Coalbed Methane Productivity Evaluation Accounting for Fracturing Fluids
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Solution Overview
Problem
Conventional methods for determining the productivity of deep coalbed methane wells do not account for the impacts of fracturing fluids and produced water, leading to inaccurate predictions.
Innovation Solution
A method involving data collection, including PVT experimental data and production rates, to establish a deliverability equation that considers the effects of fracturing fluids and produced water, using a series of steps to iteratively determine formation pressures and coefficients for a binomial deliverability equation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to determine productivity of deep coalbed methane wells, then the determination process is simple, but the accuracy of productivity evaluation is poor because the impacts of fracturing fluids and produced water are not considered
Solution Approach 1:
The method segments the productivity evaluation into multiple stages: first determining the deliverability equation coefficients (A and B) using early production data, then using this equation to calculate formation pressures at subsequent test points, and finally evaluating productivity at each stage. This segmentation allows the complex evaluation to be performed systematically while accounting for fracturing fluid and produced water impacts at each step.
Solution Approach 2:
The method performs preliminary determination of the binomial deliverability equation coefficients A and B using initial production data before conducting subsequent productivity evaluations. This preliminary action establishes a foundation for accurate productivity determination at later stages, ensuring that the impacts of fracturing fluids and produced water are already incorporated into the evaluation model.
2Reliability
If the impacts of fracturing fluids and produced water are considered in productivity determination, then the productivity evaluation accuracy is improved, but the determination process becomes more complex
Solution Approach 1:
The method uses feedback by continuously comparing calculated formation pressures with actual production data to refine the deliverability equation coefficients. The productivity evaluation at each test point feeds back into the model, allowing the coefficients A and B to be adjusted based on actual performance, thereby improving reliability while managing complexity through iterative refinement.
Solution Approach 2:
The method changes parameters by incorporating the impacts of fracturing fluids and produced water as variable factors in the deliverability equation. Instead of treating these as constant or negligible, the method adjusts the equation parameters (A and B coefficients) to reflect the changing conditions caused by fluid impacts, thereby improving prediction reliability.
3Measurement precision
If multiple production stages are tested to account for fluid impacts, then the evaluation accuracy is improved, but the time required for determination increases
Solution Approach 1:
The method performs productivity determination at multiple production stages (at least three stages as specified), which is more than the single-stage conventional approach. This partial/excessive action ensures that the impacts of fracturing fluids and produced water are captured across different production conditions, improving measurement precision despite the increased time requirement.
Solution Approach 2:
The method performs preliminary determination of deliverability equation coefficients using early production stage data before conducting full multi-stage productivity evaluations. This preliminary action reduces the overall determination time by establishing the evaluation framework early, allowing subsequent stages to focus on refinement and validation.
Data Source
AI summary
A method for determining productivity of deep coalbed methane well considering impacts of fracturing fluids and produced water includes steps of: based on coalbed methane PVT experimental data, determining a relationship table between pressure and deviation factor, and determining process parameter; recording daily gas production rates, bottomhole flow pressures, cumulative gas productions, and cumulative water production; determining formation pressures based on a coalbed methane material balance equation considering the impacts of the fracturing fluids and the produced water; according to the formation pressures, the bottomhole flow pressures and the production rates, determining coefficients in a deliverability equation for the coalbed methane well, thereby determining the deliverability equation; putting the formation pressure and the bottomhole flow pressures into the deliverability equation and solving for the productivity of the coalbed methane well. The productivity evaluation results of the method are more in line with actual production data.