Diagenetic evolution characteristics of Paleogene lacustrine carbonate reservoirs in central Bohai sea, China

Carbon and Oxygen Isotopic Composition of Saline Lacustrine Dolomite Cements and Its Palaeoenvironmental Significance: A Case Study of Paleogene Shahejie Formation, Bohai Sea

“…The study area is located in the Eastern region of the Shijiutuo Horst in the middle of the Bohai Sea area, which borders the largest hydrocarbon-generating depression in the Bohai Sea area, the Bozhong Sag ( Figure 1). The Bohai Bay Basin is located in a passive continental margin of the Pacific tectonic domain, and its Paleogene strata include the Kongdian Formation (E 1-2 k), the Shahejie Formation (E 2 s), and the Dongying Formation (E 3 d) [19,[35][36][37][38]. The Cenozoic tectonic evolution can be divided into three stages.…”

“…First, heavy saltwater formed on the surface of the lake by evaporation and moved to the bottom of the lake due to the effect of density [55,74,75]. Second, on the edge of the lake basin or in the uplifted region of grain beach facies, the highly concentrated brine was affected by gravity flows along the slopes on either side of the ancient uplift [18,19].…”

“…The QHD29-2 oil field (Qinhuangdao, China), which has reserves of 100 million tons, was found in E 2 s [18]. Although the dolomite reservoir in E 2 s is nearly 4000 m deep, its residual primary porosity is still greater than 30% [19]. Most dolomite reservoirs form in marine environments [20][21][22][23][24]; most are intercrystalline pore reservoirs that formed by dolomitization [25,26]; and some formed as karst caves or are related to hydrothermal solution and the thermochemical sulfate reduction (TSR) [27][28][29][30][31][32][33][34].…”

“…Most dolomite reservoirs form in marine environments [20][21][22][23][24]; most are intercrystalline pore reservoirs that formed by dolomitization [25,26]; and some formed as karst caves or are related to hydrothermal solution and the thermochemical sulfate reduction (TSR) [27][28][29][30][31][32][33][34]. However, the reservoir space of the dolomite reservoir in E 2 s is largely composed of primary pores, residual primary pores, and moldic pores [19,35]. The main characteristic of the dolomite reservoir in E 2 s is the development of a large amount of both syngenetic and authigenic dolomite cements [36].…”