Waterflooding is an improved oil recovery (IOR) method commonly used worldwide. Some of the world's largest waterfloods are found on Lake Maracaibo, in western Venezuela. One such project is the Bachaquero-02 (Bach-02) which was initiated in 1967 as a peripheral water injection in an unconsolidated sandstone reservoir with average permeability of 350 mD and average oil gravity of 15° API. This waterflood project has been the subject of various studies that include conventional assessments, integrated full field and simulation studies. This paper presents a diagnosis of the impact that waterflooding has on Bach-02 heavy oil recovery, in view of a new approach that reveals mechanisms of heavy oil displacement by water. The findings of this field study are in accordance with empirical, experimental and simulation investigations recently reported in technical literature. Voidage Replacement Ratio (VRR) and Water Oil Ratio (WOR) analysis in this reservoir show particular behaviors associated with fluid flow characteristics in the reservoir; namely, periods of VRR less than 1.0 which activate mechanisms that stabilize WOR at values close to 1.0 and result in increased oil recovery. These mechanisms are explained by recent investigations as the flow of water-in-oil emulsions, and in situ formation of foams that benefit from chemical changes brought about by periods of underinjection.

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