WETTABILITY ALTERATION OF CARBONATES WITH SEAWATER SALINITY BRINES EXPLORED USING A 3D MICROMODEL

This report shows experimental evidence of wettability alteration using seawater salinity brine of an oil-wet system composed by a three-dimensional carbonate micromodel, crude oil, and connate-water brine salinity in a carbonate micromodel. We designed this procedure as a first step for evaluation of using seawater as an Improved Oil Recovery (IOR) agent. Our design combines two main experimental best practices: micromodels for repeatable experiments and X-ray computed tomography (CT) as a non-invasive technique (Akin and Kovscek, 2003) for monitoring multiphase saturation in situ. Both practices merge into a new three-dimensional micromodel set-up.

Wettability alteration plays a key role to improve oil recovery from matrix blocks surrounded by water-invaded fractures in carbonate reservoir rocks. We designed a simple and replicable experimental apparatus and procedure to quantify contact angle distributions inside of porous media with a controlled level of heterogeneity in roughness and mineralogy. This experiment consists of visualizing in-situ contact angle distribution of the aqueous phase inside a three-dimensional carbonate micromodel. Using Micro Computerized Tomography (MicroCT), we obtained three-dimensional images of fluid distribution with an approximately constant resolution of 3.8 microns.

We successfully altered wettability from more oil wet to less water wet conditions. The water contact angle of the ganglia showed a 70% contact angle reduction from an oil-wet to a water-wet system in one micromodel and an 80% contact angle reduction in another. The initial average contact angles were 122.35 and 140.39, respectively. After flooding with a synthetic seawater, the average contact angles declined to 36.24 and 43.69, respectively.