The Prevention And Treatment Of Complicated Conditions And Downhole Accidents In Fuling Area

Fuling district shale has complex geological conditions. Some formations loose and have poor cementing quality, at the same time the upper formation limestone and mudstone interval formation fractured develop. It is easy to meet formation water, lost circulation, water-eroded cave, and so on and so forth when drilling. At the same time, Changxing, Longtan, Maokou group formations have gas, and also contain a certain concentration of H2S. Formation sandstone and mudstone alternating hard and soft, lead to be seriously jumping drill, damaging tool and easily occurring downhole fault. Hanjiadian group, Xiaoheiba group and purpose layer Longmaxi group formations have low bearing capacity and fractured develop. It is easy to occur Lost circulation, well collapse, sticking and so on in drilling process. It is necessary to timely analysis and summary Wells downhole accident prevention and treatment technology in Fuling district of shale gas. Eventually the solution of the prevention and treatment of complicated conditions and downhole accidents in Fuling area has been forming.Upper strata of the Jialingjiang, Feixianguan limestone, the group of shallow depth, is easy to crack formation and mudstone vulnerable to erosion surface and groundwater. So in ground surface crack and cave development, easily happened in the surface into a layer of lost circulation. Using water drilling technique can realize a trip well drilling,and achieve rapid drilling, realizing rapid drilling process of the "fast leak proof".Changxing, Longtan, Maokou formation contains a certain concentration of hydrogen sulfide gas. Before drilling into Changxing group,the corresponding prevention measures must have been prepared. When appearing H2S gas, making the corresponding treatment measures.The drilling process of deflection horizontal part is likely to produce the accidents such as sticking because of the supporting pressure in the lower part of formation. The application of hydraulic oscillator can well solve the problem of supporting pressure sticking. Hydraulic oscillator can effectively reduce the transverse and torsional vibration, reduce the surface contact between the drill and mud cake to prevent pressure and sticking. Slight vibration in the process of drilling hydraulic oscillator downhole assembly, drilling tools in hole vertical reciprocating motion, turns the static friction of drilling tools in the downhole friction, significantly reduce the friction. When using hydraulic oscillator with PDC bit drilling, increase displacement borehole cleaning, strengthened the purification of bottom hole and the hole.The purpose of the Longmaxi, Wufeng formation is fractured developing, which is prone to lost circulation. The plugging measures in the Longmaxi, Wufeng formation mainly use the bridge plugging technology. Bridge plugging technology is making use of plugging material for mechanical blockage in the process of blocking leakage layer.With counting a number of complex and drilling accidents, the paper has analyzed drilling complex and accident cause in Fuling district, presenting the corresponding prevention and treatment measures in the formation of different complex conditions and accidents, which is contribute to safety drilling, at the same time can reduce the drilling cycle and reduce the drilling cost.The research results of this paper in Fuling district have been significantly guiding for shale gas field construction.