基于风险量化的海外油气勘探项目经济评价方法

The economic evaluation method for overseas oil and gas exploration projects based on risk quantification

针对海外油气勘探项目地质风险高、资源规模不确定性大的特点,结合地质要素风险打分法、蒙特卡洛概率资源量计算法和折现现金流法,建立综合的经济评价方法,以提高投资决策的科学性。以地质风险要素打分法求取地质成功率,量化地质风险;以蒙特卡洛法计算目标内技术可采资源量的概率分布,量化资源规模的不确定性。以技术可采资源量和其对应的资源量丰度作为双变量,建立最小经济规模函数,计算商业化成功率,量化商业性风险,并求取经济可采资源量(截断后的风险前技术可采资源量)的概率分布。选取代表性经济可采资源量进行开发概念方案设计和风险前经济指标估算。以事件分支为节点,形成5个经济评价决策树分支。以量化的事件概率为系数,将各分支的风险前经济指标整合为风险后经济评价决策树模型。应用实例表明,该方法不仅可评估项目风险后的经济性,还可为不同资源量、不同地质风险的多个项目提供更科学的经济性对比数据。

The paper establishes a comprehensive methodology of economic evaluation, which combines risk-scoring method of geological factors, Monte Carlo probability calculation method of resource, and discounted cash flow method, to scientifically make the investment decision on overseas oil and gas exploration projects which have high geological risks and large uncertainties of resource scale. Specifically, it gets the probability of geological success(PG) by using risk-scoring method to quantify geological risk, calculates the probabilistic distribution of technical recoverable resource in a target through using Monte Carlo method to quantify the uncertainty of resources, builds the minimum commercial field size(MCFS) function and calculates the probability of commercial success(PC) to quantify the commercial risks by using dual variables of technical recoverable resource, gains the probabilistic distribution of commercial recoverable resource(un-risked technical recoverable resources), and selects representative economic recoverable resources to design the development concepts and estimate the economic indexes before risks. Furthermore, five branches of economic evaluation decision tree are formed by taking event branches as nodes and the pre-risk economic indexes of each branch are integrated into the decision tree model of post-risk economic evaluation by taking the quantified event probability as the coefficient. It shows that this method can not only evaluate the economy after project risk, but also provide more scientific economic comparison data for multiple projects with different resources and different geological risks.