A Case Study Of Deep Water Depositional Systems And Favorable Exploration Area Forecast Of Puffin Formation, South Of The Vulcan Sub-basin, Australia

The Vulcan Sub-basin located in western Bonaparte Basin, within Timor sea , northern Australia, is the maturing exploration area of Bonaparte Basin. After more than 40 years exploration work, the sub-basin has been getting into a high mature exploration period. It's difficult to fine new conventional structural trap, lithologic/stratigraphic trap will become the main direction for future exploration in Vulcan sub-basin.Late Cretaceous Puffin formation is the main exploration layer for the area, so is the Vulcan sub-basin. However, there are three unsolved problems restricted the proceeding of exploration and development:①The sequence classification and criterion of Puffin formation is unknown;②The direction of provenance is confusedly, sedimentary facies is unclear;③The well point of the work area is inadequate to control the distribution of sedimentary facies accurately. Considering geological setting, characterization of deposit and distribution of source rock, especially the distribution of sedimentary facies, we started to analysis the distribution of depositional system in Vulcan sub-basin and make a classification area of probability. Main knowledge obtained as follows:1. Established the high accuracy isochronal stratigraphic framework of study area, analyzed the distribution of depositional system and characterization of vertical evolvement of interested bed beyond the isochronal stratigraphic framework. Discussed the forming mechanism of sandy debris flow. The sedimentary environment of study area is deep-water, developed sandy debris flow deposits, maily are sandy debris flow channel and subaqueous fan.2. The sequence stratigraphic framework of study area appears on both north-west, south -east sides downdiping towards the center, built-up has been found in the Vesta area. Each stratum's thinkness gradually decrease from the basin center to the margin. The provenance of study area mainly come from eastern, then is south-east direction, via research of 2-D section, formation thickness and plate movement during the period of puffin formation deposition.3. Because the impaction of Regional tectonics and sedimentary, there are various kinds of traps/reserves, mainly are lithologic trap/reserve, stratigraphic trap/reserve and composite trap/reserve, especially fault block trap/reserve(structure trap/reserve) which can found in the central part of the basin and in the Puffin Horst.4. Bulit up a oil/gas migration pathway, migration mechanism and pooling pattern. Analyzed the distribution of sedimentary facies, distribution rule of lithologic-stratigraphic trap, main controlling factor and pooling pattern, predicted the probability area of each sublayer in Puffin formation. Base on the probability area, source rock and migration pattern, we divided them into three grade for the next step of exploration and development.