Coalbed Methane Production Share Calculation Method
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Solution Overview
Problem
Conventional methods for determining the production shares of free gas and adsorbed gas in deep coalbed methane wells are complex and difficult to popularize, hindering the optimization of coalbed methane development technology and prediction of development indexes.
Innovation Solution
A method involving data collection for original formation pressure and PVT sampling, isothermal adsorption experiments, Langmuir pressure and volume determination, and calculation of daily production shares of free gas and adsorbed gas under varying formation pressures, simplifying the process for obtaining production shares.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional simulation models and control equations are used to determine production shares, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and utilizes only the essential parameters (original formation pressure Pi, deviation factors Z, isothermal adsorption data, Langmuir parameters PL and VL) needed for production share determination, eliminating the need for complex simulation models and control equations while maintaining measurement precision through direct parameter measurement and calculation
Solution Approach 2:
Instead of using complex forward simulation to predict production shares, the patent inverts the approach by directly measuring current formation pressure and using established relationships (Langmuir isotherm, material balance equations) to calculate production shares, thereby simplifying the methodology while preserving accuracy
2Manufacturing precision
If complex simulation and fitting methods are applied, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent performs preliminary determination of Langmuir parameters (PL, VL) through isothermal adsorption experiments on core samples before field application. These pre-determined parameters are then used in simplified field calculations, eliminating the need for complex simulation and fitting during actual production evaluation, thus improving ease of implementation while maintaining precision
Solution Approach 2:
The patent replaces expensive and complex simulation software and iterative fitting procedures with simple algebraic calculations based on measured parameters. This substitution of simple calculation formulas for complex computational tools makes the method easier to implement in field conditions while achieving the same evaluation accuracy
3Reliability
If detailed simulation models are used, then reliability is improved, but productivity decreases
Solution Approach 1:
The patent segments the production evaluation into distinct components: free gas production calculated from material balance using measured pressure and deviation factors, and adsorbed gas production calculated from Langmuir isotherm relationships. This segmentation allows each component to be calculated independently using simple formulas, improving evaluation speed while maintaining reliable predictions through physically-based calculations
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
The method is simple, easy to implement, and provides effective production share data for optimizing coalbed methane well development, predicting development indexes, and evaluating mining effects, with strong field application value.
Implementation Method 1
collecting isothermal adsorption experimental data carried out on deep coal rocks, as well as adsorbed gas content G0a and free gas content G0f under the original formation pressure and the temperature conditions
Implementation Method 2
collecting an original formation pressure Pi and PVT sampling experimental analysis data of a target coalbed methane well, so as to obtain deviation factors corresponding to different pressures under coalbed methane well formation temperature conditions
Data Source
AI summary
A method for determining production shares of free gas and adsorbed gas in deep coalbed methane well mining includes steps of: collecting an original formation pressure and PVT sampling experimental analysis data of a coalbed methane well to obtain deviation factors; collecting isothermal adsorption experimental data as well as adsorbed gas content and free gas content under the original formation pressure and the temperature conditions; determining a Langmuir pressure and a Langmuir volume based on the isothermal adsorption experimental data; determining daily production of the free gas and the adsorbed gas, determining a coalbed methane recovery percent, and determining production shares of the free gas and the adsorbed gas under any formation pressure; and obtaining the production shares of the free gas and the adsorbed gas under different recovery percent. The method is simple, easy to understand and implement.