Lateral migration pathways of petroleum in the Zhu III subbasin, Pearl River Mouth basin, South China Sea

Citation
Fj. Nie et al., Lateral migration pathways of petroleum in the Zhu III subbasin, Pearl River Mouth basin, South China Sea, MAR PETR G, 18(5), 2001, pp. 561-575
Citations number
53
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
MARINE AND PETROLEUM GEOLOGY
ISSN journal
0264-8172 → ACNP
Volume
18
Issue
5
Year of publication
2001
Pages
561 - 575
Database
ISI
SICI code
0264-8172(200105)18:5<561:LMPOPI>2.0.ZU;2-3
Abstract
The discovery of the WC13-1 and WC13-2 oil fields in the Zhu III subbasin o f the Pearl River Mouth basin in the South China Sea has led to debate as t o the oils on Horst Qionghai (HQH) are sourced from Half-graben Wenchang-A (HGWC-A) or Half-graben Wenchang-B (HGWC-B). Using the previous findings of sequence stratigraphers, this paper further analyzes the sedimentological characteristics of the Zhuhai and Zhujiang Formations and points out that t he sandstones deposited on the unconformities (basement, T-6 and T-7) posse ss good porosity, permeability and lateral connectedness for hydrocarbon mi gration. The depositional systems and facies for the major reservoir rocks had gradually changed from fan-delta and semi-enclosed bay via barrier isla nds and washover to tidal flats, tidal channels and tide-influenced shorefa ce in response to the rise in sea level in the early Miocene. The sandy car rier beds of the transgressive systems tract in the Zhujiang Formation, esp ecially in Zhujiang Formation II, act as the principal migration conduits f or the WC13-1 and WC13-2 oil fields. Measurement of sandstones in drilling holes shows an increase in porosity in the Zhujiang Formation II and implie s that the oil had ever passed through. Furthermore, the structural morphol ogies of T-5 and T-4 demonstrate that there are two salient structural nose s connecting HQH with the HGWC-B and plunging into HGWC-B. T-5, a regional muddy seal, seals the porous standstones underneath and accounts for the ke y role played by the sandy carrier beds in transporting the oils generated in HGWC-B to HQH. Correlation of oils in HQH and HGWC-B supports the plausi bility of this migration pathway. (C) 2001 Published by Elsevier Science Lt d.