Abstract
Confined phase behavior plays a critical role in predicting production from shale reservoirs. In this work, a pseudo-potential lattice Boltzmann method is applied to directly model the phase equilibrium of fluids in nanopores. First, vapor-liquid equilibrium is simulated by capturing the sudden jump on simulated adsorption isotherms in a capillary tube. In addition, effect of pore size distribution on phase equilibrium is evaluated by using a bundle of capillary tubes of various sizes. Simulated coexistence curves indicate that an effective pore size can be used to account for the effects of pore size distribution on confined phase behavior. With simulated coexistence curves from pore-scale simulation, a modified equation of state is built and applied to model the thermodynamic phase diagram of shale oil. Shifted critical properties and suppressed bubble points are observed when effects of confinement is considered. The compositional simulation shows that both predicted oil and gas production will be higher if the modified equation of state is implemented. Results are compared with those using methods of capillary pressure and critical shift.
Highlights
Shale oil production experienced a rapid increase in recent years and has been a major contributor to oil consumption in North America [1,2,3]
With the equation of state (EOS) proposed for confined fluids, it can be incorporated into the flash calculation and compositional simulation to model oil and gas production from shale
We aim to present the process of thermodynamic modeling of confined phase behavior using pore-scale simulation and applying the knowledge learned into the reservoir-scale simulation
Summary
Shale oil production experienced a rapid increase in recent years and has been a major contributor to oil consumption in North America [1,2,3]. Vishnyakov et al [23] conducted numercial study on the phase behavior of methane in slit pores They found that a lower critical temperature and higher critical density of methane in slit pores and the shift of critical point depends on pore size and strength of fluid-solid force. In another work of Huang et al [25], the pseudo-potential LB model is applied to study the confined phase behavior of methane in a slit pore and a complex medium. With the EOS proposed for confined fluids, it can be incorporated into the flash calculation and compositional simulation to model oil and gas production from shale. The modified EOS is applied to model phase diagram in shale matrix and predict oil Energies 2021, 14, 1315 and gas production. Results are compared with those using methods of capillary pressure and critical shift
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