Study On Risk Evaluation Of Drilling Engineering Design

One unreasonable drilling engineering design often leads to the risks and accidents, and it will not only affect the drilling operation, prolonging the drilling progress, but also increase the cost of drilling. If it got worse, thw33ee whole program and the well would be ruined. Therefore, domestic and foreign research institutions and scholars have been working on the risk assessment of drilling engineering design before it’s beginning. Among them, the Osprey Risk from Schlumberger Corp, one drilling design and risk evaluation system, can quickly do the design and risk evaluation in drilling engineering. The risk assessment of drilling engineering design is one of the important functions of the system. In our country, the technology is not mature enough in this field. Therefore, in the national oil and gas major science and technology project (contract number:2011ZX05021-006), the government set up a special subject "risk evaluation of drilling design", aiming the problems of how to make the evaluation of risks which might happen in the drilling design according to the drilling data in the design. This paper is one part of the research content, which proposed a method to make full use of drilling engineering design data to make pre-drilling risk evaluation, providing technical support for the optimization of drilling design. It also provides technical support for drilling engineers to take measures timely, ensuring safe and efficient drilling progress.Based on sufficient investigation of development and applying situation of risk assessment method in drilling engineering at home and abroad, four kinds of common engineering risks in drilling engineering design and their principles were studied, finding out the main factors affecting the risks of drilling engineering design. In view of the existing uncertainty of formation pressure which the design based on, the data error analysis method was introduced in this paper, and it can cover the uncertain impact from the formation pressure uncertainty.The main method in this field is influenced by subjective factors, such as expert evaluating method, so this paper used generalized probability theory and subordinate function of fuzzy mathematics evaluation method to establish the subordinate function, according to different risk types, reducing the impact from subjective factors. The combination of these two methods can cover the uncertainty and fuzziness of the risks in drilling engineering design better. According to the model of evaluation, the risk of drilling engineering design can be quantitatively evaluated.Based on the main content above, this paper developed a kind of software for the risk evaluation of drilling engineering design via Visual Studio2010programming tool. Application of two wells, one of block in Sichuan, one of block in Xinjiang, and the application effect show that:the evaluation model of subordinate function of fuzzy mathematics based on data error is reliable, and the software is in stable operation. The risk assessment results coincide with the actual situation in comparison, with a certain value. The evaluation result can provide reference and the basis for the optimization of drilling engineering design.