Microscale Dynamics of Oil Connectivity and Mobilization by Controlled-Ionic-Composition Waterflooding at Elevated Temperature Using Synchrotron 3D X-Ray Microscopy

Abstract

Controlled-ionic-composition waterflooding improves oil displacement efficiency in heterogeneous carbonate rocks. Recent microscale experimental studies confirm that the injection of brines containing high sulfate ion concentrations alters the wettability of the pore surfaces and improves oil mobilization at elevated temperature. However, the dynamics of associated with changes in the microscale brine/oil/rock interactions at typical field flow rates is unclear due to the limited temporal resolutions of leading micro-CT scanners, which often require hours for data acquisition. The goal of this study is to investigate microscale dynamics of oil connectivity and mobilization by controlled-ionic-composition waterflooding at evaluated temperature using synchrotron-based 3D X-ray microscopy. Heterogeneous carbonate rocks were saturated and aged with formation brine and oil at 90 °C, then flooded with brine containing different ion types and concentrations at 90 °C. Each flooding cycle was visualized using 3D X-ray microscopy at Advanced Photon Source. This source is the brightest hard X-ray source in the U.S. and therefore enables us to visualize the oil displacement at high temporal resolutions (45s). The experimental results show that injection brine containing high sulfate concentration rapidly increases the oil connectivity across the porous medium within the first few minutes and consequently improves oil recovery from pores regardless of pore sizes.