Advances in simulation of hydrocarbon production from shale reservoirs

This paper tackles several challenging aspects of shale reservoir simulation including the complex physics of fluid transportation and the corresponding reservoir simulator development, fractured media modeling, and modified PVT behavior in nano-pores. In the first part of the paper, a finite-volume based compositional simulator, named GURU, is developed to incorporate the study of more advanced physics in shale reservoirs. Our fit-for-purpose simulator is able to provide a multi-porosity/multi-permeability simulation capability, which is a top priority in simulation of highly heterogeneous shale resources. The performance of our simulator in hydraulically fractured reservoirs is evaluated through some case studies. An Embedded Discrete Fracture Model (EDFM) is discussed in the second part of paper to handle arbitrary fracture geometry flexibly. Our EDFM model inherits the advantages of using a multi-porosity model to replace laborious traditional approaches to characterize multi-scale reservoir heterogeneity and the complex fracture network in shale reservoirs. In the last part of this paper, we have provided an in-depth discussion on how rock-fluid interactions can affect the phase behavior and fluid distribution in shale. Capillary pressure effect on phase behavior of reservoir fluid is analyzed where a dynamic interfacial tension calculation process is incorporated to account for the effect of pore size and fluid composition in capillary pressure calculations. In addition to that, application of a modified Peng-Robinson equation of state shows that the tight porous media in shale can act as a semi-permeable membrane and selectively filters molecules based on their sizes. This phenomenon is further investigated in a so-called 'sieving or size filtration effect'.