Abstract
Amplitude Variation Versus Offset or angle is one of the seismic-related technologies that have been used by oil companies for decades in their search for hydrocarbon, particularly gas. AVO classes for different types of gas sands have been defined from Class I to IV, and case studies successes especially for Class III and Class II AVO. However, there are pitfalls in the implementation of the technology ± for instance low gas saturated reservoir (also known as fizz gas) and highly porous wet sandstones can give strong AVO response which gives similar Class II or Class III responses. In addition, to the above-mentioned pitfalls, anisotropy and more specifically Vertically Transverse Isotropy (VTI) can also give a false AVO response. VTI is normally associated with shale whose minerals are platy in shape, thus giving the horizontal direction of a planar bed a faster velocity propagation direction as compared with the vertical direction. This research shines a light on the concept of the phenomena of anisotropy to see the difference between two cases of reservoirs the gas sand (Yoyo-1) reservoir and wet sand (Trema-1) where the wet sand gives a high response instead of no response seen in the seismic which reflected the same response of hydrocarbon such as gas sand. Anisotropic AVO gathering data were generated using the Aki & Richards equation to the highest angle of 50, and 70 degrees. As well as, demonstrating AVO attribute types that can be used to minimize or eliminate anisotropy effects, thus can be applied to prospects in the case study vicinity.