Optimal Design Of Deepwater Well Structure With Dual Gradient Drilling Technology

At present,offshore petroleum and gas exploration and exploitation are developing into deepwater zone(500m?1500m)and ultra deepwater zone(more than 1500m).Therefore,the exploration and development of offshore petroleum and gas in deepwater area has become one of the main forces of global petroleum and gas "accumulation and production" and the international frontier of petroleum and gas scientific and technological innovation.Since the environment,technology and equipment of deepwater drilling are quite different from those on land or in shallow water,deepwater drilling has its own characteristics in terms of operation flow and required technology and equipment.The well structure design of deepwater is an important part in the design and control of deepwater drilling engineering.In the process of deepwater drilling,the formation safety density window is often narrow,the operation risk is immense,the engineering cost is high technical problems.In order to solve these problems of deepwater drilling,popular at home and abroad on the deepwater dual gradient drilling technology,the unique advantages of this technology is that can effectively simplify the deep well structure,which can not only reduce casing levels and engineering cost,and can make a deepwater drilling and production process more safe and effective,but there is still a large gap between China and abroad.This thesis focuses on the analysis of the basic principle of deepwater dual gradient drilling technology,introduces several mature engineering practices and corresponding supporting equipment abroad,and briefly expounds the working principle and technical advantages of several international deepwater dual gradient drilling systems.According to the realization mode,it mainly includes three systems: submarine pump lifting scheme,no riser scheme,and low density medium injection scheme.At the same time,the research progress of this technology in China is briefly analyzed.Combining with the characteristics of dualgradient drilling technology,the original rule of safety window of drilling fluid density to determine the part of the formula and coefficient of correction,put forward a more reasonable design method of deep well structure,request the well bore structure design parameters should be based on actual well conditions are more meticulous calculation,which can effectively use narrow the safe density window of drilling process,make the well structure of deepwater reasonable design scheme is more secure.The deepwater dual-gradient drilling technology was first proposed to solve the technical problem of narrow safety density window commonly encountered in deepwater drilling engineering.Therefore,the optimized design method of well structure can simplify casing layers.In addition,in the design process of the deepwater drilling fluid properties and drilling cycle change pressure loss,the influence of the original parts of the design method of well structure constraint condition is improved,and the deep well structure optimization design scheme under the condition of dual gradient drilling is established and verified by an example.