摘要
Abstract
Extended reach well technology has been used to produce the natural gas in the offshore area from onshore in developing the Block S located in the east of Sakhalin,Russia.The designed well depth (MD) was 12,000 m (TVD 2,800 m) and the horizontal displacement was about 11,000 m.The ratio of horizontal displacement to vertical depth was 3.93.The wells were designed to have four intervals.It was found from the previous experiences that the lower Okobykaiskiy formation and the Daginskiy formation had narrow safe drilling windows (0.3-0.4 g/cm3),downhole problems such as lost circulation,borehole wall collapse and pipe sticking etc.were drilling risks that needed to be considered,especially in drilling extended reach wells.Researches on how to widen narrow safe drilling window were inadequate to meet field requirement,most of which were focused on the optimization of drilling fluid properties to widen the safe drilling window.To solve the narrow safe drilling window problem in extended reach well drilling,mechanical and chemical measurements shall be adopted.First,well profile optimization,improvement of stress state around the borehole and widening of safe drilling window should all be taken into account in the well trajectory designing stage.In this stage,the effects of the main well trajectory parameters on safe drilling window should be analyzed.Based on the analyses,the well trajectory was optimized to reduce borehole collapse pressure and increase formation fracture pressure,thereby realizing the widening of safe drilling window through mechanical method,which in turn paved the way for further widening safe drilling window through chemical method,and created favorable conditions for efficient drilling in areas with narrow safe drilling windows.The technologies of widening safe drilling window obtained have been used successfully in drilling the extended reach wells in Block S,with the safe drilling window widened by 25％-100％ compared with the safe drilling window prior to the well trajectory optimization.This work is of importance in dealing with narrow safe drilling window problem.关键词
窄安全钻井液密度窗口/扩展/井眼轨迹/优化/超大位移井Key words
Narrow safe drilling window/Widen/Well trajectory/Optimization/Extended reach well分类
能源科技
