An assessment methodology for human holistic risk in whole cycle of shale gas fracturing

In the process of shale gas fracturing, long time, high strength, and boring task could trigger psychological or physical operation fatigues, and then lead to downtime, sand blocking, or other accidents, which are the main problems in safety management. However, conventional studies either separately analyze risks without considering the interaction and relationship between humans or teams, or only form a qualitative framework for team analysis. These methods cannot be directly applied for the fracturing operators due to complex operation procedures and diversified human errors. An improved methodology, therefore, is proposed to assess human holistic risk during the whole cycle of fracturing operation. First, D-S evidence theory is introduced to obtain the individual risk, and team performance shaping factor is also presented to establish risk assessment model for fracturing teams. Second, individual and team risks are integrated to calculate the quantitative value of human holistic risk. A scatter diagram of human risk is finally designed, where the high-risk fracturing stages and human types can be clearly revealed. Results from a study of one shale gas well indicate that human holistic risk is more objective and practical, and improves accuracy of human reliability analysis.