Since 1994 SEDSIM has been applied to hydrocarbon exploration and production problems in Australia under contract to various oil companies, including Woodside Australia is an active, frontier, hydrocarbon exploration area. From the Middle Jurassic to the Tertiary the sedimentation was predominantly siliciclastic on a variable bathymetry that generally was subsiding thermally but subject to local higher amplitude tectonic movement. The paleotopography is determined relatively easily from adequate seismic coverage, and the sediment supply was dominated by large rivers with channels that are active today. Combined stratigraphic/structural plays have been proven along the shelf and the future challenge is to identify potential stratigraphic plays which have little or no seismic expression. Stratigraphic forward modeling can contribute to the development of play concepts in such circumstances. Two case studies from the Neocomian (Barrow and Browse), one from the Aptian (Yampi Shelf), and one from the Oxfordian (Kendrew) are given.The comment may be made by company personnel that "we do not have enough data to run a SEDSIM model." We show here that, as a company must build a conceptual model anyway based on whatever limited seismic and well data are available, a SEDSIM model can help to crystallize that conceptual model and allow explorationists to experiment objectively with alternatives. Every subsequent well drilled or seismic line shot adds an objective test of the model--and will lead to improvements in the quantitative predictions made by SEDSIM and in the conceptual model.

An effective inverse scheme that can be applied to complex 3-D hydrodynamic forward models has so far proved elusive. In this paper we investigate an interactive inverse methodology that may offer a possible way forward. The scheme builds on previous work in linking expert review of alternate output to rapid modification of input variables. This was tested using the SEDSIM 3-D stratigraphic forward-modelling program, varying nine input variables in a synthetic example. Ten SEDSIM simulations were generated, with subtle differences in input, and five dip sections (fences) were displayed for each simulation. A geoscientist ranked the lithological distribution in order of similarity to the true sections (the true input values were not disclosed during the experiment). The two or three highest ranked simulations then acted as seed for the next round of ten simulations, which were compared in turn. After 90 simulations a satisfactory match between the target and the model was found and the experiment was terminated. Subsequent analysis showed that the estimated input values were ‘close’ to the true values.

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A flux-corrected transport scheme due to Zalesak is used to carry out a numerical simulation of thermal convection in a two-dimensional layer of ideal, diatomic gas, which is heated from below and stratified gravitationally across many pressure scaleheights. The purpose of this calculation is to mimic the physical conditions in the outer layers of the protosolar cloud (PSC) from which the Solar system formed. The temperature T 0 at the top boundary (z = 0) and the dimensionless temperature gradient θ = (d/T 0 )∂ T /∂z at the base of the layer of thickness d are kept fixed, with θ = 10. The initial atmosphere is uniformly superadiabatic, having polytropic index m in = 1. Because the Reynolds number of the real atmosphere is so large, a subgrid-scale (SGS) turbulence approximation due to Smagorinsky is used to model the influence of motions with length-scale less than the computational grid size.The flow soon evolves to a network of giant convective cells, which span the whole layer. At cell boundaries the downflows are spatially concentrated and rapid while the upflows are broad and sluggish. The peak downflow Mach number is M peak = 1.1 at depth z = 0.55d. The descent of the cold gas eliminates much of the initial superadiabatic structure of the atmosphere for z 0.1d, thereby reducing the long-term mean temperature gradient dT lt /dz and causing a net shift of mass towards the base.In the top 10 per cent of depth, SGS modelling causes dT lt /dz to increase sharply. A steep density inversion occurs with the long-term mean densityρ lt (0) at the top boundary rising to 3.5 times the initial density ρ 0 there. This result gives new credibility to the modern Laplacian theory (MLT) of Solar system origin. Here a postulated 35-fold density increase at the surface of the PSC causes the shedding of discrete gas rings at the observed mean orbital spacings of the planets. Even so, further numerical simulations, corresponding to higher values of θ, which may yield values M peak 3 andρ lt (0)/ρ 0 35, are required before the MLT can be considered to be valid.