Gas Sorption Analysis for Shale Maturity and Free Gas Content
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Solution Overview
Problem
Current methods for assessing organic matter maturity in gas shale formations are either tedious, imprecise, or unsuitable for older gas shales, and existing techniques for measuring free gas content in shales are time-consuming and not representative due to methane chemisorption issues.
Innovation Solution
The use of conventional gas sorption techniques to characterize the microstructure of gas shale by measuring adsorbed and free gas, determining characteristics such as surface area, pore volume, and porosity, which correlates with shale maturity and fracture zone location for stimulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Rock-Eval pyrolysis is used to assess organic matter maturity, then maturity information can be obtained, but the method is time-consuming and requires complex temperature cycling procedures
Solution Approach 1:
The patent replaces the complex thermal cycling mechanical system of Rock-Eval pyrolysis with a simpler gas sorption system that measures methane adsorption at constant temperature. This substitution eliminates the need for temperature programming and complex pyrolysis equipment while obtaining equivalent maturity information through gas uptake measurements.
Solution Approach 2:
The patent changes the measurement parameter from temperature-dependent pyrolysis products to pressure-dependent gas adsorption. By measuring methane sorption at constant temperature across varying pressures, the method obtains maturity information through adsorption isotherms rather than through thermal cracking events, significantly reducing analysis time.
2Quantity of substance
If high pressure high temperature methane capacity measurement is used to measure free gas content, then gas content can be quantified, but the method is cumbersome and requires high pressure equipment
Solution Approach 1:
The patent changes the measurement conditions from high pressure and high temperature to ambient pressure and temperature. By conducting gas sorption measurements at reservoir conditions rather than requiring high pressure equipment, the method simplifies the device requirements while still accurately quantifying free gas content through adsorption isotherm analysis.
Solution Approach 2:
The patent employs simple, readily available equipment for gas sorption measurements rather than requiring expensive, complex high pressure equipment. The method uses standard laboratory apparatus that can be easily deployed at the wellsite, eliminating the need for specialized high pressure testing facilities.
3Quantity of substance
If Langmuir isotherm analysis is applied to methane sorption, then gas content can be calculated, but the analysis may not be representative because methane does not chemisorb on shale constituents
Solution Approach 1:
The patent changes the gas type from methane to a gas that does not chemisorb on shale, such as helium or argon. This parameter change ensures that the sorption measurement reflects purely physical adsorption in the pore structure rather than chemical interaction, providing accurate and representative data for pore volume and surface area calculations.
Solution Approach 2:
The patent introduces an intermediary gas (non-chemisorbing gas like helium) that acts as a probe for the pore structure without forming chemical bonds with shale constituents. This intermediary gas allows accurate measurement of physical pore characteristics without the confounding effects of chemisorption, ensuring the data truly represents the shale's pore architecture.
4Productivity
If conventional gas sorption is used to characterize microstructure, then rapid and accurate results are obtained, but the method requires degassing and sample preparation steps
Solution Approach 1:
The patent performs preliminary degassing of the sample before measurement to remove adsorbed gases that would interfere with the sorption experiment. This preliminary action, while adding a step, ensures accurate measurements and can be performed quickly using standard vacuum techniques, maintaining overall productivity.
Solution Approach 2:
The patent utilizes the sample's own structure and properties to perform the measurement. The gas sorption method inherently characterizes the microstructure through the sample's natural pore architecture, eliminating the need for complex external equipment or invasive preparation techniques. The sample itself serves as the measurement medium.
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 approach provides a rapid and accurate method to identify mature zones with high free gas content, optimizing stimulation processes and improving the understanding of shale reservoir quality by characterizing nanoporosity and pore connectivity.
Implementation Method 1
measuring adsorbed and free gas
Implementation Method 2
performing gas sorption on a sample of rock from the unconventional hydrocarbon reservoir
Implementation Method 3
measuring adsorbed and free gas, determining characteristics such as surface area, pore volume, and porosity
Data Source
AI summary
Systems and methods for gas sorption analysis, or analogous practices, of samples from unconventional reservoirs are described. The described analysis of samples is used to determine various properties of unconventional reservoirs, which are used in evaluating their worth and producibility.