Heavy Oil Potential Discovered in Low Contrast Pays in Orinoco Belt, Venezuela

Ache, Alberto¹; Cardenas, Leidy; Gonzalez, Duvraschka; Saavedra, Leiska; Sandoval, Jose; and Bustos, Ulises D.
¹[email protected]

Significant heavy oil accumulations occur in Cretaceous sands in Temblador Formation, Dobokubi Field. This field is part of the Orinoco Belt (currently the largest Heavy Oil reserves in the world, with 297 billion barrels) in eastern Venezuela and is characterized by fluvial facies deposited in transitional environments. The formation fluids are 15 degree API Oil and very low salinity formation water (typically below 10,000 ppm). The fluids identification is a challenging task for conventional electrical logs and common reservoir evaluation techniques due to the low salinity. Identical resistivity ranges and nuclear logs response are equally associated to both oil or water production. The salinity variations across sand bodies, makes the formation evaluation with standard parameters highly complex and demonstrating the high heterogeneity in reservoirs distribution. In this context, a geological model integrated with advanced wireline electrical logs strongly supported the uncertainty reduction. The new measurements involve capture spectroscopy for lithology assessment, dielectric propagation for oil mobility detection and salinity variations and radial magnetic resonance for water cut prediction and viscosity variations. A new reservoir evaluation approach integrating these advanced measurements, enable to significantly improve the expected well completion results. In addition, it was possible to detect, evaluate and produce new stratigraphic intervals represented by low contrast pays, not considered before this job. A detailed analysis of the low contrast facies and the lack of contrast between oil bearing sands and shales are analyzed. Interesting findings in the dielectric and radial magnetic resonance measurements enabled a better comprehension of petrophysical properties, providing a valuable tool to avoid bypassing hydrocarbons. Commercial hydrocarbons were produced from the new targets encountered; meanwhile water cut reduction was achieved in the targets already known. These findings supported the update of the geological model, leading to the direct incorporation of reserves and oil production increase in this field. The results obtained with this supported 143 new well locations for 2013 in this area.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013