Risk assessment of drilling site operation based on the structural equation and Monte Carlo Method

In the risk assessment of drilling site operation, the relevance between monitored data and actual on-site operation is not strong. In view of this, the structural equation model (SEM) integrated with the Monte Carlo Method (MC) was applied as a new methodology to evaluate the on-drilling-site operation risks. First, risk factors were constituted and their relevance and weights were obtained by the SEM, then the key risk factors were determined. Then, the analog values of potential data were got based upon data distribution. Finally, risk degrees were obtained in combination with SEM risk consequence weights and accident consequence degree risk degrees identified from the on-site operation, and were applied in the judgment of risk levels. This methodology was applied in a case study of a well in a gas field, Sichuan Basin. The following findings were achieved. (1) Compared with the other methods, this new methodology determined the relevance of various factors and disadvantages of each factor weight, providing a new approach for the on-site operation risk assessment. (2) The factors of operation behaviors and environmental considerat ion had little impact on the drilling risks but the man - agement factor was the most influential factor. (3) The two key factors of non-conformity and general equipment defects were determined and their correlation coefficient was 0.57. (4) A series of required sample data was obtained according to the distribution characteristic of each risk variable and probability distribution of drilling risks was thus achieved, which made the assessment results more consistent with the actual situation. In conclusion, this new methodology provides not only a better way to apply the monitored on-site data to evaluate the drilling risk levels, but a reference for risk management i n drilling sites. © 2019, Natural Gas Industry Journal Agency. All right reserved.