致密储层数字岩心重构及核磁共振响应模拟

基于物理过程法模拟沉积岩的沉积、压实和胶结过程,构建致密岩石的三维数字岩心。利用随机行走法模拟不同成岩过程岩石的核磁共振响应以及不同润湿性岩石孔隙中流体的核磁共振响应。模拟结果表明,岩石胶结成岩后孔隙半径减小导致核磁共振横向弛豫(T_2)分布的峰值向短弛豫方向移动,流体视扩散系数略小于自由扩散系数;致密岩石中随润湿相流体饱和度减小,润湿相T_2分布向短弛豫方向偏移,受限扩散越来越明显。

Reconstruction of digital core of tight reservoir and simulation of NMR response

A 3D digital core model of tight rock was constructed by simulating the sedimentation, compaction and cementation processes of sedimentary rocks. The nuclear magnetic resonance (NMR) responses of different diagenetic processes of the sedimentary rock, and the NMR responses of fluid in tight rock under different wetting conditions were simulated using a random walk method. The simulation results show that the decreasing of pore radius caused by cementation process leads to the peaks of NMR transverse relaxation time (T₂) distribution shifting to short relaxation time, and results in slightly smaller apparent diffusion coefficient of fluids than its free diffusion coefficient. In tight rock, when the saturation of wetting phase decreases, the peaks of its T₂ distributions shift to short relaxation time and the restricted diffusion becomes more obvious.