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

摘要： 由于海域勘探作业难度大、成本较高,深层储层非均质性较强,珠江口盆地东部致密油气的勘探相对滞后。通过深入剖析珠江口盆地东部致密油气的成藏条件,明确了其致密油气的富集规律以及资源潜力。研究结果表明:①珠江口盆地东部发育优质烃源岩,具备多个富烃/生烃洼陷,为致密油气藏的形成提供了物质基础。②珠江口盆地东部深层发育陆相致密砂岩储层,非均质性较强,主要发育孔隙型和裂缝型2种储层类型;浅水区(海底水深在300~1 500 m)的致密砂岩储层主要为恩平组辫状河三角洲平原、文昌组长源大型辫状河三角洲前缘和湖底扇沉积;深水区(海底水深＞1 500 m)的致密砂岩储层主要为珠海组陆架边缘三角洲沉积。③致密油气藏规模分布在浅水区洼陷深层的古近系中以及深水区中/深层珠海组中,具备低孔-超低渗、非均质性强、地层超压的特点;致密油气在浅水区的成藏模式主要表现为源内包裹型、下生上储型、旁生侧储型3种类型,在深水区的成藏模式主要表现为下生上储型。综合评价认为,浅水区致密油气的有利勘探区围绕惠州26洼、陆丰13洼和恩平17洼等富烃/生烃洼陷,储集体主要为古近系大型扇三角洲-辫状河复合沉积体系中的优质砂体;深水区致密油气的有利勘探区为白云凹陷北部斜坡近洼带,储集体主要为珠海组三角洲-深水扇沉积体系中的砂体。

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