Resistivity/porosity/velocity relationships from downhole logs: an aid for evaluating pore morphology

Abstract

Shows that although resistivity and velocity are controlled by porosity, the "connectiveness' of the solid phase (velocity) and fluid phase (resistivity) may be more important controls than porosity in these environments. Velocity logs in this environment are shown to be controlled primarily by the bulk properties of the solid fraction and fluid phases, with interparticle cementation causing significant increases in velocity during lithification. Downhole electrical resistivity logs, in contrast to velocity logs, are shown to respond to the fluid phase in these marine carbonate sediments, where the terrigenous clay fraction is small. Velocity and resistivity log responses are compared in different diagenetic carbonate environments. The effects of diagenetic processes in shallow-water reefal carbonates are contrasted with the effects of the normal compaction/lithification depth profile in carbonate-rich hemipelagic sediments. -from Authors