Organic matter enrichment mechanism in saline lacustrine basins: A review

Abstract

Organic‐rich shale in saline lacustrine basins holds significant importance as a source rock for conventional hydrocarbon exploration and has emerged as a prominent target for unconventional hydrocarbon exploration and development in recent years. Based on saline lacustrine basins, this paper provides a summary of the organic matter enrichment mechanisms in saline lacustrine basins, considering sedimentary characteristics, biological activities, factors for the organic matter enrichment and consumption, and hydrocarbon generation. The implications for these factors are discussed in relation to the distribution prediction of high‐quality lacustrine shale district settings and the exploration and development of shale oil. Saline lacustrine basins undergo distinct evolutionary stages, each corresponding to different sedimentary stages involving carbonate minerals, sulphate minerals, and alkaline minerals. Moreover, these basins exhibit diverse biological types and experience extensive biological activities. The prosperity of organisms and the accumulation of sedimentary organic matter are ensured by halophilic organisms. Organic matter enrichment in saline lacustrine basins is influenced by two main aspects: the primary productivity of organic matter, which is promoted by the proliferation of halophilic organisms, and the efficient preservation of organic matter facilitated by the strong reducing environment resulting from promoted water salinity stratification. The organic matter consumption in saline lacustrine basins involves bacterial sulphate reduction (BSR) in the early stages, thermochemical sulphate reduction (TSR) in the late stages, and dilution of salt minerals with higher depositional rates. of the presence of salt beds and saline minerals positively influences hydrocarbon generation and expulsion in organic‐rich shale within saline lacustrine deposition. Consequently, continental saline lacustrine basins in China offer favourable conditions for the formation of organic‐rich shale and present broad prospects for the exploration of shale oil and gas resources.

Lithofacies Characteristics of Continental Lacustrine Fine-Grained Sedimentary Rocks and Their Coupling Relationship with Sedimentary Environments: Insights from the Shahejie Formation, Dongying Sag

“…Paleosalinity refers to the salinity of water bodies during sediment deposition and has a significant impact on the development of organic-rich fine-grained sedimentary rocks [61]. Typically, elevated salinity levels can induce water stratification, impeding convective mixing and hindering sediment-oxygen contact, thereby promoting the preservation of organic matter [62,63]. Sr/Ba ratios are commonly used to indicate changes in paleosalinity, with fine-grained sedimentary rocks having higher Sr/Ba values considered to have experienced high-salinity depositional environments [64].…”

Paleoenvironment and Hydrocarbon Potential of Salinized Lacustrine Shale with High Terrigenous Input in the Paleogene Biyang Depression (East China): Evidence from Organic Petrography and Geochemistry

“…It includes the Xiangzao, Nanyang, and Biyang depressions, as well as the Shigang, Xinye, Tanghe, and Sheqi uplifts (Figure 1B). The hydrocarbon-rich Biyang Depression spans nearly 1000 km 2 and boasts conventional oil reserves of 306 million tons and shale oil reserves of 285 million tons [16,20]. The depression takes the form of a half-graben rift, further divided into the northern slope belt, central deep sag, and southern steep slope belt (Figure 1C,D).…”

“…The enrichment process includes biological bloom, primary productivity, water stratification, and organic matter preservation. Water stratification in saline lacustrine basins facilitates the preservation of sedimentary organic matter by inducing bottom water anoxia [16].…”