石油与天然气地质 ›› 2023, Vol. 44 ›› Issue (3): 613-625.doi: 10.11743/ogg20230307

• 油气地质 • 上一篇    下一篇

珠江口盆地惠州26洼东南缘古近系恩平组上段断-拗转换期源-汇系统及勘探意义

彭光荣(), 王绪诚, 陈维涛, 靳瑶瑶, 王菲, 王文勇, 全涵   

  1. 中海石油(中国)有限公司 深圳分公司,广东 深圳 518054
  • 收稿日期:2023-01-13 修回日期:2023-03-13 出版日期:2023-06-01 发布日期:2023-06-05
  • 第一作者简介:彭光荣(1978—),男,高级工程师,油气地质。E?mail: penggr@cnooc.com.cn
  • 基金项目:
    中国海洋石油集团有限公司“十四五”重大科技项目(KJGG2022-0403);中海石油(中国)有限公司深圳分公司2023年勘探项目(SCKY-2023-SZ-03)

Source-to-sink system during rifting-depression transition period and its exploration significance: A case study of the Upper Enping Formation at southeastern margin of Huizhou 26 sub-sag, Pearl River Mouth Basin

Guangrong PENG(), Xucheng WANG, Weitao CHEN, Yaoyao JIN, Fei WANG, Wenyong WANG, Han QUAN   

  1. Shenzhen Branch of CNOOC,Shenzhen,Guangdong 518054,China
  • Received:2023-01-13 Revised:2023-03-13 Online:2023-06-01 Published:2023-06-05

摘要:

断-拗转换期是断陷盆地由伸展体制向热冷却沉降机制转变的重要阶段,伴随着拉张作用的减弱,构造活动逐渐趋于稳定,从而影响裂陷晚期沉积体系及有利储层分布。以源-汇系统要素耦合为指导,基于源-汇区岩石学、测井相、地震相特征分析,结合珠江口盆地惠州26洼东南缘古近系恩平组上段断-拗转换期边界断层活动差异,提出以“构造控相、沟断控储”分析有利储层成因及分布规律。研究表明:①研究区恩平组上段物源为东沙隆起中生代酸性侵入岩,在恩平组上段断-拗转换期发育5大汇水单元,其供源能力强弱以汇水单元面积与物源区落差进行量化表征;②输砂通道由“沟谷-边界断层”组合而成,物源区沟谷形态及规模造成各水系水动能强弱差异,而边界断层的平面组合样式(凹面墙角型、平直陡坡型及平直断阶型)和垂向落差影响沉积物汇聚入湖的方式与砂体展布;③以“源-沟-断-汇”4要素进行源-汇耦合,建立断-拗转换期构造活动趋稳背景下由边界断层差异活动形成的“南扇北辫”沉积格局,刻画沉积特征并揭示有利相带及优质储层分布,即顺“沟-断”优势通道入湖的辫状河三角洲平原河道亚相高成熟度粗粒沉积,该沉积具有原生孔隙发育和渗透率高的特征。新认识推动了研究区内恩平组研究与勘探进程,为惠西南地区深层古近系油气勘探指明方向。

关键词: 断-拗转换期, 源-汇系统, 恩平组, 古近系, 惠州26洼, 珠江口盆地

Abstract:

Rifting-depression transition period is a significant stage of transition for a rifted basin from extension to subsidence, during which the tectonic activities get stable along with declining extension, affecting the sedimentary system and favorable reservoir distribution in the late rifting period. With the guidance of the “source-to-sink” coupling ideology and based on the analysis of petrological characteristics, logging and seismic facies, we propose the idea of “tectonic activity-controlling facies, and valley/fault-controlling reservoir” to analyze the origin and distribution pattern of favorable reservoirs according to the differential activities of boundary faults during the rifting-depression transition period of the Upper Enping Formation at southeastern margin of Huizhou 26 sub-sag. The major conclusions can be drawn as follows. First, the Mesozoic intrusive rocks of the Dongsha uplift serve as the provenance to the upper member of the Enping Formation in the study area, with five major catchment units developed during the rifting-depression transition period. The supply capacity can be characterized by the quantitative analysis of the area and head of these catchment units. Second, the sediment-transport pathways are composed of the valleys and boundary faults. The morphology and scale of valleys within provenance affect the water kinetic energy of each drainage, and the planar combination pattern of boundary faults (i.e. the concave corner type, the straight and flat slope type, and the straight and flat fault type) and their vertical throws serve to influence the way of sediments converging in lake, as well as the distribution of sand bodies. Third, the “source-to-sink” coupling with four elements including source, valley, boundary fault and sedimentary system helps establish a sedimentary framework of “fan deltas in the south and braided deltas in the north” resulting from the differential activities of boundary faults at the tectonically quiet stage of the rifting-depression transition period. Sedimentary characteristics are finely depicted to disclose favorable facies zone and quality reservoir distribution, that is, the coarse-grained deposits of channel sub-facies, braided river delta plain facies, that is formed by sediments transported along the “valley-boundary faults” to lake, and characterized by well-developed primary pores and high permeability. These new understandings serve to promote the exploration progress of the Enping Formation and manifest exploration direction of the Paleogene deep strata at the southwestern area of Huizhou Sag.

Key words: rifting-depression transition period, source-to-sink system, Enping Formation, Paleogene, Huizhou 26 sub-sag, Pearl River Mouth Basin (PRMB)

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