Source rock potential and organic geochemistry of carboniferous source rocks in Santanghu Basin, NW China

Abstract

Carboniferous source rocks identified by drilling in Santanghu (三塘湖) Basin were evaluated for their source potential, employing organic geochemistry and RockEval pyrolysis. The organic matter origin and depositional environment of these samples were also determined through biomarker analysis. Most of the Carboniferous source rocks in Santanghu Basin are characterised by high values of total organic carbon (TOC) content and high extractable organic matter content and hydrocarbon yields, indicating that they are organic-rich source rocks with high oil generative potential. The organic matter is predominantly Type I and Type II kerogen with a minor contribution of Type III kerogen, as demonstrated by its pyrolysis parameters and carbon isotope values. According to Ro (%) and T max values, most of the studied samples are at early- to middle-thermal mature stage; only a few of the samples are at a highly mature stage (past peak oil generation). The biomarker analysis reveals a dominance of algal/bacterial organic matter input, with a minor contribution of land plant material. Pr/Ph ratio supports a suboxic depositional condition, consistent with a neritic or marine-continental alternating environment proposed by predecessor.