Optimization Design and Application of Well Structure in Water Injection Risk Well Area of Gangdong Oilfield

Gangdong Oilfield is an old oilfield in the east of Dagang Oilfield. In the early stage, water injection was used to develop the Minghuazhen Formation reservoir of the upper Tertiary system. It has been injected and produced for 30 ~ 50 years. In order to develop the lower Tertiary Dongying Formation reservoir, the newly drilled wells which designed two sections often “encounter” the high pressure waterflood layer of the upper Minghuazhen Formation in the drilling process, if the drilling fluid density is too high, it is easy to leak the surface casing shoe and the lower Guantao conglomerate formation, and if the density is too low, it is easy to cause oil and gas invasion and overflow, which has a high well control safety risk. If all the wells are designed as three section structure, and lack of pertinence, excessive design economy is poor. On the basis of detailed analysis of completed drilling data and in-depth analysis of pressure system in Gangdong oilfield in recent years, the risk assessment is carried out for the whole area of Gangdong oilfield, and the risk levels are divided. The targeted design methods of different casing depths, different sections and spare small holes are adopted for the well depth structure of different risk levels, which not only ensures the well control safety, but also ensures the well control safety. It also improves the pertinence and economy of the design. Thirty-five wells were designed with this method, and all of them were successfully constructed without any complicated flood overflow. Compared with the previous design of large hole, the drilling cost is about 3.7 million yuan, which effectively promotes the optimization of drilling design to reduce cost and increase efficiency, and has important reference and guiding significance for other water injection blocks.