Conventionally, there has been an entrenched aversion to explore oil and gas in regions with volcanic geology. In other words, petroleum systems affected by igneous geology have not been considered with substantial oil and gas discoveries. However, the presence of volcanics is well known in many petroleum basins although not published in great details (including the North West Shelf of Australia), and there has been an increase in the number of hydrocarbon discoveries in volcanic basins worldwide.On the other hand, there has been volcanics geology factor associated with unsuccessful exploration wells. In the NWS of Australia, explorers care about the evidences as several unsuccessful wells, widely distributed in the area, have penetrated volcanics within the Triassic-Jurassic succession, which indicates a significant exploration risk.A primary purpose in writing this article was to illustrate that the presence of volcanics and their impacts on sedimentary rocks may lead to complex overprints for oil and gas exploration. Several 2D and 3D seismic datasets in addition to well information, from Barcoo Sub-basin of the NWS of Australia, were analysed and interpreted to demonstrate the fact that features we sometimes get with volcanics can be very misleading for hydrocarbon exploration.Volcanic rocks within the Triassic-Jurassic succession at the NWS of Australia are not considered favourable conditions for hydrocarbon accumulation. It is therefore important to develop an approach to better understand their impact on petroleum system and derisk prospects for exploration.

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A development campaign offshore Australia, with a total of 15 laterals in a challenging geological environment, has been successfully completed by Quadrant Energy. The main objectives were to geosteer and place the well path at an optimum standoff from the oil/water contact (OWC), while drilling at the interface of the gas/oil contact (GOC), when present, and at 1-1.5m TVD from the reservoir top when not.The field is characterized by a series of transverse and longitudinal seismic and sub-seismic faults that bisect hydrocarbon-bearing sands which represent the greatest challenges in this development campaign. Evidence from exploration wells showed a thin column of heavy oil and a gas cap in the fault-bonded reservoir. A new multi-disciplinary methodology not only enabled Quadrant Energy to achieve its development objectives, but to develop a full subsurface picture of the Coniston field reservoir.The use of the Reservoir Mapping-While-Drilling (RMWD) combined with Bed Boundary Mapping Tool (BBMT) and Multi-Function LWD services enabled the laterals to be placed at 1-2m TVD below the reservoir top or gas cap, when present, even in highly faulted sections. In addition to this precise placement the extreme depth of investigation of the RMWD service, in conjunction with the real-time multilayer inversion capability, constantly mapped the OWC at a distance up to 19m TVD below the wellbore. While drilling, different qualities of reservoir sands were identified and enabled the extensions of the wells' TDs based on reservoir properties. The distance to boundary information, provided in real-time by the RMWD service, was used in real-time by the Quadrant Energy geology and geophysics team to update and validate the seismic model that provided increased confidence in the reservoir model and a more precise planning for future development wells. This paper will illustrate the use of the latest LWD RMWD technology in a challenging geological environment. The paper will explore the close collaboration, teamwork, and integration necessary to drive innovation and demonstrate the outcomes of this successful campaign which have not only exceeded the development goals, but have also generated a full 3D view of the reservoir.

This reference is for an abstract only. A full paper was not submitted for this conference. Abstract The Upper Swan sandstones represent a key exploration target in the Caswell Sub-basin and are the main reservoir units for the large Ichthys-Prelude gas-condensate field. The sandstones are present west of the Yampi Shelf margin from Leveque-1 in the southwest to Maret-1 in the northeast, and in the central portion of the Caswell Sub-basin extend to the northwest as far as Caswell-2. Within the Caswell Sub-basin the Upper Swan sandstones are best understood in the Ichthys-Prelude gas-condensate field where twelve wells have been drilled to date. Interpretation of nearly 600m of conventional core, wireline logs, image logs and 3D seismic surveys have contributed significantly to the understanding of the depositional environment. The Upper Swan sandstones is a lithostratigraphic term for sandstones that range in age from Latest Jurassic (Tithonian) to early Cretaceous (Berriasian) and are calibrated to the P. iehiense, K. wisemaniae and C. delicata Biozones. These sandstones are sourced from the Yampi Shelf and typically onlap and overstep Tithonian-aged mudstones. The sandstones are quartz rich, dominantly fine - medium grained with occasional very fine to coarse grained units present. Individual sandstone units range in thickness from centimetre scale up to several metres and are typically relatively featureless, homogeneous beds with occasional dewatering structures. Thin claystones typically centimetre to tens of centimetres thick, but up to 15m thick locally, are interbedded with the sandstones. Core data suggests they were deposited as a series of stacked sand-rich gravity flows comprising repeated massive suspension (S3) and thin traction flows (T1 and T2) (dense flows of Lowe, 1982) in a shallowing Outer to Middle shelf characterised by vertically shallowing ichnofossil associations of Chondrites, Phycosiphon/Chondrites to Zoophycus/Phycospihon. In the Prelude Field, the Tithonian and Berriasian-aged sandstones are mineralogically similar, with a complex diagenetic history consisting of compaction, quartz cementation, framework grain dissolution, precipitation of kaolinite/dickite, and the formation of authigenic illite. Authigenic clays appear to be of the greatest importance in the Upper Swan Sandstone in terms of reservoir quality with the data indicating the older sandstones tend to have higher total clay content and these are typically tight.