Target-based sedimentary diagenesis simulation and three-dimensional diagenesis evolution modeling

Abstract

Deposition and diagenesis are important factors affecting the quality of oil and gas reservoirs. Previously reported diagenesis studies mainly involve qualitative analysis, such as the determination of diagenetic events and diagenetic evolution sequences and modeling of two-dimensional diagenetic evolution, with less effort devoted to quantitative numerical simulation and three-dimensional diagenetic evolution models. This study proposes a new method for target-based diagenesis simulation by integrating the discrete element method, the quartet structure generation set method, and morphological algorithms. This new hybrid method can quantitatively simulate the effects of mineral grain deposition, compaction, cementation, dissolution, and replacement. Since specific minerals can undergo specific diagenetic alterations through mineral labeling, the sequence and path of diagenesis can be predefined in this method. Taking the sandstone reservoir of Lower Member 3 of the Shahejie Formation in Linnan Sag, Huimin Depression, Bohai Bay Basin, East China as an example, the new simulation method used the constructed diagenetic evolution sequence based on thin section identification and geochemical analysis to systematically simulate deposition and diagenesis in the study area and to construct a three-dimensional diagenetic evolution model. The predicted porosity, permeability, and pore size distribution of the simulated digital rocks are in good agreement with the experimental values, which validates the high accuracy of the simulation method. Based on these three-dimensional multi-mineral evolution models, the evolution trends of porosity and permeability during the sedimentation and diagenesis process were elucidated, revealing the variation in reservoir quality in the studied area and indicating reservoir sweet spots. The constructed 3D diagenesis evolution models are widely applicable and can be used not only for permeability simulation but also for the study of electrical, acoustic, and mechanical properties of reservoirs.