中高煤阶煤层气井产量递减类型及控制因素——以晋城和韩城矿区为例

Production decline types and their control factors in coalbed methane wells: a case from Jincheng and Hancheng mining areas

通过对晋城、韩城矿区煤层气井生产动态资料的分析和研究,认为煤层气井产量递减具有指数递减、调和递减、复合递减、突变递减和周期性递减等5种类型;而影响煤层气产量和递减类型的主要因素是边界条件、煤层气吸附特性、煤储层渗透率、解吸过程中的渗透率反弹、井间干扰、层间干扰和排采制度。研究还显示,通过对煤储层进行二次压裂、合理布设井网、合理调整排采制度、低产合采井选择性封层、准确把握合适的合采时机以及实施侧钻技术,有利于恢复和提高煤层气单井产量,延缓产量递减期,减缓递减速度,使递减类型趋向双曲线或调和递减类型,从而提高煤层气最终采收率。

Based on the analysis and study on production dynamic data of CBM wells in Jincheng and Hancheng mining areas, index decline, harmonic decline, composite decline, abrupt decline and periodic decline are suggested as five types in CBM production decline period. Boundary condition, adsorption feature of CBM, coal-seam per- mcability, permeability rebound in desorption, interference between wells, interlayer interference and production system are major factors for CBM yield and its decline features. This research also shows that twice fracturing, reasonable well grid, adjusting production system reasonably, sealing some layer of low-yield wells, choosing right time to commingle and applying sidetracking well technology are effective strategies to recover and raise CBM yield of single well, delay decline period and decrease decline rate. These measures can make production decline trend to hyperbolic decline and harmonic decline, and improve final recovery of CBM.