Reservoir fluid saturation calculation method
By establishing a reservoir fluid saturation calculation model based on conventional logging, the problem of difficulty in obtaining various reservoir saturations at once in existing technologies has been solved, realizing rapid and economical reservoir fluid saturation calculation, and supporting production capacity prediction and remaining oil distribution research.
Patent Information
- Application Number
- CN202510968828.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-15
- Publication Date
- 2025-10-17
AI Technical Summary
Existing technologies make it difficult to obtain reservoir movable oil saturation, residual oil saturation, movable water saturation, and irreducible water saturation at one time through conventional logging methods, and the reliance on nuclear magnetic resonance or core analysis results in high costs and long cycles.
Based on conventional logging curves, a reservoir fluid saturation calculation model was established. The reservoir bound water saturation, movable water saturation, movable oil saturation, and residual oil saturation were solved by mathematical model and logging parameters. The reservoir water saturation was calculated using sonic transit time, density and neutron porosity logging curves and Archie's formula. The apparent resistivity of mixed formation water was calculated by combining mud filtrate resistivity and formation water resistivity.
It enables rapid and economical calculation of reservoir fluid saturation based on conventional logging, providing technical support for production capacity prediction and remaining oil distribution research, with errors within the interpretation standard range.
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Figure CN120804466A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of mine geophysical well logging interpretation, in particular to a reservoir fluid saturation calculation method. BACKGROUND
[0002] The interpretation of well logging data is a key technology for oilfield exploration and development, and the calculation of reservoir fluid saturation is its core. Currently, the Arpich formula or its improved version is used to calculate the oil saturation of the reservoir. The interpretation of the irreducible water saturation and residual oil saturation is not completely based on the evaluation method of conventional logging data, and mostly relies on the determination of new logging technology (nuclear magnetic resonance) or core analysis data, which has a long cycle and high cost. So far, there is no method for one-time calculation of the movable oil saturation, residual oil saturation, movable water saturation and irreducible water saturation of the reservoir through conventional logging interpretation. SUMMARY
[0003] The present application aims to solve the above problems by one-time calculation of the residual oil saturation, movable oil saturation, irreducible water saturation and movable water saturation based on conventional logging curves, and to provide a simple and convenient model for the interpretation of various oil and water saturations in the reservoir.
[0004] The technical scheme of the present application is as follows: A reservoir fluid saturation calculation method, the method being as follows.
[0005] 1. Establishing a unit volume of original rock model as shown in the following figure: Figure 1 ; obtaining the following formula: (1) (2) Based on the unit volume of the original rock model, the following formula is established in combination with the definition of the water saturation of the reservoir: (3).
[0006] 2. Establishing a volume model of the reservoir after being flushed by mud filtrate as shown in the following figure: Figure 2 ; obtaining the following formula: (4) In the formula: is the cross-sectional area of the irreducible water in the unit volume; is the cross-sectional area of the movable water in the unit volume; is the cross-sectional area of the movable oil in the unit volume; is the cross-sectional area of the residual oil in the unit volume; is the total porosity of the reservoir; is the effective porosity of the reservoir; is the water saturation of the reservoir. is the mud filtrate resistivity; is the formation water resistivity; is the flushed zone mixed formation water apparent resistivity.
[0007] 3. solving the related parameters in formula (1), formula (2), formula (3) and formula (4); the total porosity of the reservoir is calculated through an acoustic travel time AC logging curve; the effective porosity of the reservoir is obtained through intersection of a density RHOB and a neutron porosity NPHI two logging curves or is measured through a laboratory core analysis; the water saturation of the reservoir is calculated through an Archie formula; the mud filtrate resistivity is calculated through a mud resistivity; the formation water resistivity is calculated through a formation water salinity; the flushed zone mixed formation water apparent resistivity is calculated through the following formula: (5) in the formula, is the eight-lateral resistivity; is the cementation exponent; is the lithology coefficient.
[0008] 4. the above related parameters are substituted into formula (1), formula (2), formula (3) and formula (4) to obtain: (6) (7) (8) (9).
[0009] 5. calculating the irreducible water saturation , the movable water saturation , the movable oil saturation and the residual oil saturation , specifically: (10) (11) (12) (13).
[0010] The technical effect of the present application is that: This method establishes a raw rock model and a mud filtrate invasion reservoir model, converting them into a mathematical model. Based on the definitions of well logging parameters, a system of equations is established, incorporating well logging curves as known data to determine key reservoir parameters: irreducible water saturation, movable water saturation, residual oil saturation, and movable oil saturation. This method provides a well logging interpretation model that calculates various reservoir fluid saturations based on conventional well logging methods, providing technical support for productivity prediction and residual oil distribution research. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 This is the original reservoir model.
[0012] Figure 2 This is a mud filtrate invasion reservoir model. DETAILED DESCRIPTION
[0013] Specific experimental steps A method for calculating reservoir fluid saturation is as follows: 1. Establish the original rock model per unit volume such as Figure 1 ; Get equation (1)-equation (2); Combined with reservoir water saturation The definition of , we get formula (3); 2. Establish the volume model of the reservoir after being flushed by mud filtrate. Figure 2 ; get formula (4); 3. Solve the relevant parameters in equations (1), (2), (3) and (4); specifically, the total porosity of the reservoir Calculated by AC logging curve; effective porosity of reservoir The water saturation of the reservoir is obtained by intersecting the two well logging curves of density RHOB and neutron porosity NPHI or by laboratory core analysis. Calculated by Archie's formula; Mud filtrate resistivity Calculated by mud resistivity; formation water resistivity Calculated by formation water salinity; apparent resistivity of mixed formation water in flushing zone Through formula (5); 4. Substitute the above parameters into equations (1), (2), (3) and (4) to obtain the cross-sectional area of bound water per unit volume: , the cross-sectional area of movable water per unit volume , cross-sectional area of movable oil per unit volume and the cross-sectional area of residual oil per unit volume ; See formula (6)-formula (9); 5. Calculate the bound water saturation using equations (10) to (13) , movable water saturation , movable oil saturation and residual oil saturation .
[0014] Specific experimental example 1 The total porosity of a certain layer of a certain well is determined by conventional logging, core analysis and nuclear magnetic resonance to be 8.2%, the effective porosity of the reservoir is 5.74%, the formation water resistivity is 0.2 Ω·m, the eight lateral resistivity is 32 Ω·m, the mud filtrate resistivity is 0.35 Ω·m, the cementation exponent is 1.78, the lithology coefficient is 1.27, and the water saturation is 63.0%.
[0015] The irreducible water saturation is measured to be 20.16%, the movable water saturation is 42.84%, the movable oil saturation is 29.53%, and the residual oil saturation is 7.47%.
[0016] The method provided by the application is used to calculate each saturation, and the specific mode is as follows: The flushed zone mixed formation water apparent resistivity is calculated by formula (5); The cross-sectional area of irreducible water per unit volume , the cross-sectional area of movable water per unit volume , the cross-sectional area of movable oil per unit volume , and the cross-sectional area of residual oil per unit volume are sequentially solved: The irreducible water saturation , the movable water saturation , the movable oil saturation , and the residual oil saturation are further calculated by formula (10)-formula (13), and the specific modes are as follows: ; ; ; .
[0017] Error of model calculation and measured data: bound water saturation Error of model calculation and measured data: bound water saturation Error of model calculation and measured data: bound water saturation Error of model calculation and measured data: bound water saturation Error of model calculation and measured data: bound water saturation The error of model calculation and actual value can meet the requirement of interpretation standard.
[0018] Specific experimental example 2 A certain exploration well, through core analysis, the total porosity of reservoir is determined as 14.2%, the effective porosity of reservoir is 10.74%, the formation water resistivity is 0.18Ω.m, the eight lateral resistivity is 23Ω.m, the mud filtrate resistivity is 0.623Ω.m, the cementation index is 1.5, the lithology coefficient is 2.4 and the water saturation is 46.32%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%.
[0019] The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%.
[0020] The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. The measured bound water saturation is 9.12%, the movable water saturation is 37.20%, the movable oil saturation is 37.54%, and the residual oil saturation is 16.14%. , in particular: ; ; ; .
[0021] Error of the model calculation and the measured data: bound water saturation is 1.88%, the error of the movable water saturation is 1.88%, the error of the movable oil saturation is 0.99%, the error of the residual oil saturation is 0.99%. The error of the model calculation value and the actual value can meet the requirements of the interpretation standard.
Claims
1. A method for calculating reservoir fluid saturation, characterized in that: A unit volume model of the original rock and a volume model of the reservoir after being flushed with mud filtrate are established. Based on the volumes of irreducible water, movable water, movable oil, and residual oil per unit volume and their definitions, these models are converted into mathematical models. Well logging curves are introduced as known data to solve the mathematical model, and the cross-sectional areas of irreducible water, movable water, movable oil, and residual oil per unit volume are obtained. The irreducible water saturation, movable water saturation, movable oil saturation, and residual oil saturation are then solved according to their definitions.
2. The reservoir fluid saturation calculation method according to claim 1, characterized in that: By constructing the following system of equations: Where: is the cross-sectional area of bound water per unit volume; is the cross-sectional area of movable water per unit volume; is the cross-sectional area of movable oil per unit volume; is the cross-sectional area of residual oil per unit volume; is the total porosity of the reservoir; is the effective porosity of the reservoir; is the reservoir water saturation; is the resistivity of the mud filtrate; is the formation water resistivity; The apparent resistivity of the mixed formation water in the flushing zone; Solve the equations together to get the bound water cross-sectional area per unit volume , the cross-sectional area of movable water per unit volume , cross-sectional area of movable oil per unit volume and the cross-sectional area of residual oil per unit volume ; According to the irreducible water saturation , movable water saturation , movable oil saturation and residual oil saturation The irreducible water saturation can be obtained by solving the definition of , movable water saturation , movable oil saturation and residual oil saturation .
3. The reservoir fluid saturation calculation method according to claim 2, characterized in that: The irreducible water saturation , movable water saturation , movable oil saturation and residual oil saturation The definitions are: ； ； ； 。 4. The reservoir fluid saturation calculation method according to claim 2, characterized in that: The bound water cross-sectional area per unit volume , the cross-sectional area of movable water per unit volume , cross-sectional area of movable oil per unit volume and the cross-sectional area of residual oil per unit volume The specific solution process is: ； ； ； 。 5. The reservoir fluid saturation calculation method according to claim 2, characterized in that: The total porosity of the reservoir Calculated from the sonic transit time AC logging curve.
6. The reservoir fluid saturation calculation method according to claim 2, characterized in that: The effective porosity of the reservoir It is obtained by intersecting the density RHOB and neutron porosity NPHI logging curves, or by laboratory core analysis.
7. The reservoir fluid saturation calculation method according to claim 2, characterized in that: The reservoir water saturation Calculated by Archie's formula.
8. The reservoir fluid saturation calculation method according to claim 2, characterized in that: The resistivity of the mud filtrate Calculated by mud resistivity.
9. The reservoir fluid saturation calculation method according to claim 2, characterized in that: The formation water resistivity Calculated through formation water salinity.
10. The reservoir fluid saturation calculation method according to claim 2, characterized in that: The apparent resistivity of the mixed formation water in the flushing zone Calculated by the following formula: Where: is the eight-dimensional lateral resistivity; is the cementation index; is the lithology coefficient.