Fractured Reservoir Saturation Calculation via Percolation Network
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Solution Overview
Problem
Existing methods for calculating oil or gas saturation in fractured reservoirs, such as those based on simple fracture models and dual laterolog electrical logs, fail to accurately reflect the complex distribution of fractures and their influence on electrical properties, leading to significant errors in saturation evaluation.
Innovation Solution
A quantitative calculation method that combines full-diameter core experiment data, sealed coring analysis, dual laterolog data, and imaging logging data to establish a percolation network model of the reservoir, calibrating numerical simulation results to match core and coring analysis, and interpolating resistivity index and water saturation relationships at varying fracture porosities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If classic saturation models based on simple fracture models are used, then the calculation method is simple and easy to implement, but the accuracy of saturation calculation is poor and cannot reflect actual reservoir conditions
Solution Approach 1:
The patent transforms the simple fracture model parameters into complex pore structure parameters that reflect actual reservoir conditions. By changing from generic fracture porosity indices to specific pore throat radius distributions and percolation network parameters, the model achieves both accuracy and computational feasibility through parameter transformation rather than model complexity increase.
Solution Approach 2:
The patent replaces the traditional electrical log-based mechanical calculation system with a percolation network model that uses fluid flow dynamics principles. This substitution allows the model to capture complex fracture-matrix interactions through physical flow mechanisms rather than empirical electrical relationships, improving accuracy while maintaining computational efficiency.
2Adaptability or versatility
If pure numerical simulation is used, then the model can reflect relative variation rules, but the results differ greatly from actual reservoir conditions and cannot be used in practical log evaluation
Solution Approach 1:
The patent performs preliminary calibration of the percolation network model using core analysis data and sealed coring results before practical application. By pre-adjusting model parameters to match actual reservoir measurements, the simulation maintains flexibility for relative variation analysis while ensuring accuracy against actual reservoir conditions through prior calibration.
Solution Approach 2:
The patent establishes a feedback mechanism where numerical simulation results are continuously compared with core analysis and sealed coring data. This feedback loop allows the model to maintain adaptability for various scenarios while correcting deviations from actual reservoir conditions through iterative parameter adjustment and validation.
3Ease of operation
If simple serial and parallel calculation methods are used, then the computational process is straightforward, but the electrical properties of rock under fracture influence cannot be completely reflected
Solution Approach 1:
The patent segments the reservoir into distinct pore structure units (fractures, vugs, matrix pores) with specific percolation characteristics. This segmentation allows the complex electrical properties to be represented through modular percolation network elements, maintaining computational simplicity while capturing the complete electrical behavior through systematic unit combinations.
Solution Approach 2:
The patent creates a composite percolation network model that integrates multiple pore types (fractures, vugs, matrix) with different fluid saturation states. This composite approach represents the complete electrical properties of fractured reservoirs by combining the electrical characteristics of individual pore structures, achieving comprehensive representation without overly complex calculations.
Data Source
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AI summary
A quantitative calculation method for oil(gas) saturation of fractured reservoir during petroleum exploitation is provided. The method comprises: obtaining the fracture porosity and calculating resistivity index at different depth of fractured reservoir with known full diameter core data and imaging logging data; establishing the percolation network model of matrix and fracture combination with known pore structure feature; calibrating the numerical simulation results obtained from percolation network model based on the data of core experiment and sealed coring analysis results, then obtaining the relationship between the resistivity index (I) and water saturation (Sw) at different fracture porosity; calculating the oil (gas) saturation of fractured reservoir through selecting an interpolation function. The oil(gas) saturation calculated with said method is 0.67, however 0.49 with common method in some fractured reservoir. The accuracy is improved by more than 0.18 in the studied fractured reservoir.