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The Daning-Jixian block, located in the eastern margin of the Ordos Basin, is abundant in deep coalbed methane (CBM) resources and serves as a pilot test block for deep CBM development in China. Currently, the exploration and development of a deep CBM are in the early stages. The production characteristics and development laws across different production stages are not fully elucidated, leading to uncertainties in discharge and production control measures as well as the optimization of the production system. This study addresses these challenges by analyzing actual production data from deep CBM wells. It establishes a classification standard for deep CBM wells and a production stage model diagram. Based on this, it compares and analyzes the production characteristics of deep CBM wells with middle and shallow CBM wells as well as the variations among different types of deep CBM wells. The findings reveal the following key points: (1) gas wells are categorized as low-, medium- and high-production wells based on average daily gas production of 1500 and 3000 m3/d, respectively; (2) deep CBM production is delineated into four stages: gas production rise, gas production decline, stable gas production, and gas production depletion; (3) in contrast to middle and shallow CBM wells, deep CBM wells predominantly produce free gas in the early stage, characterized by rapid and high gas production; and (4) the production capacity of deep CBM wells is mainly influenced by reservoir stress characteristics, the effectiveness of fracturing, and the continuity of production. This study provides a valuable reference for the formulation of deep CBM drainage and production systems and development strategies.
Zhang et al. (Tue,) studied this question.