In Situ Gas Evaluation in Shale Reservoirs
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Solution Overview
Problem
Current methods for evaluating gas and liquid content in low permeability reservoirs, such as shale formations, are inefficient as they require core sampling and laboratory analysis, and do not directly assess the in-situ gas or liquid composition, especially in heterogeneous formations with complex fracture networks.
Innovation Solution
A method involving drilling a wellbore into a shale formation, casing, and perforating to liberate and solubilize trapped gases and liquids, forming a plume that is then analyzed for identity and quantity using spectral analysis techniques, allowing for in-situ evaluation of gas and liquid content without the need for core sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If core sampling and laboratory analysis are used to evaluate gas and liquid content, then measurement precision is improved, but productivity deteriorates due to time-consuming sampling and lab procedures
Solution Approach 1:
The patent replaces mechanical core sampling and laboratory analysis with in-situ optical spectroscopy measurement. The system uses electromagnetic radiation (NIR, MIR, or Raman spectroscopy) to directly measure gas and liquid content in the formation without physical sampling, eliminating the mechanical extraction and lab processing steps while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces an intermediary fluid (such as CO2, N2, or other gases) that is injected into the formation to liberate trapped gases and liquids. This intermediary fluid acts as a mediator between the measurement system and the target hydrocarbons, enabling their release and subsequent detection without direct contact with the formation matrix.
2Device complexity
If traditional seismic imaging and total organic carbon analysis are used, then device complexity is reduced, but measurement precision deteriorates as these methods do not directly analyze gas or liquids
Solution Approach 1:
The patent replaces indirect geological indicators (seismic imaging, total organic carbon content) with direct spectroscopic measurement of gas and liquid composition. By using optical spectra to directly detect molecular signatures of hydrocarbons, the system achieves precise compositional analysis without complex geological interpretation chains.
Solution Approach 2:
The patent utilizes spectral absorption and emission characteristics (analogous to color changes in optical domain) of different gas and liquid components. Each hydrocarbon component has unique spectral fingerprints in NIR, MIR, or Raman regions, allowing direct identification and quantification based on these characteristic spectral responses.
3Productivity
If in-situ spectral analysis is implemented, then productivity is improved by eliminating core sampling, but device complexity increases due to specialized measurement equipment
Solution Approach 1:
The patent employs a multi-functional measurement system that can perform multiple types of spectral analysis (NIR, MIR, Raman) using a unified platform. The same basic spectroscopic apparatus can be configured for different measurement modes and can analyze various hydrocarbon components simultaneously, reducing overall system complexity compared to multiple specialized systems.
Solution Approach 2:
The patent extracts only the essential measurement function from complex laboratory analysis. By isolating the key task of hydrocarbon detection and implementing it through focused spectral measurement in the wellbore environment, the system achieves high productivity with a streamlined device that performs only the critical measurement function rather than full laboratory characterization.
4Measurement precision
If heterogeneity in fracture networks and hydrocarbon accumulation is considered, then measurement precision is improved, but device complexity increases due to need for multiple measurement points
Solution Approach 1:
The patent uses a dynamic measurement approach where the measurement tool is moved along the wellbore to acquire spectral data at multiple locations. This dynamic positioning allows sampling of heterogeneous formation zones without requiring a permanently complex multi-point fixed system. The mobility of the measurement device provides spatial resolution while maintaining system simplicity.
Solution Approach 2:
The patent divides the formation evaluation into discrete measurement segments along the wellbore trajectory. Each spectral measurement captures the local hydrocarbon content and composition in a specific formation interval, and these segmented measurements are subsequently integrated to build a comprehensive picture of the heterogeneous reservoir, simplifying the measurement approach while capturing spatial variability.
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 enables accurate determination of gas and liquid composition and quantity within the reservoir, improving the assessment of hydrocarbon accumulation and recovery potential by directly analyzing the liberated gases and liquids in the wellbore fluid plume, overcoming the limitations of traditional methods.
Implementation Method 1
solubilizing in the wellbore fluid the free and absorbed gas, forming a plume comprising solubilized gas
Implementation Method 2
determining an identity and amount of solubilized gas in the plume
Data Source
AI summary
A method may include drilling a wellbore, the wellbore intersecting a shale formation at an interval of the shale formation and casing at least a portion of the wellbore. The method may also include perforating the casing at the interval to fluidly couple the interval and the wellbore, and liberating free and absorbed gas entrapped within the interval. In addition, the method may include solubilizing in the wellbore fluid the free and absorbed gas, forming a plume comprising solubilized gas, and determining an identity and amount of solubilized gas in the plume.