澳洲西北海域Vulcan次盆地石油系統整合研究

An Integrated Study of Petroleum System in the Vulcan Sub-basin, Offshore Northwest Australia

周颖蔚(Ying-Wei Chou) ； 巫慶鐘(Ching-Chung Wu)

《石油季刊》 43卷1期 (2007/03) Pp. 1-4

https://doi.org/10.30128/JP.200703.0001

摘要

澳洲西北海域Vulcan次盆地因沉積了產油的封閉型海相及三角洲相生油岩，深埋於幾處主要地塹內而進入油窗，提供成熟油氣。晚侏羅紀張裂期之後沉積了大範圍厚層之區域性蓋岩，使其底下之封閉構造內儲集層可以形成密封，且根據模擬及地化對比確認油氣可作長距離移棲。截至2001年底統計發現之油氣藏中約有170百萬桶原油，31百萬桶凝結油及約1.2 Tcf天然氣尚未開發出來。鑒於地區石油系統完整，具頗佳探油潛能，因此Vulcan次盆地一直被列為中油公司國外探勘目標盆地之一。
雖然Vulcan次盆地歷經多年之油氣探勘，有人認為可能已達探勘成熟狀態，但經本次石油系統之整合研究後認為，仍有許多油氣生成排放及移棲之控制因素與關鍵時問仍有修正之需要，因之未來探勘仍有許多新構想空間待進一步發掘。諸如最新盆地模擬研究結果發現，油氣從白堊紀早期一直生成與排放到現今，比之前學者所提出之理論都來得早。又如在3D之模擬中，Jabiru油田之油氣除了從Swan地塹北方油廚區於白堊紀初期即已開始移棲進入外，也可從Cartier地槽南方油廚區於中新世以後開始移棲進入。此外大斷層的走向在油氣移棲方面也是一項控制油氣田分布相當重要的因素；例如油氣從Swan地塹東邊沿著大斷層移棲進入東北走向之Eclipse-Cassini-Challis儲油氣構造群，便是其中最明顯的一例。
尤其近年來，三維震測施測結果，陸續發現許多可探勘構造，透過最新高解析之2D/3D盆地模擬研究，未來可再突破原先探勘觀念之障礙，再獲大量新油氣發現。

關鍵字

Vulcan次盆地 ； 石油系統 ； 油氣生成 ； 排放及移棲 ； 大斷層 ； 盆地模擬

並列摘要

The Vulcan Sub-basin, offshore northwest Australia is a well-established hydrocarbon province with several commercial oil discoveries due to the deep buried oil prone source rocks deposited in the restricted marine and deltaic environments, entering into the oil window within some main grabens in the basin. The Late Jurassic widespread and thick marine shale of the post-rift sequences acted as a regional cap rock sealing the reservoired oil and gas from leakage.
In accordance with the geohistory modelling and geochemical correlation, hydrocarbons in the Vulcan Sub-basin region could have evidently migrated with a long distance into some presently discovered accumulations.
The Vulcan Sub-basin at the end of 2001 contained 18 oil and gas discoveries. Of these the estimated reserves some 170 million bbls of oil, 31 million bbls of condensate and some 1.2 Tcf of gas are still undeveloped. In view of its proven petroleum system and higher exploration potential, the Vulcan Sub-basin has been listed as one of the most important target areas for overseas oil exploration business in CPC.
Since the first exploratory drilling commenced in 1953, the Vulcan Sub-basin has been one of the Australia's most actively explored basins. Some might consider it has entered into a mature status by the Australian exploration standards.
Numerous new insights for the dominant controlling factors and critical timing of petroleum systems in the Vulcan Sub-basin have been obtained via this integrated study. Controls and timing on petroleum generation, expulsion and migration should be reconsidered when assessing exploration plays in the region. A good example of this is the estimated age of oil and gas expulsion that was presently thought from the Early Cretaceous to the present day. Timing of the onset of expulsion appears to be much earlier than suggested by many of previous workers. In particular, 3D modelling simulated oil migration into the Jabirustructure, not only from the northern Swan Graben in the Early Cretaceous time, but also from the southern Cartier Trough after the Miocene. Additionally, in term of hydrocarbon migration, the trend of major faults was also a significant controlling factor in distributions of the hydrocarbon accumulations. The oil/gas migration along the eastern major fault bounding the Swan Graben into the culmination of the Eclipse-Cassini-Challis structural trends was also a typical example.
In recent years, new 3D seismic surveys have continually created many new prospects in the region. New oil and gas finds will be achieved in the near future through the new highresolution basin modeling and integrated studies of the petroleum system which should establish new play concepts and the innovative exploration ideas in the Vulcan Sub-basin.

並列關鍵字

Vulcan Sub-basin ； Petroleum System ； Hydrocarbon Generation ； Expulsion and Migration ； Major Faults ； Basin Modeling