Assessment Method And Application Of Deep Drilling Risk

Along with the exploration and development of hydrocarbon reservoirs, the depth of reservoir is deeper, and the formation environment is more complex, which makes the description of formation’s message inaccurately and the occurrence of drilling risk frequently. Therefore, it is helpful to research risk assessment theory and methods of drilling engineering. In this article, for the nondeterminacy existed in the formation pressure prediction of deep drilling, a certain range in the same formation group was considered as sample range, and then the formation pressure in the sample range was viewed as measuring samples, according to the related theory of probability distribution, uncertainty analysis methods were proposed for drilling the formation pressure. Using analysis methods the formation pressure profiles with reliability are proposed by Monte Carlo method. In this paper, the regional characteristic of formation pressure is analyzed, and geostatistical methods are used in the regional calculation of formation pressure, through the analysis of relativity and variability of geological structure, the regional clouds of formation pressure of a block in Sichuan Basin are proposed. According to the determined formation pressure the safe mud density window is established with pressure constraint criterion. Pointed at uncertainty during the calculation of formation pressure, the safe mud density window with reliability is established by uncertainty analysis methods. In this article, in the light of the upper and lower limit and distributed state of safe mud density, the risk assessment model of drilling is established based on the theoretical basis of probability analysis, and risk probability is used as risk evaluation factor. The result of practical application shows that the risk assessment model can be used in engineering field. The risk assessment of full hole can be made to any casing programs and mud designs in vertical dimension by risk assessment model, but it is hard to do the same thing in the horizontal dimension. Here the practicability of geostatistical methods in the regional description of drilling risk is determined by analyzing the regional characteristics of drilling risk, and the regional calculation method of drilling risk is established, which makes the two dimensional description of drilling risk in stratigraphic group units coming true. And then the regional calculation method of drilling risk is be used to analyze the region of drilling risk in a block in Sichuan Bash, besides the advice tentative design is provided. Lastly, on the basis of theoretical research, assessment software of drilling risk is developed. This software can obtain the formation pressure with log data, and analyze drilling risks according to casing programs and mud designs. Meanwhile, it can achieve the regional description of the formation pressure and drilling risk.