Open Access

ARTICLE

A New Approach for Evaluating and Optimizing Hydraulic Fracturing in Coalbed Methane Reservoirs

Xia Yan¹, Wei Wang¹, Kai Shen^2,*, Yanqing Feng¹, Junyi Sun¹, Xiaogang Li¹, Wentao Zhu¹, Binbin Shi¹, Guanglong Sheng^2,3
1 China United Coalbed Methane National Engineering Research Center Co. Ltd., Beijing, 100095, China
2 School of Petroleum Engineering, Yangtze University, Wuhan, 430100, China
3 PetroChinaCoalbed Methane Company Limited, Beijing, 100028, China
* Corresponding Author: Kai Shen. Email:

Energy Engineering https://doi.org/10.32604/ee.2025.070360

Received 14 July 2025; Accepted 29 August 2025; Published online 19 September 2025

Abstract

In the development of coalbed methane (CBM) reservoirs using multistage fractured horizontal wells, there often exist areas that are either repeatedly stimulated or completely unstimulated between fracturing stages, leading to suboptimal reservoir performance. Currently, there is no well-established method for accurately evaluating the effectiveness of such stimulation. This study introduces, for the first time, the concept of the Fracture Network Bridging Coefficient (FNBC) as a novel metric to assess stimulation performance. By quantitatively coupling the proportions of unstimulated and overstimulated volumes, the FNBC effectively characterizes the connectivity and efficiency of the fracture network. A background grid calibration method is developed to quantify the stage-controlled volume, effectively stimulated volume, unstimulated volume, and repeatedly stimulated volume among different stages of horizontal wells. Furthermore, an optimization model is constructed by taking the FNBC as the objective function and the fracturing injection rate and fluid volume as optimization variables. The Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm is employed to iteratively perturb and optimize these variables, progressively improving the FNBC until the optimal displacement rate and fluid volume corresponding to the maximum FNBC are obtained. Field application in a typical CBM multistage fractured horizontal well in China demonstrates that the FNBC increased from 0.358 to 0.539 (a 50.6% improvement), with the injection rate rising from 16 m³/min to 24 m³/min and the average fluid volume per stage increasing from 2490 m³ to 3192 m³, significantly enhancing the stimulation effectiveness. This research provides theoretical support for designing high-efficiency stimulation strategies in unconventional reservoirs under dynamic limits.

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Keywords

Coalbed methane; FNBC; fracturing stimulation parameters; background grid method

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