The existing perceptions of the offshore Uruguay petroleum system assessment may be challenged by an analysis of the failure modes of three exploration wells drilled in the basin. This is an underexplored basin with a poor exploration record. Arguably, the wells tested prospect-specific locations but left other plays of interest untested. A careful review of recent sub-surface data and a deeper research into the rift play development has revealed a new model for extensional rift basin evolution in time and space. The two rift play tests described by the Lobo-1 and Gaviotin-1 penetrations are now considered to have tested only the ‘earliest’ development of the Inner Rift Basin Play segment which is interpreted to be devoid of both regional syn-rift source rock facies and regional top seal (Aptian) lithologies. In contrast to the apparent rift play test, the Raya-1 exploration well tested the Oligocene deep-water passive margin play concept of Block 14. The result of this well was negative, and once again the consideration of the play prognosis provides an important insight into whether the Passive Margin sequence has been adequately explored. The comparison might be drawn between the Uruguay prospectivity assessment and the perception of the Kwanza basin potential prior to the Cameia discovery by Cobalt. Whilst the Common Risk Segment (CRS) map methodology previously applied offshore Uruguay highlighted a more extensive prospective play fairway, the new interpretation provides a higher fidelity model that better describes the more limited extent of hydrocarbon accumulations and likely value density. This conclusion is consistent with syn-rift conjugate margin exploration and a more detailed evaluation of the pre-salt potential of the Kwanza basin, previously believed to be a non-prospective play concept. By comparison and by adapting a more empirical approach to play mapping, the value proposition can be better adapted to high-grade rift-basin acreage yet to be forensically explored.
Successful companies hunt for the optimal basin position to find hydrocarbons in commercial quantities using CRS maps. Parameters describing the Red, Yellow, and Green play segments are not equal between the basins and have to be well defined for every basin. This paper contends that the ‘absence of evidence’ does not necessarily suggest ‘evidence of absence’ for the potential of a material petroleum province hosted in syn-rift and post-rift offshore Uruguay plays. To be able to draw these conclusions one needs to have access to the regional data set composed of available seismic, potential fields and seismic data. The value of the play specific geologic controls in the potential plays is not equal to the large play extent and one cannot be a substitute for the other. “Zooming-in” on the prospect/block specific data too early in the evaluation will not provide an adequate data coverage for play definition.
Today there are still opportunities for commercial discoveries along the Atlantic margin. To find them will require all of the experience that industry has gained in the last two decades. Extending our knowledge of the successful plays beyond drilled prospects and into the new basins cannot be done on oversimplified schematics of the plays and without understanding the
differences between the basins. Equally, with a move into the detailed analysis of the prospect- specific risks too early, a company might miss the risks critical to the play. In different basins the same colors on the CRS maps represent different play risks and uncertainties and the interpretation and assignment of each color has to be well understood.
The selection of focus areas for exploration activities of oil and gas companies commonly is driven by 1) scope = volumes of the discoveries; 2) scale = size of the individual discoveries; 3) repeatability = number of look-alike prospects. This approach dictates that a valuable play must have a significant geographic extent, and drilling decisions are often dominated by plays with recent discoveries, which causes companies to engage in convergent thinking which leads to bypassing of untested opportunities in the basin.
