Fast wettability assessment on small rock samples using a 3D, high-resolution, image-based Amott-like test

Abstract

In this paper, we propose a new experimental set-up to carry out a full Amott-like cycle on small core samples (4 mm. diameter, 15 mm. length), imaged with a high-resolution micro-CT scanner. We conduct this experiment on two core samples from a carbonate reservoir. Each step of the cycle was followed by a 3D highresolution scan along the entire sample length and analysed using digital image-processing algorithms. The characterization of wettability is based on multiple criteria: a) a pseudo-wettability index, analogous to the Amott-Harvey index, calculated from both resolved and unresolved pores; b) experimental observations during the spontaneous phases, and c) analysis of the spatial fluid distribution in the pore space. This new type of experiment has several advantages: a) it respects the experimental sequence of the industry standard Amott test, yet with a significantly reduced test duration; b) it provides complementary information describing the spatial distribution of the fluids in the visible pore network during spontaneous and forced phases; c) it is less sensitive to imaging resolution than existing approaches based on topological characteristics and contact angles.