CN-121993188-A - Method, system, equipment and medium for calculating water saturation of low-resistance oil layer

CN121993188ACN 121993188 ACN121993188 ACN 121993188ACN-121993188-A

Abstract

The invention belongs to the technical field of oil field production oil gas, and relates to a water saturation calculation method, a system, equipment and a medium of a low-resistance oil layer. The method comprises the steps of obtaining stratum water resistivity, porosity, rock electricity parameters and capillary parameters of a reservoir in the area, determining critical thickness of the water film based on a function relation between a built resistivity increase coefficient and the thickness of the water film and the capillary parameters, combining the critical thickness of the water film and the capillary parameters to obtain a quantitative relation between water saturation and resistivity increase coefficient applicable to the area, fitting the quantitative relation to obtain fitting parameters, determining a relation between the resistivity increase rate and the water saturation, and calculating the water saturation of a low-resistance oil layer based on the obtained stratum water resistivity, the porosity and the rock electricity parameters and the determined relation between the resistivity increase rate and the water saturation. The calculation method can be used for calculating the saturation of the low-resistance oil layer with high bound water, so that the productivity development is optimized.

Inventors

LIU YONGFU
YAN NAN
YIN YUANHUA
ZHANG YUANJUN
QIN XUE
LI SHU
LI HONG
ZHANG CHENGGUANG
LUO SHENCHAO
ZHANG LEI
DENG RUI
ZHANG BO
ZHOU BIHUI
ZHANG YUE

Assignees

中国石油天然气股份有限公司

Dates

Publication Date: 20260508
Application Date: 20241107

Claims (10)

1. A method for calculating the water saturation of a low-resistance oil layer, comprising the steps of: s1, acquiring formation water resistivity, porosity, rock electricity parameters and capillary parameters of a reservoir in the region; S2, determining the critical thickness of the water film based on the functional relation between the built resistivity increase coefficient and the thickness of the water film and the capillary parameters; S3, combining critical thickness of the water film and capillary parameters to obtain a quantitative relation between the water saturation and the resistivity increase coefficient applicable to the area, fitting the quantitative relation to obtain fitting parameters, and determining a relation between the resistivity increase coefficient and the water saturation; And S4, calculating the water saturation of the low-resistance oil layer based on the stratum water resistivity, the porosity and the rock electricity parameters acquired in the step S1 and the relation between the resistivity increasing rate and the water saturation determined in the step S3.
2. The method for calculating the water saturation of a low-resistance oil layer according to claim 1, wherein in S1, the capillary parameters include a small capillary average pore throat radius, a large capillary average pore throat radius, a proportion of the small capillary and a proportion of the large capillary; The petroelectricity parameters include a cementation index and a coefficient related to lithology.
3. The method for calculating the water saturation of a low-resistance oil layer according to claim 1, wherein in S2, the constructed resistivity increase rate is expressed as a function of the thickness of the water film: ; Wherein R t /R o represents the resistivity increase rate, R C1 is the average pore throat radius of the small capillary, R C2 is the average pore throat radius of the large capillary, C 1 is the proportion of the small capillary, C 2 is the proportion of the large capillary, X is the thickness of a water film bound in the oil-containing capillary, and C 2 =1-C 1 .
4. A method for calculating the water saturation of a low resistivity oil layer according to claim 3, wherein the resistivity increase rate as a function of the thickness of the water film is constructed by: S2.1, firstly establishing a conductive model of the rock The conductive model of the rock is obtained by connecting a rock framework, argillaceous and pore fluid in parallel, and the specific relation is as follows: (01) in the formula, ; Wherein, the Is the rock resistance; is a skeleton resistance; is a muddy resistance; Is a fluid resistance; Is the argillaceous resistivity; The mud mass distribution length is represented by the formula, A cross-sectional area representing a muddy distribution; s2.2, according to a capillary theory, pore fluid, argillaceous and a rock framework act together to obtain: (02) Wherein N is the number of types of capillary, F i is the number of capillary root with radius R ci , R i is the resistance of single capillary with radius R ci , L c is the length of capillary with radius R ci , mu is the viscosity of formation water, M is the mobility of salt ions in the formation water, R w is the resistivity of the formation water, R ci is the radius of capillary, B is the number of types of small capillary containing water in rock, X is the thickness of a water film, R t is the total resistance of rock, R sh is the resistivity of clay, A sh is the cross section of clay, and L sh is the conductive length of clay; In formula (02), when x=r ci , the resistance r o is obtained when the rock is fully hydrated, and the muddy effect is ignored, formula (03) is obtained: (03) Wherein R t is the oil-bearing rock resistivity, and R o is the full water-bearing rock resistivity; According to the formula (03), the microscopic contribution of the large capillary to the resistivity is replaced by the average capillary contribution to obtain the formula (1), and the average pore throat radius R C1 of the small capillary, the average pore throat radius R C2 of the large capillary and the proportion of the small capillary are C 1 , the proportion of the large capillary is C 2 =1-C 1 , and the resistivity increasing rate is abbreviated as: (1)。
5. The method for calculating the water saturation of a low-resistance oil layer according to claim 1, wherein S2 is specifically that a relation curve of the resistivity increase rate and the water film thickness is fitted according to a function relation of the resistivity increase coefficient and the water film thickness and capillary parameters, and the water film thickness corresponding to the resistivity increase rate being equal to 3 is taken as the critical thickness of the water film for forming the low-resistance oil layer.
6. The method for calculating the water saturation of a low-resistance oil layer according to claim 1, wherein in S3, the relation between the resistivity increase rate and the water saturation is expressed as: Wherein R t /R o is resistivity increase rate, R t is oil-bearing rock resistivity, R o is complete water-bearing rock resistivity, R w is formation water resistivity, sw is water saturation; Is porosity, C, D is a fitting parameter, m is a cementation index, and A is a coefficient related to lithology.
7. A water saturation computing system for a low resistance reservoir, comprising: the data acquisition module is used for acquiring formation water resistivity, porosity, rock electricity parameters and capillary parameters of the regional reservoir; The critical thickness determining module of the water film is used for determining the critical thickness of the water film based on the function relation between the built resistivity increase coefficient and the thickness of the water film and the capillary parameter; the fitting module is used for combining critical thickness of the water film and capillary parameters to obtain a quantitative relation between the water saturation and the resistivity increase coefficient applicable to the area, fitting the quantitative relation to obtain fitting parameters, and determining a relation between the resistivity increase rate and the water saturation; And the water saturation calculation module is used for calculating the water saturation of the low-resistance oil layer based on the acquired formation water resistivity, porosity and rock electricity parameters and the relation between the determined resistivity increase rate and the water saturation.
8. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor, when executing the computer program, carries out the steps of the method for calculating the water saturation of a low-resistance oil layer according to any one of claims 1 to 6.
9. A computer-readable storage medium storing a computer program, characterized in that the computer program, when executed by a processor, implements the steps of the method for calculating the water saturation of a low-resistance oil layer according to any one of claims 1 to 6.
10. A computer program product comprising computer program/instructions which, when executed by a processor, carry out the steps of the method for calculating the water saturation of a low-resistance oil reservoir according to any one of claims 1 to 6.

Description

Method, system, equipment and medium for calculating water saturation of low-resistance oil layer Technical Field The invention belongs to the technical field of oilfield production, and particularly relates to a method, a system, equipment and a medium for calculating water saturation of a low-resistance oil layer. Background With the continued increase in global energy demand, oilfield development has become critical to maintaining a stable development of socioeconomic. However, the intricate geologic structures and diverse reservoir properties of oil fields make optimizing oil recovery strategies a mission that combines technical and economic challenges. Low-resistance reservoirs, one of the important sandstone reservoir types, are widely distributed and of considerable scale throughout the basin. The factors of the formation of the low-resistance oil layer mainly comprise macroscopic influencing factors such as regional geological structure, sedimentation effect, diagenetic effect and the like, the development degree of the low-resistance oil layer is relatively low in a high-quality reservoir region, and factors such as pore structure, irreducible water saturation, clay mineral additional conduction, rock conduction mineral and the like of the reservoir also form one of important factors of the formation of the low-resistance oil layer. However, in the aspect of quantitative calculation of the water saturation of the low-resistance oil layer, the oil reservoir height is mostly adopted for calculation, however, the oil reservoir height can be determined only under the condition of known oil-water interface in the oil reservoir height calculation, so that the oil reservoir height is difficult to determine, the calculation result of the water saturation is inaccurate, and the fine interpretation of well logging data and the accurate prediction of the oil reservoir yield are seriously affected. Disclosure of Invention The invention aims to provide a method, a system, equipment and a medium for calculating the water saturation of a low-resistance oil layer, which solve the problem that the calculation result of the water saturation of the existing low-resistance oil layer is inaccurate. The invention is realized by the following technical scheme: A method for calculating the water saturation of a low-resistance oil layer, comprising the following steps: s1, acquiring formation water resistivity, porosity, rock electricity parameters and capillary parameters of a reservoir in the region; S2, determining the critical thickness of the water film based on the functional relation between the built resistivity increase coefficient and the thickness of the water film and the capillary parameters; S3, combining critical thickness of the water film and capillary parameters to obtain a quantitative relation between the water saturation and the resistivity increase coefficient applicable to the area, fitting the quantitative relation to obtain fitting parameters, and determining a relation between the resistivity increase coefficient and the water saturation; And S4, calculating the water saturation of the low-resistance oil layer based on the stratum water resistivity, the porosity and the rock electricity parameters acquired in the step S1 and the relation between the resistivity increasing rate and the water saturation determined in the step S3. Further, in S1, the capillary parameters include average pore throat radius of the small capillary, average pore throat radius of the large capillary, proportion of the small capillary and proportion of the large capillary; The petroelectricity parameters include a cementation index and a coefficient related to lithology. Further, in S2, the constructed function relation between the resistivity increase rate and the water film thickness is expressed as: ; Wherein R t/Ro represents the resistivity increase rate, R C1 is the average pore throat radius of the small capillary, R C2 is the average pore throat radius of the large capillary, C 1 is the proportion of the small capillary, C 2 is the proportion of the large capillary, X is the thickness of a water film bound in the oil-containing capillary, and C 2=1-C1. Further, the construction process of the function relation of the resistivity increase rate and the water film thickness is as follows: S2.1, firstly establishing a conductive model of the rock The conductive model of the rock is obtained by connecting a rock framework, argillaceous and pore fluid in parallel, and the specific relation is as follows: (01) in the formula, ; Wherein, the Is the rock resistance; is a skeleton resistance; is a muddy resistance; Is a fluid resistance; Is the argillaceous resistivity; The mud mass distribution length is represented by the formula, A cross-sectional area representing a muddy distribution; s2.2, according to a capillary theory, pore fluid, argillaceous and a rock framework act together to obtain: (02) Wherein N is the nu