Soaking and hydrous pyrolysis of Indian oil shale: Identification of produced hydrocarbons and moieties

Abstract

In the present study, soaking and hydrous pyrolysis experiments were performed on Indian oil shale in the presence of de-ionized (DI) water and brine solution under isothermal conditions of 300, 350, and 400 °C, and residence time of 72 h to simulate the effect of underground aquifers on the expulsion and composition of hydrocarbons from source rocks. During soaking pyrolysis, the oil yield increased minutely with the increase in soaking time from 1 to 4 weeks but was not influenced by the presence of brine solution (8.82 wt/wt%) or DI water (8.46 wt/wt%). A similar trend in the generation of oil yield was observed during hydrous pyrolysis in both DI water and brine solution. GC analysis of the gas samples showed methane (CH4) as the prominent gas produced during soaking and hydrous pyrolysis. During soaking pyrolysis, the concentration of C2 to C5 gases decreased with increased pyrolysis temperature. However, during hydrous pyrolysis, the concentration of C4 and C5 gases increased with an increase in pyrolysis temperature. GC-SimDist analysis of the oil samples obtained from soaking pyrolysis at 400 °C showed the compounds ranged from C8 to C38 in brine solution and from C6 to C34 in DI water. Nevertheless, during hydrous pyrolysis in both DI water and brine solution, the carbon number distribution of the oil samples was observed to be in the range of C8 to C38. GC–MS analysis of the oil samples obtained from the soaking and hydrous pyrolysis experiments showed that the molecular weight of the identified compounds ranged from 86 to 380 g/mol. GC–MS, ATR, and 1H NMR analyses showed that the oil samples obtained from soaking and hydrous pyrolysis experiments were rich in aliphatic compounds. The organic acids content appeared to be higher in the presence of DI water as compared to the brine solution.