Velocity-Porosity relationship in clastic formations – a case study from some parts of Niger Delta, Nigeria

Abstract

Velocity-Porosity relationship in some parts of Niger Delta was studiesd with a view to establish the velocity-porosity relationship and the generalized equation(s) that best describe this relationship in clastic formations. Five wireline logs were acquired for the study. Neutron porosity log data was converted to synthetic velocity (V_TA) using time-average equation of Wyllie (1956), and the sonic porosity log was converted to sonic velocity (V_sonic). The results were presented as velocity-porosity crossplots with the trend line equations and the coefficient of correlation. The results give a distinct inverse velocity-porosity relationship; i.e. velocity decreasing with increasing porosity. The velocity-porosity relationships established from both sonic log (V_sonic) and time-average formulation are best described by polynomial fitting of 2^nd order. Two generalized equations of high coefficient of correlation, which can be used to calculate compressional velocity (V_p) from porosity values in clastic formations, were established from these relationship.

Keywords: porosity, velocity, compressional, polynomial and clastic

Global Journal of Pure and Applied Sciences Vol. 12(1) 2006: 125-128