part (a) of [reference] shows the relationship between the downstream pressure and the upstream pressure over time when the injected fluid is 1wt% oil displacement agent for the core numbered S-3; refer to Figure 9Part (b) shows the dimensionless pressure change during the displacement of the core numbered S-3 with a 1 wt% displacement agent; Table 3 presents the liquid permeability test results at different displacement agent concentrations. The liquid permeability of the 3 cores ranges from 0.00056 to 0.00880 mD, and the average permeability is 0.0073 mD.

[0090] Table 3

[0091] Serial number Core number Conductivity coefficient Liquid permeability / mD 1 S-1 -0.0142 0.00880 2 S-2 -0.0113 0.00700 3 S-3 -0.0102 0.00632

[0092] Referring to Table 4 for the results of the above embodiments, these results indicate that the core permeability measurement method of the present invention solves the inaccuracy and deviation in the measurement of low-permeability tight cores by the steady-state method. In addition, the application of the displacement agent has greatly improved the permeability of the cores, making a great improvement in enhancing the permeability and production of low-permeability tight reservoirs. The embodiments of the present invention solve a major technical problem for the on-site application of displacement agents in tight reservoirs and provide valuable support for further research. The present invention can evaluate the permeability enhancement effect of different external fluids on low-permeability tight reservoirs and can analyze the sensitivity of the permeability of low-permeability reservoirs to the concentration of displacement agents; the embodiments of the present invention can evaluate the permeability enhancement effect of displacement agents on low-permeability tight reservoirs.

[0093] Table 4

[0094]

[0095] It should be noted that although the operations of the method of the present invention are described in a specific order in the above embodiments and the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the shown operations must be performed to achieve the desired result. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step for execution, and / or one step may be decomposed into multiple steps for execution.

[0096] The implementation of the core permeability measurement device can refer to the implementation of the above method, and the repeated parts will not be elaborated. The terms "module" or "unit" used hereinafter can be a combination of software and / or hardware that realizes a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware is also possible and contemplated.

[0097] Based on the same inventive concept, the present invention also proposes a core permeability measurement device, as Figure 10 shown, the device includes:

[0098] The first control module 1001 is used to control the injection pump to inject a preset fluid in the first intermediate container into the upstream container of the core slice until the pressure in the upstream container of the core slice is equal to the first preset pressure; wherein, the preset fluid is any one of formation water, drilling fluid, fracturing fluid, and oil displacement agent; the core slice is placed at a preset position of the core holder, and the core slice divides the internal space of the core holder into a sealed space at the top of the core slice and a sealed space at the bottom of the core slice; the upstream container of the core slice is the sealed space at the top of the core slice; the first intermediate container is communicated with the upstream container of the core slice through the injection pump;

[0099] The second control module 1002 is used to control the injection pump to inject the crude oil sample in the second intermediate container into the downstream container of the core slice until the pressure in the downstream container of the core slice is equal to the second preset pressure; wherein, the second preset pressure is less than the first preset pressure; the downstream container of the core slice is the sealed space at the bottom of the core slice; the second intermediate container is communicated with the downstream container of the core slice through the injection pump;

[0100] The pressure monitoring module 1003 is used to monitor the change of the pressure in the downstream container of the core slice and determine the change curve of the pressure in the downstream container of the core slice with the elapsed time; during the monitoring process, control the pressure in the upstream container of the core slice to always remain unchanged at the first preset pressure;

[0101] The permeability determination module 1004 is used to determine the core permeability according to the change curve of the pressure in the downstream container of the core slice with the elapsed time.

[0102] In an embodiment of the present invention, the thickness of the core slice is a preset thickness value, and the periphery of the core slice is surrounded by epoxy resin; wherein, the epoxy resin is used to increase the tightness of the upstream container of the core slice and the downstream container of the core slice.

[0103] In an embodiment of the present invention, the core slice is a core slice that has been pre-saturated with crude oil or n-dodecane.

[0104] In an embodiment of the present invention, the pressure monitoring module 1003 is specifically used for:

[0105] Control the nitrogen cylinder to fill nitrogen into the upstream container of the core slice so that the pressure in the upstream container of the core slice always remains unchanged at the first preset pressure, wherein the nitrogen cylinder is communicated with the upstream container of the core slice.

[0106] In an embodiment of the present invention, the permeability determination module 1004 is specifically used for:

[0107] According to the change curve of the pressure in the downstream container of the core slice with the elapsed time, determine The functional relationship with t; wherein, The functional relationship with t is expressed as follows:

[0108]

[0109] According to the functional relationship with t, determine the slope with respect to t;

[0110] According to the slope with respect to t, determine the core permeability according to the following formula:

[0111]

[0112] where P(t) represents the curve of the pressure in the downstream container of the core slice changing with the elapsed time, t represents the elapsed time; P m represents the second preset pressure; P0 represents the first preset pressure; γ represents the slope with respect to t; k represents the core permeability; μ represents the viscosity of the crude oil sample; C represents the compressibility of the crude oil sample; V represents the volume of the downstream container of the core slice; L represents the height of the core slice; A represents the cross-sectional area of the core slice.

[0113] It should be noted that although several modules of the core permeability measurement device are mentioned in the above detailed description, this division is merely exemplary and not mandatory. In fact, according to the embodiments of the present invention, the features and functions of two or more of the above-described modules can be embodied in one module. Conversely, the features and functions of one module described above can be further divided and embodied by multiple modules.

[0114] Based on the foregoing inventive concept, as Figure 11 shown, the present invention also provides a computer device 1100, including a memory 1101, a processor 1102, and a computer program 1103 stored in the memory 1101 and executable on the processor 1102. When the processor 1102 executes the computer program 1103, the foregoing core permeability measurement method is implemented.

[0115] Based on the foregoing inventive concept, the present invention provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the foregoing core permeability measurement method is implemented.

[0116] Based on the foregoing inventive concept, the present invention provides a computer program product including a computer program, and when the computer program is executed by a processor, the core permeability measurement method is implemented.

[0117] The core permeability measurement method and device proposed in the embodiments of the present invention can solve the problems of low accuracy and efficiency in core permeability measurement in the prior art; in the embodiments of the present invention, a preset fluid in a first intermediate container is injected into the upstream container of the core slice by controlling an injection pump until the pressure in the upstream container of the core slice is equal to a first preset pressure; wherein, the preset fluid is any one of formation water, drilling fluid, fracturing fluid, and oil displacement agent; the core slice is placed at a preset position of a core holder, and the core slice divides the internal space of the core holder into a sealed space at the top of the core slice and a sealed space at the bottom of the core slice; the upstream container of the core slice is the sealed space at the top of the core slice; the first intermediate container is connected to the upstream container of the core slice through an injection pump; the crude oil sample in a second intermediate container is injected into the downstream container of the core slice by controlling the injection pump until the pressure in the downstream container of the core slice is equal to a second preset pressure; wherein, the second preset pressure is less than the first preset pressure; the downstream container of the core slice is the sealed space at the bottom of the core slice; the second intermediate container is connected to the downstream container of the core slice through an injection pump; the change in the pressure in the downstream container of the core slice is monitored to determine the change curve of the pressure in the downstream container of the core slice with the elapsed time; during the monitoring process, the pressure in the upstream container of the core slice is controlled to always remain unchanged at the first preset pressure; the core permeability is determined according to the change curve of the pressure in the downstream container of the core slice with the elapsed time. The embodiments of the present invention can improve the accurate measurement of the core permeability under different preset fluids, improve the measurement efficiency of the core permeability, and provide data support for oilfield exploration and development; it can quickly and efficiently evaluate the influence of drilling fluid, fracturing fluid or oil displacement agent on the core permeability.

[0118] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, system, or computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can 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.

[0119] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows 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 the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate for implementing in the process Figure 1One or more processes and / or blocks Figure 1 Apparatus for the functions specified in one or more blocks

[0120] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the processes Figure 1 One or more processes and / or blocks Figure 1 The functions specified in one or more blocks

[0121] These computer program instructions may also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are performed on the computer or other programmable device to produce a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in the processes Figure 1 One or more processes and / or blocks Figure 1 The functions specified in one or more blocks

[0122] In the above-described specific embodiments, the objectives, technical solutions, and beneficial effects of the present invention have been further described in detail. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring core permeability, characterized in that, Including: Controlling an injection pump to inject a preset fluid in a first intermediate container into an upstream container of a core slice until the pressure in the upstream container of the core slice is equal to a first preset pressure; wherein, the preset fluid is any one of formation water, drilling fluid, fracturing fluid, and oil displacement agent; the core slice is placed at a preset position of a core holder, and the core slice divides the internal space of the core holder into a sealed space at the top of the core slice and a sealed space at the bottom of the core slice; the upstream container of the core slice is the sealed space at the top of the core slice; the first intermediate container is communicated with the upstream container of the core slice through the injection pump; Controlling the injection pump to inject a crude oil sample in a second intermediate container into a downstream container of the core slice until the pressure in the downstream container of the core slice is equal to a second preset pressure; wherein, the second preset pressure is less than the first preset pressure; the downstream container of the core slice is the sealed space at the bottom of the core slice; the second intermediate container is communicated with the downstream container of the core slice through the injection pump; Monitoring the change of the pressure in the downstream container of the core slice to determine the change curve of the pressure in the downstream container of the core slice with the elapsed time; during the monitoring process, controlling the pressure in the upstream container of the core slice to always remain unchanged at the first preset pressure; Determining the core permeability according to the change curve of the pressure in the downstream container of the core slice with the elapsed time.

2. The method according to claim 1, characterized in that, The thickness of the core slice is a preset thickness value, and the periphery of the core slice is surrounded by epoxy resin; wherein, the epoxy resin is used to increase the tightness of the upstream container of the core slice and the downstream container of the core slice.

3. The method according to claim 1, wherein The core slice is a core slice that has been pre-saturated with crude oil or n-dodecane.

4. The method according to claim 1, characterized in that Controlling the pressure in the upstream container of the core slice to always remain unchanged at the first preset pressure includes: Controlling a nitrogen cylinder to fill nitrogen into the upstream container of the core slice so that the pressure in the upstream container of the core slice always remains unchanged at the first preset pressure, wherein the nitrogen cylinder is communicated with the upstream container of the core slice.

5. The method according to claim 1, characterized in that, Determining the core permeability according to the change curve of the pressure in the downstream container of the core slice with the elapsed time includes: Determine according to the curve of the pressure in the downstream container of the core slice changing with the elapsed time the functional relationship with t; where the functional relationship with t is expressed as follows: According to the functional relationship with t, determine the slope with t; According to the slope with respect to t, the core permeability is determined by the following formula: Among them, P(t) represents the curve of the pressure in the downstream container of the core slice changing with the elapsed time, t represents the elapsed time; P m represents the second preset pressure; P0 represents the first preset pressure; γ represents the slope of vs. t; k represents the core permeability; μ represents the viscosity of the crude oil sample; C represents the compressibility of the crude oil sample; V represents the volume of the downstream container of the core slice; L represents the height of the core slice; A represents the cross-sectional area of the core slice.

6. A core permeability measurement device, characterized in that, Including: A first control module for controlling the injection pump to inject a preset fluid in a first intermediate container into an upstream container of the core slice until the pressure in the upstream container of the core slice is equal to a first preset pressure; wherein, the preset fluid is any one of formation water, drilling fluid, fracturing fluid, and oil displacement agent; the core slice is placed at a preset position of a core holder, and the core slice divides the internal space of the core holder into a sealed space at the top of the core slice and a sealed space at the bottom of the core slice; the upstream container of the core slice is the sealed space at the top of the core slice; the first intermediate container is communicated with the upstream container of the core slice through the injection pump; A second control module for controlling the injection pump to inject a crude oil sample in a second intermediate container into a downstream container of the core slice until the pressure in the downstream container of the core slice is equal to a second preset pressure; wherein, the second preset pressure is less than the first preset pressure; the downstream container of the core slice is the sealed space at the bottom of the core slice; the second intermediate container is communicated with the downstream container of the core slice through the injection pump; A pressure monitoring module, which is used to monitor the change in pressure in the downstream container of the core slice, and determine the change curve of the pressure in the downstream container of the core slice with the elapsed time; during the monitoring process, control the pressure in the upstream container of the core slice to always remain unchanged at a first preset pressure; A permeability determination module, which is used to determine the core permeability according to the change curve of the pressure in the downstream container of the core slice with the elapsed time.

7. The device according to claim 6, wherein The thickness of the core slice is a preset thickness value, and the periphery of the core slice is surrounded by epoxy resin; wherein, the epoxy resin is used to increase the tightness of the upstream container of the core slice and the downstream container of the core slice.

8. The device according to claim 6, characterized in that, The core slice is a core slice that has been pre-saturated with crude oil or n-dodecane.

9. The device according to claim 6, characterized in that, The pressure monitoring module is specifically used for: Control the nitrogen cylinder to fill nitrogen into the upstream container of the core slice, so that the pressure in the upstream container of the core slice always remains unchanged at a first preset pressure, wherein the nitrogen cylinder is communicated with the upstream container of the core slice.

10. The device according to claim 6, wherein The permeability determination module is specifically used for: Determine according to the curve of the pressure in the downstream container of the core slice changing with the elapsed time the functional relationship with t; wherein, the functional relationship with t is expressed as follows: According to the functional relationship with t, determine the slope with t; According to the slope with respect to t, the core permeability is determined by the following formula: Among them, P(t) represents the curve of the pressure in the downstream container of the core slice changing with the elapsed time, t represents the elapsed time; P m represents the second preset pressure; P0 represents the first preset pressure; γ represents the slope of with t; k represents the core permeability; μ represents the viscosity of the crude oil sample; C represents the compressibility of the crude oil sample; V represents the volume of the downstream container of the core slice; L represents the height of the core slice; A represents the cross-sectional area of the core slice.

11. A computer device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method according to any one of claims 1 to 5.

12. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the method according to any one of claims 1 to 5.

13. A computer program product, characterized in that, The computer program product includes a computer program, and when the computer program is executed by a processor, it implements the method according to any one of claims 1 to 5.

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