Drilling Technology for Long-Offset 3D Horizontal Shale Oil Wells in the Longdong Area of the Changqing Oilfield

Abstract

Ravines and gullies criss-cross the shale oil reservoirs of the Longdong Area in the Changqing Oilfield, where there are also numerous protected zones for water and forest resources, plus prime farmlands. The development of horizontal wells is greatly restrained by the topography and protection zones, and the offset of 3D horizontal wells directly affects the number of horizontal well platforms and the factory-like operation of large platforms, and affects the effective utilization of subsurface resources. Based on the analysis of the characteristics and drilling difficulties of long-offset 3D horizontal wells, the wellbore profile design was optimized, and kick-off points, azimuths, deviation angles, and well sections for eliminating offset were selected to improve the control mode of hole trajectories. In the absence of a rotary steering system, conventional positive displacement motors (PDM) and polycrystalline diamond compact (PDC) bits were upgraded. In addition, tools for reducing friction and a water-based CQSP-4 drilling fluid system suitable for long-offset horizontal shale oil wells were employed. Finally, the drilling technology for long-offset 3D horizontal shale oil wells in the Longdong Area was developed. This technology was applied to 6 3D horizontal wells with offsets over 900 m in Longdong Area. Friction torque was reduced significantly and the drilling process was safe and efficient, with good field application effect achieved. The successful application of the technology can support factory-like efficient development of the large shale oil platforms in the Longdong Area, which have multilayered systems and multiple drilling rigs. Further, it can facilitate the transformation of the drilling operation mode from single-rig and single-team to industrialized and clustered production.