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Pushing technological boundaries in ultradeep waters
Published on Apr 7, 2011 - by Pre-salt.com - Source: Schlumberger
The discovery of a giant oil accumulation in ultradeep waters off Brazil’s southeast coast is opening a new frontier for exploration and production. This pre-salt play, in the Santos basin, contains potentially recoverable reserves ranging from 795 million m3 to 1.3 billion m3 of oil equivalent. Just one of several structures found beneath a thick layer of salt, the Tupi structure, is pushing technological boundaries as E&P teams seek to define its geographic limits.
Types of reserves
Pre-salt, postsalt and subsalt formations are all capable of forming traps and seals for migrating hydrocarbons. Pre-salt wells target reservoirs beneath the layer of autochthonous salt. Subsalt wells target reservoirs beneath the mobile allochthonous salt canopy. Postsalt wells target formations above the salt.
Geology
From a geologic perspective, this play is a product of interminably slow tectonic and depositional processes involving continental rifting, seafloor spreading, and sedimentation. These processes were associated with the split between South America and Africa during the Cretaceous breakup of Gondwana. The depositional processes created source, reservoir, and sealed layers necessary to successfully produce an active petroleum system.
Technology
From a technological perspective, the feasibility of the pre-salt play is a result of operator experience gained through overcoming the challenges of constructing wells in deep and ultradeep waters off the coast of Brazil. Just as important are improvements to seismic imaging, which allow geophysicists to identify potential structures masked beneath layered evaporites that may be as thick as 2,000 m [6,560 ft].
E&P challenges
Expertise and techniques developed to exploit deepwater fields of the Campos basin have been adapted to wells in the Santos basin. Exploration models from the Santos basin pre-salt play, in turn, have led to significant discoveries in neighboring basins. This article discusses the geology and history of Brazil’s pre-salt play. It describes challenges associated with exploration and production of presalt carbonate reservoirs and their impact on the advancement of new models.
Available at: <http://www.slb.com/news/inside_
news/2011/2011_0310_brazil_pre-salt.aspx>.
Retrieved on: 14 Nov. 2011. Adapted.
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