Lithological Estimation with Vp/Vs Ratio from 3D3C Seismic in Uncosolidated Sands at Orinoco Oil Belt, Venezuela

PDVSA Petrocedeño is a joint venture oil production company at the Orinoco Oil Belt, Venezuela. The sediments which are currently in production belong to the Oficina formation. This formation is characterized by fluvial deposits sequences dominated by intertwined rivers, meandering rivers and floodplains, its top is defined as a transitional environment with fluvial- delta deposits, where is the presence of distributary channel, delta progradation bar, alluvial fan and delta plain shales with some coal layer.

One of the biggest challenges is to drill without uncertainty to locate the bodies of sands interbedded with shales of fluvial-transitional system, isolated channels with lateral changes and lithology in thickness between 15 and 45 feet. Detailed analysis of seismic data and its attributes provided a better understanding of the complexity in sand distribution. This is a case of study of a heavy oil reservoir using registration method to estimated Vp/Vs ratio and cross plot, which allowed us to combine elastic and acoustic rock properties identifying among which Vp/Vs ratio values sands body are related to.

The uses of the 3D3C seismic data can help us to reduce uncertainty drilling sands with lateral lithological changes.