Organic geochemistry and petrographic characteristics of the shales from the Late Miocene Zeit Formation in the Tokar area, Red Sea Basin: Implications for depositional environment and hydrocarbon potential

红海盆地Tokar地区晚-中新生世Zeit页岩有机地球化学和岩石学特征：对沉积环境和油气潜力的启示

Shangru Yang ^a,b, Gang Gao ^a,b,*, Yong Liu ^c, Wenzhe Gang ^a,b,**, Wenlong Dang ^a,b

a State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, 102249, China

b College of Geosciences, China University of Petroleum, Beijing, 102249, China

c Bureau of Geophysical Prospecting INC., China National Petroleum Corporation, Hebei, 072750, China

Abstract: According to the geochemistry, organic petrography, stable carbon isotopic compositions and biomarker analyses of the Late Miocene Zeit Formation shale samples in the Tokar area, Red Sea Basin, the paleoenvironment and hydrocarbon-generating potential were analyzed. The Zeit Formation shales from the Wells S. Suakin-1 and Tokar-1 contain mostly Type III kerogens with minor Type II organic matter (OM), indicating more favorable gas generating potential. OM of the shale samples from the Late Miocene Zeit Formation are predominantly of terrigenous higher plants. Kerogens from the Well Tokar-1 show abundant brown liptinites, indicating the mixed origin of planktonic/bacterial and terrigenous OM. The Late Miocene Zeit Formation was deposited in dysoxic/suboxic, reducing and salt water environments. According to the results of Tmax, Ro and biomarker maturity parameters, the most shale samples from the Zeit Formation are in early mature to mature stages. The shales from the Late Miocene Zeit Formation are generally fair to good source rock. The shales from wells Suakin-2, Talla-2 and Tokar-1 have high hydrocarbon-generating potential.

Keywords: Geochemistry; Depositional environment; Shale; Organic petrography; Biomarker; Red sea basin

摘要：通过对红海盆地Tokar地区晚中新世Zeit组页岩样品的地球化学、有机岩石学、稳定碳同位素组成和生物标志物分析，研究了该地区晚中新世Zeit组页岩的古环境和生烃潜力。S. Suakin-1井和Tokar-1井Zeit组页岩以III型干酪根为主，II型有机质(OM)较少，具有较好的产气潜力。晚中新世Zeit组页岩样品有机质以陆源高等植物为主。Tokar-1井的干酪根显示出丰富的棕色脂质岩，表明浮游/细菌和陆源有机质的混合成因。晚中新世Zeit组沉积于缺氧/亚缺氧、还原和咸水环境中。从Tmax、Ro和生物标志化合物成熟度参数来看，Zeit组大部分页岩样品处于早成熟到成熟阶段。晚中新世Zeit组页岩总体上为较好的烃源岩。Suakin-2井、Talla-2井和Tokar-1井的页岩具有较高的生烃潜力。

关键词: 地球化学; 沉积环境; 页岩; 有机岩石学; 生物标志化合物; 红海盆地

Yang, S.R., Gao, G., Liu, Y., Gang, W.Z., Dang, W.L., 2020. Organic geochemistry and petrographic characteristics of the shales from the Late Miocene Zeit Formation in the Tokar area, Red Sea Basin: Implications for depositional environment and hydrocarbon potential. Journal of Petroleum Science and Engineering 195: 107757.

https://doi.org/10.1016/j.petrol.2020.107757