CN-121994759-A - Water flooding microscopic displacement observation and quantitative analysis method

CN121994759ACN 121994759 ACN121994759 ACN 121994759ACN-121994759-A

Abstract

The invention relates to a method for observing and quantitatively analyzing water-flooding microscopic displacement, belonging to the technical field of oilfield development. The method comprises the steps of preparing a rock core sample into a visual rock slice assembly, injecting fluid into the visual rock slice assembly for displacement experiments, recording video of distribution conditions of the fluid in the slice, simultaneously intercepting pictures, establishing fluorescent picture standard samples of the rock slice in different states, analyzing oil-containing areas before and after displacement from the pictures, and analyzing occurrence states of residual oil. The defects that a glass etching model cannot reflect a real core pore structure, a recorded displacement video or a recorded picture is low in definition are overcome.

Inventors

LI ZHONGCHENG
CHEN LI
LI JINLONG
WANG HONGXUE
HUANG MINGXIN

Assignees

中国石油天然气股份有限公司

Dates

Publication Date: 20260508
Application Date: 20241108

Claims (12)

1. A method for observing and quantitatively analyzing water-flooding microscopic displacement is characterized in that, Step one, preparing a core sample into a visual rock slice assembly; Vacuumizing the visual rock slice assembly, then injecting fluid into the visual rock slice assembly for displacement experiments, recording video of distribution conditions of the fluid in the slice, simultaneously intercepting pictures, and establishing fluorescent picture standard samples of the rock slice in different states; analyzing oil-containing areas before and after displacement from the pictures; and step four, analyzing the occurrence state of the residual oil.
2. The method for observing and quantitatively analyzing water flooding microscopic displacement according to claim 1, wherein the first step is specifically to test porosity and permeability of a core, prepare a cast sheet from the core, analyze the image of the cast sheet, and prepare a core sample into a visual rock sheet assembly according to physical parameters of an original core.
3. The method for observing and quantitatively analyzing water flooding microscopic displacement according to claim 2, wherein in the first step, the core porosity and permeability are tested by selecting a plurality of original cores, taking out columnar samples from the cores, and testing the core porosity and permeability after oil washing.
4. The method for observing and quantitatively analyzing water flooding microscopic displacement according to claim 2, wherein the core is used for preparing a cast sheet and performing image analysis, specifically, a plurality of columnar samples which are subjected to porosity and permeability tests are respectively cut into block-shaped samples, the block-shaped samples are prepared into the cast sheet and then subjected to image analysis, and the structure, the components, the cracks and the surface porosity of the core sample are obtained.
5. The method for observing and quantitatively analyzing water flooding microscopic displacement according to claim 1, wherein in the second step, the vacuum is pumped, specifically, after the visual rock slice assembly is connected with the high-temperature high-pressure visual microscopic displacement equipment.
6. The method for observing and quantitatively analyzing water flooding microscopic displacement according to claim 1, wherein the different states in the second step comprise dry sample, saturated oil and oil-water mixture.
7. The method for observing and quantifying water flooding microscopic displacement according to claim 1, wherein the different states in the second step further comprise saturated water.
8. The method for observing and quantitatively analyzing the water-flooding microscopic displacement according to claim 6 is characterized by comprising the steps of injecting fluid into a visual rock slice assembly for displacement experiments, recording video of distribution of the fluid in the slice, intercepting pictures, establishing fluorescent picture standard samples of the rock slice in different states, particularly observing the whole slice by means of a fluorescent microscope and acquiring micro-nano pore images, recording fluorescent pictures of the slice before displacement, establishing fluorescent color standard pictures of slice dry samples, injecting formation oil into the slice according to set oiling displacement parameters and recording video of the displacement process until the formation oil flows out of the slice, judging that the displacement of the saturated oil is finished when the fluorescent color of the slice is not changed, establishing fluorescent color standard pictures of the saturated oil of the slice, then injecting formation water into the slice according to set water-injection displacement parameters and recording video of the displacement process until the formation water flows out of the slice, judging that the water-oil displacement is finished when the fluorescent color of the slice is not changed, and establishing the fluorescent color standard pictures of the slice oil-water-oil mixture.
9. The method for observing and quantitatively analyzing water flooding microscopic displacement according to claim 7 is characterized in that in the second step, fluid is injected into a visual rock slice assembly to conduct displacement experiments, video of distribution of the fluid in slices is recorded, pictures are taken at the same time, fluorescent picture standards of the rock slices in different states are established, specifically, the whole slices are observed by means of a fluorescent microscope and micro-nano pore images are collected, formation water is injected into the slices according to set water injection displacement parameters, video of the displacement process is recorded until the formation water flows out of the slices, when the fluorescent color of the slices is not changed any more, the end of saturated water displacement is judged, and a fluorescent color map of the saturated water of the slices is established.
10. The method for observing and quantitatively analyzing microscopic displacement of water flooding according to claim 1, wherein the oil-containing areas before and after the displacement are analyzed in the step three, specifically the oil-containing areas before and after the displacement are obtained by quantitatively analyzing the images by using Image J-fiji software.
11. The method for observing and quantitatively analyzing the microscopic displacement of the water flooding of claim 10, wherein in the third step, the Image J-fiji software is used for quantitatively analyzing the images to obtain the oil-containing areas before and after the displacement, specifically, unified analysis standards are established by using the Image J-fiji software, fluorescent colors and white colors in the photographed fluorescent pictures of the slices after the saturated oil and water flooding are respectively extracted automatically, gray scale treatment is carried out, the proportion of the fluorescent colors to the white areas is automatically calculated, and the oil-containing areas before the water flooding and the oil-containing areas after the water flooding are calculated by using the Image J-fiji software.
12. The method for observing and quantitatively analyzing microscopic displacement of water flooding according to claim 1, wherein the analysis of the occurrence of the residual oil in the fourth step is performed by observing the occurrence position and the occurrence form of the residual oil in the pores of the sheet by means of a fluorescence microscope.

Description

Water flooding microscopic displacement observation and quantitative analysis method Technical Field The invention relates to a method for observing and quantitatively analyzing water-flooding microscopic displacement, belonging to the technical field of oilfield development. Background In the current petroleum exploration process, more and more complex stratum are involved, low-permeability, unconventional and high-water-content oil and gas reservoirs become one of the main targets of exploration and development in recent years, but the laws of oil-water distribution and residual oil occurrence state of the complex stratum are not clearly known at the present stage, so that the difficulty of water injection development in later development work is high, the recovery ratio is low, and a large amount of residual oil is distributed. The theoretical guidance of the field development of the oil field is mainly based on the indoor experimental study, so that the comprehensive and deep understanding of the complex stratum oil displacement process, the fluid distribution and the microscopic occurrence state of the residual oil is particularly important, and the support is provided for improving the recovery ratio and reducing the residual oil distribution in the later work of the oil field. The microscopic surplus oil is surplus oil which remains in the rock pore structure in different occurrence states (film-like, cluster-like, corner-like, etc.). The current microscopic residual oil research method can be divided into two aspects according to different experimental equipment, wherein the first category is to obtain the relative content of residual oil in different occurrence states based on two-dimensional core sheet analysis, the research method comprises casting body sheet, scanning electron microscope, fluorescent microscope, glass etching oil displacement experiment and the like, and the second category is to obtain the relative quantity and absolute quantity of residual oil in different occurrence states based on three-dimensional small core layer by layer scanning and then through an image processing technology, and the research method comprises a nano CT technology and nuclear magnetic resonance. At present, research on microscopic visual core model production at home and abroad is mature, and the method mainly comprises visual models such as a glass etching model, a quartz sand bonding model, a conventional rock slice model and the like, but the visual core displacement process dynamic observation technology is still basically limited to a displacement agent dyeing observation method. At present, although a plurality of microscopic displacement methods or devices are proposed in China, china patent grant publication No. CN 107831148B discloses a visual rock core model microscopic displacement dynamic observation method, specifically, a visual rock core model is manufactured by using rock core slices, after the visual rock core model is vacuumized, stratum water containing nano fluorescent materials A is saturated, saturated stratum crude oil is displaced, an original oil-water distribution picture is shot by using a fluorescence microscope, displacement fluid containing nano fluorescent materials B is injected into the rock core for carrying out a displacement experiment, fluid distribution images in the rock core in the displacement process are shot, the picture after being analyzed by MATLAB software is used for determining pixel values of an area occupied by fluid to be characterized, and oil-containing areas before and after the displacement of the area shot by the visual model are counted. The Chinese patent grant publication number CN 113158594B discloses an oil displacement efficiency analysis method based on microscopic displacement simulation of a cast body sheet, which comprises the steps of converting a standard image into a gray image of a cast body sheet of an obtained target reservoir rock core, dividing the gray image of the cast body sheet, extracting a core skeleton, using an eight-neighborhood edge tracking algorithm to extract a core pore boundary, using a lattice Boltzmann method pseudo potential model to develop pore displacement flow simulation, referring to oil-water density and viscosity to determine fluid parameters, using a speed boundary at an inflow end, using a free boundary at an outflow end, using a mirror rebound boundary at an pore inner boundary, setting an initial state that an oil phase is filled in the pore, using an initial condition that the water phase flows in from the inflow end at a specific speed, combining with a displacement multiple expected value, performing iterative operation, outputting an oil-water phase distribution result, using a threshold segmentation algorithm to count the oil phase area, calculating a displacement multiple and oil displacement efficiency relation curve, and completing microscopic displacement simulation efficiency analysis of the