Pore-level Reservoir Characterization

John G. Kaldi
Australian School of Petroleum, University of Adelaide, Australia

Pore level heterogeneities commonly determine the amounts, types and rates of fluids that can be produced or injected into a reservoir. These heterogeneities are best understood by evaluating the architecture of the pore system of the various flow units making up the reservoir. Pore geometry refers to the size, shape, and distribution of pores and pore throats in a reservoir rock. It can be compared to the architecture of a building - i.e. the configuration of rooms (pores) and doors (pore throats) of various shapes and sizes.

Pore geometry of reservoirs is evaluated using fairly routine analytical techniques such as thin-section petrography, Scanning Electron Microscopy (SEM), pore casts, mercury injection capillary pressure (MICP) and relative permeability curves. Examples of various pore geometries (macro, micro, moldic, inter and intra-particle) from reservoirs around the world are presented to demonstrate the significant influence pore geometry has on both drainage and imbibition cycle capillarity and relative permeability properties. These in turn control saturation vs. height functions and recovery efficiencies (the relative quantities of fluids produced on primary depletion as well as the distribution of remaining fluids for secondary production).

In addition, potential formation damage prone intervals can be identified from the understanding of pore geometry in conjunction with detailed rock properties such as mineralogy and clay morphology. An understanding of the pore geometry of reservoir rocks early in production is desirable in order to predict reservoir behaviour during field life.

AAPG Search and Discovery Article #90101 © 2010 AAPG Foundation Distinguished Lecturer Series 2009-2010