Study On Method Of Casing Program Design Based On Coordination Mechanism Of Risk And Cost

Oil and gas drilling has characteristics of high risk and high investment,all kinds of risks,like kick,fracture,collapse and stick,are the main factors that influence drilling efficiency and cost.Reasonable casing program is the safeguard of drilling safety and efficiency.How to forecast and evaluate drilling risks accurately,determine the reasonable the casing program are the problem in drilling design and casing program decision.For the cost of risk management and risk aversion,in this paper,the calculation models of risk management cost and risk aversion cost are established with investigating and analyzing the calculation model and the components of drilling cost.For the forecast and evaluation of drilling risks,in this paper,through the establishment of the formation pressure profile under the uncertain strata information and the safety of drilling fluid density window with credibility,the drilling risk evaluations of complex deep wells in Sichuan basin and Qaidam basin are accomplished.According to the analysis of the drilling risk evaluation of many complex deep wells,the risk level division is established with the theory of fuzzy identification.There are three areas for risk level division.They are safe area,transition area and danger area.On the basis of the cost of risk management and risk aversion and the risk level division,the determination method of casing program under the coordination mechanism of cost and risk is built.According to this method,The risk section and level are determined by the risk assessment and the risk level division.The adjustment of casing program is determined on the comparison of the cost of risk management and the cost of risk aversion.This method can provide the basis for the decision of casing program.Finally,the design and optimization software for the casing program is completed on the basis of theoretical research.The software is able to tell the degree of risk of the designed casing program,at the same time,the optimization for the casing program is developed under the coordination mechanism of casing program cost and risk.