CN117147610A - Method and device for quantitatively detecting mobility of unconventional resource core fluid - Google Patents
Method and device for quantitatively detecting mobility of unconventional resource core fluid Download PDFInfo
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Abstract
The embodiment of the application provides a method and a device for quantitatively detecting the mobility of unconventional resource core fluid, wherein the method comprises the following steps: obtaining physical parameters of the core after oil washing treatment; determining a displacement pressure gradient based on the physical property parameters and the displacement pressure in the core displacement testing process; acquiring accumulated nuclear magnetic resonance T2 signal quantities of fluid in the core under different displacement pressure gradients; and carrying out mobility quantitative detection on the core fluid based on the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients. The quantitative detection method and the quantitative detection device for the mobility of the core fluid of the unconventional resource can realize quantitative detection of the mobility of the core fluid under different displacement pressure gradients, and the detection process is closer to the resource development process, so that the test result has higher accuracy and can accurately guide production.
Description
Technical Field
The application relates to the technical field of oil and gas field development, in particular to a method for quantitatively detecting the mobility of unconventional resource core fluid, a device for quantitatively detecting the mobility of unconventional resource core fluid and a machine-readable storage medium.
Background
At present, the large amount of unconventional resources such as shale oil gas, compact oil gas and the like becomes a very important strategic alternative resource, and the movable fluid quantity is one of key parameters in the processes of reservoir calculation and development scheme formulation. In the prior art, conventional reservoir fluid mobility evaluation generally adopts a centrifugal method, wherein a centrifugal machine is used for centrifuging fluid-containing rocks at different rotation speeds, and then nuclear magnetic resonance measurement is used for calculating to obtain movable fluid. But the shale oil gas, the compact oil gas and other unconventional resource reservoir rock Dan Zhimi has small pore radius, the average pore radius is generally hundreds of nanometers, partial pores are only a few nanometers and tens of nanometers, and the centrifugal force provided by the centrifugal machine is difficult to drive out the fluid in the nanoscale pores. If the movable fluid data is obtained by adopting a conventional centrifugal method, the movable fluid data is very small, even no movable fluid exists, which is not consistent with the actual development on site, and the production cannot be guided accurately.
Disclosure of Invention
The embodiment of the application aims to provide a quantitative detection method and a quantitative detection device for the mobility of unconventional resource core fluid, which are used for solving the problems that the conventional centrifugation method is adopted to obtain movable fluid data, the movable fluid data is very small and even no movable fluid exists, and the movable fluid data is not consistent with the actual development on site.
In order to achieve the above objective, an embodiment of the present application provides a method for quantitatively detecting fluid mobility of a core of an unconventional resource, including:
obtaining physical parameters of the core after oil washing treatment;
determining a displacement pressure gradient based on the physical property parameters and the displacement pressure in the core displacement testing process;
acquiring accumulated nuclear magnetic resonance T2 signal quantities of fluid in the core under different displacement pressure gradients;
and carrying out mobility quantitative detection on the core fluid based on the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients.
Optionally, the physical property parameter is the length of the core; the displacement pressure is the pressure difference between the inlet end and the outlet end of the clamp holder of the nuclear magnetic resonance apparatus in the oil displacement test process.
Optionally, the acquiring cumulative nmr T2 signal of the fluid in the core under different displacement pressure gradients includes:
sequentially acquiring nuclear magnetic resonance T2 spectrums and accumulated nuclear magnetic resonance T2 signal amounts of fluid in the core under different displacement pressure gradients from small to large according to the displacement pressure, and stopping until the difference value of the acquired nuclear magnetic resonance T2 spectrums of the fluid in the two adjacent cores is smaller than a preset difference value.
Optionally, the cumulative nmr T2 signal of the fluid in the core is obtained by:
based on nuclear magnetic resonance T2 spectrum of the fluid in the core, the corresponding cumulative nuclear magnetic resonance T2 signal quantity of the fluid in the core is obtained through an area function.
Optionally, the performing mobility quantitative detection on the core fluid based on the accumulated nuclear magnetic resonance T2 signal under different displacement pressure gradients includes:
determining a target T2 relaxation time at different displacement pressure gradients based on the accumulated nuclear magnetic resonance T2 signal magnitude at the different displacement pressure gradients;
and determining the minimum pore radius which can be entered by the fluid under different displacement pressure gradients based on the target T2 relaxation time under the different displacement pressure gradients, and taking the minimum pore radius as a quantitative detection result of the mobility of the core fluid.
Optionally, the determining the target T2 relaxation time under different displacement pressure gradients based on the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients includes:
drawing a relation curve of accumulated nuclear magnetic resonance T2 semaphore along with T2 relaxation time under different displacement pressure gradients, wherein the T2 relaxation time adopts a logarithmic coordinate;
fitting a straight line segment in a relation curve of the accumulated nuclear magnetic resonance T2 signal quantity corresponding to the accumulated nuclear magnetic resonance T2 signal quantity obtained finally along with the T2 relaxation time to obtain a calculation formula;
substituting the maximum value in the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients into the calculation formula respectively, and calculating to obtain target T2 relaxation time under different displacement pressure gradients.
Optionally, the target T2 relaxation time is calculated by using the following calculation formula:
wherein Q is the maximum value of the cumulative nmr T2 signal of the fluid in the core; t is the target T2 relaxation time; k and b are fitting coefficients, and are obtained by fitting straight line segments in a graph of the cumulative nuclear magnetic resonance T2 signal quantity of the fluid in the core along with the T2 relaxation time change relation.
Optionally, the determining the minimum pore radius that the fluid can enter under the different displacement pressure gradients based on the target T2 relaxation time under the different displacement pressure gradients includes:
based on target T2 relaxation times at different displacement pressure gradients, mercury intrusion data is utilized to obtain minimum pore radii into which fluids can enter at different displacement pressure gradients.
Optionally, the minimum pore radius is calculated using the following formula:
r＝T·μ
wherein r is the minimum pore radius; t is the target T2 relaxation time; μ -conversion coefficient, determined from mercury intrusion data.
Optionally, the fluid is shale oil, tight oil, white oil or hydrocarbons.
The second aspect of the application provides a device for quantitatively detecting the mobility of unconventional resource core fluid, which comprises:
the first acquisition module is used for acquiring physical parameters of the core after the oil washing treatment;
the determining module is used for determining a displacement pressure gradient based on the physical property parameters and the displacement pressure in the core displacement testing process;
the second acquisition module is used for acquiring cumulative nuclear magnetic resonance T2 signal quantities of fluid in the core under different displacement pressure gradients;
and the detection module is used for quantitatively detecting the mobility of the core fluid based on the acquired accumulated nuclear magnetic resonance T2 signal quantity of the fluid in the core.
In another aspect, the present application provides a machine-readable storage medium having stored thereon instructions for causing a machine to perform the above-described method for quantitatively detecting fluid mobility of unconventional resource cores.
According to the technical scheme, the physical property parameters of the rock core after oil washing treatment are obtained, the displacement pressure gradient is determined based on the physical property parameters and the displacement pressure in the rock core oil displacement testing process, the accumulated nuclear magnetic resonance T2 signal quantity of fluid in the rock core under different displacement pressure gradients is obtained, the quantitative detection of the mobility of the rock core fluid under different displacement pressure gradients is realized based on the obtained accumulated nuclear magnetic resonance T2 signal quantity of the fluid in the rock core, and the detection process is closer to the resource development process, so that the testing result has higher accuracy, and production can be accurately guided.
Additional features and advantages of embodiments of the application will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain, without limitation, the embodiments of the application. In the drawings:
FIG. 1 is a flow chart of a method for quantitatively detecting the mobility of unconventional resource core fluid;
FIG. 2 is a schematic structural diagram of a device for quantitatively detecting the mobility of unconventional resource core fluid;
FIG. 3 is a graph showing the relationship between the nuclear magnetic resonance T2 spectrum and the T2 relaxation time under different displacement pressure gradients;
FIG. 4 is a graph showing the cumulative NMR T2 signal magnitude versus T2 relaxation time for different displacement pressure gradients provided by the present application;
FIG. 5 is a graph showing the relationship between the maximum value of the cumulative nuclear magnetic resonance T2 signal and the corresponding minimum pore radius for different displacement pressure gradients provided by the present application.
Description of the reference numerals
10-a first acquisition module; 20-a determination module; 30-a second acquisition module;
40-detection module.
Detailed Description
The following describes the detailed implementation of the embodiments of the present application with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the application, are not intended to limit the application.
In the embodiments of the present application, unless otherwise indicated, terms such as "upper, lower, left, and right" and "upper, lower, left, and right" are used generally referring to directions or positional relationships based on those shown in the drawings, or those conventionally used in the use of the inventive products.
The terms "first," "second," "third," and the like are used merely to distinguish between descriptions and are not to be construed as indicating or implying relative importance.
The terms "parallel", "perpendicular", and the like do not denote that the components are required to be absolutely parallel or perpendicular, but may be slightly inclined. For example, "parallel" merely means that the directions are more parallel than "perpendicular" and does not mean that the structures must be perfectly parallel, but may be slightly tilted.
The terms "horizontal," "vertical," "overhang," and the like do not denote that the component is required to be absolutely horizontal, vertical, or overhang, but may be slightly inclined. As "horizontal" merely means that its direction is more horizontal than "vertical", and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.
Furthermore, the terms "substantially," "essentially," and the like, are intended to be limited to the precise form disclosed herein and are not necessarily intended to be limiting. For example: the term "substantially equal" does not merely mean absolute equal, but is difficult to achieve absolute equal during actual production and operation, and generally has a certain deviation. Thus, in addition to absolute equality, "approximately equal to" includes the above-described case where there is a certain deviation. In other cases, the terms "substantially", "essentially" and the like are used in a similar manner to those described above unless otherwise indicated.
In the description of the present application, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
FIG. 1 is a flow chart of a method for quantitatively detecting the mobility of unconventional resource core fluid; FIG. 2 is a schematic structural diagram of a device for quantitatively detecting the mobility of unconventional resource core fluid; FIG. 3 is a graph showing the relationship between the nuclear magnetic resonance T2 spectrum and the T2 relaxation time under different displacement pressure gradients; FIG. 4 is a graph showing the cumulative NMR T2 signal magnitude versus T2 relaxation time for different displacement pressure gradients provided by the present application; FIG. 5 is a graph showing the relationship between the maximum value of the cumulative nuclear magnetic resonance T2 signal and the corresponding minimum pore radius for different displacement pressure gradients provided by the present application.
As shown in fig. 1, the application provides a method for quantitatively detecting the mobility of unconventional resource core fluid, which comprises the following steps:
step 101, obtaining physical parameters of a rock core after oil washing treatment;
102, determining a displacement pressure gradient based on the physical parameters and the displacement pressure in the core displacement testing process;
step 103, acquiring accumulated nuclear magnetic resonance T2 signal quantities of fluid in the core under different displacement pressure gradients;
and 104, performing mobility quantitative detection on the core fluid based on the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients.
Specifically, the core in this embodiment may be a matrix core or a fracture core; the sample can be an irregular sample, and the sample can be simply processed into a cylindrical sample, the two ends of the sample are cut flat, and the diameter of the cylindrical sample can be set to be 2.5cm or 3.8cm. Before detection, the obtained core is washed with oil by adopting a solvent, then is dried, nuclear magnetic resonance measurement is carried out after drying, if nuclear magnetic resonance signals exist, the residual crude oil in the core is indicated, the oil washing step is required to be repeated until the nuclear magnetic resonance signals in the core are zero, the core is ensured to be cleaned, no residual crude oil in the core is ensured, the subsequent experimental result is not influenced, and the detection accuracy is ensured. And secondly, measuring physical properties of the rock core subjected to oil washing treatment, loading a sample into a holder of a nuclear magnetic resonance instrument, enabling the rock core to be located in the middle of the holder, adding Fang Yanxin plugs on two sides of the holder and screwing up, then installing the holder on the nuclear magnetic resonance instrument, ensuring that the nuclear magnetic resonance instrument can accurately measure nuclear magnetic resonance signals of the rock core, setting the temperature in the detection process as the oil reservoir temperature, setting the outlet end of the holder as normal pressure or oil reservoir pressure, setting the pressure of an inlet end injection pump to form a displacement pressure difference correspondingly, setting the initial displacement pressure difference to a small value, such as 0.001MPa, detecting each displacement pressure correspondingly, determining displacement pressure gradients in each detection, gradually increasing the displacement pressure gradients along with the increase of detection times, obtaining a plurality of displacement pressure gradients, injecting fluid according to the set injection pump pressure constant pressure, ensuring that the fluid is injected from an inlet, passing through the rock core in the holder, measuring at the outlet end, continuously scanning the signals of the rock core in the whole process, keeping the signals of the rock core constant pressure, and accumulating the displacement pressure gradient when the nuclear magnetic resonance signals are not changed at the outlet end of the rock core, and quantitatively accumulating the displacement pressure gradient under the condition that the nuclear magnetic resonance fluid is not changed in the conventional rock core, and the displacement gradient is not being equal to the displacement fluid is obtained, and the displacement gradient is quantitatively accumulating fluid is obtained, and the displacement fluid is quantitatively accumulating fluid is based on the displacement fluid in the displacement of the core pressure 2 at the inlet end of the core. The types of the samples are different, and the corresponding permeabilities are different, so that the displacement pressure is also different, and the smaller the permeability of the core is, the larger the displacement pressure value is when the detection is started.
Further, the physical property parameter is the length of the core; the displacement pressure is the pressure difference between the inlet end and the outlet end of the clamp holder of the nuclear magnetic resonance apparatus in the oil displacement test process.
Specifically, because the lengths of the cores in the holders of the nuclear magnetic resonance apparatus are different, the size of the path through which the fluid passes is also different, so that a certain influence can be exerted on the displacement pressure gradient, because the diameter of the core is already determined, the length of the core is measured in advance before detection, the pressure value of the outlet end of the holder is set in advance according to the actual detection condition and is kept unchanged, the pressure value of the inlet end is correspondingly changed during detection, the displacement pressure is formed, and the displacement pressure gradient is calculated.
Further, the acquiring cumulative nmr T2 signal of the fluid in the core under different displacement pressure gradients includes:
sequentially acquiring nuclear magnetic resonance T2 spectrums and accumulated nuclear magnetic resonance T2 signal amounts of fluid in the core under different displacement pressure gradients from small to large according to the displacement pressure, and stopping until the difference value of the acquired nuclear magnetic resonance T2 spectrums of the fluid in the two adjacent cores is smaller than a preset difference value.
Specifically, since the pressure at the outlet end of the holder is fixed, the pressure at the inlet end of the holder needs to be changed to form a displacement pressure during each detection, and the nuclear magnetic resonance T2 spectrum and the accumulated nuclear magnetic resonance T2 signal quantity of the fluid in the core under the corresponding displacement pressure gradient are sequentially acquired according to the order from small to large, and the displacement pressure during each detection is used as a variable, the nuclear magnetic resonance T2 spectrum and the accumulated nuclear magnetic resonance T2 signal quantity of the fluid in the core obtained during each detection are different, so that the nuclear magnetic resonance T2 spectrum of the fluid in the core obtained during the detection under the current displacement pressure gradient is compared with the nuclear magnetic resonance T2 spectrum of the fluid in the core obtained during the detection under the previous displacement pressure gradient, and if the difference between the two is smaller than a preset difference value, it is indicated that the fluid capable of flowing in the core has all flows and does not need to continue to be detected. The constant fluid volume of the fluid in the core can be understood as that the nuclear magnetic resonance signal is kept unchanged under the displacement pressure, the output speed of the fluid at the outlet end is consistent with the injection speed of the fluid at the inlet end, the fluid volume in the unconventional resource core is not changed any more, and the subsequent displacement pressure gradient is not detected any more.
Further, the cumulative nuclear magnetic resonance T2 signal of the fluid in the core is obtained by the following method:
based on nuclear magnetic resonance T2 spectrum of the fluid in the core, the corresponding cumulative nuclear magnetic resonance T2 signal quantity of the fluid in the core is obtained through an area function.
Specifically, during each round of detection, the nuclear magnetic resonance T2 spectrum of the fluid in the core can be directly output through the nuclear magnetic resonance spectrometer, and then the area function (area integral) is used to obtain the corresponding cumulative nuclear magnetic resonance T2 signal quantity of the fluid in the core, so that the mobility quantitative detection of the core fluid is realized. The cumulative nmr T2 signal obtained based on the nmr T2 spectrum using the area function is an existing maturation step, and will not be described here.
Specifically, the method for quantitatively detecting the mobility of the core fluid based on the accumulated nuclear magnetic resonance T2 signal under different displacement pressure gradients comprises the following steps:
determining a target T2 relaxation time at different displacement pressure gradients based on the accumulated nuclear magnetic resonance T2 signal magnitude at the different displacement pressure gradients;
and determining the minimum pore radius which can be entered by the fluid under different displacement pressure gradients based on the target T2 relaxation time under the different displacement pressure gradients, and taking the minimum pore radius as a quantitative detection result of the mobility of the core fluid.
Specifically, in this embodiment, when the difference between the nuclear magnetic resonance T2 spectra of the fluids in the two adjacent cores is smaller than the preset difference, the nuclear magnetic resonance T2 spectrum under the subsequent displacement pressure gradient is not acquired any more, the target T2 relaxation time under the different displacement pressure gradients is determined directly according to the accumulated nuclear magnetic resonance T2 signal quantity of the fluid in the core corresponding to the nuclear magnetic resonance T2 spectrum of the fluid in the core under the different displacement pressure gradients, and then the minimum pore radius that the fluid can enter under the different displacement pressure gradients is determined based on the obtained target T2 relaxation time, which is used as the quantitative detection result of the mobility of the core fluid.
Further, the determining the target T2 relaxation time for the different displacement pressure gradients based on the accumulated nuclear magnetic resonance T2 semaphores for the different displacement pressure gradients includes:
drawing a relation curve of accumulated nuclear magnetic resonance T2 semaphore along with T2 relaxation time under different displacement pressure gradients, wherein the T2 relaxation time adopts a logarithmic coordinate;
fitting a straight line segment in a relation curve of the accumulated nuclear magnetic resonance T2 signal quantity corresponding to the accumulated nuclear magnetic resonance T2 signal quantity obtained finally along with the T2 relaxation time to obtain a calculation formula;
substituting the maximum value in the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients into the calculation formula respectively, and calculating to obtain target T2 relaxation time under different displacement pressure gradients.
Specifically, in the present embodiment, the relationship of the cumulative nmr T2 signal of the fluid in the core under different displacement pressure gradients with the T2 relaxation time is plotted on the same coordinate system, and the abscissa T2 relaxation time adopts a logarithmic coordinate. Under a certain displacement pressure gradient condition, the accumulated nuclear magnetic resonance T2 signal quantity gradually increases along with the gradual reduction of the T2 relaxation time; when the T2 relaxation time is reduced to a certain value, the accumulated nmr T2 signal is no longer changed. This process reflects the gradual flow of fluid within pores of different sizes under the displacement pressure gradient conditions: the fluid in the larger pores flows first and then the fluid in the smaller pores flows gradually. When the cumulative nmr T2 signal is unchanged, it indicates that the fluid flowable in the pores has been completely determined under the displacement pressure gradient. And selecting a relation curve of the accumulated nuclear magnetic resonance T2 signal quantity of the fluid in the core, which is finally obtained, along with the T2 relaxation time, selecting a straight line segment from the relation curve for fitting to obtain a corresponding calculation formula, wherein the calculation formula reflects that the used pore radius gradually decreases along with the increment of the displacement pressure gradient, the flowable fluid gradually increases, and the maximum value in the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients is respectively substituted into the calculation formula for calculation to obtain the target T2 relaxation time under different displacement pressure gradients.
In another embodiment, only a change relation curve of the last obtained accumulated nuclear magnetic resonance T2 signal quantity along with the T2 relaxation time is drawn, a calculation formula is obtained by fitting straight line segments in the change relation curve, and the maximum value in the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients is substituted into the calculation formula to calculate the target T2 relaxation time under different displacement pressure gradients.
Further, the target T2 relaxation time is calculated by the following calculation formula:
wherein Q is the maximum value of the cumulative nmr T2 signal of the fluid in the core; t is the target T2 relaxation time; k and b are fitting coefficients, and are obtained by fitting straight line segments in a graph of the cumulative nuclear magnetic resonance T2 signal quantity of the fluid in the core along with the T2 relaxation time change relation.
Further, the determining a minimum pore radius that fluid can enter under different displacement pressure gradients based on the target T2 relaxation time under the different displacement pressure gradients includes:
based on target T2 relaxation times at different displacement pressure gradients, mercury intrusion data is utilized to obtain minimum pore radii into which fluids can enter at different displacement pressure gradients.
Specifically, after the T2 relaxation time under different displacement pressure gradients is determined through the scheme, the mercury-pressing data (obtained through a mercury-pressing method) is utilized, the minimum pore radius which can be entered by the fluid under the different displacement pressure gradients can be obtained, the minimum pore radius is used as a quantitative detection result of the mobility of the core fluid, the minimum pore radius is determined under the condition that the fluid flows in the core, the movable fluid of the core under different conditions is determined, and the quantitative evaluation of the mobility of the unconventional resource core fluid is realized.
Further, the minimum pore radius is calculated using the following formula:
r＝T·μ
wherein r is the minimum pore radius; t is the target T2 relaxation time; μ -conversion coefficient, determined from mercury intrusion data.
Further, the fluid is shale oil, tight oil, white oil or hydrocarbons.
Specifically, the fluid can be shale oil and compact oil which are filtered to remove solid impurities, white oil, hydrocarbons with higher purity such as n-pentane, n-hexane, n-heptane, n-octane and the like, and gases such as methane, ethane, propane, butane and the like.
As shown in fig. 2, the embodiment of the present application further provides a device for quantitatively detecting the mobility of the unconventional resource core fluid, which includes:
the first acquisition module 10 is used for acquiring physical parameters of the core after the oil washing treatment;
a determining module 20, configured to determine a displacement pressure gradient based on the physical parameter and a displacement pressure during the core flooding test;
a second acquisition module 30 for acquiring cumulative nmr T2 signal of fluid in the core under different displacement pressure gradients;
the detection module 40 is configured to quantitatively detect mobility of the core fluid based on the acquired cumulative nmr T2 signal of the fluid in the core.
The embodiment of the application also provides a machine-readable storage medium, which is stored with instructions for causing a machine to execute the unconventional resource core fluid mobility quantitative detection method.
Examples
Obtaining a sample: and obtaining a shale oil sample of the target block, processing the sample into a cylinder shape, and cutting the two ends of the sample flat. The sample had a diameter of 2.54cm and a length of 3.83cm.
Sample wash oil: and washing the sample with a solvent, drying, and performing nuclear magnetic resonance measurement after drying to ensure that the sample is clean and free of any residual crude oil so as not to influence the subsequent experimental results. The air permeability was measured to be 0.257mD.
Shale core fluid mobility detection experiment: and loading the oil-washed sample into a holder of a nuclear magnetic resonance apparatus, and then loading into the nuclear magnetic resonance apparatus, so as to ensure that the nuclear magnetic resonance signal of the sample can be accurately measured. The experimental temperature was set at reservoir temperature 80 ℃. The outlet end of the clamp holder is set to be 20MPa, the pressure of the injection pump at the inlet end is set, the displacement pressure difference is ensured to be formed, the displacement pressure difference is set to be 0.5MPa just after the beginning, and the displacement pressure gradient is calculated to be 0.13MPa/cm according to the length of the core being 3.83cm. And injecting fluid at constant pressure according to the set injection pump pressure, wherein the fluid is n-dodecane. During the experiment, it was ensured that fluid was injected from the inlet, passed through the shale core in the holder, produced from the outlet, and metered at the outlet end. In the whole process, nuclear magnetic resonance signals of shale samples are continuously scanned, when the nuclear magnetic resonance signals of the samples are kept unchanged, and the output speed of fluid at the outlet end is consistent with the injection speed of a pump at the inlet end, the fluid quantity in the shale core is not changed any more, and nuclear magnetic resonance T2 spectrum of the core is recorded. Setting the displacement pressure difference to be 0.5MPa and the core length to be 3.83cm, and calculating to obtain the displacement pressure gradient to be 0.13MPa/cm. At this time, the nuclear magnetic resonance T2 spectrum of the flowable fluid in the core can be obtained under the condition of the displacement pressure gradient, and the cumulative nuclear magnetic resonance T2 signal quantity of the flowable fluid in the shale core can be obtained through area integration. And (3) increasing the pressure at the inlet end to increase the displacement pressure difference to 1MPa, and repeating the steps to obtain the nuclear magnetic resonance T2 spectrum and the accumulated nuclear magnetic resonance T2 signal quantity of the flowable fluid in the core under the condition of a second displacement pressure gradient of 0.26 MPa/cm. By analogy, nuclear magnetic resonance T2 spectra and cumulative nuclear magnetic resonance T2 signal of the core flowable fluid under a series of displacement pressure gradient conditions are obtained. And (3) obtaining nuclear magnetic resonance T2 spectrums with displacement pressure gradients of 0.52MPa/cm, 1.04MPa/cm and 1.31MPa/cm, wherein after the displacement pressure gradient is continuously increased to 1.57MPa/cm, the nuclear magnetic resonance T2 spectrums of the flowable fluid in the shale core are not greatly changed compared with the previous displacement pressure gradient of 1.31MPa/cm, and at the moment, the complete flow of the fluid energy flow in the shale core is considered, and the fluid mobility detection experiment is ended. A schematic diagram of the relationship between the nuclear magnetic resonance T2 spectrum and the T2 relaxation time change under different displacement pressure gradients can be obtained as shown in fig. 3.
The shale core fluid mobility quantitative detection method comprises the following steps: the relationship of the cumulative nmr T2 signal under different displacement pressure gradients with T2 relaxation time is plotted on the same graph, as shown in fig. 4, with the abscissa T2 relaxation time taking a logarithmic scale. Under a certain displacement pressure gradient condition, the accumulated nuclear magnetic resonance T2 signal quantity gradually increases along with the gradual reduction of the T2 relaxation time; when the T2 relaxation time is reduced to a certain value, the accumulated nmr T2 signal is no longer changed.
Fitting a linear segment which is linearly increased on a cumulative nuclear magnetic resonance T2 signal quantity curve and corresponds to the maximum displacement pressure gradient of 1.57MPa/cm to obtain a corresponding relation A:wherein Q is the maximum value of the cumulative nmr T2 signal of the fluid in the core; t is the target T2 relaxation time; the maximum value of the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients is brought into a relation A obtained by fitting under the condition of the maximum displacement pressure gradient of 1.57MPa/cm, the relation A is used for determining the target T2 relaxation time corresponding to the maximum value of the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients, and the conversion relation between the relaxation time and the pore radius determined by mercury-pressing data is as follows: r=t·180, where r is the minimum pore radius; t is the target T2 relaxation time, and the target T2 relaxation time is converted into the pore radius, so that the minimum pore radius which can be accessed by the shale fluid under different displacement pressure gradients is determined, as shown in the figure5 and table 1 below:
TABLE 1 cumulative Nuclear magnetic resonance T2 semaphore and T2 relaxation time Change Table
The detection method is realized under the condition of fluid flow, fluid is permeated in the unconventional resource core under the action of pressure gradient in the whole process, the lower limit of the flowable pore of the fluid is determined after the fluid flow is stabilized, the whole process is a real simulation of the fluid flow in the unconventional resource stratum, the detection process accords with the unconventional resource development process, and the result is more accurate. And fluid mobility under different displacement pressure gradient conditions can be continuously detected, so that the experimental conditions are completely consistent, and a large amount of time is saved.
The foregoing details of the optional implementation of the embodiment of the present application have been described in detail with reference to the accompanying drawings, but the embodiment of the present application is not limited to the specific details of the foregoing implementation, and various simple modifications may be made to the technical solution of the embodiment of the present application within the scope of the technical concept of the embodiment of the present application, and these simple modifications all fall within the protection scope of the embodiment of the present application.
In addition, the specific features described in the above embodiments may be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, various possible combinations of embodiments of the present application are not described in detail.
Those skilled in the art will appreciate that all or part of the steps in implementing the methods of the embodiments described above may be implemented by a program stored in a storage medium, including instructions for causing a single-chip microcomputer, chip or processor (processor) to perform all or part of the steps of the methods of the embodiments described herein. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
In addition, any combination of various embodiments of the present application may be performed, so long as the concept of the embodiments of the present application is not violated, and the disclosure of the embodiments of the present application should also be considered.
Claims (12)
1. The method for quantitatively detecting the mobility of the unconventional resource core fluid is characterized by comprising the following steps of:
obtaining physical parameters of the core after oil washing treatment;
determining a displacement pressure gradient based on the physical property parameters and the displacement pressure in the core displacement testing process;
acquiring accumulated nuclear magnetic resonance T2 signal quantities of fluid in the core under different displacement pressure gradients;
and carrying out mobility quantitative detection on the core fluid based on the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients.
2. The method of claim 1, wherein the physical property parameter is a length of the core; the displacement pressure is the pressure difference between the inlet end and the outlet end of the clamp holder of the nuclear magnetic resonance apparatus in the oil displacement test process.
3. The method of claim 1, wherein the acquiring cumulative nmr T2 signal of fluid in the core at different displacement pressure gradients comprises:
sequentially acquiring nuclear magnetic resonance T2 spectrums and accumulated nuclear magnetic resonance T2 signal amounts of fluid in the core under different displacement pressure gradients from small to large according to the displacement pressure, and stopping until the difference value of the acquired nuclear magnetic resonance T2 spectrums of the fluid in the two adjacent cores is smaller than a preset difference value.
4. The method of claim 3, wherein the cumulative nmr T2 signal of the fluid in the core is obtained by:
based on nuclear magnetic resonance T2 spectrum of the fluid in the core, the corresponding cumulative nuclear magnetic resonance T2 signal quantity of the fluid in the core is obtained through an area function.
5. The method of claim 1, wherein the quantitatively detecting mobility of the core fluid based on accumulated nuclear magnetic resonance T2 signal amounts at different displacement pressure gradients comprises:
determining a target T2 relaxation time at different displacement pressure gradients based on the accumulated nuclear magnetic resonance T2 signal magnitude at the different displacement pressure gradients;
and determining the minimum pore radius which can be entered by the fluid under different displacement pressure gradients based on the target T2 relaxation time under the different displacement pressure gradients, and taking the minimum pore radius as a quantitative detection result of the mobility of the core fluid.
6. The method of claim 5, wherein determining the target T2 relaxation time for different displacement pressure gradients based on the accumulated nuclear magnetic resonance T2 signal magnitude for the different displacement pressure gradients comprises:
drawing a relation curve of accumulated nuclear magnetic resonance T2 semaphore along with T2 relaxation time under different displacement pressure gradients, wherein the T2 relaxation time adopts a logarithmic coordinate;
fitting a straight line segment in a relation curve of the accumulated nuclear magnetic resonance T2 signal quantity corresponding to the accumulated nuclear magnetic resonance T2 signal quantity obtained finally along with the T2 relaxation time to obtain a calculation formula;
substituting the maximum value in the accumulated nuclear magnetic resonance T2 signal quantity under different displacement pressure gradients into the calculation formula respectively, and calculating to obtain target T2 relaxation time under different displacement pressure gradients.
7. The method of claim 6, wherein the target T2 relaxation time is calculated using the following calculation formula:
wherein Q is the maximum value of the cumulative nmr T2 signal of the fluid in the core; t is the target T2 relaxation time; k and b are fitting coefficients, and are obtained by fitting straight line segments in a graph of the cumulative nuclear magnetic resonance T2 signal quantity of the fluid in the core along with the T2 relaxation time change relation.
8. The method of claim 5, wherein determining a minimum pore radius that fluid can enter at different displacement pressure gradients based on target T2 relaxation times at different displacement pressure gradients comprises:
based on target T2 relaxation times at different displacement pressure gradients, mercury intrusion data is utilized to obtain minimum pore radii into which fluids can enter at different displacement pressure gradients.
9. The method of claim 8, wherein the minimum pore radius is calculated using the formula:
r＝T·μ
wherein r is the minimum pore radius; t is the target T2 relaxation time; μ -conversion coefficient, determined from mercury intrusion data.
10. The method of claim 1, wherein the fluid is shale oil, tight oil, white oil, or hydrocarbons.
11. The utility model provides a unconventional resource rock core fluid mobility quantitative determination device which characterized in that includes:
the first acquisition module is used for acquiring physical parameters of the core after the oil washing treatment;
the determining module is used for determining a displacement pressure gradient based on the physical property parameters and the displacement pressure in the core displacement testing process;
the second acquisition module is used for acquiring cumulative nuclear magnetic resonance T2 signal quantities of fluid in the core under different displacement pressure gradients;
and the detection module is used for quantitatively detecting the mobility of the core fluid based on the acquired accumulated nuclear magnetic resonance T2 signal quantity of the fluid in the core.
12. A machine-readable storage medium having instructions stored thereon for causing a machine to perform the irregular resource core fluid mobility quantitative detection method of any one of claims 1-10.
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| CN117345216B (en) * | 2023-12-05 | 2024-03-15 | 西南石油大学 | Determination method for movable critical pore throat radius of water-immersed gas well Zhou Shuiti |
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