Accurate drilling technology for horizontal wells in continental shale formation geology-engineering integration—Taking Jiyeyou 1HF well in Songliao Basin as an example

Objective Continental shale oil is an important replacement field of energy in China, and precise drilling of long horizontal wells is a key technology to achieve commercial development of shale oil. However, due to the characteristics of continental shale such as high clay mineral content, strong heterogeneity and bedding development, serious instability of horizontal well wall and difficulties in precise steering of thin target layer are caused.

Methods Taking the shale of the first member of Qinghe Formation in the south of Songliao Basin as the research object, the integrated research of geological engineering is carried out by comprehensively using geochemical, geophysical, rock mechanics, geostress analysis and other means.

Results The shale in the upper part of Qing-1 Member is bedding shale, which is not suitable for horizontal wells to pass through. The thin oil-bearing sand bars in the lamellar shale in the middle and lower part of Qing-1 Member are both oil-bearing, drillable and compressible, which can be used as the crossing target layer; For shale formation, strong inhibition KCL polyamine drilling fluid system and oil-based drilling fluid system should be selected for horizontal well drilling. The mud density window increases with the increase of horizontal stress difference and well trajectory inclination angle; Logging GR and logging total hydrocarbon can accurately reflect the lithological heterogeneity change of target layer, and combined with high-precision geophysics, it can accurately control the drilling trajectory in real time.

Conclusions Through application and practice, Jiye 1HF well has safely drilled 1252m along 1.94m ultra-thin target bed, with a penetration rate of 100%, which has achieved a technical breakthrough in accurate drilling of long horizontal section of continental shale oil, laid a foundation for Jiye 1HF well to obtain high-yield industrial oil flow, and has guiding and reference significance for accurate drilling of long horizontal section of continental shale oil of the same type in China.