OUTCROP ANALOGS FOR RESERVOIR CHARACTERIZATION OF JURASSIC MICROBIAL BUILDUPS, GULF OF MEXICO

Upper Jurassic microbial buildups in the northern Gulf of Mexico are excellent petroleum reservoirs in this region. However, because these thrombolites are not exposed at the surface in this region, determination of their specific reservoir characteristics, geometries and lateral extent are difficult to determine. Knowledge of this information is critical in the design of successful exploration and development strategies for these buildups. Upper Jurassic microbial buildups are exposed in Western Europe where they attain a thickness of 30 m and are present over an area of as much as 2.3 square km. These layered to dendroidal thrombolites were best developed on a firm substrate during a rise in sea level under initial zero to low background sedimentation rates in low energy paleoenvironments in middle to outer ramp settings. The demise of the thrombolites corresponded to changes in environmental conditions associated with an overall regression of the sea. Although the Upper Jurassic buildups in the northern Gulf of Mexico consist primarily of inner ramp, shallow water thrombolites, the use of the microbial outcrops in Europe to characterize the thrombolite reservoirs in the subsurface of the northern Gulf of Mexico facilitates the design of exploration and development strategies for these carbonate buildups.