基于应力-应变曲线形态的致密气储层脆性研究

Brittleness of tight gas reservoirs based on stress-strain curves

岩石的脆性研究对致密气的勘探开发具有重要意义。储层岩石脆性越高,压裂后裂缝越发育,产能越高。以鄂尔多斯盆地东北部二叠系致密气储层为研究对象,通过研究脆性岩石的单轴压裂起裂机制,以单轴压裂曲线的起裂点和峰值点的应力与应变为基础,结合多种脆性计算公式,建立了新的脆性指数计算模型。研究表明:利用新模型计算的脆性指数与基于静态岩石力学参数计算的脆性指数具有很明显的函数关系,可以有效表征研究区岩石的脆性;基于单轴抗压实验的压裂效果,利用新建立的脆性指数和初裂点指数可以有效地建立储层的压裂效果划分标准。该研究成果丰富了储层脆性计算的方法,建立了新的脆性评价标准。

The brittleness of rocks is one of the most important parameters in tight gas exploration and development.The higher the reservoir rock brittleness is,the more fracturing fracture develops,and the higher the productioncapacity will be.A variety of brittleness calculation formulas were used to establish a new calculation modelof brittleness index of the Permian tight gas reservoir in northeastern Ordos Basin by researching the uniaxialcompression crack mechanism of brittle rock,and the stress and strain of the first crack point and the peak underuniaxial compression.The results show that the brittleness index calculated by the new model can characterizethe brittleness of the rocks effectively,because it has obvious function relationship with the brittleness calculatedby static rock mechanics parameters in the experiments.Based on the fracturing effect in uniaxial compressive experiments,the new brittleness index and the initial crack point index could be used to establish the standard of reservoirfracturing effect.This result enriches the reservoir brittleness calculation method,and sets a new standard ofbrittleness evaluation.