--> ABSTRACT: Finding Oil in a Mixed Carbonate-Siliciclastic, Compartmentalized, Fractured Reservoir. A Sedimentary Model, the Fractured Patterns and Drilling Subtleties, by Miguel Mora-Glukstad, Germán Rodriguez, Phil de Gruyter, René Robertson, Schuman Wu, Fernando Arango, Andrés Fuenzalida, and Lina Maya; #90906(2001)

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Miguel Mora-Glukstad1, Germán Rodriguez2, Phil de Gruyter1, René Robertson2, Schuman Wu1, Fernando Arango2, Andrés Fuenzalida2, Lina Maya3

(1) Repsol-YPF, Englewood, CO
(2) SIPETROL, Bogotá - Colombia
(3) DUNIA Consultants, Bogotá Colombia

ABSTRACT: Finding Oil in a Mixed Carbonate-Siliciclastic, Compartmentalized, Fractured Reservoir. A Sedimentary Model, the Fractured Patterns and Drilling Subtleties

The Middle Magdalena Valley (MMV) in Colombia hosts huge hydrocarbon reserves. The reservoirs tapped to date are mainly from Tertiary successions. The Cretaceous intervals, containing the La Luna source rock, are not known to have classic sandy reservoirs, but have fractured calcareous units. Only two fields in the MMV have successfully penetrated fractured intervals and yielded initial productions of several thousands of BOPD. One of these, the Guaduas field, lies in a structurally elevated syncline, and the producing wells are on the eastern limb near the synclinal axis.

SIPETROL and REPSOL-YPF are exploring and drilling the western side of the structure. The target formation is a westerly sourced Maastrichtian succession. The reservoir intervals are a combination of limestones, sandstones and conglomerates with shaly intervals. A new sedimentary model, using well and field data, was successfully tested. This model considers the interaction of starved periods of carbonate precipitation and limestone formation, and fluxes of high siliciclastic input coming from the unroofing of the Central Andean Cordillera. Detailed fault kinematics and fracture analysis, paired with oriented microstructural studies and FMI correlations, allowed to also predict the orientation and timing of the main conductive fractured sets. Drilling is complicated by an over-pressured seal and an under-pressured reservoir.

One well to date, tested the main geological concepts, and a new well, to be completed in early 2001, might define the continuity of the Guaduas accummulation and open-up large reserve potential for the fractured Cretaceous play in the MMV.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado