Petroleum Geology of the Bass Basin : Interpretation Report

The Bass Basin is a moderately explored Cretaceous to Cainozoic intracratonic rift basin on Australia's southeastern margin, underlying the shallow seabed between Tasmania and the Victorian mainland (Bass Strait; Figure 1). The basin contains proven commercial reserves of gas and condensate that are soon to be developed (Yolla gas field, Origin Energy Resources Ltd-operated BassGas Project). Other discoveries in the basin include the White Ibis and Pelican gas fields. To date, the 32 wells drilled have targeted Upper Cretaceous to Middle Eocene reservoirs within fault blocks and anticlinal structures. The targeted succession comprises interbedded fluvio-deltaic and lacustrine sandstones, siltstones and shales. The principal source rocks in the Bass Basin are interbedded coals (ranging from 5 to 25 m thick) and lacustrine shales of early Palaeogene age. Geochemical analyses show these source rocks have generated liquid and gaseous hydrocarbons, with the coals being the dominant source for the liquids (Boreham et al., 2003).

巴斯盆地（Bass Basin）是澳大利亚东南缘勘探程度中等的白垩纪（Cretaceous）至新生代（Cainozoic）克拉通内裂谷盆地（intracratonic rift basin），坐落于塔斯马尼亚州与维多利亚州本土之间的浅海海底之下（即巴斯海峡；图1）。该盆地拥有即将投入开发的探明商业天然气与凝析油储量，对应开发对象为由Origin能源资源有限公司（Origin Energy Resources Ltd）运营的巴斯天然气项目（BassGas Project）旗下的约拉气田（Yolla gas field）。盆地内其余已发现油气田包括白朱鹭气田（White Ibis gas field）与鹈鹕气田（Pelican gas field）。迄今，该区已钻的32口井均以断块与背斜构造内的上白垩统至中始新统储层为钻探目标，目标层系由互层的河流-三角洲相及湖相砂岩、粉砂岩和页岩构成。巴斯盆地的主要烃源岩为厚度5至25米的互层煤层与古近纪（Palaeogene）早期湖相页岩，地球化学分析表明，此类烃源岩已生成液态与气态烃类，其中煤层是液态烃的主要母源（Boreham等，2003）。