Organic Geochemical Characterization and Exploration Prospects of Hydrocarbon Source Rocks in Nepal

ABSTRACT This study aims to evaluate the hydrocarbon generation potential and exploration prospects of hydrocarbon source rocks in the Dailekh to Dang–Tansen area of Nepal. Despite sharing a similar geological setting with India's Assam Basin and Pakistan's Potwar Basin, this region has remained relatively under‐explored, with a lack of systematic geochemical data to support comprehensive assessments of its hydrocarbon source rocks. Drawing on hydrocarbon source rock samples collected in recent years, this study integrates multiple organic geochemical analysis techniques—including total organic carbon (TOC) determination, Rock‐Eval pyrolysis, maceral analysis, biomarker analysis, and vitrinite reflectance measurement—to systematically assess the abundance, type, and maturity of organic matter in the source rocks. Results indicate that the hydrocarbon source rocks in this area are predominantly of continental‐mixed facies origin, with Type III organic matter as the primary component, generally exhibiting a “gas‐prone” trait. The TOC content shows significant heterogeneity across formations (0.15%–4.88%), with the Sangram Formation and Melpani Formation emerging as “sweet spots” for high‐quality hydrocarbon source rocks. Maturity levels span a broad range, from mature to over‐mature (Ro: 0.61%–1.57%, T max : 261°C–513°C), suggesting substantial natural gas generation potential overall. From an exploration perspective, while the region has established a solid foundation for hydrocarbon generation, uncertainties in preservation conditions—driven by intense regional tectonic activity—may limit further improvements in its exploration value. Consequently, subsequent studies should prioritize more detailed investigations into preservation conditions to address this critical knowledge gap.