弹性特征约束下的矿物成分页岩脆性评价方法研究

脆性评价对页岩储层可压裂性评估、设计压裂层段、提升压裂改造效果具有重要意义.但传统基于矿物成分的脆性评价方法将不同矿物成分对脆性指数贡献程度进行平均化, 忽略了不同矿物对岩石脆性影响的差异性.
本文采用数字岩石物理实验来标定不同矿物成分对岩石脆性整体特征的影响程度, 定量分析了岩石弹性参数随矿物组分含量的变化关系, 采用基于弹性参数的脆性指数来建立不同矿物成分对页岩脆性的差异性影响关系, 建立不同矿物组分相较于黏土矿物与脆性指数的相对关系及敏感因子, 在弹性参数脆性指数的约束下确定了不同矿物成分在脆性指数中的权重, 提出了基于矿物成分贡献程度自适应变化的脆性评价方法.矿物脆性评价结果与弹性参数脆性评价结果的相关性分析及下寺湾地区岩样脆性评价测试表明, 考虑不同矿物成分的差异性所构建的脆性评价方法更加合理有效.

Method for evaluating the brittleness of shale minerals under the constraints of elastic characteristics

Brittleness evaluation is important for fracturability assessment of shale reservoirs, design of fractured sections, and improvement of fracture transformation effects. However, the traditional brittleness evaluation method based on mineral composition averages the degree of contribution of different mineral compositions to the brittleness index, ignoring the variability of the influence of different minerals on the brittleness of rocks.
In this paper, digital petrophysical experiments are used to calibrate the degree of influence of different mineral components on the overall characteristics of rock brittleness, quantitatively analyze the relationship between the variation of rock elasticity parameters with the content of mineral components, adopt the brittleness index based on elasticity parameters to establish the differential influence of different mineral components on shale brittleness, establish the relative relationship and sensitivity factors of different mineral components compared with clay minerals to the brittleness index, and determine the brittleness index under the brittleness evaluation method based on the adaptive change of the contribution of mineral components is proposed. The correlation analysis between the mineral brittleness evaluation results and the brittleness evaluation results of elastic parameters and the brittleness evaluation test of rock samples in the Xiajiwan area show that the brittleness evaluation method constructed by considering the differences of different mineral components is more reasonable and effective.