Risk Assessment Of Underbalance Drilling For CBM In The Basin Of Qinshui

The underbalance drilling in the Basin of Qin Shui is a complex and high risk project. There are a lot of uncertainties and random factors in the whole process so it is prone to a variety of accidents. Taking into account the large-scale equipment and the complexity of technology during underbalanced drilling, in the event of an accident, it will cause significant harm to persons and property once accident happens. So the risk assessment for the underbalance drilling in this paper has very important practical significance.This article is based on the actual situation in the region Qinshui Basin, and establishes the model of risk assessment of underbalanced drilling. First the paper analysis the risk factors of the balanced drilling, the analysis of the risk factor is the basis of the risk assessment for the underbalance drilling. In addition, the paper analysis the stability of wellbore based on FLAC software. The paper establishes the hierarchical structure of the risk factors, and quantifies the risk factors mainly using fuzzy mathematics and expertise method. And then confirm the weight of the risk factors by means of analytical hierarchy process. Finally the paper establishes the model of risk assessment using fuzzy comprehensive method. The paper also composes the risk assessment software for underbalanced drilling, and the whole work of risk assessment can be done through the software, so it greatly improves the efficiency of assessment. The key risk factors are analyzed importantly such as wellbore stability and drilling fluid density. We analyze the value by changing their parameters.The thesis model, the software and the project combine together in this paper, and this facilitates the promotion of project results.