Experimental study of the effects of thermochemical sulfate reduction on low molecular weight hydrocarbons in confined systems and its geochemical implications

Downhole Kinetics of Reactions Involving Alcohol-Based Hydraulic Fracturing Additives with Implications in Delayed H2S Production

“…Several authors have presented results which indicated that pH significantly influences the TSR of hydrocarbons at relatively similar conditions (similar pressures but higher temperatures). − In previous work we concluded that lowering the pH favors the equilibrium reaction of aqueous oxo-sulfur species and H 2 S, forming S. − As a result, the steady-state concentration of S will increase at low pH, and the instantaneous rate constant is expected to increase with time. In this particular case, we are assuming that the S has already formed inside the reservoir either by shifting chemical equilibrium or by oxidation of H 2 S with dissolved oxygen (this oxidation is rapid).…”

Discovery and Molecular Characterization of Organic Caged Compounds and Polysulfanes in Zhongba81 Crude Oil, Sichuan Basin, China

“…Oil and gas with high levels of H 2 S and CO 2 are largely thermochemical sulfate reduction (TSR) genesis. − TSR is a process wherein hydrocarbons are oxidized by aqueous sulfates at high reservoir temperatures (usually >120 °C), yielding high concentrations of CO 2 , H 2 S, and refractory sulfur-rich solid bitumen . In the past two decades, great progress has been made in TSR research through case studies conducted in many fields − and through laboratory simulation experiments, − which has enhanced our understanding of the conditions, rates, and products of TSR and of the associated effects on petroleum molecular composition . The formation of exogenous sulfur compounds in crude oil is closely related to TSR .…”

Thermal Cracking of Oil under Water Pressure up to 900 Bar at High Thermal Maturities: 2. Insight from Light Hydrocarbon Generation and Carbon Isotope Fractionation

“…Gasoline-range hydrocarbons, usually called light hydrocarbons in the range of C 5 –C 12 (LHs), are important components of crude oil. The molecular and stable carbon isotopic compositions of LHs have been widely used for oil/gas-source correlations, − maturity assessment of crude oil, − migration pathway and accumulation history of crude oil, − and in-reservoir secondary alteration identification, e.g., biodegradation, evaporation, water washing, thermochemical sulfate reduction. − Hunt proposed that LHs are formed from the combined effects of various biological, geological, and chemical processes on the dispersed organic matter in sediments. Three types of reactions are involved in LH generation, including biodegradation of sedimentary organic matter in the biochemical and early diagenetic stages, low-temperature chemical degradation of kerogen and sedimentary organic matter in the diagenetic stage, and high-temperature thermal degradation of kerogen, bitumen, and crude oil in the catagenetic and metagenetic stages.…”