Assessment of Risks Related to Wellbore Safety in Deepwater Drilling

This book divides the wellbore into two parts based on the characteristics of deepwater drilling engineering: the section from sea level to the subsea wellhead and the section below the mud line. Above the subsea wellhead is connected a blowout preventer and a long riser, while below is a series of casings, causing the subsea wellhead to bear stress from both the upper and lower parts simultaneously, posing a risk of instability in a complex stress environment; Although the construction below the mud line in deepwater drilling is not significantly different from land drilling, there are still challenges such as deep water depth, low temperature, narrow safety density window, shallow geological hazards, natural gas hydrates, and difficulty in determining drilling geological parameters, which greatly increase the risk of drilling engineering.

On the basis of systematically explaining the basic theories and methods of the subsea wellhead mechanical stability, wellbore temperature and pressure field calculation during gas kick, prediction of natural gas hydrate generation, and casing program design method and so on, this book analyzes those with higher risks such as wellhead instability, gas kick and blowout, gas hydrate generation and casing program design. And the characteristics and influence rules of uncertain parameters and empirical coefficients are analyzed emphatically by using methods such as probability statistics, and the risk assessment methods of deepwater drilling related to the wellhead and wellbore safety which consider the uncertain parameters are established. This will be of great significance for risk prevention and control in deepwater drilling, optimizing deepwater drilling design and construction plans, improving the lifespan and investment returns of deepwater oil and gas wells, and promoting the development of deepwater drilling technology.

Yuqiang Xu, Taishan Scholar, winner of provincial Excellent Youth Fund, professor from China University of Petroleum (East China), visiting scholar at Texas A&M University. He is the Editor in Chief of Trends in Petroleum Engineering, Editorial Board of Natural Gas Industry and Journal of China University of Petroleum (Edition of Natural science), and the lead guest editor of special issues for several international journals. He is the PI for 3 National Natural Science Foundation of China and published more than 70 publications in important academic journals and conferences. His research interests include: Drilling geological and engineering integration, Wellbore multi-phase flow and well control, Drilling engineering risk diagnosis and control, and Intelligent drilling technology. For the first time, he used reliability to quantitatively evaluate the uncertainty of deep formation information, and on this basis, a set of theories and technologies for quantitative evaluation and control of drilling risks was proposed. His relevant achievements have been applied to more than 2000 wells in more than 10 oil and gas fields around the world, and won several science and technology rewards (got the following rewards with the first place: First Prize of China Invention Association, Second Prize of Provincial Government for Science and Technology Progress).