水平井薄储层内地质导向难点剖析及对策研究——以鄂西渝东红星地区二叠系吴家坪组页岩为例

Difficulties Analysis and Countermeasure Research of Geosteering in Thin Reservoir of Horizontal Well—A Case Study of Permian Wujiaping Formation Shale in Hongxing Area, Western Hubei and Eastern Chongqing

摘要: 鄂西渝东二叠系页岩气储层取得勘探开发新突破，整套地层受限于纵向沉积不稳定、横向产状变化且优质页岩气储薄的特点，实钻过程地质导向调控井身轨迹困难。为了实现优质页岩气层高穿行率，本研究基于区域地质特征和导向工具适配性现状，剖析地质导向入靶精度低、井身轨迹调控难等问题原因，并结合红星地区实钻井地质导向经验，总结提出预先轨迹模拟、标志层控制、井斜滚动调整的入靶前地质导向方法，随钻过程井震结合校正地质模型，梳理总结靶窗岩性、气测等特征，形成“两低夹一高”围点穿行水平段导向方案，并根据钻头与层界面接触关系细化地层视倾角计算、预演地层产状变化细化微幅构造决策，显著提高了靶点预测和轨迹控制精度。验证运用10井次，优质储层平均钻遇率提升至93.4%、平均节省单井钻井周期13.6 d，实现研究区优质页岩气储层高穿行率，提速增效。

Abstract: A new breakthrough has been achieved in the exploration and development of Permian shale gas reservoirs in western Hubei and eastern Chongqing. The entire stratigraphic sequence is characterized by vertically unstable deposition, laterally variable occurrences, and thin layers of high-quality shale gas reservoirs, making it difficult to control the wellbore trajectory during actual drilling through geological steering. To achieve a high penetration rate through high-quality shale gas layers, this study analyzed the causes of low target entry accuracy in geological steering and difficulties in wellbore trajectory control, based on regional geological characteristics and the current status of steering tool compatibility. Combining the geological steering experience from actual drilling in the Hongxing area, this study proposed pre-target geological steering methods, including pre-trajectory simulation, marker horizon control, and well deviation rolling adjustment. During drilling, the geological model was corrected using well-seismic integration, and the lithological and gas logging characteristics within the target window were summarized. This formed a horizontal section steering strategy with a “two-low surrounding one-high” approach for traversing the target zone. Additionally, detailed calculations of apparent dip angles based on the bit-formation interface contact relationship and microstructural decision-making through pre-visualization of stratigraphic occurrence changes were implemented, significantly improving target prediction and trajectory control accuracy. After applying these methods in 10 wells, the average drilling encounter rate of high-quality reservoirs increased to 93.4%, and the average drilling cycle per well was shortened by 13.6 days. This led to a high penetration rate through high-quality shale gas reservoirs in the study area, achieving speed-up and efficiency enhancement.