Fracture Density Correlation for Time-Lapse Water Saturation
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Solution Overview
Problem
Naturally fractured reservoirs pose challenges in reservoir characterization and modeling due to fluid flow pathways influenced by natural fractures, particularly in water encroachment and high water cut ratios, which complicate field development plans.
Innovation Solution
A method and system for determining a time lapse water saturation model in naturally fractured subsurface reservoirs using a mechanical earth model, fracture network model, and pulsed neutron lifetime logs, incorporating fracture density index (FDI) to correlate water saturation over time, and validate the model with water production measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If natural fractures are present in the reservoir, then fluid flow pathways are enhanced, but water encroachment and high water cut ratios occur
Solution Approach 1:
The patent applies preliminary action by performing geomechanical modeling and fracture network characterization before water encroachment becomes severe. The system predicts future water saturation patterns by analyzing stress changes and fracture behavior in advance, allowing operators to plan well placements and production strategies proactively to mitigate water encroachment impacts
Solution Approach 2:
The patent implements feedback by integrating time-lapse water saturation measurements and production data into the geomechanical model. This feedback loop allows the system to update fracture network predictions, correlate water saturation with fracture density, and refine predictions of water encroachment patterns based on actual reservoir response to production
2Measurement precision
If comprehensive fracture characterization is performed, then reservoir modeling accuracy is improved, but data integration complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the complex reservoir characterization into distinct modules: geomechanical stress modeling, fracture network generation, water saturation prediction, and production data integration. Each module processes specific inputs and generates targeted outputs, making the overall system more manageable and interpretable despite the complexity of integrating multiple data sources
Solution Approach 2:
The patent uses an intermediary approach by introducing a fracture density index as a mediator between fracture network geometry and water saturation predictions. This index simplifies the complex relationship between fracture characteristics and fluid flow, enabling correlation without requiring direct integration of all fracture network parameters into the saturation model
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate prediction of water saturation dynamics, facilitating informed well placement and hydrocarbon production strategies by minimizing water encroachment and optimizing reservoir management.
Implementation Method 1
obtaining a plurality of pulsed neutron lifetime (PNL) logs over a respective plurality of time periods and determining the water saturation from the plurality of PNL logs
Data Source
AI summary
A time lapse water saturation model for a naturally fractured subsurface reservoir. A fracture model may be generated using a deformation and geomechanical model, and a fracture density index (FDI) is determined from the fracture model using a critical stress analysis. Additionally, a water saturation vs time is determined using from pulsed neutron lifetime (PNL) logs and a corresponding water saturation log. A time lapse water saturation model is determined using a cross-correlation of the fracture density index (FDI) and water saturation.