Blow out risk analysis of oil and gas drilling operation in exploration wells using Bow tie analysis (BTA) and Bayesian network

Exploration and development of onshore oil and gas fields involve a number of risks related to loss of human lives, pollution, and loss of material assets. One of the major concerns in the oil and gas drilling industry are Blowouts. Blowout could have severe consequences, such as fire and explosion, releases of toxic gases and environmental disasters. The aim of this study is to identify and analyze of basic events that lead to kick and blowout in drilling industry by using Bow tie Analysis and Bayesian network (BN), in exploration well of Iranian onshore drilling industry.
In this study, Fault Trees Analysis (FTA) investigates basic events of a kick while Event Tree Analysis (ETA) explores the possible consequences (including blowout) arising from a kick. The Bow Tie Analysis (BTA) combines FTA and ETA to represent the potential accident scenarios, their causes and the associated consequences of a kick. Finally BN is constructed to investigate the blowout probability and to determine the relationship and effectiveness of various blowout safety barriers in the well.
24 basic event (root causes) have been identified for kick. Also to mitigate kick consequences, 7 safety barriers recognized. The probability of kick and blowout was calculated as 9× 10-2 and 3.5× 10-5 , respectively. The order of importance measure of each root causes also was listed.
In this study, getting into the high pressure zone and decrease of bottom hole pressure (BHP), was identified as the most important root causes of kick. Furthermore, early detection of kick and the proper functioning of Blowout Preventer (BOP) were recognized as the first safety barrier to prevent the blowout.