Quantifying mineral surface energy by scanning force microscopy

Abstract

Fundamental understanding of the wettability of carbonate formations can potentially be applied to the development of oil recovery strategies in a complex carbonate reservoir. In the present study, surface energies of representative carbonate samples were evaluated by direct quantitative force measurements, using scanning force microscopy (SFM) at sub-micron scale, to develop a reliable method to predict reservoir wettability. Local adhesion force measurements were conducted on appropriate calcite and dolomite samples and performed in air as well as in the presence of polar and nonpolar fluids. This study demonstrated that, by comparing measurements of adhesion forces between samples of the same mineral in different fluids, it is feasible to determine the surface energy of a given mineral as well as its polar and nonpolar components. The derived values are in agreement with literature. A proof-of-principle protocol has been established to quantify surface energy using SFM-based adhesion measurements. This novel methodology complements the conventional contact angle measurement technique, where surface energy can only be examined at large length scale. The reported methodology has great potential for further optimization into a new standard method for fast and accurate surface energy determination, and hence provides a new tool for reservoir rock wettability characterization.

Low Salinity Waterflooding in Carbonate Reservoirs: Review of Interfacial Mechanisms

“…When the brine was diluted, the freshly grown material was dissolved and the stearic acid patches, formerly incorporated into the crystal during the growth phase, were exposed. Sauerer et al [48] measured the surface free energy of calcite and dolomite samples using AFM adhesion force measurements, in order to predict carbonate reservoir wettability. Adhesion forces, between the installed colloidal calcite and dolomite particles on the AFM tip ( Figure 7) and the planar cleaved calcite and dolomite samples, both in air and in the presence of organic solvents (ethylene glycol, bromonaphthalene and heptane) were measured.…”

“…Carbonate surfaces are originally water-wet, containing positively charged surface electrostatics over a wide range of pH [47]. However, adsorption of negatively charged carboxylic materials (-COO − ), present in the heavy end fractions of crude oil such as resin and asphaltene fractions, onto positively charged carbonate rock surfaces, results in large crude oil particles covering the carbonate surface and could promote mixed-wet or oil-wet characteristics [45,[47][48][49][50]. Carbonate reservoir rocks have inherently higher chemical activities compared to minerals in sandstone reservoirs (quartz); additionally, there have been difficulties in modelling the distribution of permeability in carbonates and predicting reservoir behaviour, due to poor correlation between permeability and porosity.…”

Mechanisms of Surface Charge Modification of Carbonates in Aqueous Electrolyte Solutions

“…It has been argued that there may be more than one mechanism, or even an undiscovered mechanism, involved in LSW in carbonates [5]. Although wettability alteration, towards a more desirable state for oil to be recovered, is widely accepted as the main reason to improve oil recovery during LSW [6][7][8][9][10][11], the question of how this alteration happens is still the subject of debate, with no single design fitting all reservoirs. Understanding the wettability mechanism involved in LSW, under controlled laboratory conditions, and the colloidal interactions at oil-rock-brine interfaces are essential in improving the efficiency of LSW.…”

Wetting Behavior of Tight Rocks: From Core Scale to Pore Scale

“…The magnitude of the adhesion forces for quartz are ranged from 0.021 ± 0.006 μN to 0.032 ± 0.005 μN (Leite et al, 2003) and from 0.015 to 0.060 μN (Jones et al, 2002). Several studies have investigated the adhesive forces for the cleaved calcite crystals immersed in different liquids (Karoussi et al, 2008;Ricci et al, 2015;Røyne et al, 2015;Sauerer et al, 2016;Stipp et al, 1994). To the authors' knowledge, there are a few studies reported in the literature investigating the adhesion forces for calcite at the ambient air conditions.…”