Research On Risk Assessment And Risk Decision-Making For Natural Gas Exploration Project

As one of the most efficient clean energies and chemical raw materials, natural gas shows great potential. Nowadays, natural gas is during a period of rapid development. It is expected that in 2030 natural gas will alternate coal and oil and become the world's major energy. According to the National Development and Reform Commission, in 2020, the domestic demand gap of natural gas will reach 800×108m3~1000×108m3, and the dependence on external gas supply will be up to 50%. Therefore, as the origin of natural gas industry, gas exploration is put in an important strategic position. However, more than one hundred years of oil & gas industry has demonstrates that the project of gas exploration has the feature of high investment, high risk, high profit and long period. So how to evaluate and select the program scientifically from the view of'risk-benefit', then improve the successful ratio and economic benefits of exploration projects has become a hot issue to each oil company.Because of long-term influence by planned economy, our oil companies have little awareness of risk, and give few attentions to risk management and related researches. So our capability of risk aversion and risk control is weak, which seriously affected the overall economic benefits of oil companies. With the deepening of enterprise reforming and global competition, with the innovation of mineral right registration and management, with the transformation of operation objective, risk analysis will be destined increasingly become one of the indispensable parts of exploration and development investment decision-making in China.The total gas geologic resources of Sichuan Basin reached 72000×10~8m~3, and in 2007 the production volume reached 173.72×10~8m~3 that accounting one fourth of China's gas production. And Sichuan Basin is also an important base for'West-East natural gas transmission'. So this paper took gas exploration in Sichuan Basin as an entry point to deploy a theoretic and piratical research systematically on the subject of'risk assessment and risk decision for natural gas exploration'. Firstly, this paper summarized domestic and international study status of risk analysis for oil & gas exploration and then pointed out the research trend of this issue. Secondly, this paper summarized the characteristics of gas exploration investment project, and built a comprehensive index system of risk evaluation. Then, the advantages and disadvantages of traditional methods of risk evaluation and risk decision were deeply analyzed. According to the different features of geological risk, technical-economical risk and environment risk, the'Play-Trap'model,'Partial Least Square-Monte Carlo'model and'G1-Fuzzy Comprehensive Evaluation'model were integrated to establish a combined risk assessment model, which was used to evaluate the total risk of exploration play and search the best group of prospects. Based on that, the Multi-Attribute Utility Theory (MAUT) was introduced to build a risk decision model, which was used to select the optimal drilling target from the group of prospects. Finally, the combined risk assessment model and the MAUT risk decision model were applied to XC Gas-field in Sichuan Basin. The result is reasonable and consistent with the fact, indicating that these methods are feasible and also useful for reference to the congener research.The progresses of this thesis gotten are as follows:(1) According to the feature of technical-economical risk, Partial Least Square was integrated with Monte Carlo to build a PLS-MC model. It can effectively solve the problem of multicollinearity among risk factors, improving the application effects of Monte Carlo Simulation, so the result was more scientific and reasonable.(2) In the guidance of integrity, three appropriate methods were selected for each types of exploration risk to establish a combined risk assessment model. This method overcame the deficiency of traditional methods just considered only one type of risk, completing the contents of risk assessment.(3) Giving more consideration to the risk propensity of the decision-maker in the process of decision-making, a risk decision model based on MAUT was established. Combined with High dimensional Sensitive Algorithm, this model makes decision-makers be able to evaluate the natural gas exploration project form a dynamic view, so the process of decision-making fit real situation more.