中国煤层气高效开发井型与钻完井技术进展

Technical advances in well types and drilling&completion for high-efficient development of coalbed methane in China

较之于美国、澳大利亚、加拿大等国家,中国的煤层气储层具有低地层压力、低渗透率、低含气饱和度及强非均质性等基本特征,增加了储层改造的难度,制约了煤层气单井产量与采收率的提高。为了给中国煤层气水平井工程技术发展提供借鉴与支持,针对我国煤层气高效开发所面临的工程技术难题,综述了国内外煤层气水平井钻完井技术研究及应用进展,介绍了煤层气井型设计与井身结构优化、井眼轨迹控制、井壁稳定、优化完井与储层保护等一系列技术,讨论了水平井双管柱筛管完井与洗井增产、径向水平井筛管完井及磁导向钻井等新技术及其适应性,提出了地下“井工厂”绿色开发模式以及深地煤层气与煤炭一体化绿色开发之道。结论认为:①针对我国煤层地质条件与地表环境,在进一步精细化高煤阶水平井钻井与完井技术的同时,需要兼顾煤系气综合开发;②加强中—低煤阶与碎软煤层水平井钻完井技术创新研究,深入探索复杂煤层气藏高效开发模式;③针对我国深地煤矿、低品位煤矿及薄煤层等非常规煤矿绿色高效开发面临的重大技术难题,有必要积极探索地下“井工厂”与非常规能矿原位转化开发模式,力求实现深部煤层气与煤炭一体化绿色高效开发的目标;④高质量推进我国能源低碳绿色转型,既要保障国家能源安全,又要实现“碳达峰和碳中和”战略目标。

Compared with the United States,Australia,Canada and other countries,China's coalbed methane reservoir has the characteristics of low formation pressure,low permeability,low gas saturation and strong heterogeneity,which increases the difficulty in the reservoir stimulation and restricts the single well production and recovery efficiency of coalbed methane(CBM).Focusing on the engineering technology issues faced by the efficient development of CBM in China,the research and application progress in horizontal drilling and completion technology of CBM at domestic and abroad are reviewed to provide references and theoretical supports for horizontal well engineering technology progress of CBM in China.This paper describes a series of horizontal drilling and completion technologies such as well type design,well structure optimization,well trajectory control,wellbore stability,well completion optimization,reservoir protection and so on.The advanced technologies and their adaptability including screen pipe completion and stimulation with dual-layer tubular strings,radial horizontal well screen pipe completion and magnetic steering drilling are dialectically discussed in this paper.A novel integrated engineering mode for efficient and green development of the deep CBM and coal through the underground'well factory'is presented.The deduced some conclusions are:(1)In view of the geological conditions and surface environment of coal seams in China,the horizontal drilling and completion technologies of high rank coalbed methane should be refined furtherly,and the coal measure gas needs the integrated development;(2)Innovation research of horizontal drilling and completion technology in low-medium rank coals and the broken coal seam should be strengthened,thus the efficient development mode needs to be probed for complex coalbed methane reservoir.(3)Facing the major technical challenges in green and efficient development of unconventional coal mines such as deep coal mines,lowgrade coal mines and thin coal seams in China,it is necessary to explore the development mode by in-situ conversion process based on underground"well factory"for the integrated green and efficient development of deep coalbed methane and coal;(4)Promoting the high quality transformation with low-carbon and green energy in China,it will not only ensure national energy security,but realize the'carbon peaking and carbon neutrality'goal.