CO2 exchange method is one of the extraction techniques that is under development for the production of methane from gas hydrate resources, and the mechanisms and kinetics of the CO2-CH4 exchange process still remain unclear. We model this process with molecular dynamics (MD) simulation to reveal the reaction mechanism, find the optimal operating condition and enhance the conversion rate. The simulations are carried out at three different temperatures to study the impact of temperature on the exchange rate and the kinetics. The production runs are carried out at microsecond level in the NPT ensemble with pressure held at 5 MPa. The simulation results and the associated analysis show that at the investigated conditions, the CO2-CH4 exchange process involves a direct swap of the guest molecules without complete breakage of the water cages. Also, temperature has a significant impact on the kinetics of the process that the increase of temperature from 250K to 270K accelerates the procedure by at least 1.5 times. The reactions mainly occur at the hydrate surface, so that it is critical to enhance the penetration of CO2 into hydrate structures for large scale application of the CO2-CH4 exchange method.
Shale formations exhibit multi-scale geological features such as nanopores in formation matrix and fractures at multiple length scales. Accurate prediction of relative permeability and capillary pressure are vital in numerical simulations of shale reservoirs. The multi-scale geological features of shale formations present great challenges for traditional experimental approach. Compared to nanopores in formation matrix, fractures, especially connected fractures, have much more significant impact on multiphase flows. Traditional flow models like Darcy's law are not valid for modeling fluid flow in fracture space nor in nanopores. In this work, we apply multiphase lattice Boltzmann simulation for unsteady-state waterflooding process in highly fractured samples to study the effects of fracture connectivity, wetting preference, and gravitional forces.
Zhang, Kaiyi (Virginia Polytechnic Institute and State University) | Nojabaei, Bahareh (Virginia Polytechnic Institute and State University) | Ahmadi, Kaveh (Pometis Technology) | Johns, Russell (Pennsylvania State University, University Park)
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