Shale Gas Lost Content Estimation via Desorption Fitting
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Solution Overview
Problem
Current methods for estimating lost gas in shale gas content tests are inaccurate due to differences between shale gas and coalbed methane, leading to a high proportion of lost gas that cannot be directly estimated using existing coalbed methane methods.
Innovation Solution
A method involving acquiring a shale core, conducting a desorption experiment, fitting desorption data using a specific objective function, correcting the core acquisition time based on fitting parameters, and calculating the lost gas content using these parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the coalbed methane lost gas estimation method is used for shale gas, then the estimation process is simple, but the estimation accuracy is poor due to the high proportion of lost gas in shale gas coring
Solution Approach 1:
The patent transforms the lost gas estimation problem from a direct calculation based on coalbed methane methods to an indirect estimation through desorption experiment parameters. By changing the estimation parameters from direct gas loss measurement to desorption kinetics parameters (diffusion coefficient, reaction order, pre-exponential factor), the method achieves better accuracy for shale gas while maintaining reasonable complexity
Solution Approach 2:
The patent introduces desorption experiments as an intermediary process between core acquisition and lost gas estimation. The desorption experiment serves as a mediator that provides kinetic parameters which are then used to calculate lost gas content, bridging the gap between simple measurement and accurate estimation
2Ease of operation
If the direct desorption method is used to measure gas content, then the measurement is straightforward, but the lost gas content cannot be directly measured and must be estimated
Solution Approach 1:
The patent performs desorption experiments as a preliminary action before final gas content determination. By conducting the desorption experiment first and obtaining kinetic parameters, the method prepares the necessary data to subsequently calculate lost gas content, ensuring that the information is captured before it is lost
Solution Approach 2:
The patent uses desorption experiment results as feedback to refine the lost gas estimation. The kinetic parameters obtained from desorption (diffusion coefficient, reaction order) are fed back into the lost gas calculation model, creating a closed-loop estimation process that improves accuracy
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 improves the precision of lost gas estimation by nonlinear fitting and least square methods, better representing actual coring conditions and providing more accurate calculations of lost gas content.
Implementation Method 1
a desorption experiment on the core is carried out to measure the content of desorbed gas in the core
Data Source
AI summary
The present invention discloses a method for determining a content of lost gas in a shale gas content test. The method includes: acquiring a shale core and recording the time required for acquiring the shale core; carrying out a desorption experiment on the shale core to obtain desorption data; acquiring a fitting objective function; fitting the desorption data by using the fitting objective function to obtain fitted desorption data; determining fitting parameters according to the desorption data and the fitted desorption data; correcting the time required for acquiring the shale core according to the fitting parameters; and obtaining the content of lost gas according to the fitting parameters and the corrected time required for acquiring the shale core. The present invention can improve the determining precision of the content of the lost gas.