硬脆性泥页岩地层气体钻井最小注气量影响因素分析

INFLUENTIAL FACTOR ANALYSIS OF THE MINIMAL GAS VOLUME USED IN DRYNESS SHALE GAS DRILLING

气体钻井由于其低压,具有机械钻速高、避免井漏、消除泥页岩水化及保护储层等不可比拟的优势,目前已受到钻井界越来越多的青睐。但该技术在川西地区三叠系须家河组硬脆性泥页岩钻进过程中,经常发生井下掉块、崩落等现象,造成扭矩增大、钻具憋跳,严重时可能造成井壁坍塌、卡钻、埋钻等井下事故。目前气体钻井对于该类地层钻井可供借鉴经验并不多,还缺乏理论和实践的指导。通过对泥页岩性能分析,并建立与其相对应的单位时间岩屑量方程与安全携岩最小注气量的关系,结合修正的携岩模型进行数值模拟,计算结果与川西某区块实际钻进情况较为吻合。这对今后该地层硬脆性泥页岩钻进最小注气量和机械钻速提供了重要的参考依据。

Gas drilling can improve ROP,avoid lost circulation,eliminate hydration of the shale and protect reservoir because of its low pressure,so it is very popular in drilling realm now.The phenomena of downhole falling is common in Xiujiahe group Triassic formation in Sichuan,which makes torque augment,drilling tool hold back,and even borehole collapse,stuck and build up in the hole accident.For the present,there is no much experience used for reference,and no much guidance of theory and practice,so the dissertation analyzed the performances of the shale,and built the concerned equation between the cuttings volume and the minimal gas volume.With the help of the computer,the modified carrying cuttings model was obtained,which was fitted with the actual drilling cases in Sichuan.It could offer important reference for the minimal gas volume and ROP in dryness shale gas drilling for the future.