Dissolution Evaluation of Coquina, Part 1: Carbonated-Brine Continuous Injection Using Computed Tomography and PHREEQC

• Published in: Energy & fuels 2018-04, Vol.32 (4), p.5289-5301
• Main Authors: Yasuda, Eric Y, Koroishi, Erika T, Vidal Vargas, Janeth A, Trevisan, Osvair V
• Format: Article
• Language: English
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/acs.energyfuels.7b03970

Carbonate reservoirs are susceptible to dissolution and precipitation effects when an acid solution enters into contact with its matrix rock, and the main interest with regard to fluid flow and storage is the alteration of the petrophysical properties, such as porosity and permeability. Dynamic experiments of injection of carbon dioxide enriched brine through the outcrop sample (coquina) was carried out at T = 20 °C and P = 2000 psi at flow rates of 0.5, 1, and 2 mL/min. X-ray computerized tomography (CT) was used to determine the porosity of the sample throughout the test, and rock permeability was evaluated by a series of pressure transducers installed at a special core holder with six pressure taps. The results include the variation of the petrophysical properties along the core sample and its evolution over time. The research covers experimental and simulation approaches; for instance, the PHREEQC was used to develop a geochemical model to fit results from calcium content analysis from effluents and porosity profiles obtained by CT scan. A very instructive sequence of images documents the formation of a highly conductive flow channel, initiated and formed as a dominant wormhole, which dramatically increases permeability and porosity through the experiment course. The dissolution regime was characterized by the Damköhler and Péclet numbers. The robust perspective of this paper showed that it is feasible to estimate the chemical and physical alterations from laboratory results on future application in the reservoir field scale by coupling experimental data and numerical modeling.