基于三角模糊数的煤层气欠平衡钻井风险评估模型研究

Risk Assessment Model Study for Coal-bed Methane Underbalanced Drilling Based on Triangular Fuzzy Numbers

煤层气欠平衡钻井过程中存在大量不确定性,具有高投入、高风险的特点。在进行煤层气欠平衡钻井风险识别的基础上,总结出钻井风险主要来源于煤岩特性、钻井液性能和井壁稳定性3类,建立钻井风险因素的递阶层次结构模型。并针对传统层次分析法确定因素权重具有很大主观性的缺点,引入模糊数学方法,提出基于三角模糊数的风险因素权重确定方法,并确定风险因素的隶属度,最终建立煤层气欠平衡钻井风险综合评估模型。该模型能客观、定量化地评价钻井风险,确定欠平衡钻井因素的各类风险值,为煤层气欠平衡钻井提供降低规避风险提供理论依据。

There are many uncertainties which have the characteristics of high investment and high risk in coal-bed methane underbalanced drilling.On the basis of risk identification of coal-bed methane underbalanced drilling,it concludes that the drilling risks mainly lie in three aspects of coal rock properties,drilling fluid properties and wellbore stability.The hierarchical structure of drilling risk factors is established.According to the disadvantages of determining factor weight by traditional analytic hierarchy process,the method of determining risk factors weight based on triangular fuzzy numbers is proposed by introducing fuzzy mathematics.The memberships of qualitative and quantitative risk factors are determined respectively.The comprehensive drilling risk evaluation model for coal-bed methane underbalanced drilling is established.This model can evaluate the drilling risk objectively and quantificationally,determine the risk values of various underbalanced drilling risk factors,and supply the theoretical basis of decreasing and avoiding risk for coal-bed methane underbalanced drilling.