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ORIGINAL PAPER-EXPLORATION ENGINEERING

Dynamic design method of wellbore structure during drilling operation based on LWD Sheng Ya‑nan1 · Li Weiting1 · Lan Kai2 · Jiang Jinbao1 · Kong Hua1 Received: 16 July 2020 / Accepted: 13 November 2020 © The Author(s) 2020

Abstract At present, there is no good method or technology for quantitative evaluation of wellbore structure and engineering risk in the process of deep well drilling in complex formation, and there is no rational understanding of engineering risk mechanism. With the development of MWD and transmission technology, the formation pressure and rock mechanics parameters of the drilled section can be accurately determined in the process of drilling, which provides a basis for the well bore structure and engineering risk assessment in the process of drilling. This paper makes full use of the advantages of MWD and other technologies to seek a method to improve the accuracy of formation pressure prediction with narrow safe density window On this basis, the risk identification methods of leakage, blowout, collapse, sticking and other engineering risks in the process of drilling are studied, and the risk assessment method of dynamic wellbore structure in the process of drilling is established; at the same time, the uncertain parameters in the existing wellbore structure design method are studied, and the design method is improved, so as to minimize the risk of well structure design. Keywords  Formation pressure with credibility · LWD (logging while drilling) · Dynamic evaluation of drilling risk · Optimization design of wellbore structure

Introduction The problem of narrow safe density window in the drilling of deep and complex formation is always one of the prob‑ lems faced by the well structure design and safe construc‑ tion. With the increase in well depth, the problem of narrow safe density window becomes more and more prominent (Xiwen 2006; Deli 2004; Yijin and Jian 2005). Therefore, advanced technologies such as underbalanced drilling, pres‑ sure controlled drilling and gas filled drilling are adopted at home and abroad, as well as risk assessment technolo‑ gies such as pre drilling wellbore structure design and risk assessment method based on probability statistics, which solve this problem to a certain extent (Sayers et al. 2006; Zhou yingcao, Yang Xiongwen, Fang Shiliang,, et al. 2011; * Sheng Ya‑nan [email protected] 1



Drilling Engineering and Technology Research Institute, Zhongyuan Petroleum Engineering Co., Ltd., SINOPEC, Puyang 457001, China



Southwest Drilling Company, Zhongyuan Petroleum Engineering Co., Ltd., Chengdu 610000, China

2

Mingyan 2007). Among them, the risk assessment technol‑ ogy can quantitatively assess the engineering risk based on the existing equipment and technology, combined with the theory of risk analysis and so on. It is very necessary for the deep well complex formation drilling with high risk and high investment, and is conducive to the realization of the purpose of safe and efficient deep well complex formation dr