川东北嘉四段-嘉五段地层岩石力学参数不确定性研究

Study on the Uncertainty of Rock Mechanics Parameters in the Jia-4-Jia-5 Interval of Jialingjiang Formation in Northeast Sichuan

针对川东北油气田嘉陵江组嘉四-嘉五段地层普遍出现的套管变形损坏现象,有必要对该地层段岩石力学性质进行统计分析。采用随机-模糊统计法对静态岩石力学参数样本数据进行粗差分析,并基于Kolmogorov-Smirnov(K-S)假设检验方法,研究嘉陵江组四段-嘉五段地层的弹性模量、泊松比、单轴抗压强度和内聚力等岩石力学参数的概率分布特征,以确定各岩石力学参数最优的概率分布形式和概率密度函数。结果表明:嘉陵江组嘉四段-嘉五段地层的弹性模量、泊松比、单轴抗压强度和内聚力都具有较强的离散性,且其大样本最优概率分布形式并不一致,分别为威布尔分布、威布尔分布、对数正态分布和对数正态分布。计算得到的岩石力学参数概率分布区间,能够更为准确地描述嘉陵江组四-五段地层的力学性质,研究结果为盐膏岩地层钻井设计及井壁稳定性研究等提供了数据支持。

In view of the common casing deformation and damage in the Jia-4-Jia-5interval of Jialingjiang formation of oil and gas field in Northeast Sichuan,it is necessary to analyze the rock mechanical properties of the formation.The random-fuzzy statistics method was used to analyze the gross errors of the sample data of static rock mechanics parameters of the Jia-4-Jia-5 interval of Jialingjiang formation to eliminate the abnormal values of the elastic parameters.Based on the Kolmogorov-Smirnov(K-S)hypothesis test method,the probability distribution characteristics of rock mechanics parameters such as elastic modulus,Poisson s ratio,uniaxial compressive strength and cohesion of the Jia-4-Jia-5 interval of Jialingjiang formation were studied to determine the optimal probability distribution forms and probability density functions of rock mechanics parameters.The results show that the elastic modulus,Poisson s ratio,uniaxial compressive strength,and cohesion of the Jia-4-Jia-5 interval of Jialingjiang formation were all highly discrete,and the optimum probability distributions of them are different,which are Weibull distribution,Weibull distribution,lognormal distribution,and lognormal distribution.The calculated probability distribution interval of rock mechanics parameters can describe the mechanical properties more accurately of the Jia-4-Jia-5 interval of Jialingjiang formation.The research results provide data support for drilling design and wellbore stability study in gypsum formations.