Petro physical analysis of among hydrocarbon field fluid and lithofaciesusing Well Log Data

Petrophysical imaging of two reservoirs of Amangi hydrocarbon field of the Niger Delta of Nigeria was conducted based on crossplot analysis using AVO information from well log data of five appraisal wells in the field. The field consists of series of reservoirs stacked in channelized shoreface sands encased in shales. Two reservoirs H1000 and H4000 which constituted the first phase of development of this field formed the pivot of this study. Firstly, we extractedpetrophysical parameters such as P and S impedances, Lam's parameters, etc. Secondly, appropriate pairs of rock attributes and properties were crossplotted so that common lithologies and fluid types cluster together for quick identification and interpretation. Furthermore, crossplotsof AVO intercept versus gradient and reflectivity versus incidence angle were analyzed to determine the class of AVO anomaly. The lithology and fluid contents of both reservoirs were adequately discriminated by the crossplot analyses of the rock properties and attributes. However, whereas there was a marked separation of litho-fluids in the density domain, the acoustic impedance domain proved incapable of separating the litho-fluids of these horizons. The reservoirs' sands were found to be "hard" sands as a result of mixed lithologies (heterolithics) exhibitingClass II AVO anomaly.