复杂构造条件下页岩气水平井轨迹控制方法探讨

Discussion on Trajectory Control Method of Shale Gas Horizontal Wells under Complex Structures

页岩气开发主要以水平井施工为主,随着勘探开发的深入,开发区域逐渐深入到构造复杂带和构造边缘地带,断层、褶皱等复杂构造频繁出现。当钻遇复杂构造时,由于地震数据解释精度较低,不能提供准确的钻探依据,导致轨迹来回调整,最终造成轨迹质量差,影响钻井周期,甚至为钻井安全埋下隐患。利用"标志层井斜设定法"能够有效解决入靶过程中褶皱频繁发育的难题,每套标志层之间的厚度基本稳定,是使用标志层井斜设定控制入靶轨迹的必要条件。水平段出层后通过连续的角差控制,在实现顺利回靶体的同时保障井眼轨迹圆滑。为了确保顺利穿过复杂地带,除合理控制轨迹外,地质导向还应会同各施工方做好各项保障工作。在川渝地区9口构造复杂井施工中,取得了一次中靶成功率100%、复杂构造段二次入靶成功率100%、平均优质页岩钻遇率95.7%的较好指标。

The development of Changning shale gas has the characteristics of few evaluation wells and low density of vertical wells.In addition,due to that low accuracy of the seismic interpretation,the lack of drilling data available for analyzing geological and structural characteristics increases the difficulty of geological mod-eling of horizontal wells.So it is difficult to achieve precise control of the track in the"desserts"segment.So,the technology of comprehensive horizontal logging guidance has formulated a horizontal well steering method suitable for this block.The seismic depth relation is corrected by using the real drilling elevation of the marker layer,the reasonable selection of contrast mark layer,and the design principle of the"three-segment system"of the target-entering trajectory,which realize the accurate entry of the track into the target.Through the subdivision of the shale reservoirs box and surrounding rock features,the trajectory position is accurately judged and the trajectory adjustment principle is strictly carried out to realize the precise guidance of the horizontal segment.The comprehensive horizontal logging guidance technology makes up the defect of insufficient data of the adjacent well and effectively improves the drilling-encounter ratios of high quality shale reservoirs in the horizontal section.15 wells were appliedand implemented in 2018,and it got fine effect.The box of shale reservoirs drilling-encounter ratios was 95.84%,the 1 layer drilling-encounter ratios was 80.92%,and the class I reservoir drilling-encounter ratios was 99.11%.