A novel model for assessing the pore structure of tight sands and its application

Abstract

Pore-structure poses great influence on the permeability and electrical property of tight sand reservoirs and is critical to the petrophysical research of such reservoirs. The uncertainty of permeability for tight sands is very common and the relationship between porestructure and electrical property is often unclear. We propose a new parameter δ, integrating porosity, maximum radius of connected pore-throats, and sorting degree, for investigating the permeability and electrical properties of tight sands. Core data and wireline log analyses show that this new δ can be used to accurately predict the tight sands permeability and has a close relation with electrical parameters, allowing the estimation of formation factor F and cementation exponent m. The normalization of the resistivity difference caused by the porestructure is used to highlight the influence of fluid type on Rt, enhancing the coincidence rate in the Pickett crossplot significantly.