Friction reduction of horizontal wells of continental shale oil in Fuxing Block
The friction resistance of horizontal well of continental shale oil in Fuxing Block is abnormally high,which makes well completion difficult.In order to reveal the cause of the abnormal friction of horizontal wells in Fuxing Block,the paper carried out rock mechanics and drilling fluid performance analysis and other related experiments,and the geological characteristic differences of continental shale and marine shale were compared and analyzed.The influence laws of cutting bed and pressure difference on friction were studied by establishing a pipe string mechanical model considering cutting bed and difference between drilling fluid column pressure and formation pore pressure.The research results show that the root causes of abnormally high friction are the development of micro-fractures in continental shale,fast pressure transfer rate,large difference between drilling fluid column pressure and formation pore pressure,and excessive pressure difference adhesion between pipe string and formation caused by excessive low density solid content in drilling fluid.Engineering measures to reduce friction such as drilling fluid property control,low density solid content control and pressure difference reduction were formulated and field pilot tests were carried out,and the horizontal section friction was greatly improved.The research results provide a reference for solving the engineering problem of abnormally high drilling friction in the horizontal section of continental shale in Sichuan Basin.
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