非均质致密储层微观力学特征分析及脆性评价方法研究

Micromechanical Analysis and Brittleness Evaluation of Heterogeneous tight Reservoir

脆性指数是非常规储层压裂造缝的重要影响参数之一,现有脆性评价方法众多,差异巨大,且大多从宏观角度出发,在非常规储层缝网压裂领域中的应用受到制约。由于非常规储层的非均质性强,对其进行脆性表征时,需从微观领域进行研究。以辽河油田某致密储层为研究对象,测定岩心样品弹性模量、泊松比及岩心样品中矿物成分含量,采用逐步回归分析方法建立力学参数与矿物成分之间的回归模型,对微观领域岩心脆性分布进行定量表征,描述岩心微观破裂至整体失稳的变化特征。结果表明:岩石弹性模量主要由石英、方解石、方沸石、菱铁矿以及黏土的含量决定,泊松比主要由石英、方解石、白云石以及黏土的含量决定;新脆性模型从微观领域评价了非均质储层岩石脆性分布,且修正了矿物分析法计算偏低的情况。该研究为非均质储层脆性分析提供了一种科学有效的评价方法。

Brittleness index is one of the crucial influencing parameters for the unconventional reservoir stimulation.There are many available brittleness evaluation methods with great differences,and most of them are classified as macroscopic evaluation and limited in the unconventional reservoir stimulation.Micromechanical brittleness characterization is preferable due to the strong reservoir heterogeneity.A tight reservoir in Liaohe Oilfield was taken to test the elastic modulus,Poisson’s ratio and mineral content of core samples.A stepwise regression analysis was used to establish a regression model between the mechanical parameters and mineral composition.The microscopic brittleness distribution was quantitatively characterized to describe the variation from core micro-fracture to the overall instability.Result indicates that the elastic modulus is mainly dependent on the contents of quartz,calcite,analcite,siderite and clay.The Poisson’s ratio is mainly dependent on the contents of quartz,calcite,dolomite and clay.The new brittleness model evaluates the brittleness distribution of heterogeneous reservoir rocks from the microscopic perspective and corrects the underestimation of mineral analysis method.This research could provide a scientific and effective evaluation method for the analysis of heterogeneous reservoir brittleness.