煤层气多分支水平井钻井工艺研究

Study on Multi-branch Horizontal Coalbed Methane Well Drilling Technology

基于沁水盆地郑庄区块3#煤层的地质和力学特征,其适于采用多分支水平井钻井技术开发煤层气。但由于煤层较脆,且存在互相垂直的天然裂缝,钻进极易引起井下垮塌、卡钻等复杂事故的发生,更严重的甚至会使井眼报废。郑1平-3H井是渤海钻探在沁水盆地郑庄区块的一口科学实验井,为解决煤层气多分支水平井钻井难题,首先将郑1平-3H井的排采直井"洞穴"置于稳定的煤层顶板上,与水平井主支实现硬穿针,从而根除排采洞穴垮塌和上下井眼错位的问题;其次使主井眼在煤层顶部延伸,钻主支时优化钻井液,解决井眼稳定和井眼重入问题,确保形成稳定的排水输灰通道。煤层气多分支水平井井眼轨迹控制技术、U型井联通技术及悬空侧钻技术的采用较好地解决了煤层气多分支水平井钻井的上述难题,具有重要实践意义。

Zheng-1-ping-3H well is a scientific experiment well drilled by Bohai Drilling Corporation in Zhengzhuang Block,Shanxi Province. According to geological and mechanical characteristics of 3# coal seam in this block,multi-branch horizontal well drilling technology is suitable for coalbed methane development in the block. Because coal seam is brittle,there are natural fractures perpendicular to each other in the coal seam,drilling in such brittle stratum will easily cause borehole stratigraphic collapse and other complex accidents,or even more seriously,it will scrap the borehole probably. In order to solve this problem,analyzed deeply are horizontal well technologies applied in coalbed methane development and effects obtained from different sites,developed and applied is a new technology according to the analysis results and introduced is the technology through its actual application in the above-mentioned scientific experiment well,including wellbore trajectory control technique,technique for connecting U type wells together with each other and suspended sidetrack drilling technique in roof clay rocks.