Shale Gas Reservoir Simulator with Modified Darcy Flow
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Solution Overview
Problem
Existing reservoir simulators, such as ECLIPSE, face limitations in accurately quantifying gas transport in shale gas reservoirs due to the validity of Darcy's law in low permeability formations and highly permeable fractures, particularly in unconventional reservoirs with complex hydraulic fracture networks.
Innovation Solution
A reservoir model that accounts for fluid flow and transport mechanisms like gas adsorption/desorption, molecular diffusion, pore size effects, non-Darcy flow behavior, and thermal constraints, using modified transport equations and apparent permeability to provide a more rigorous and accurate simulation of hydrocarbon production in shale gas reservoirs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Darcy's law is used to simulate fluid flow in shale gas reservoirs, then the simulation can be performed using conventional reservoir simulators, but the accuracy of gas transport quantification deteriorates due to low permeability formation matrix and highly permeable fractures
Solution Approach 1:
The patent modifies the transport equations by introducing non-Darcy flow parameters and dual-porosity parameters to account for the complex flow behavior in shale gas reservoirs. The modified equations incorporate terms for molecular diffusion, Knudsen diffusion, and slip flow effects that become significant in low permeability formations, thereby improving accuracy while maintaining computational feasibility through parameter-based modifications rather than fundamental equation changes
Solution Approach 2:
The patent employs a dual-porosity model that treats the reservoir as a composite system consisting of the low permeability formation matrix and highly permeable fracture network. This composite approach allows simultaneous representation of both flow regimes within a unified simulation framework, capturing the interaction between matrix storage and fracture flow pathways
2Device complexity
If conventional reservoir simulators are used for shale gas reservoirs, then the device complexity remains low, but the reliability of production forecasting deteriorates due to inability to account for complex transport mechanisms
Solution Approach 1:
The patent segments the gas transport process into distinct mechanisms: advection through fractures, molecular diffusion in the matrix, Knudsen diffusion in nanopores, and adsorption/desorption at rock surfaces. Each mechanism is modeled with appropriate transport equations that can be selectively activated based on reservoir conditions, improving reliability without requiring complete redesign of the simulator architecture
Solution Approach 2:
The modified transport equations are designed to be universally applicable across different shale gas reservoir conditions. The same framework can handle both Darcy and non-Darcy flow regimes, single-phase and multiphase flow, and varying degrees of fracture development, making the simulator more reliable across diverse applications while maintaining a unified code structure
3Productivity
If Darcy's law is applied to highly permeable hydraulic fractures, then the simulation remains computationally efficient, but the accuracy of fluid flow quantification deteriorates due to high flow velocity and rapid variations
Solution Approach 1:
The patent introduces dynamic non-Darcy flow terms that activate automatically when flow conditions exceed Darcy's law applicability limits. The modified equations include velocity-dependent terms that capture inertial effects and rapid pressure gradients in high-velocity fracture flow, allowing the simulator to adapt its complexity based on local flow conditions rather than applying fixed complexity throughout the 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
Enhances the accuracy of hydrocarbon production forecasting and optimization by accounting for complex transport mechanisms in shale gas reservoirs, leading to improved decision-making and increased production efficiency.
Implementation Method 1
the simulator of the subject disclosure also accounts for the mechanisms such as gas adsorption/desorption
Implementation Method 2
hydrocarbon molecular diffusion
Implementation Method 3
effect of pore size on hydrocarbon transport (Knudsen diffusion, Klinkenberg effect)
Implementation Method 4
thermal constraint on gas adsorption/desorption, fluid flow and transport processes
Data Source
AI summary
Methods for analyzing a reservoir in a formation containing hydrocarbon fluid are described. Information characterizing the formation is collected and applied to a formation simulator that is provided with a modified Darcy's law equation that accounts for at least one of gas adsorption/desorption, various modes of diffusive transport, and non-Darcy flow behavior, and the simulator is used to generate indications of the state of the reservoir and/or the state of production of hydrocarbon fluid from the reservoir. The modified Darcy's law equations are particularly useful in analyzing any type of formation containing any type of hydrocarbon fluid including shale formations containing hydrocarbon gases. According to one embodiment, a dual-porosity shape factor useful in a formation simulator is also provided.