基于岩石物理模型的页岩储层裂缝属性及各向异性参数反演

Fracture Properties and Anisotropic Parameters Inversion of Shales Based on Rock Physics Model

针对富有机质页岩储层复杂的矿物组分与微观孔缝结构,本文提出基于岩石物理模型和改进粒子群算法的页岩储层裂缝属性及各向异性参数反演方法。应用自相容等效介质理论与Chapman多尺度孔隙理论建立裂缝型页岩双孔隙系统岩石物理模型。开发基于岩石物理模型的反演流程,引入模拟退火优化粒子群算法解决多参数同时反演问题,反演算法能够避免陷入局部极值且收敛速度快。将本文方法应用于四川盆地龙马溪组页岩气储层,反演得到的孔隙纵横比、裂缝密度等物性参数和各向异性参数与已有研究结果一致,能为页岩储层的评价提供多元化信息。

Organic-rich shale reservoirs usually have complex mineral compositions and pore system in a small scale. This study presents a workflow of the fracture properties and anisotropy parameter inversion of shales based on the rock physics model and improved particle swarm optimization algorithm. A two-pore system for fractured shales was built through applying the self-consistent equivalent medium theory and Chapman＇s multi-scale porosity model. This inversion workflow can be used to estimate multi-parameter simultaneously by utilizing the simulated annealing-based particle swarm optimization algorithm. The intelligence algorithm has the ability to find global optimization and fast convergence. The workflow was applied in the Longmaxi shale-gas reservoir in the Sichuan basin to estimate the aspect ratio of pores, fracture density, and anisotropy parameters. The result is consistent with the existing research and provides diversified information for the shale reservoir evaluation.