Primary oil recovery from fractured unconventional formations, such as shale or tight sands, is typically less than 10%. The development of an economically viable enhanced oil recovery (EOR) technique applicable to unconventional liquid reservoirs (ULRs) would lead to tremendous increases in domestic oil production. Although injection techniques such as waterflooding and CO2 EOR have proven profitable in conventional formations for decades, EOR in ULRs presents a far more difficult challenge. The extremely low permeability and mixed wettability of unconventional formations are the foremost obstacles to success. Because of the challenges associated with water-based EOR techniques (a.k.a., chemical EOR) in shale, several nonaqueous injection fluids have been considered, including CO2, natural gas, and (to a lesser degree) nitrogen. All these fluids have significantly lower viscosities than water, allowing them to more easily penetrate shale nanopores. Unlike water, they also each possess some degree of miscibility with oil, which enables the gas to extract oil through a combination of mechanisms. Based on laboratory-scale experimentation, CO2 and rich natural gas (methane-rich natural gas containing high concentrations of ethane, propane, and butane) are the most promising EOR fluids. The interpretation of results from field tests in the Bakken and Eagle Ford formations have been complicated by interference of frac-hits or well-bashing caused by hydraulic fracturing at nearby wells. In this review we cover mechanisms, laboratory experiments, numerical simulations, and field tests involving high-pressure CO2, natural gas, ethane, nitrogen, and water.

We converted palmitic and oleic acids to fuel range hydrocarbons using two activated carbons in near- and supercritical water with no H2 added. The main products from palmitic acid were C8−C15 n-alkanes. The major products from oleic acid were C12−C17 n-alkanes and some C17 olefins. The pseudo-first-order rate constants displayed Arrhenius behavior. The apparent activation energy of 125 kJ/mol for palmitic acid decarboxylation is higher than that observed with a 5% Pt/C catalyst. Nevertheless, these results show that activated carbons possess catalytic activity for the hydrothermal decarboxylation of fatty acids.

In this work, the grand canonical Monte Carlo method was employed to study the adsorption and separation characteristics of CH 4 /H 2 on MOF-5 and five zeolitic imidazolate frameworks (ZIFs), including two sodalite (SOD), ZIF-8 and -67, two merlinoite (MER), ZIF-10 and -60, and one DFT, ZIF-3. Simulations show that more CH 4 molecules are adsorbed in all frameworks than H 2 , which is consistent with a higher pure gas isosteric heat of adsorption of CH 4 as compared with that of H 2 . For both gases, adsorbed amounts primarily rely on the physical and chemical parameters of the adsorbent. Results of density distribution profiles and equilibrium snapshots of the ZIFs indicate that the most preferential gas adsorption sites for both CH 4 and H 2 are the positions near linkers. At high pressures, CH 4 begins to fill up in the center of the SOD cage. We also found that the selectivity for CH 4 increased with the difference between the isosteric heats of adsorption of CH 4 and H 2 , ∆q st , but decreased to some extent due to the packing effect. Both the isosteric heats of adsorption and the packing effect are mainly influenced by the topology of the framework.