In the heart of China, researchers are unraveling the mysteries of deep coalbed methane (CBM), a resource that could significantly bolster the country’s energy portfolio. Shida Chen, a leading expert from the School of Energy Resources at China University of Geosciences in Beijing, has published groundbreaking research that sheds light on the dynamic gas supply mechanisms and theoretical production modes of free gas-rich deep coal reservoirs. This work, published in the journal ‘Meitian dizhi yu kantan’ (translated as ‘Petroleum Geology and Engineering’), promises to reshape the future of CBM exploration and production.
Deep coalbed methane, trapped within coal seams, has long been a tantalizing target for energy companies. However, the complex interplay between adsorbed and free gases has posed significant challenges to efficient extraction. Chen’s research delves into the heart of this issue, providing a comprehensive analysis of the production processes and dynamic partitioning mechanisms behind the production efficiency of both gas types.
The study, based on extensive core testing and assay data from exploration wells, reveals that during the production of a deep CBM well, free and adsorbed gases exhibit a continuous, synergistic gas supply characteristic. “The produced gas is identified as a mixture of both gas types at any given time,” Chen explains. This finding challenges conventional wisdom and opens up new avenues for optimizing production strategies.
One of the key insights from Chen’s research is the identification of the dynamic partitioning ratios of methane with varying occurrence states. These ratios depend on the superposition of free gas mass transfer efficiency and adsorbed gas desorption efficiency within the pressure propagation domain in varying production stages. This understanding is crucial for developing more effective extraction techniques.
The research also highlights the challenges posed by the inherent contradiction between high reservoir pressure and low desorption efficiency in the early stages of production, and high desorption efficiency with limited pressure drop in the late stages. Chen’s work suggests that constructing a “dynamic regulation system for drainage and production” could help balance gas well lifecycle and fluid production efficiency, ultimately releasing the full production potential of deep CBM reservoirs.
The implications for the energy sector are profound. By understanding the synergistic gas supply mechanism and theoretical production modes of methane with multiple occurrence states, energy companies can develop more efficient extraction methods. This could lead to increased production rates, reduced costs, and a more sustainable energy future.
Chen’s research also underscores the importance of high-density well group co-production and the heterogeneity of gas-water distribution in adjusting the adsorbed and free gas proportion. This dynamic matching relationship between gas supply unit expansion and fluid supply capacity could be a game-changer for the industry.
Looking ahead, Chen’s work suggests that the core strategies for production growth include increasing the stimulated reservoir volume, extending the horizontal sections of wells, and pinpointing free gas-rich zones with high porosity and permeability. Moreover, enhancing the desorption efficiency of adsorbed gas and the overall influential depth of pressure drop could be key to increasing exploration depths.
As the energy sector continues to evolve, research like Chen’s will play a pivotal role in shaping the future of deep coalbed methane exploration and production. By providing a deeper understanding of the dynamic gas supply mechanisms and production modes, Chen’s work paves the way for more efficient and sustainable energy extraction. The insights gained from this research could revolutionize the industry, making deep coalbed methane a more viable and attractive energy source.
