Palaeolake Environment and Depositional Model of Source Rocks of the Lower Submember of Sha1 in Raoyang Sag, Bohai Bay Basin
Yin Jie
Wang Quan
Hao Fang
Guo Liuxi
Zou Huayao
Abstract：Despite successful studies on source rocks of Raoyang sag, existing studies on the ancient lake environment during lower submember of Sha1 source rocks development period are not systematic, an important factor controlling the geochemical characteristics and temporal and spatial distribution of source rocks, is often ignored.In this study, samples of source rocks in the lower submember of Sha1 were analyzed with palaeontological material, organic geochemistry, trace element and isotopic geochemistry to reveal the paleolake environment including the paleoclimate, water depth, salinity, organic matter preservation and productivity, and to construct depositional model for high-quality source rocks of the lower submember of Sha1.Results show that the high-quality source rocks mainly formed in the transgressive system tracts period.Meantime, the climate was in the transition from arid to humid, and the water depth of the paleolake was about 2-14 meters, wave base depth was 7.5 meters.Paleosalinity parameters such as Sr/Ba and B/Ga indicate the lower submember of Sha1 belonged to the saline environment due to the effect of water evaporation.High salinity was favorable to stable halocline formation, resulting in the bottom water in an anoxic condition for the preservation of organic matter.And the stable carbon isotope and nutrient elements distribution characteristics display that the surface water had high initial productivity in the stage of the lower submember of Sha1.Such paleolake environment caused wide distribution of strong reducing salt water semi-deep lake organic facies, beneficial to the growth of high-quality hydrocarbon source rocks.
Keywords：Raoyang sagthe lower submember of Sha1paleolakehigh-quality source rockdevelopment modelpetroleum geology.
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：14( 1209-1222 )