High-resolution Sequence Stratigraphy and Reservoir Characterization Applied to Mature Fields: Example from Eastern Venezuela Basin

Abstract

Abstract The Mata-Araibel Concession (Eastern Venezuela Basin – Mata 3, Mata 16, Mata 19, Mata 20, Mata 14, Mata 7 and Zorro Fields-) records Miocene shallow-marine sedimentation in the distal zone of the foreland basin, which was formed by the eastward migration of the Caribbean Plate in oblique convergence with the South American Plate. This work aims to integrate high-resolution sequence stratigraphy with historical production data to optimize production in this mature area, through the reactivation of abandoned reservoirs and the definition of flow units to implement secondary recovery projects. The shallow marine paleophysiography in a ramp setting, distal to the collision front of the foreland, allowed the development of multiple high frequency sequence boundaries within a broad estuarine system. The main reservoir rocks were deposited during 5th order lowstand/transgressive systems tracts, represented by estuarine (channels and tidal bars) and platform (sand ridges) sediments. Isolated transgressive sand ridges and tidal bars encased in estuarine mud constitute the main targets for by-passed oil. Higher frequency (4th and 5th order) erosional surfaces within 3rd order lowstand/transgressive systems tracts and minor extensional faulting allowed communication among different reservoirs. Based on this communication, simultaneous development of (formerly) different reservoirs is possible through the identification of hydraulic flow units. A volumetric review of each stratigraphical unit, the reallocation of the production records to appropriate units and the analysis of pressure as a function of recovery factor were completed. The results of this work, supplemented with newly acquired data, indicated the entire Oficina L sand package may be considered as one hydraulic unit (historically, the L sands in Mata were produced as 12 discrete reservoirs). Similar conclusions were reached for the Oficina S and U (Oficina and Merecure) sand packages. Additional studies have been undertaken to identify the existence of other hydraulic units as already shown in the Oritupano Area, also operated by Perez Companc SA(1). Mata wells are deep and expensive to drill or recomplete. The economic viability of producing this mature field will be greatly enhanced by allowing commingled production from identified and proven hydraulic units and from a set of reservoirs which proven to be economically unviable under individual production scheme.(2).