Characteristics of Pre-Cenozoic Basement in Bohai Sea and its Significance in Oil and Gas Exploration

doi:10.19657/j.geoscience.1000-8527.2019.04.11

Abstract

Abstract:

Based on the Bohai drilling and 3D seismic data, lithology, stratigraphy and structural features of the Pre-Cenozoic basement in the Bohai sea have been integrated. The Bohai sea basement is divided into three structural layers: Pre-Cambrian, Paleozoic and Mesozoic. Distribution characteristics of the residual layers in each structural layer are discussed, and the basement structure is divided into three types: single, double and three level. Tectonic evolution of the basement comprises six stages: vertical rise and fall, strong extrusion, local extension, strong extension and inversion, overall uplift, stretch and strike-slip compound transformation. Combining the rock sheet and material data, the development regularity of the basement reservoir is explored. Precambrian metamorphic rocks of the single-layer type, carbonate or volcanic rocks at the top of the double-layer type, and Mesozoic volcanic rocks at the top of the three-layer type are favorable exploration targets. Buried hill around the hydrocarbon rich sag has a good exploration potential under the coupling of lithology and oil-supply window.

Key words: Bohai sea, basement structure, buried hill, Pre-Cenozoic, oil and gas exploration

CLC Number:

TE121.2

WU Qingxun, GAO Kunshun, WU Haoming, GUO Ying, CHEN Xinlu. Characteristics of Pre-Cenozoic Basement in Bohai Sea and its Significance in Oil and Gas Exploration[J]. Geoscience, 2019, 33(04): 802-810.

Figures/Tables 11

Fig.1 Regional geologic map of Bohai sea(modified after Zhou et al. [2])

Fig.2 Drill core and microscopic photographs of the major lithologies from the Pre-Cenozoic basement of Bohai sea

Fig.3 Seismic reflection characteristics of buried hill formation in Bohai sea

Fig.4 Schematic diagram of basement structural evolution in Bohai sea(profile location shown in Fig.1)

Fig.5 Division of the basement structural sequence of the Pre-Cenozoic Bohai sea

Fig.6 Basement structural types in Bohai sea

Fig.7 Thin bottom structure and bald bottom structure in western Bohai sea (profile location shown in Figure 1)

Fig.8 Distribution map of Paleozoic residual sequence in Bohai sea

Fig.9 Distribution map of Mesozoic residual sequence in Bohai sea

Table 1 Fracture statistics of different lithology core

岩性	岩心长度/m	裂缝总数/条	裂缝总密度/(条/m)	未充填裂缝数/条	未充填裂缝密度/(条/m)	充填率/%
变质岩	74.95	267	3.56	80	1.07	70
花岗岩	29.51	23	0.78	21	0.71	9
火山岩	64.23	242	3.77	60	0.93	75
碳酸盐岩	138.73	662	4.77	166	1.2	75

Fig.10 Schematic diagram of basement reservoir development model in Bohai sea

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