North Carnarvon盆地Exmouth低隆起成藏条件及勘探潜力研究

Accumulation conditions and exploration potential of Exmouth Plateau in North Carnarvon Basin

近年来,随着勘探技术的革新,North Carnarvon盆地Exmouth低隆起深水区的油气勘探获得了巨大突破。Exmouth低隆起主要发育一套遍及全盆地的优质烃源岩,即中上三叠统Mungaroo组浅水辫状河三角洲相的暗色泥岩夹薄煤层,其有机质丰度较高(平均质量分数为4.61%),有机质类型为Ⅱ2—Ⅲ型,以生气为主,成熟度适中(0.46%<Ro<1.89%),有较强的供烃能力。晚三叠世开始的构造隆升作用使得上覆侏罗系与下白垩统厚度均较薄,机械压实作用较弱,使中上三叠统水道砂体储集性能较好;晚侏罗世—早白垩世期间,Exmouth低隆起同样发育牛津组大型滩坝砂体与Barrow三角洲优质储层。Exmouth低隆起发育了自生自储式和下生上储式2套成藏组合,其中自生自储式成藏组合以Mungaroo组水道砂体为储集层,以Mungaroo组暗色泥岩为烃源岩和局部盖层,勘探潜力最好。综合考虑Exmouth低隆起的烃源岩条件、储集条件及成藏组合条件,避开油气渗漏带展布范围,预测油气勘探有利区带位于其东部及西南部。

In recent years, some breakthroughs has been made in the exploration of deep-water areas in Exmouth Plateau, North Carnarvon Basin. The dark mudstone and thin coal strata of the giant shallow water braided fluvial delta of Mungaroo Formation are the main high-quality hydrocarbon source rocks during the Middle and Upper Trassic（the mean TOC is 4.61% and Rois from 0.46% to 1.89%）. The kerogen type is from Ⅱ2to Ⅲ, which has superior hydrocarbonoffering capability. The high-quality reservoir of Mungaroo Formation developed in the Emouth Plateau because of the overlying strata of Jurassic and Lower Cretaceous are thin and the compaction is not strong. The beach-bar of Oxfordian Jansz sandstone and the Barrow delta are also good reservoirs from Late Jurassic to Early Cretaceous. The Exmouth Plateau developed two types of play： self-generation and self-storage, below-generation and above-storage. The exploration potential of the self-generation and self-storage is the best with channel sand body of Mungaroo Formation as the reservoir and dark mudstone of Mungaroo Formation as the source rock or the seal. In terms of the hydrocarbon source rock, reservoir and hydrocarbon generation and storage pattern, combined with the distribution of oil and gas leakage system, the favorable prospect areas should be mainly located in the east and southwest of Exmouth Plateau.