Molecular Dynamics simulations of multiphase flow in nanopores with organic and inorganic substrates

The increasing demand for fossil fuels - driven by a fast proliferation of energy-intensive lifestyles over the globe (Mokhatab, 2006) (Wang et al., 2016) - requires the unlocking of ever more oil and gas reservoirs where hydrocarbons are trapped in porous or fractured rock formations in a subsurface. Hydrocarbon reservoirs can be divided in conventional and unconventional reservoirs.
With the rapid decline in conventional hydrocarbon resources, one of the unconventional resources, shale gas, plays an important role in the oil and gas industry (Civan, 2010; Javadpour, 2009; Fathi et al ., 2013) especially in United States of America. In 2009, 87% of the consumption rate of natural gas in the United States was produced domestically. Potential natural gas resources from shale play in the United States amount to 2,552 trillion cubic feet (Tcf) according to EIA Annual Energy Outlook 2011, enough to provide the US for at least 100 years with natural gas consumption rate of 67.1 billion cubic feet per day (EIA, August 2017) .
In Britain, according to British Geological Survey and UK Oil &Gas Authority, central estimation of shale oil in place from Jurassic shale of the Wessex area and the Weald basin in south-east England is 5.5 billion barrels (bbl) in total. The central estimations of shale gas in place are 6.0 billion bbl and 1329 trillion cubic feet from the midland valley of Scotland and Bowland shale gas in part of central Britain in an area between Wrexham and Blackpool in the west, and Nottingham and Scarborough in the east.
Shale oil and gas is produced from shale plays which are organic-rich, fine-grained, low-permeability sedimentary rocks (US DOE, 2009). Pores in shale matrix are considered to be of nanometer-scale (Loucks et al., 2009; Javadpour et al., 2009). At this scale, significant surface adsorption and inhomogeneous molecular distribution are reported (Li et al., 2014). The surface adsorption is important for oil/ gas in place in shale reservoirs as it strongly hinders the mobility of the hydrocarbons. Analysis of flow and transport in shale requires careful attention since macroscopic / continuum approaches based on Darcy's law and the Navier-Stokes equations have limited validity at the nano-scale (Bitsanis et al., 1988).
As a result, enhanced hydrocarbon recovery in ultra-low permeable reservoirs is not fully apprehended. The process of enhanced oil recovery (EOR) - for instance through injection of brine or carbon dioxide - accentuates the need for understanding multiphase-transport phenomena at the nano-scale. Since in EOR the injected fluid is intended to displace hydrocarbons, important factors influencing the efficiency of the process are the levels of miscibility of the fluids, their viscosities, the contact angle and surface tension. In this research, Molecular Dynamics (MD) is used to achieve insight in these complex pore-scale transport processes. MD is a powerful method that enables us to understand physical and chemical processes at the nano-scale such as the adsorption of various fluids on organic and inorganic substrates (Jin et al., 2016). MD has the capacity of modelling heterogeneity in phase, composition and geometry.
This research project thus is about developing an understanding of flow phenomena in nano-scale pores for EOR purpose.