关键词: 珠江口盆地东部, 致密油气, 资源潜力, 成藏条件, 成藏模式

Abstract: Due to the great difficulty and high cost of hydrocarbon exploration in the sea area, as well as strong heterogeneity of deep reservoirs, there is less progress in the development of tight oil and gas in the eastern Pearl River Mouth Basin. The enrichment regularities and resource potential of tight oil and gas in the study area were clarified through a deep analysis of their accumulation conditions. The results show as follows. (1) High-quality source rock is developed in the eastern Pearl River Mouth Basin, where there are several hydrocarbon-rich or hydrocarbon-generating subsags, providing a material foundation for the formation of tight oil and gas reservoirs. (2) Two types of terrestrial tight sandstone reservoirs, i.e., porous-type and fractured-type, are developed in the eastern Pearl River Mouth Basin, showing strong heterogeneity. In the shallow water zone (at the depth from 300 m to 1500 m under the sea), the tight sandstone reservoirs are mainly found in the braided river delta plain of Enping Formation, the front edge of the large-scale braided river delta in Changyuan reservoir of Wenchang Formation, and the bottom fan deposition. In the deep water zone (at a depth of more than 1500 m under the sea), the tight sandstone reservoirs are mainly delta deposits at the continental shelf margin of Zhuhai Formation. (3) Large-scale tight oil and gas reservoirs are distributed in deep layers of the Paleogene subsags in the shallow water zone, and middle-deep layers of Zhuhai Formation in the deep water zone, which are characterized with low porosity, ultra-low permeability, strong heterogeneity, and formation overpressure. The accumulation model of tight oil and gas in the shallow water zone is presented as intra-source inclusion, lower generating and upper accumulation, and lateral hydrocarbon migration and accumulation. Moreover, the lower generating and upper accumulation model plays a dominant role in the deep water zone. The comprehensive assessment indicates that the favorable exploration zones for tight oil and gas in shallow water area are located around the hydrocarbon-rich or hydrocarbon-generating subsags such as Huizhou26 subsag, Lufeng13 subsag, and Enping17 subsag, and the reservoir bodies are mainly high-quality reservoirs in the Paleocene large-scale fan delta to braid river composite depositional system. The favorable exploration zones in deep water area are in the northern slope of Baiyun sag and near the subsag, and the reservoir bodies many includes sand bodies in the delta and deepwater fans depositional system of Zhuhai Formation.

Key words: eastern Pearl River Mouth Basin, tight oil and gas, resource potential, accumulation condition, accumulation model