CN115753864A

CN115753864A - Low-permeability reservoir oil-water micro distribution quantitative characterization method and device

Info

Publication number: CN115753864A
Application number: CN202111033748.8A
Authority: CN
Inventors: 田冷; 王恒力; 黄灿; 顾岱鸿; 刘宗科; 王嘉新; 柴晓龙; 蒋丽丽
Original assignee: China University of Petroleum Beijing
Current assignee: China University of Petroleum Beijing
Priority date: 2021-09-03
Filing date: 2021-09-03
Publication date: 2023-03-07

Abstract

The specification relates to the technical field of low-permeability reservoir development, and particularly discloses a method and a device for quantitatively characterizing oil-water micro distribution of a low-permeability reservoir, wherein the method comprises the following steps: vacuumizing and pressurizing the first rock core to saturated water, and performing nuclear magnetic resonance test to obtain saturated water nuclear magnetic resonance T ₂ A spectrum; performing a constant-speed mercury pressing experiment on the second core to obtain constant-speed mercury pressing experiment data; drying the first rock core, vacuumizing, pressurizing saturated deuterium water, then saturating the crude oil of the formation by a displacement method, and carrying out nuclear magnetic resonance test to obtain saturated oil nuclear magnetic resonance T ₂ A spectrum; displacing the first rock core with deuterium water, and performing nuclear magnetic resonance test on the displaced first rock core to obtain residual oil nuclear magnetic resonance T ₂ A spectrum; saturated water nuclear magnetic resonance T based on constant-speed mercury-pressing experimental data ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectrum and residual oil NMR T ₂ And (4) spectrum determination of oil-water micro distribution characteristics of the target reservoir. The scheme realizes the quantitative characterization of the oil-water micro distribution of the low-permeability reservoir.

Description

Low-permeability reservoir oil-water micro distribution quantitative characterization method and device

Technical Field

The specification relates to the technical field of low-permeability reservoir development, in particular to a method and a device for quantitatively characterizing oil-water micro distribution of a low-permeability reservoir.

Background

In the low permeability reservoir development process, the microscopic distribution of oil and water phases in the porous medium is extremely important. On one hand, the micro distribution of oil and water is the embodiment of the macro distribution of the oil and water and is the basis for determining the macro distribution of the oil and water, and the aggregation of crude oil and the distribution of residual oil are influenced by the micro distribution of the oil and water. On the other hand, oil-water micro-distribution has close influence on the oil-water two-phase seepage rule and the water-flooding efficiency in the water-flooding process, so that the oil-water micro-distribution is an important factor to be considered in the stages of well distribution, development technical policy formulation and tertiary oil recovery enhancement of a low-permeability reservoir.

However, the prior art cannot accurately and quantitatively represent the oil-water micro distribution of the low-permeability reservoir.

In view of the above problems, no effective solution has been proposed.

Disclosure of Invention

The embodiment of the specification provides a method and a device for quantitatively characterizing oil-water micro-distribution of a low-permeability reservoir, and aims to solve the problem that the oil-water micro-distribution of the low-permeability reservoir cannot be quantitatively characterized accurately in the prior art.

The embodiment of the specification provides a quantitative characterization method for oil-water micro distribution of a low-permeability reservoir, which comprises the following steps: vacuumizing and pressurizing the first rock core to obtain saturated water nuclear magnetic resonance T ₂ Performing spectroscopy; to the second rockPerforming a constant-speed mercury pressing experiment to obtain constant-speed mercury pressing experiment data; the first core and the second core are cores of a target reservoir of a low-permeability oil reservoir; drying the first rock core, vacuumizing, pressurizing saturated deuterium water, then saturating the formation crude oil by a displacement method, and performing nuclear magnetic resonance test to obtain saturated oil nuclear magnetic resonance T ₂ A spectrum; displacing the first core by using deuterium water, and carrying out nuclear magnetic resonance test on the displaced first core to obtain residual oil nuclear magnetic resonance T ₂ A spectrum; based on the constant-speed mercury-pressing experimental data and the saturated water nuclear magnetic resonance T ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ And (4) spectrum, determining the oil-water micro distribution characteristics of the target reservoir.

The embodiment of the specification further provides a quantitative characterization method for oil-water micro distribution of a low-permeability reservoir, which comprises the following steps: obtaining saturated water nuclear magnetic resonance T of first rock core ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectrum and residual oil NMR T ₂ A spectrum; acquiring constant-speed mercury pressing experiment data of a second core, wherein the first core and the second core are cores in a target reservoir of a low-permeability reservoir; based on the constant-speed mercury-pressing experimental data and the saturated water nuclear magnetic resonance T ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ And (4) spectrum determining the oil-water micro distribution characteristics of the target reservoir.

The embodiment of the present specification also provides a low permeability reservoir oil water micro distribution quantitative characterization device, including: a first obtaining module for obtaining saturated water nuclear magnetic resonance T of the first core ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectrum and residual oil NMR T ₂ A spectrum; the second obtaining module is used for obtaining constant-speed mercury pressing experiment data of a second core, wherein the first core and the second core are cores in a target reservoir of a low-permeability reservoir; a determination module for determining the nuclear magnetic resonance T of the saturated water based on the constant-speed mercury intrusion experimental data ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ The spectrum, trueAnd determining the oil-water micro distribution characteristics of the target reservoir.

The embodiment of the present specification further provides a computer device, which includes a processor and a memory for storing processor executable instructions, where the processor executes the instructions to implement the steps of the method for quantitatively characterizing oil and water micro-distribution of a low permeability reservoir described in any of the embodiments above.

Embodiments of the present specification further provide a computer-readable storage medium, on which computer instructions are stored, and when executed, the instructions implement the steps of the method for quantitatively characterizing oil and water micro-distribution in low permeability reservoirs described in any of the embodiments above.

In the embodiment of the specification, a quantitative characterization method for oil-water micro distribution of a low-permeability reservoir is provided, wherein a first core is vacuumized and pressurized with saturated water, and a nuclear magnetic resonance test is performed to obtain a saturated water nuclear magnetic resonance T ₂ Performing a constant-speed mercury pressing experiment on a second core to obtain constant-speed mercury pressing experiment data, wherein the first core and the second core are cores of a target reservoir of a low-permeability oil reservoir, drying the first core, vacuumizing, pressurizing saturated deuterium water, saturating the crude oil in the formation by a displacement method, and performing nuclear magnetic resonance test to obtain saturated oil nuclear magnetic resonance T ₂ And performing spectrum, namely displacing the first rock core by using deuterium water, and performing nuclear magnetic resonance test on the displaced first rock core to obtain residual oil nuclear magnetic resonance T ₂ Spectrum based on the constant-speed mercury intrusion experimental data and the saturated water nuclear magnetic resonance T ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ And (4) spectrum, determining the oil-water micro distribution characteristics of the target reservoir. In the scheme, the micro-distribution characteristics of oil and water in the original saturated oil state and the micro-distribution characteristics of oil and water in the residual oil state after water flooding are represented in a combined manner by combining a constant-speed mercury pressing experiment and a nuclear magnetic resonance experiment, the problem that the oil and water distribution is difficult to quantitatively represent in the development process of the low-permeability oil reservoir is solved, the quantitative representation of the oil and water distribution in the initial saturated oil state and the oil and water distribution in the residual oil state is realized, a well distribution scheme is formulated for the low-permeability oil reservoir, development parameters are formulated, and a residual oil excavation potential scheme is formulated to realizeThe high-efficiency development provides a solid and reliable reference basis and has very important significance for improving the recovery ratio of the low-permeability reservoir. In addition, the method has the advantages of low operation cost, convenience in calculation, high accuracy and strong applicability, and is convenient to popularize and apply in a large range in each low-permeability oil field.

Drawings

The accompanying drawings, which are included to provide a further understanding of the specification, are incorporated in and constitute a part of this specification, and are not intended to limit the specification. In the drawings:

FIG. 1 is a drawing of a sampling site of an experimental sample according to an embodiment of the present disclosure;

FIG. 2 shows a saturated water NMR T in an embodiment of the present disclosure ₂ Performing spectroscopy;

FIG. 3 is a plot of pore throat radius distribution in an embodiment of the present description;

FIG. 4 shows the NMR T of the saturated oil and residual oil states in one embodiment of the present disclosure ₂ A spectrum;

FIG. 5 is a graph of a quasi-full pore distribution curve and NMR T in one embodiment of the present disclosure ₂ A schematic of the spectrally scaled relaxation rate;

FIG. 6 is a graph of full pore distribution and throat size and frequency distribution in an embodiment of the present disclosure;

FIG. 7 is a graph of pore throat size and distribution frequency in an embodiment of the present description;

FIG. 8 is a graph of the size and distribution frequency of oil droplets in a core under a saturated oil condition according to an embodiment of the present disclosure;

FIG. 9 is a graph of the frequency of the oil droplet size and distribution in the pore throat under saturated oil conditions in an embodiment of the present disclosure;

FIG. 10 is a graph of pore and pore droplet size and distribution frequency under saturated oil conditions in one embodiment of the present disclosure;

FIG. 11 is a graph of oil droplet size and distribution frequency in a core under residual oil conditions in an example of the present disclosure;

FIG. 12 is a graph of the residual oil droplet size and distribution frequency in the pore throat for the residual oil condition in an embodiment of the present disclosure;

FIG. 13 is a graph of the pore space and the residual oil droplet size and distribution frequency in the pore space in the residual oil state in an embodiment of the present disclosure;

FIG. 14 is a partial view of a saturated oil condition in an embodiment of the present disclosure;

FIG. 15 is a partial view of a residual oil state in one embodiment of the present disclosure;

FIG. 16 is a flow chart of a method for quantitatively characterizing oil-water micro distribution of a low permeability reservoir in an embodiment of the present disclosure;

FIG. 17 is a flow chart of a method for quantitatively characterizing oil-water micro distribution of a low permeability reservoir in an embodiment of the present disclosure;

FIG. 18 is a schematic diagram of a device for quantitatively characterizing oil-water micro distribution of a low permeability reservoir in an embodiment of the present disclosure;

FIG. 19 is a schematic diagram of a computer device in one embodiment of the present description.

Detailed Description

The principles and spirit of the present description will be described with reference to a number of exemplary embodiments. It is understood that these embodiments are given solely to enable those skilled in the art to better understand and to implement the present description, and are not intended to limit the scope of the present description in any way. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

As will be appreciated by one skilled in the art, embodiments of the present description may be embodied as a system, an apparatus, a method, or a computer program product. Accordingly, the present disclosure may be embodied in the form of: entirely hardware, entirely software (including firmware, resident software, micro-code, etc.), or a combination of hardware and software.

At present, the main means for researching the micro-distribution of oil and water are as follows: CT imaging technology, oil-containing slice identification, nuclear magnetic resonance technology and numerical simulation method. Among them, the CT imaging technology can rapidly, accurately and nondestructively acquire high-resolution images representing the pore structure of rock, and in recent years, the CT imaging technology is also used in the visualization research of multi-phase flow and reaction flow of porous media. The occurrence positions and distribution characteristics of three fluids (water, benzyl alcohol and alkane respectively) in pore space and the saturation distribution of each phase of fluid are obtained by means of a micro CT imaging device, and a new research approach is provided for researching the distribution and flow characteristics of microscopic residual oil. However, the CT imaging technology has the problems of high experimental cost and incapability of quantitative characterization, so that it is difficult to develop application on a large scale. Oil-containing thin slice identification a rock core which is not polluted and can truly reflect underground fluid distribution is made into the oil-containing thin slice by using a bonding agent with low viscosity and high strength. The method has the greatest advantages that the distribution state of the fluid in the underground pore space is basically maintained, and the occurrence form of the residual oil can be observed more easily. However, the flake preparation process is difficult, has low image resolution, and is generally used for simple qualitative evaluation. The nuclear magnetic resonance technology can separate oil-water signals by adding water-soluble paramagnetic ions so as to obtain an oil-water distribution image, and the method is used for observing the flow of oil-water two phases in a pore space of a rock core and quantitatively researching the saturation distribution characteristics of oil-water. But the analysis error is large due to the poor image imaging quality. The numerical simulation method is a mesoscopic simulation method between macroscopic and microscopic, and is mainly used for researching the thermodynamic property and the migration mechanism of fluid, flow simulation under the micro-scale, the flow of complex fluid in a porous medium and the like. The numerical simulation method has the characteristics of simple calculation, low cost, strong repeatability and the like, and a large amount of research is carried out on the aspects of micro seepage, residual oil distribution and the like. However, the real core has the characteristics of pore structure characteristics, complexity, uneven rock surface roughness and the like, so that the result of numerical simulation cannot represent the real distribution and migration characteristics of the fluid in the rock.

Based on the above problems, the embodiments of the present specification provide a quantitative characterization method for oil-water micro distribution of a low permeability reservoir. In this embodiment, the method for quantitatively characterizing the oil-water micro distribution of the low permeability reservoir may include the following steps.

The first step is as follows: preparing a reservoir core with the length of 4.5-7.5 cm and the width of 2.5cm in a low-permeability reservoir, washing the core with oil, drying, and cutting a short core with the length of 0.5cm and the width of 2.5cm from one side of the core, as shown in figure 1. In fig. 1, core No. 1 is a long core, and core No. 2 is a short core. The porosity and permeability of the two cores were measured, respectively, and the measurement results are shown in table 1 below.

TABLE 1

And after the measurement result is obtained, judging whether the porosity and the permeability of the long core and the short core are close to each other, if so, executing the following steps. Otherwise, the core is prepared again. In one embodiment, whether the difference between the permeabilities of the long core and the short core is within a preset range or not may be determined, if yes, whether the difference between the porosities of the long core and the short core is within a preset range or not may be determined, and if yes, the subsequent steps may be performed. The preset range can be set according to actual conditions.

The second step is that: and vacuumizing and pressurizing the No. 1 rock core with saturated water, wherein the applied pressure is 17MPa. The nuclear magnetic resonance test parameters are as follows: the radio frequency distribution range is 1-30 MHz, the control precision is 0.1MHz, the echo time is set to 0.12ms, the waiting measurement time is 1.125s, and the scanning times are 64 times. After nuclear magnetic resonance detection, saturated water nuclear magnetic resonance T can be obtained ₂ Spectrum, as shown in fig. 2. The No. 2 rock core is used for a constant-speed mercury-pressing experiment, the model of the constant-speed mercury-pressing experiment equipment is ASPPE-730, and the mercury feeding speed is 6 multiplied by 10 ^- ⁵ mL/min. The constant rate of mercury intrusion yields pore throat size and frequency distribution curves, namely a pore radius distribution frequency curve (alternatively referred to as a pore size and frequency distribution curve, alternatively referred to as a pore size distribution curve) and a throat radius distribution frequency curve (alternatively referred to as a throat size and frequency distribution curve, alternatively referred to as a throat size distribution curve), as shown in FIG. 3.

The third step: and (3) drying the No. 1 rock core at 105 ℃ for 10 hours, cooling, vacuumizing and pressurizing again (17 MPa), and saturating deuterium solution with the purity of 99.99%. The formation crude oil is then saturated with a displacement process,and the displacement pressure is 17MPa, the displacement differential pressure is 2MPa, and the confining pressure is 19MPa until the outlet end is not producing water within 30 minutes, and the core is kept stand and aged for 600 hours at the temperature of 52 ℃ and the pressure of 17MPa. Performing nuclear magnetic test again after the aging is finished to obtain the saturated oil nuclear magnetic resonance T of the crude oil ₂ Spectrum, as shown by the solid line in fig. 4. Since saturated deuterium water in the core before the oil saturation process cannot detect a hydrogen atom signal, the nuclear magnetic detection after oil saturation is a hydrogen signal in the oil.

The fourth step: and displacing the No. 1 rock core with deuterium water under the conditions of 52 ℃, 17MPa of displacement pressure, 2MPa of displacement differential pressure and 19MPa of confining pressure, displacing to an outlet end, and performing nuclear magnetic testing again within 30 minutes. The nuclear magnetic test then yields the residual oil NMR T ₂ Spectrum, as shown by the dashed line in fig. 4. Wherein residual oil NMR T ₂ The spectra may reflect the resonance signal of the residual oil.

The fifth step: by using constant-speed mercury-pressing experimental data and saturated water nuclear magnetic resonance T ₂ The spectra jointly characterize the full pore distribution curve in the saturated water regime. Firstly, establishing a relationship between relaxation time and pore throat size, and determining the relaxation rate. According to the nuclear magnetic resonance mechanism, because the relaxation time of water in the porous medium mainly reflects the surface relaxation characteristics of water, namely the strength of interaction force between the water and the pore surfaces of the porous medium, the stronger the force between liquid and solid is, the shorter the relaxation time of the liquid is, and the longer the relaxation time of the liquid is otherwise. The transverse relaxation time of atoms in a single pore of saturated water in a homogeneous magnetic field can be approximated as:

wherein, T ₂ Is the atomic transverse relaxation time, c represents the shape factor, the pore shape factor is 3, the throat shape factor is 2; v represents the pore volume in μm ³ (ii) a S represents the surface area in μm ² (ii) a ρ is the relaxation rate in μm/ms and r is the pore radius in μm.

Referring to FIG. 5, an embodiment of the present disclosure is shownMedium-based quasi-full pore distribution curve and nuclear magnetic resonance T ₂ Graph of the spectral calibration relaxation rate. The size and distribution frequency curve of the throat and the size and distribution frequency curve of the pores obtained by constant-speed mercury pressing can be superposed to obtain a quasi-full pore distribution curve. As shown in fig. 5, the quasi-full pore distribution curve form and the full pore distribution obtained by nuclear magnetic resonance are both bimodal, and two peaks in the quasi-full pore distribution curve represent throat distribution and pore distribution, respectively. As can be seen from FIG. 5, the quasi-full pore distribution curve has a higher morphological similarity with the left peak of the full pore distribution curve, and has the condition of NMR relaxation rate calibration, so the left peak of the quasi-full pore distribution curve is used for calibrating T ₂ And (4) spectrum, and determining the relaxation rate. The abscissa of the left peak of the quasi-full pore distribution curve is 0.4 μm, the abscissa of the left peak of the full pore distribution curve is 0.63ms, which is a fine throat, the shape factor c is 2, and the relaxation rate ρ of 0.317 μm/ms is calculated by substituting the above 3 data into formula 1.

Secondly, applying a calibrated relaxation rate to carry out the nuclear magnetic resonance T on the saturated water ₂ The spectra were converted to pore and throat radius profiles, referred to as full pore profiles, as shown in FIG. 6.

Thirdly, subtracting the distribution frequency of the throat size and the distribution frequency of the distribution curve from the distribution frequency of the full pore distribution curve to obtain the pore size and the distribution frequency, and then multiplying the pore radius by a tubular-to-spherical scale factor (3/2) to obtain the full pore distribution curve under the tubular throat and spherical pore volume, namely the size and the distribution curve of all pores in the rock core and the size and the distribution curve of the throat, as shown in fig. 7.

Regarding the scale factor from tubular to spherical, where tubular is the throat and spherical is the aperture, the aperture shape factor in equation (1) is 3 and the throat shape factor is 2. Since the relaxation rate is calibrated by the throat in fig. 5, which is only suitable for the throat, the relaxation rate of the calibrated throat is converted into the relaxation rate of the calibrated pore by multiplying the pore by a tubular to spherical scaling factor.

And a sixth step: nuclear magnetic resonance T of saturated oil in FIG. 4 by relaxation rate ₂ Spectrum conversion into crude oil drop size distribution curve in full pore under saturated oil stateIt can also be called pore and throat crude oil size and distribution frequency curve, and the result is shown in the solid curve in fig. 8. Wherein the shape factor is 2 and the relaxation rate is 0.317 μm/ms.

Illustratively, the oil saturation is 77.5%, so the oil content in the throat is approximately considered to be 77.5% of the throat volume. The ordinate of the throat size distribution curve in the saturated water state may be multiplied by 0.775 to obtain the size and distribution frequency curve of the crude oil in the throat in the saturated oil state (i.e., the size distribution curve of the drops of crude oil in the throat, or the size and distribution frequency of the crude oil in the throat), and the result is shown in the dashed curve in fig. 8.

The size and distribution frequency curve of the crude oil in the throat in fig. 8 is subtracted from the size and distribution frequency curve of the crude oil in the pore and throat in fig. 8, and the abscissa of the obtained curve multiplied by 3/2 is converted into the size and distribution frequency curve of the crude oil in the pore, as shown by the solid line in fig. 9. FIG. 9 also shows the plot of crude oil size and distribution frequency in the throat under saturated oil conditions. As can be seen from FIG. 9, the radius of the crude oil drop or oil film in the throat is 0.04 μm to 1.5 μm, wherein the radius of the oil drop with the largest number corresponds to 0.4 μm; the radius of crude oil drop or oil film in the pore space is 0.15-603 μm, wherein the radius of the oil drop with the largest number is 25.4 μm, and the volume of the oil drop accounts for 2.78% of the total pore volume. In the low-permeability oil reservoir, pores are the main storage space of crude oil, and a throat is the flowing space of the crude oil, so the oil-water distribution condition in the pores is mainly analyzed. FIG. 10 is a graph showing pore oil droplet size and distribution frequency in pore and saturated oil states. As can be seen from FIG. 10, in the range of radius greater than 40 μm, the distribution frequency of oil is less than that of pores, indicating that crude oil does not completely fill the pores, and the remaining space is occupied by water, so that superposition of the crude oil signal in large pores and the crude oil signal in medium and small pores causes the frequency of crude oil to be greater than the pore frequency in the range of radius less than 40 μm. The frequency of the size and distribution of oil droplets can be quantitatively characterized by combining fig. 10 with the partial view graph of saturated oil in fig. 14. The local visual field map of the saturated oil can be obtained by slicing the core in the saturated oil state and observing under a microscope.

The seventh step: by usingRelaxation Rate residual oil NMR T in FIG. 4 ₂ The spectrum is converted into a pore and throat radius size and distribution frequency curve, i.e. a size distribution curve of residual oil droplets in the full pores in the state of residual oil, which can also be referred to as pore and throat residual oil size and distribution frequency, and the result is shown in a solid curve in fig. 11. Wherein the shape factor is 2 and the relaxation rate is 0.317 μm/ms.

Illustratively, the residual oil saturation is 44.9%, so the oil content in the throat is approximately 44.9% of the throat volume. The ordinate of the throat size and distribution frequency curve (i.e., the throat size distribution curve in the saturated water state) in fig. 7 may be multiplied by 0.449 to obtain the residual oil droplet size distribution curve in the throat, and the result is shown by the dashed curve (i.e., the throat residual oil size and distribution frequency curve in fig. 11) in fig. 11.

The pore and throat residual oil size and distribution frequency in the residual oil state of fig. 11 can be subtracted by the throat residual oil size and distribution frequency, and the abscissa of the resulting curve multiplied by 3/2 is converted into the pore residual oil droplet size distribution curve, as shown by the solid line in fig. 12 (i.e., the pore residual oil size and distribution frequency in fig. 12). The throat residual oil size and frequency of distribution are also shown in figure 12. As can be seen from FIG. 12, the radius of the residual oil drop or oil film in the throat is 0.04 μm to 1.5 μm, wherein the radius of the oil drop corresponding to the largest amount is 0.4 μm, accounting for 0.42% of the total pore volume; the radius of crude oil drop or oil film in the pore space is 0.15-318 μm, wherein the radius of the oil drop with the largest number is 11.29 μm, and the volume of the oil drop or oil film accounts for 1.58% of the total pore volume. Compared with the distribution of the crude oil in a saturated oil state, the maximum oil drop radius is reduced from 603 mu m to 318 mu m, which shows that the large oil drops are completely or partially displaced out of the rock core through water flooding, and the residual part is changed into oil drops with smaller radius and is retained in the rock core. Fig. 13 shows the pore space and the residual oil droplet size and distribution frequency curve in the pore space in the residual oil state. As can be seen from FIG. 13, the radius and distribution frequency of the residual oil drops are reduced, especially the reduction amplitude is larger for the oil drops with the radius larger than 20 μm, which indicates that the large oil drops in the pores are mainly displaced in the water flooding process. FIG. 15 is a partial view of the residual oil state, which in combination with FIG. 13, quantifiably characterizes the residual oil size and distribution.

Exemplarily, the residual oil distribution pattern in fig. 15 is mainly the large oil drop residue caused by the giardia effect and the dead-end small oil drop residue caused by the pore structure, and the residual oil with a radius larger than 10 μm, that is, the large oil drop residue in the pore is the main component, so that the large oil drop in the pore should be driven out mainly by emulsification during tertiary oil recovery by the analysis of fig. 13.

The method in the embodiment combines the constant-speed mercury injection and nuclear magnetic resonance experiments to represent the size and distribution of oil drops in the original saturated oil state and the size and distribution of residual oil drops in the residual oil state after water flooding. The method solves the problem that the oil-water distribution is difficult to quantitatively characterize in the low-permeability reservoir development process, realizes the quantitative characterization of the oil-water distribution in the initial state and the oil-water distribution in the residual oil state, provides a solid and reliable reference basis for formulating a well distribution scheme, developing development parameters and a residual oil excavation potential scheme for the low-permeability reservoir to realize high-efficiency development, and has very important significance for improving the recovery ratio of the low-permeability reservoir. The method is low in operation cost, convenient to calculate, high in accuracy, strong in applicability and convenient to popularize and apply in a large range in low-permeability oil fields.

The embodiment of the specification further provides a quantitative characterization method for the oil-water micro distribution of the low-permeability reservoir. Referring to fig. 16, a flow chart of a method for quantitatively characterizing oil-water micro distribution of a low permeability reservoir in an embodiment of the present disclosure is shown. As shown in fig. 16, a method for quantitatively characterizing oil-water micro distribution of a low permeability reservoir provided by an embodiment of the present disclosure may include the following steps.

Step S161, vacuumizing and pressurizing the first rock core to saturated water, and performing nuclear magnetic resonance test to obtain saturated water nuclear magnetic resonance T ₂ A spectrum; performing a constant-speed mercury pressing experiment on the second core to obtain constant-speed mercury pressing experiment data; the first core and the second core are cores of a target reservoir of a low permeability reservoir.

Specifically, the first core and the second core are cores in a target reservoir of a low permeability reservoir. The first core is used for performing nuclear magnetic resonance testing, and the second core is used for performing a constant-speed mercury-pressing experiment. Due to the experiment requirements of nuclear magnetic resonance tests and constant-speed mercury injection experiments, the length of the first core is larger than that of the second core under the ordinary condition. For example, the first core may have a length of 5cm or more, and the second core may have a length of 0.5cm to 1cm. For another example, a reservoir core with a length of 4.5cm to 7.5cm and a width of 2.5cm may be prepared, the core may be washed with oil, dried, and a short core with a length of 0.5cm and a width of 2.5cm may be cut from one side of the core, leaving a long core. Wherein, the long core is the first core, and the short core is the second core.

In one embodiment, the first core may be evacuated to a pressure of 17MPa of saturated water. The nuclear magnetic resonance test parameters are as follows: the radio frequency distribution range is 1-30 MHz, the control precision is 0.1MHz, the echo time is set to 0.12ms, the waiting measurement time is 1.125s, and the scanning times are 64 times. Obtaining saturated water nuclear magnetic resonance T by nuclear magnetic resonance ₂ Spectra. The second core can be used for a constant-speed mercury-pressing experiment, the model of the constant-speed mercury-pressing experiment equipment is ASPPE-730, and the mercury feeding speed is 6 multiplied by 10 ^-5 mL/min. And (5) pressing mercury at a constant speed to obtain experimental data of pressing mercury at a constant speed. The experimental data of the constant-speed mercury pressing can comprise a pore size distribution frequency curve in a saturated water state and a throat size distribution frequency curve.

Step S162, drying the first rock core, pressurizing saturated deuterium water after vacuumizing, then saturating the formation crude oil by a displacement method, and performing nuclear magnetic resonance test to obtain saturated oil nuclear magnetic resonance T ₂ Spectra.

Specifically, the first core may be dried at 105 ℃ for 10 hours, and after cooling, the first core may be re-vacuumized and pressurized (17 MPa) to saturate deuterium water with a purity of 99.99%. And then, saturating the crude oil of the formation by a displacement method, wherein the displacement pressure is 17MPa, the displacement pressure difference is 2MPa, and the confining pressure is 19MPa until the outlet end is not producing water within continuous 30 minutes, and standing and aging the core for 600 hours at the temperature of 52 ℃ and the pressure of 17MPa. Performing nuclear magnetic test again after the aging is finished to obtain saturated oil nuclear magnetic resonance T ₂ Spectra. Since saturated deuterium water in the core before the oil saturation process cannot detect a hydrogen atom signal, the nuclear magnetic detection after oil saturation is a hydrogen signal in the oil.

Step S163, displacing the first core with deuterium water, and performing nuclear magnetic resonance test on the displaced first core to obtain residual oil nuclear magnetic resonance T ₂ Spectra.

Specifically, the No. 1 rock core can be displaced by deuterium water under the conditions of 52 ℃, the displacement pressure of 17MPa, the displacement pressure difference of 2MPa and the confining pressure of 19MPa, no oil is produced when the rock core is displaced to the outlet end within 30 minutes, and the nuclear magnetic resonance T of the residual oil is obtained by performing the nuclear magnetic test again ₂ Spectra. At this point the nuclear magnetic test yields T ₂ The spectra reflect the resonance signals of the residual oil.

Step S164, based on the constant-speed mercury pressing experiment data and the saturated water nuclear magnetic resonance T ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ And (4) spectrum, determining the oil-water micro distribution characteristics of the target reservoir.

Obtaining the constant-speed mercury-pressing experimental data and the saturated water nuclear magnetic resonance T ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectrum and residual oil NMR T ₂ After spectroscopy, the oil-water micro-distribution characteristics of the target reservoir may be determined based on these data. The micro oil-water distribution characteristics can include micro oil-water distribution characteristic data of the reservoir in a saturated oil state and a residual oil state.

In the embodiment, the micro-distribution characteristic of oil and water in the original saturated oil state and the micro-distribution characteristic of oil and water in the residual oil state after water flooding are represented in a combined manner by combining a constant-speed mercury pressing experiment and a nuclear magnetic resonance experiment, the problem that the oil and water distribution is difficult to quantitatively represent in the development process of the low-permeability reservoir is solved, the quantitative representation of the oil and water distribution in the initial saturated oil state and the oil and water distribution in the residual oil state is realized, a well distribution scheme is formulated for the low-permeability reservoir, development parameters are formulated, and a residual oil excavation potential scheme is formulated to realize high-efficiency development, so that a solid and reliable reference basis is provided, and the method has very important significance in improving the recovery ratio of the low-permeability reservoir. In addition, the method has the advantages of low operation cost, convenience in calculation, high accuracy and strong applicability, and is convenient to popularize and apply in a large range in each low-permeability oil field.

In some embodiments of the present description, after determining the oil-water micro-distribution characteristics of the target reservoir, the method may further include: and determining development parameters of the target reservoir based on the oil-water micro distribution characteristics. By the mode, the reservoir development efficiency can be improved.

In some embodiments of the present description, the saturated water NMR T is based on the constant-rate mercury intrusion experimental data ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ The spectrum for determining the oil-water micro distribution characteristics of the target reservoir layer can comprise the following steps: based on the constant-speed mercury-pressing experimental data and the saturated water nuclear magnetic resonance T ₂ Determining a relaxation rate parameter through spectrum; determining a full pore size distribution curve in a saturated water state according to the constant-speed mercury intrusion experiment data, the relaxation rate parameter and the saturated water nuclear magnetic resonance T2 spectrum; according to the constant-speed mercury injection experimental data, the relaxation rate parameter and the saturated oil nuclear magnetic resonance T ₂ Determining an oil drop size distribution curve in a saturated oil state; according to the constant-speed mercury pressing experimental data, the relaxation rate parameters and the residual oil nuclear magnetic resonance T ₂ Spectra, determine the oil droplet size distribution curve in the residual oil state. By the mode, the method can be based on constant-speed mercury pressing experimental data and nuclear magnetic resonance T ₂ The spectra jointly determine the oil drop size distribution curve in the original saturated oil state and the oil drop size distribution curve in the residual oil state after water flooding.

In some embodiments herein, the constant rate mercury intrusion experimental data may include a pore size distribution curve and a throat size distribution curve; correspondingly, based on the constant-speed mercury-pressing experimental data and the saturated water nuclear magnetic resonance T ₂ Spectra, determining relaxation rate parameters, may include: superposing the pore size distribution curve and the throat size distribution curve to obtain a quasi-full pore size distribution curve; calibrating the saturated water nuclear magnetic resonance T by using the left peak of the quasi-full pore size distribution curve ₂ And (4) spectrum determination of relaxation rate parameters. By the mode, the constant-speed mercury pressing experimental data and the saturated water nuclear magnetic resonance T can be utilized ₂ And calibrating the relaxation rate by a spectrum.

In this specificationIn some embodiments, the measured constant rate mercury intrusion is based on the constant rate mercury intrusion experimental data, the relaxation rate parameter, and the saturated water NMR T ₂ The spectrum, determining the full pore size distribution curve at saturated water conditions, may include: utilizing the relaxation rate parameter to carry out the nuclear magnetic resonance T on the saturated water ₂ The spectrum is converted into a full pore size distribution curve in a saturated water state; subtracting the distribution frequency of the throat size distribution curve from the distribution frequency of the full pore size distribution curve to obtain a pore size distribution curve in the full pore size distribution curve; and multiplying the pore size distribution curve in the full pore size distribution curve by a tubular-to-spherical scale factor to obtain the pore size distribution curve under the tubular throat and spherical pore volume. In this manner, the pore size distribution curve for a tubular throat and spherical pore volume can be determined.

In some embodiments of the present description, the relaxation rate parameter is determined based on the constant rate mercury intrusion experimental data, the relaxation rate parameter, and the saturated oil NMR T ₂ The spectrum, determining the oil droplet size distribution curve in the saturated oil regime, may include: according to the relaxation rate and the saturated oil nuclear magnetic resonance T ₂ A spectrum is generated, and a crude oil drop size distribution curve in the full pores under the saturated oil state is generated; multiplying the throat size distribution curve by the oil saturation to obtain a crude oil drop size distribution curve in the throat under the saturated oil state; obtaining a crude oil drop size distribution curve in the pores under the saturated oil state based on the crude oil drop size distribution curve in the full pores under the saturated oil state and the crude oil drop size distribution curve in the throat under the saturated oil state; and determining an oil drop size distribution curve in the saturated oil state according to the crude oil size distribution curve in the pores in the saturated oil state and the saturated oil local view graph of the first core. By the method, an oil drop size distribution curve in a saturated oil state, namely an oil-water micro distribution characteristic in the saturated oil state can be obtained.

In some embodiments of the present description, the relaxation rate parameter and the residual oil NMR T are determined from the constant rate mercury intrusion experimental data ₂ Spectrum, determination of oil in residual oil StateThe droplet size distribution curve may include: according to said relaxation rate and said residual oil NMR T ₂ A spectrum is generated, and a residual oil drop size distribution curve in the full pore under the state of residual oil is generated; multiplying the throat size distribution curve by the residual oil saturation to obtain a residual oil drop size distribution curve in the throat under the state of residual oil; obtaining a crude oil size distribution curve in the pores under the residual oil state based on the residual oil droplet size distribution curve in the full pores under the residual oil state and the residual oil droplet size distribution curve in the throat under the residual oil state; and determining an oil drop size distribution curve in the residual oil state according to the original oil size distribution curve in the pores in the residual oil state and the residual oil local view graph of the first core.

In some embodiments of the present disclosure, the first core is subjected to vacuum pumping and pressurized saturated water, and subjected to nuclear magnetic resonance testing to obtain saturated water nuclear magnetic resonance T ₂ Performing spectroscopy; performing a constant-speed mercury pressing experiment on the second core to obtain constant-speed mercury pressing experiment data, which may include: measuring a first porosity and a first permeability of the first core; measuring a second porosity and a second permeability of the second core; determining whether a difference between the first porosity and the second porosity is within a first preset range; under the condition that the difference value between the first porosity and the second porosity is determined to be within a first preset range, judging whether the difference value between the first permeability and the second permeability is within a second preset range or not; under the condition that the difference value between the first permeability and the second permeability is judged to be within a second preset range, vacuumizing and pressurizing saturated water is carried out on the first rock core, and a nuclear magnetic resonance test is carried out to obtain saturated water nuclear magnetic resonance T ₂ A spectrum; and performing a constant-speed mercury pressing experiment on the second core to obtain constant-speed mercury pressing experiment data. By the method, the method is executed only under the condition that the porosity and the permeability of the first core and the second core are close to each other, the accuracy of the determined oil-water micro-distribution characteristics can be improved, and further the efficiency of reservoir development based on the oil-water micro-distribution characteristics is further improved.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. For details, reference may be made to the description of the related embodiments of the related processing, and details are not repeated herein.

The foregoing description has been directed to specific embodiments of this disclosure. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing may also be possible or may be advantageous.

The embodiment of the specification further provides a quantitative characterization method for the oil-water micro distribution of the low-permeability reservoir. Although the present specification provides method operational steps or apparatus configurations as illustrated in the following examples or figures, more or fewer operational steps or modular units may be included in the methods or apparatus based on conventional or non-inventive efforts. In the case of steps or structures which do not logically have the necessary cause and effect relationship, the execution sequence of the steps or the module structure of the apparatus is not limited to the execution sequence or the module structure described in the embodiments and shown in the drawings. When the described method or module structure is applied in an actual device or end product, the method or module structure according to the embodiments or shown in the drawings can be executed sequentially or executed in parallel (for example, in a parallel processor or multi-thread processing environment, or even in a distributed processing environment).

Specifically, fig. 17 shows a flowchart of a method for quantitatively characterizing oil-water micro distribution of a low permeability reservoir in an embodiment of the present specification. As shown in fig. 17, a method for quantitatively characterizing oil-water micro distribution of a low permeability reservoir provided by an embodiment of the present specification may include the following steps:

step S171, obtaining saturated water nuclear magnetic resonance T of first rock core ₂ Spectrum, saturated oil coreMagnetic resonance T ₂ Spectrum and residual oil NMR T ₂ Spectra.

Step S172, acquiring constant-speed mercury pressing experiment data of a second core, wherein the first core and the second core are cores in a target reservoir of a low-permeability reservoir.

The method in this embodiment may be applied to a computer device. The computer equipment can acquire the saturated water nuclear magnetic resonance T of the first core ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectrum and residual oil NMR T ₂ Spectra. And the computer equipment can also acquire the constant-speed mercury injection experimental data of the second core.

In one embodiment, the saturated water nuclear magnetic resonance T of the first core ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectrum and residual oil NMR T ₂ The spectrum and the constant-speed mercury intrusion experimental data of the second core can be input by a user through an input device.

In yet another embodiment, the saturated water nuclear magnetic resonance T of the first core is obtained in a nuclear magnetic resonance device ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectrum and residual oil NMR T ₂ After the spectrum is obtained, the saturated water nuclear magnetic resonance T of the first core can be automatically obtained ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectral and residual oil NMR T ₂ The spectra are sent to a computer device.

The first core and the second core are cores in a target reservoir of a low permeability reservoir. The first core is used for performing nuclear magnetic resonance testing, and the second core is used for performing a constant-speed mercury-pressing experiment. Due to the experiment requirements of nuclear magnetic resonance tests and constant-speed mercury injection experiments, the length of the first core is generally larger than that of the second core. For example, the first core may have a length of 5cm or more, and the second core may have a length of 0.5cm to 1cm. For another example, a reservoir core 4.5cm to 7.5cm long and 2.5cm wide may be prepared, washed with oil, dried, and a short core 0.5cm long and 2.5cm wide may be cut from one side of the core, leaving a long core. The long core is a first core, and the short core is a second core.

In one embodiment, canThe first core was evacuated and pressurized with saturated water under a pressure of 17MPa. The nuclear magnetic resonance test parameters are as follows: the radio frequency distribution range is 1-30 MHz, the control precision is 0.1MHz, the echo time is set to 0.12ms, the waiting measurement time is 1.125s, and the scanning times are 64 times. Nuclear magnetic resonance to obtain saturated water nuclear magnetic resonance T ₂ Spectra. The second core can be used for a constant-speed mercury-pressing experiment, the model of the constant-speed mercury-pressing experiment equipment is ASPPE-730, and the mercury feeding speed is 6 multiplied by 10 ^-5 mL/min. And (5) pressing mercury at a constant speed to obtain experimental data of pressing mercury at a constant speed. The experimental data of the constant-speed mercury pressing can comprise a pore size distribution frequency curve in a saturated water state and a throat size distribution frequency curve.

In one example, the first core may be dried at 105 ℃ for 10 hours, cooled, and then re-pumped to vacuum (17 MPa) to saturate deuterium water with 99.99% purity. And then, saturating the crude oil of the formation by a displacement method, wherein the displacement pressure is 17MPa, the displacement pressure difference is 2MPa, and the confining pressure is 19MPa until the outlet end is not producing water within continuous 30 minutes, and standing and aging the core for 600 hours at the temperature of 52 ℃ and the pressure of 17MPa. Performing nuclear magnetic test again after the aging is finished to obtain saturated oil nuclear magnetic resonance T ₂ Spectra. Since saturated deuterium water in the core before the oil saturation process cannot detect a hydrogen atom signal, the nuclear magnetic detection after oil saturation is a hydrogen signal in the oil.

In one embodiment, the number 1 rock core can be displaced by deuterium water under the conditions of 52 ℃, the displacement pressure of 17MPa, the displacement pressure difference of 2MPa and the confining pressure of 19MPa, oil is not produced when the rock core is displaced to the outlet end within 30 minutes continuously, and the nuclear magnetic test is carried out again to obtain the nuclear magnetic resonance T of residual oil ₂ Spectra. At this point the nuclear magnetic test gave T ₂ The spectra reflect the resonance signals of the residual oil.

Step S173, based on the constant-speed mercury pressing experiment data and the saturated water nuclear magnetic resonance T ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ And (4) spectrum, determining the oil-water micro distribution characteristics of the target reservoir.

Obtaining the constant-speed mercury-pressing experimental data and the saturated water nuclear magnetic resonance T ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectrum and residual oilNuclear magnetic resonance T ₂ After spectroscopy, the oil-water micro-distribution characteristics of the target reservoir may be determined based on these data. The micro oil-water distribution characteristics can include micro oil-water distribution characteristic data of the reservoir in a saturated oil state and a residual oil state.

In some embodiments of the present description, the saturated water nmr T is based on the constant-rate mercury intrusion experimental data ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ And (3) spectrum, determining the oil-water micro distribution characteristics of the target reservoir, wherein the spectrum comprises the following steps: based on the constant-speed mercury-pressing experimental data and the saturated water nuclear magnetic resonance T ₂ Determining a relaxation rate parameter through spectrum; according to the constant-speed mercury-pressing experimental data, the relaxation rate parameters and the saturated water nuclear magnetic resonance T ₂ Determining a full pore size distribution curve in a saturated water state; according to the constant-speed mercury-pressing experimental data, the relaxation rate parameters and the saturated oil nuclear magnetic resonance T ₂ Determining the size distribution curve of oil drops in a saturated oil state; according to the constant-speed mercury pressing experimental data, the relaxation rate parameters and the residual oil nuclear magnetic resonance T ₂ Spectra, the oil droplet size distribution curve in the residual oil state was determined.

In some embodiments herein, the constant-rate mercury intrusion experimental data includes pore size distribution curve and throatRoad size distribution curve; correspondingly, based on the constant-speed mercury-pressing experimental data and the saturated water nuclear magnetic resonance T ₂ Spectra, determining relaxation rate parameters, may include: superposing the pore size distribution curve and the throat size distribution curve to obtain a quasi-full pore size distribution curve; calibrating the saturated water nuclear magnetic resonance T by using the left peak of the quasi-full pore size distribution curve ₂ And (4) spectrum determination and relaxation rate parameter determination.

In some embodiments herein, the constant rate mercury intrusion test data, the relaxation rate parameter, and the saturated water NMR T are based on ₂ The spectrum, determining the full pore size distribution curve at saturated water conditions, may include: nuclear magnetic resonance T of the saturated water by utilizing the relaxation rate parameter ₂ The spectrum is converted into a full pore size distribution curve in a saturated water state; subtracting the distribution frequency of the throat size distribution curve from the distribution frequency of the full pore size distribution curve to obtain a pore size distribution curve in the full pore size distribution curve; and multiplying the pore size distribution curve in the full pore size distribution curve by a tubular-to-spherical scale factor to obtain the pore size distribution curve under the tubular throat and spherical pore volume.

In some embodiments herein, the constant rate mercury intrusion test data, the relaxation rate parameter, and the saturated oil NMR T are based on ₂ The spectrum, determining the droplet size distribution curve in the saturated oil regime, may include: according to the relaxation rate and the saturated oil nuclear magnetic resonance T ₂ A spectrum is generated, and a crude oil drop size distribution curve in the full pores under the saturated oil state is generated; multiplying the throat size distribution curve by the oil saturation to obtain a crude oil drop size distribution curve in the throat under the saturated oil state; obtaining a crude oil size distribution curve in the pores under the saturated oil state based on the crude oil drop size distribution curve in the whole pores under the saturated oil state and the crude oil drop size distribution curve in the throat under the saturated oil state; determining the oil in the saturated oil state according to the size distribution curve of the crude oil in the pores in the saturated oil state and the local view field diagram of the saturated oil of the first coreDrop size distribution curve.

In some embodiments herein, the constant rate mercury intrusion test data, the relaxation rate parameter, and the residual oil NMR T are based on ₂ The spectrum, determining the oil droplet size distribution curve in the residual oil state, may include: according to the relaxation rate and the residual oil NMR T ₂ A spectrum is generated, and a residual oil drop size distribution curve in the full pore under the state of residual oil is generated; multiplying the throat size distribution curve by the residual oil saturation to obtain a residual oil drop size distribution curve in the throat under the state of residual oil; obtaining a crude oil size distribution curve in the pores under the residual oil state based on the residual oil droplet size distribution curve in the full pores under the residual oil state and the residual oil droplet size distribution curve in the throat under the residual oil state; and determining an oil drop size distribution curve in the residual oil state according to the original oil size distribution curve in the pores in the residual oil state and the residual oil local view graph of the first core.

In some embodiments of the present description, a saturated water nuclear magnetic resonance T of a first core is obtained ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectrum and residual oil NMR T ₂ A spectrum, which may include: obtaining a first porosity and a first permeability of a first core; obtaining a second porosity and a second permeability of a second core; determining whether a difference between the first porosity and the second porosity is within a first preset range; under the condition that the difference value between the first porosity and the second porosity is determined to be within a first preset range, judging whether the difference value between the first permeability and the second permeability is within a second preset range or not; obtaining the saturated water nuclear magnetic resonance T of the first core under the condition that the difference value between the first permeability and the second permeability is judged to be within a second preset range ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectral and residual oil NMR T ₂ Spectra.

The foregoing description has been directed to specific embodiments of this disclosure. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing may also be possible or may be advantageous.

Based on the same inventive concept, the embodiment of the present specification further provides a device for quantitatively characterizing oil-water micro distribution of a low permeability reservoir, as described in the following embodiments. Because the principle of solving the problems of the low-permeability reservoir oil-water micro-distribution quantitative characterization device is similar to that of the low-permeability reservoir oil-water micro-distribution quantitative characterization method, the implementation of the low-permeability reservoir oil-water micro-distribution quantitative characterization device can refer to the implementation of the low-permeability reservoir oil-water micro-distribution quantitative characterization method, and repeated parts are not repeated. As used hereinafter, the term "unit" or "module" may be a combination of software and/or hardware that implements a predetermined function. Although the means described in the embodiments below are preferably implemented in software, an implementation in hardware or a combination of software and hardware is also possible and contemplated. Fig. 18 is a structural block diagram of a low permeability reservoir oil-water micro distribution quantitative characterization device according to an embodiment of the present disclosure, as shown in fig. 18, including: a first obtaining module 181, a second obtaining module 182, and a determining module 183, the structure of which will be described below.

The first obtaining module 181 is configured to obtain a saturated water nuclear magnetic resonance T of the first core ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectral and residual oil NMR T ₂ Spectra.

The second obtaining module 182 is configured to obtain constant-speed mercury intrusion experimental data of a second core, where the first core and the second core are cores in a target reservoir of a low-permeability reservoir.

The determination module 183 is configured to determine the nuclear magnetic resonance T of the saturated water based on the constant-speed mercury intrusion experimental data ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ And (4) spectrum determining the oil-water micro distribution characteristics of the target reservoir.

From the above description, it can be seen that the embodiments of the present specification achieve the following technical effects: by combining a constant-speed mercury-pressing and nuclear magnetic resonance experiment, the oil-water micro-distribution characteristic in the original saturated oil state and the oil-water micro-distribution characteristic in the residual oil state after water flooding are represented in a combined manner, the problem that the oil-water distribution is difficult to quantitatively represent in the development process of the low-permeability reservoir is solved, the quantitative representation of the oil-water distribution in the initial saturated oil state and the oil-water distribution in the residual oil state is realized, a solid and reliable reference basis is provided for establishing a well distribution scheme, development parameters and a residual oil excavation potential scheme for the low-permeability reservoir to realize high-efficiency development, and the method has very important significance for improving the recovery ratio of the low-permeability reservoir. In addition, the method has the advantages of low operation cost, convenience in calculation, high accuracy and strong applicability, and is convenient to popularize and apply in a large range in each low-permeability oil field.

The embodiment of the present specification further provides a computer device, which may specifically refer to a schematic structural diagram of the computer device shown in fig. 19 and based on the quantitative characterization method for oil-water micro distribution of a low permeability reservoir provided in the embodiments of the present specification, where the computer device may specifically include an input device 191, a processor 192, and a memory 193. The memory 193 is used for storing processor-executable instructions, among other things. The processor 192, when executing the instructions, implements the steps of the method for quantitatively characterizing oil-water micro distribution of a low permeability reservoir as described in any of the embodiments above.

In this embodiment, the input device may be one of the main apparatuses for information exchange between a user and a computer system. The input device may include a keyboard, a mouse, a camera, a scanner, a light pen, a handwriting input board, a voice input device, etc.; the input device is used to input raw data and a program for processing these numbers into the computer. The input device can also acquire and receive data transmitted by other modules, units and devices. The processor may be implemented in any suitable way. For example, the processor may take the form of, for example, a microprocessor or processor and a computer-readable medium that stores computer-readable program code (e.g., software or firmware) executable by the (micro) processor, logic gates, switches, an Application Specific Integrated Circuit (ASIC), a programmable logic controller, an embedded microcontroller, and so forth. The memory may in particular be a memory device used in modern information technology for storing information. The memory may include multiple levels, and in a digital system, the memory may be any memory as long as it can store binary data; in an integrated circuit, a circuit without a physical form and with a storage function is also called a memory, such as a RAM, a FIFO and the like; in the system, the storage device in physical form is also called a memory, such as a memory bank, a TF card and the like.

In this embodiment, the functions and effects of the specific implementation of the computer device can be explained in comparison with other embodiments, and are not described herein again.

The embodiment of the present specification further provides a computer storage medium based on the low permeability reservoir oil-water micro distribution quantitative characterization method, where the computer storage medium stores computer program instructions, and the computer program instructions, when executed, implement the steps of the low permeability reservoir oil-water micro distribution quantitative characterization method in any of the above embodiments.

In the present embodiment, the storage medium includes, but is not limited to, a Random Access Memory (RAM), a Read-Only Memory (ROM), a Cache (Cache), a Hard Disk Drive (HDD), or a Memory Card (Memory Card). The memory may be used to store computer program instructions. The network communication unit may be an interface for performing network connection communication, which is set in accordance with a standard prescribed by a communication protocol.

In this embodiment, the functions and effects specifically realized by the program instructions stored in the computer storage medium can be explained by comparing with other embodiments, and are not described herein again.

It will be apparent to those skilled in the art that the modules or steps of the embodiments of the present specification described above may be implemented by a general purpose computing device, they may be centralized on a single computing device or distributed over a network of multiple computing devices, and alternatively, they may be implemented by program code executable by a computing device, such that they may be stored in a storage device and executed by a computing device, and in some cases, the steps shown or described may be performed in an order different from that described herein, or they may be separately fabricated into individual integrated circuit modules, or multiple ones of them may be fabricated into a single integrated circuit module. Thus, embodiments of the present description are not limited to any specific combination of hardware and software.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Many embodiments and many applications other than the examples provided will be apparent to those of skill in the art upon reading the above description. The scope of the description should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

The above description is only a preferred embodiment of the present disclosure, and is not intended to limit the present disclosure, and various modifications and changes may be made to the embodiment of the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present specification shall be included in the protection scope of the present specification.

Claims

1. A quantitative characterization method for oil-water micro distribution of a low permeability reservoir is characterized by comprising the following steps:

vacuumizing and pressurizing the first rock core to obtain saturated water nuclear magnetic resonance T ₂ A spectrum; performing a constant-speed mercury pressing experiment on the second core to obtain constant-speed mercury pressing experiment data; wherein the first core and the second coreThe core is the core of a target reservoir of the low permeability reservoir;

drying the first rock core, vacuumizing, pressurizing saturated deuterium water, then saturating the formation crude oil by a displacement method, and performing nuclear magnetic resonance test to obtain saturated oil nuclear magnetic resonance T ₂ A spectrum;

displacing the first core by using deuterium water, and carrying out nuclear magnetic resonance test on the displaced first core to obtain residual oil nuclear magnetic resonance T ₂ A spectrum;

based on the constant-speed mercury-pressing experimental data and the saturated water nuclear magnetic resonance T ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ And (4) spectrum, determining the oil-water micro distribution characteristics of the target reservoir.

2. The method according to claim 1, wherein the saturated water nuclear magnetic resonance T is based on the constant-speed mercury intrusion experimental data ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ And (3) spectrum, determining oil-water micro distribution characteristics of the target reservoir, comprising:

based on the constant-speed mercury-pressing experimental data and the saturated water nuclear magnetic resonance T ₂ Spectrum, determining relaxation rate parameters;

according to the constant-speed mercury-pressing experimental data, the relaxation rate parameters and the saturated water nuclear magnetic resonance T ₂ Determining a full pore size distribution curve in a saturated water state;

according to the constant-speed mercury-pressing experimental data, the relaxation rate parameters and the saturated oil nuclear magnetic resonance T ₂ Determining an oil drop size distribution curve in a saturated oil state;

according to the constant-speed mercury injection experimental data, the relaxation rate parameter and the residual oil nuclear magnetic resonance T ₂ Spectra, determine the oil droplet size distribution curve in the residual oil state.

3. The method of claim 2, wherein the constant rate mercury intrusion experimental data includes a pore size distribution curve and a throat size distribution curve;

correspondingly, based on the constant-speed mercury injection experimental data and the saturated water nuclear magnetic resonance T ₂ Spectrum, determining relaxation rate parameters, comprising:

superposing the pore size distribution curve and the throat size distribution curve to obtain a quasi-full pore size distribution curve;

calibrating the saturated water nuclear magnetic resonance T by using the left peak of the quasi-full pore size distribution curve ₂ And (4) spectrum determination of relaxation rate parameters.

4. The method according to claim 3, wherein determining a full pore size distribution curve in a saturated water state from the constant-rate mercury intrusion experimental data, the relaxation rate parameter and the saturated water nuclear magnetic resonance T2 spectrum comprises:

utilizing the relaxation rate parameter to carry out the nuclear magnetic resonance T on the saturated water ₂ The spectrum is converted into a full pore size distribution curve in a saturated water state;

subtracting the distribution frequency of the throat size distribution curve from the distribution frequency of the full pore size distribution curve to obtain a pore size distribution curve in the full pore size distribution curve;

and multiplying the pore size distribution curve in the full pore size distribution curve by a tubular-to-spherical scale factor to obtain the pore size distribution curve under the tubular throat and spherical pore volume.

5. The method of claim 3, wherein the constant rate mercury intrusion test data, the relaxation rate parameter, and the saturated oil NMR T are measured ₂ Spectrum, determining the oil drop size distribution curve in the saturated oil state, comprising:

according to the relaxation rate and the saturated oil nuclear magnetic resonance T ₂ A spectrum is generated, and a crude oil drop size distribution curve in the full pores under the saturated oil state is generated;

multiplying the throat size distribution curve by the oil saturation to obtain a crude oil drop size distribution curve in the throat under the saturated oil state;

obtaining a crude oil size distribution curve in the pores under the saturated oil state based on the crude oil drop size distribution curve in the whole pores under the saturated oil state and the crude oil drop size distribution curve in the throat under the saturated oil state;

and determining an oil drop size distribution curve in the saturated oil state according to the crude oil size distribution curve in the pores in the saturated oil state and the saturated oil local view graph of the first core.

6. The method of claim 3, wherein the constant rate mercury intrusion test data, the relaxation rate parameter, and the residual oil NMR T are measured ₂ Spectra, determining the oil droplet size distribution curve in the residual oil state, comprising:

according to said relaxation rate and said residual oil NMR T ₂ Performing spectrum to generate a size distribution curve of residual oil drops in the full pore under the state of residual oil;

multiplying the throat size distribution curve by the residual oil saturation to obtain a residual oil drop size distribution curve in the throat under the state of residual oil;

obtaining a crude oil size distribution curve in the pores under the residual oil state based on the residual oil droplet size distribution curve in the full pores under the residual oil state and the residual oil droplet size distribution curve in the throat under the residual oil state;

and determining an oil drop size distribution curve in the residual oil state according to the original oil size distribution curve in the pores in the residual oil state and the residual oil local view graph of the first core.

7. The method as claimed in claim 1, wherein the first core is subjected to vacuum pumping and pressurizing saturated water, and subjected to nuclear magnetic resonance test to obtain saturated water nuclear magnetic resonance T ₂ A spectrum; and performing a constant-speed mercury pressing experiment on the second core to obtain constant-speed mercury pressing experiment data, wherein the constant-speed mercury pressing experiment data comprises the following steps:

measuring a first porosity and a first permeability of the first core; measuring a second porosity and a second permeability of the second core;

determining whether a difference between the first porosity and the second porosity is within a first preset range;

under the condition that the difference value between the first porosity and the second porosity is determined to be within a first preset range, judging whether the difference value between the first permeability and the second permeability is within a second preset range or not;

under the condition that the difference value between the first permeability and the second permeability is judged to be within a second preset range, vacuumizing and pressurizing saturated water is carried out on the first rock core, and a nuclear magnetic resonance test is carried out to obtain saturated water nuclear magnetic resonance T ₂ A spectrum; and performing a constant-speed mercury pressing experiment on the second core to obtain constant-speed mercury pressing experiment data.

8. A quantitative characterization method for oil-water micro distribution of a low permeability reservoir is characterized by comprising the following steps:

obtaining saturated water nuclear magnetic resonance T of first rock core ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectrum and residual oil NMR T ₂ A spectrum;

acquiring constant-speed mercury pressing experiment data of a second core, wherein the first core and the second core are cores in a target reservoir of a low permeability reservoir;

9. The utility model provides a hyposmosis oil reservoir profit microcosmic distribution quantitative characterization device which characterized in that includes:

a first obtaining module for obtaining saturated water nuclear magnetic resonance T of the first core ₂ Spectrum, saturated oil nuclear magnetic resonance T ₂ Spectral and residual oil NMR T ₂ A spectrum;

the second obtaining module is used for obtaining constant-speed mercury pressing experiment data of a second core, wherein the first core and the second core are cores in a target reservoir of a low-permeability reservoir;

a determination module for determining the nuclear magnetic resonance T of the saturated water based on the constant-speed mercury intrusion experimental data ₂ Spectrum, said saturated oil nuclear magnetic resonance T ₂ Spectra and said residual oil NMR T ₂ And (4) spectrum, determining the oil-water micro distribution characteristics of the target reservoir.

10. A computer device comprising a processor and a memory for storing processor-executable instructions that when executed by the processor implement the steps of the method of claim 8.