Abstract
Spontaneous water imbibition plays an imperative role in the development of shale or tight oil reservoirs. Spontaneous water imbibition is helpful in the extraction of crude oil from the matrix, although it decreases the relative permeability of the hydrocarbon phase dramatically. The dynamic pore-scale network modeling of water imbibition in shale and tight reservoirs is presented in this work; pore network generation, local capillary pressure function, conductance calculation and boundary conditions for imbibition are all presented in detail in this paper. The pore network is generated based on the characteristics of Barnett shale formations, and the corresponding laboratory imbibition experiments are matched using this established dynamic pore network model. The effects of the wettability, throat aspect ratio, viscosity, shape factor, micro-fractures, etc. are all investigated in this work. Attempts are made to investigate the water imbibition mechanisms from a micro-scale perspective. According to the simulated results, wettability dominates the imbibition characteristics. Besides this, the viscous effects including viscosity, initial capillary pressure and micro-fractures increase the imbibition rate, while the final recovery factor is more controlled by the capillarity effect including the cross-area shape factor, contact angle and the average pore-throat aspect ratio.
Highlights
The spontaneous water imbibition phenomenon is commonly encountered in the development of shale or tight reservoirs
Water imbibition is helpful for the replacement of oil from the matrix and increases the oil recovery, while it decreases the relative permeability of the hydrocarbon phase dramatically, which is detrimental to the production rate and recovery factor [1,2]
We propose a dynamic pore-scale network fluid flow simulation model that simulates the process of spontaneous water imbibition in shale or tight formations
Summary
The spontaneous water imbibition phenomenon is commonly encountered in the development of shale or tight reservoirs. Based on the calculated capillary pressure and relative permeability from quasi-static models, the spontaneous imbibition process can be simulated using conventional reservoir simulators or some simple analytical solutions [23,24,25,26]. We propose a dynamic pore-scale network fluid flow simulation model that simulates the process of spontaneous water imbibition in shale or tight formations. The proposed model is first applied and validated for Barnett shale formations for the single-phase flow, and the spontaneous imbibition process is simulated and corresponding systematical sensitivity studies are conducted. Attempts are made to propose an approach to investigate the spontaneous water imbibition mechanisms from a micro-scale perspective
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