Matrix Permeability Measurement Using Pressure-Pulse Decay on Core Segments
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Solution Overview
Problem
Measuring ultra-low matrix permeability in shale formations is challenging due to limitations in conventional laboratory methods, particularly when dealing with induced fractures and the need for accurate characterization of subsurface formations for hydrocarbon production.
Innovation Solution
A method involving the acquisition of a core from a subsurface formation, saturation with fluid, and conducting a pressure-pulse decay (PD) method on both upstream and downstream sides to determine matrix permeability, using a laboratory measurement system that applies confining pressure and records pressure pulses to calculate permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional laboratory methods (SS or PD) are used to measure matrix permeability, then measurement time is reduced, but the measurement precision deteriorates due to induced fractures and sampling errors
Solution Approach 1:
The core sample is divided into multiple segments along its length, with each segment having distinct upstream and downstream faces. This segmentation allows independent pressure pulse application and measurement at different locations, enabling the system to distinguish between matrix permeability and fracture permeability contributions by analyzing pressure decay patterns in each segment separately.
Solution Approach 2:
A pressure pulse is introduced as an intermediary mechanism to temporarily alter the fluid pressure distribution within the core sample. By applying controlled pressure pulses and monitoring the decay patterns, the system can isolate the matrix permeability signal from the confounding effects of induced fractures, using the pressure pulse as a temporary mediator to reveal the true matrix properties.
2Measurement precision
If core plugs are used instead of crushed rocks, then measurement precision improves, but device complexity increases due to the need for confining stress application
Solution Approach 1:
The pressure pulse decay system is designed to perform multiple functions: it applies confining stress to maintain core plug integrity, introduces pressure pulses to measure permeability, and monitors pressure decay to calculate matrix permeability values. By making the system multi-functional, the patent reduces the need for separate complex equipment for each function, thereby reducing overall device complexity while maintaining measurement precision.
3Measurement precision
If the GRI method is used on crushed cores, then measurement precision improves for unconfined stress conditions, but adaptability deteriorates due to sensitivity to particle size and Knudsen diffusion corrections
Solution Approach 1:
The system changes the physical parameters of the core sample by applying confining stress to restore the original in-situ conditions of the formation. This parameter change allows the use of standard pressure pulse decay methodology on core plugs while eliminating the need for complex corrections for particle size effects and Knudsen diffusion that plague crushed rock methods, thereby improving both precision and adaptability.
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
This method allows for accurate measurement of matrix permeability, even in partially fractured cores, providing reliable data for hydrocarbon production predictions and overcoming limitations of existing methods.
Implementation Method 1
conducting a pressure-pulse decay (PD) method on an upstream and a downstream side of the core by applying a pressure-pulse on the upstream and the downstream side of the core, and determining the matrix permeability from decays of the pressure-pulses
Implementation Method 2
using a laboratory measurement system that applies confining pressure and records pressure pulses to calculate permeability
Data Source
AI summary
A method for determining a matrix permeability of a subsurface formation, including the steps: acquiring a core from the subsurface formation, imposing a fluid to the core until the core is saturated with the fluid, conducting a pressure-pulse decay (PD) method on an upstream and a downstream side of the core by applying a pressure-pulse on the upstream and the downstream side of the core, and determining the matrix permeability from decays of the pressure-pulses on the upstream side and downstream side, respectively.