TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Sunrise-Troubadour giant gas-condensate fields lie on a massive, broad, low-relief structure 75km long and 50km wide. The fields have a gross reservoir thickness of 80m. They are located on the northwestern boundary of the Australian Plate and form the basis of a proposed green-field LNG project and an Australian domestic gas development.Statistical volumetric analysis has shown that reservoir quality, distribution and Net-To-Gross ratio (NTG) are the main static uncertainties affecting Gas-Initially-In-Place (GIIP). These parameters are a function of the environment of deposition of the reservoir interval. The low average NTG in some wells (as low as 30%) indicates potential for depositional heterogeneity which can impact dynamic fluid flow through the reservoir. Depositional modelling has therefore been a major focus for field evaluation and appraisal.The reservoir interval was deposited in a marginal marine setting on a slowly subsiding, broad, low-relief shelf. The overall retrogradational character of the reservoir interval is illustrated by the upward increase in the open marine character of the interbedded shales. There are two major relative sea level falls interpreted which resulted in the deposition of incised-valley and sharp-based, forced regressive shoreface deposits. These sandbodies form the major reservoir units in the fields. Highstand and transgressive deposits are characterised by relatively thin and discontinuous sandbodies.In order to fully capture the depositional uncertainty inherent in a field of this scale which only has limited well control (six wells), three groups consisting of sedimentologists, stratigraphers and biostratigraphers have independently interpreted the core and wireline data. The result was three different depositional interpretations.From these interpretations a most likely depositional model was developed. Low and high case 3-D depositional models were generated by varying NTG and sandbody correlatibility and geometries. The adjustment of these parameters reflected the range of depositional interpretations from the three individual expert groups.These models form the basis of multi-scenario reservoir simulation studies which indicate that development options for these fields are technically robust for the range of perceived subsurface scenarios.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Sunrise and Troubadour Fields form a massive offshore gas-condensate resource located in the Timor Sea, 450 kilometres northwest of Darwin. The commercialisation, marketing and contract negotiations for such a world scale gas development requires confidence in reservoir performance and product composition, plus a clear appreciation of their uncertainties. This paper discusses how the key dynamic uncertainties have been identified, evaluated and modelled to determine their impact on development decisions.Early cross section models identified connected gasinitially-in-place and reservoir quality as key uncertainties, impacting field performance. Simultaneously, preliminary marketing efforts and facility design recognised fluid properties as a key parameter. This directed data acquisition through appraisal wells, which were fully cored and production tested.Iso-kinetic sampling and careful well test design has resulted in representative compositional data and identified compositional variations across the field. High rate dependent skins measured in appraisal wells have been evaluated and requantified for development wells. Detailed single well models have evaluated the effects of condensate banking.As marketing efforts progressed, full field simulation became warranted to capture remaining uncertainty on reservoir quality and distribution, and fault transmissibility. A suite of full field dynamic models built around the key dynamic uncertainties has provided confidence that uncertainties are manageable and that the development and customer commitments are robust. The case for further data acquisition, aimed at optimising the final development, can readily be made using the suite of dynamic models which integrate the input from all sub-surface disciplines.Focused appraisal has reduced and quantified the key uncertainties. The leading edge evaluation methods have removed the need for several additional appraisal wells that might otherwise have been required.Effective communication and teamwork between subsurface, facility engineering, commercial and marketing has proved crucial to ensure that the appropriate uncertainties were addressed in a timely manner as each discipline matured their part of the project.