Hydrocarbon generation and expulsion efficiency and influence on oil bearing property of shale in the second member of Paleogene Kongdian Formation in Cangdong Sag
The shale oil potential of the second member of Kongdian Formation in Cangdong Sag,Bohai Bay Basin,is substan-tial,with stable industrial oil flow achieved through horizontal well drilling and control.In this paper,the routine rock-eval py-rolysis and shale play rock-eval pyrolysis techniques are utilized to optimize the hydrocarbon generation and expulsion mass bal-ance method.A hydrogen index balance calculation method for shale hydrocarbon generation and expulsion efficiency,based on both the original and residual hydrocarbon generation potential,is proposed.Investigating the primary controlling factors,aside from maturity,on hydrocarbon expulsion efficiency in the shale,sheds light on the relationship between hydrocarbon expulsion efficiency and oil bearing property.In this study,samples with similar depth and maturity are selected to exclude the influence of maturity variation,a recognized indicator of hydrocarbon generation and expulsion efficiency.The results show the signifi-cance of organic matter abundance and type,pore structures,and rock types as key factors controlling hydrocarbon generation and expulsion efficiency in the shale of the second member of the Paleogene Kongdian Formation in Cangdong Sag.The prod-ucts of type Ⅲ kerogen are mainly light hydrocarbons,exhibiting considerable variation in hydrocarbon expulsion efficiency,generally higher than that of type Ⅰ and type Ⅱ kerogen.When the TOC content of type Ⅰ and type Ⅱ kerogen exceeds 3%,hy-drocarbon expulsion efficiency increases with TOC.Ink-bottle pores exhibit stronger retention of liquid hydrocarbons compared to slit pores.But for gaseous hydrocarbons,ink-bottle pores are the dominant channel to expel hydrocarbon.Additionally,lami-nated shale demonstrates lower hydrocarbon expulsion efficiency than thin laminated shale.The total oil content in shale is the outcome of co-controlled generation and expulsion of hydrocarbons.It shows a negative correlation with hydrocarbon expulsion efficiency,but a significant positive correlation with the product of hydrocarbon generation potential,hydrocarbon generation ef-ficiency,and hydrocarbon retention rate,affirming the reliability and practicality of the proposed calculation method of hydro-carbon expulsion efficiency.
Cangdong sagthe second member of Paleogene Kongdian Formationshale oilhydrocarbon expulsion efficien-cytotal oil contenthydrocarbon generation potential balance method
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维普
