Zhichuan Guan1 , Ya-Nan Sheng This email address is being protected from spambots. You need JavaScript enabled to view it.1, Chuan-Ming Xi2 , Ming Luo3 and Wentuo Li3

1College of Petroleum Engineering, China University of Petroleum, Qingdao 266580, P.R. China
2Engineering Technology Research Institute of Xinjiang Oilfield Company, PetroChina, Karamay, Xinjiang 834000, P.R. China
3CNOOC China Limited Zhanjiang Branch, Zhanjiang 524057, Guangdong, P.R. China


Received: June 21, 2017
Accepted: March 10, 2018
Publication Date: December 1, 2018

Download Citation: ||https://doi.org/10.6180/jase.201812_21(4).0005  


Oil and gas drilling engineering has the characteristics of high investment and high risk, especially when drilling in the deep and complex or offshore formation. Through the investigation of the existing drilling risk assessment methods, we found that the traditional methods often neglected the mechanism of drilling risk. These methods only transplant the risk assessment methods, which is commonly used in other engineering areas to the drilling engineering. We can only get the results of qualitative or semi-quantitative risk assessment. The existing methods cannot guarantee the safety of high risk drilling. Therefore, it is necessary to establish the quantitative drilling risk assessment method. Firstly, the uncertainty of the formation pressure was analyzed and the probability distribution of formation pressure was obtained by using the Monte-Carlo method. Then according to the pressure constraint criterion, we established the safe window of drilling fluid density with confidence. Based on that, through the risk mechanism analysis and based on quantitative risk assessment method (QRA), the quantitative analysis method for oil and gas drilling risk was established. The risk profile of the whole well section can be gotten. Through case studies, this method can be used to predict the probability of drilling risk, and the prediction results were in good agreement with the actual drilling risk.

Keywords: Drilling Risk, Formation Pressure with Confidence, Monte-Carlo Method, QRA


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