Print this pageOolite-Microbialite-Coral Reef 3-D Reservoir 
Analog
Model of the Miocene Terminal Carbonate Complex, SE Spain
Microbial (thrombolite, stromatolite), oolitic, coral reef, and bioclastic carbonates dominate upper Miocene strata in the Mediterranean. The Terminal Carbonate Complex (TCC) is a distinctive upper Miocene unit deposited in association with high-amplitude cyclic glacioeustacy and evaporitic drawdown. It consists of four sequences exposed at two locations in SE Spain: La Molata (Molata), at an intermediate substrate elevation (181 - 212 m); and Ricardillo-Rellana (Rellana), which reached higher elevations (187 - 258 m).
At Molata, the TCC ranges from 2 - 25 m in thickness over 0.8 km and at Rellana it ranges from 4 - 22 m in thickness over 3.2 km. At both locations the TCC typically drapes and partially onlaps paleotopography.
Facies distribution is controlled by paleotopographic interactions with rapid relative sea-level changes. At Molata, sequence 1 (S1) consists of basal microbial buildups that transition vertically and laterally to oolite; at Rellana, S1 is oolite throughout. At Molata, S2 contains microbial buildups overlain by oolite; at Rellana, S2 contains microbial buildups at low elevations and bivalve grainstone at high elevations overlain by oolite. At Molata, S3 consists of oolite with minor microbial build-ups; at Rellana, S3 consists of oolite with coralgal patch reefs. At Molata and Rellana, S4 contains basal microbial buildups that become interbedded with oolite and gastropod grainstone.
Stratigraphic sections, field tracing of facies, surfaces and geometries, ground penetrating radar data and core petrophysical data are being used to build a 3D reservoir analog model. Non-microbial reservoir facies include oolite (mean porosity 24.4%, mean permeability 884md; bioclastic grainstone (mean porosity 26.6%, mean permeability 2144 mD); and coral reef (mean porosity 18.6%; mean permeability 423 mD). Importantly, as many as eight microbial facies have been identified in the field, with apparent wide ranging reservoir properties. Those with good reservoir properties include vuggy thrombolite (mean porosity 32.1%, mean permeability 5313 mD) and others, dense thrombolites, exhibit poorer reservoir properties (mean porosity 16.1%, mean permeability 49.32 mD) and may constrain flow within the model.
The emerging results indicate excellent reservoir potential, but internal complexity for oolite-microbial-coral reef systems. Our 3D reservoir analog
model can provide insight on how best to exploit such facies in the subsurface.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009