Rock typing across disciplines

Abstract

Petrophysical units, or rock types, are defined to help petrophysicists assign characteristics to different zones of a reservoir. Rocks are clustered into groups assumed to have similar flow and storage capacity. Facies are identified by geologists, who use depositional and diagenetic criteria tied to porosity-permeability data. Relationships are used to link the petrophysical to the geological models, along with log typing to estimate initial hydrocarbons-in-place. Reservoir engineers also wish to define rock types based on their two-phase flow characteristics (i.e. relative permeability). In this case fluid properties (i.e. viscosity, interfacial tension) can be a major factor controlling the flow and distribution of fluids in porous rocks which in turn greatly impacts ultimate recovery of hydrocarbons. Integrating conventional geologic, petrophysical and multiphase flow rock typing methods requires studies which incorporate 3D imaging of rock material, 2D petrographic studies, fluid-fluid and fluid-solid interactions (i.e. wettability) and geological facies descriptions. In this paper we describe the integration of various imaging and analysis techniques which will enhance our ability to undertake such multidisciplinary studies. First, Scanning Electron Microscopy with X-ray microanalysis (i.e. scanning electron microscopy-energy dispersive x-ray spectrometer, SEM-EDS) enables one to obtain spatial and numeric 2D mineralogical information from plug samples. This analysis allows high quality 2D mapping of key parameters used in characterizing rocks include mineralogy, modal mineral proportions, mineral relationships and associations, porosity, and fracture distribution. Secondly, fluid flow and recoveries are dependent on the pore geometrical and topological complexities in reservoir rock, coupled with variability in core wettability; these can be directly probed via 3D imaging modalities including micro-computed tomography (μ-CT). Integration of these techniques allows one to more accurately map the mineralogy and wettability characteristics of reservoir rocks in 3D and therefore better couple relevant information from geologists, petrologists, petrophysicists and reservoir engineers. Show more