沁水煤层气田成藏条件及勘探开发关键技术

沁水盆地历经了油气普查和煤层气勘探开发2个阶段（共60余年）的探索,现已成为中国最大的煤层气产业化基地,也是世界上高煤阶含煤盆地煤层气成功实现商业化的典范。尽管高煤阶煤层气田具有低压力、低渗透率、低饱和度、非均质性强的"三低一强"特征,但勘探实践和研究表明,沁水盆地煤层气成藏条件优越,主力产层太原组15#煤层和山西组3#煤层为陆表海碳酸盐台地沉积体系及陆表海浅水三角洲沉积体系,煤层厚度大、多由腐殖煤类构成,主要含镜质组。受燕山期构造热事件影响,煤层煤阶高、吸附能力强、含气量大。煤层气成藏经历了两次生烃、气体相态转化和水动力控制顶、底板封闭的3个阶段。针对沁水盆地地形及高煤阶特征,形成了山地地震采集、处理和解释技术,丛式井钻完井技术,"复合V型"为主的多水平井钻完井技术,解堵性二次压裂增产技术,高煤阶煤层气排采控制工艺,煤层气集输技术等一系列关键勘探开发技术,有效支撑了沁水盆地高煤阶煤层气的规模开发和工业化发展。

Gas accumulation conditions and key exploration & development technologies in Qinshui coalbed methane field

The Qinshui Basin has been explored for more than 60 years through two stages of oil and gas reconnaissance survey and exploration & development of coalbed methane (CBM), it has become the largest CBM industrialization base in China and also is a model which successfully realize commercialization of CBM of high rank coal-bearing basin in the world. Although the high-rank coal field is characterized by low pressure, low permeability, low saturation and strong heterogeneity, the exploration practice and research show that the accumulation conditions of CBM reservoir in Qinshui Basin are superior. As main productive intervals, No.15 coal seam of Taiyuan Formation and No.3 coal seam of Shanxi Formation respectively belong to the epicontinental-sea carbonate platform sedimentary system and the epicontinental-sea shallow-water delta sedimentary system. The coal seam has large thickness, and is mostly composed of humic coal and mainly contains vitrinite. Affected by tectonic thermal events in Yanshanian period, the coal rank is high, the adsorption capacity is strong, and the gas content is large. Formation of the CBM reservoir goes through three stages including two stages of hydrocarbon generation, gas phase transformation and sealing of hydrodynamics and roof and floor. In view of the characteristics of Qinshui Basin topography and the high rank coal, a series of key technologies for exploration and development are developed, including mountainous region seismic acquisition, processing and interpretation technology, drilling and completion technology of multiple wells, drilling and completion technology of multiple horizontal wells dominated by compound V type, deplugging secondary fracturing stimulation technology, control technology of high rank CBM drainage, and CBM gathering and transportation technology, which effectively supports the scale and industrialization development of high rank CBM in Qinshui Basin.