An Analytical Study for High-Pressure Air Injection Applicability in a Potentially Candidate Sandstone Light Oil Reservoir

Abstract

Two experimental and analytical methods were employed to screen a candidate crude oil for compatibility with the application of the High-Pressure Air Injection (HPAI) process of Enhanced Oil Recovery (EOR). The studied methods are thermal processes used to assess and evaluate the oxidation reaction kinetic parameters of a reservoir oil and core samples; they are heated in the presence of air at specific reservoir conditions of pressure and temperature, and then analyzed for apparent kinetic behaviour. Kinetic parameters provide the initial indicators of the viability of the air injection application. The studies were carried out under sandstone reservoir conditions for a Mexican oil field in the Miocene geological era with a high American Petroleum Institute (API) gravity oil. The first method studied, Accelerating-Rate Calorimetry (ARC) evaluated the ignition and oxidation/combustion characteristics of the reservoir in the presence of air at reservoir conditions, using the reservoir core and oil samples. The results identified the temperature intervals where the oil reacted. This information was used to determine the rate and continuity of these reactions based on temperature and time. Based on this information, the Arrhenius parameters for the oxidation kinetics of the oil were determined. Four ARC tests in ‘closed’ mode and one in ‘flowing’ mode were conducted, where the exotherms found are associated with bond-scission reactions in light oil reservoirs. The second method, High-Pressure Ramped Temperature Oxidation (HPRTO), enabled the identification of the temperature at which important changes in the energy generation and oxygen consumption rates occurred. The data allowed the derivation of the oxidation kinetic parameters for the reservoir system. In this study, two oxidation and one thermal cracking experiments were conducted, demonstrating that an elevated temperature oxidation front travelled across the core, the carbon oxide-forming reactions were dominating over the oxygen-addition reactions. The results from these two studies and their post-test analysis indicate that the proposed reservoir is a good candidate for the application of the High-Pressure Air Injection (HPAI) method for Enhanced Oil Recovery.