Air injection studies for enhanced oil recovery

Thesis Abstract

Conventionally, air injection has been used for recovery of heavy crude oil in the production field, but studies have shown that depletion of light crude oil in the reservoir leads to abandonment of such wells. Hence, this work studied the kinetics and combustion of light crude oil in-situ the reservoir to understand their potentials for high-pressure air injection (HPAI) enhanced oil recovery (EOR). Advanced thermo-kinetic simulation and Pressure-Volume-Temperature tools (AKTS and PVTsim) were coupled with non-isothermal Differential Scanning Calorimetry (DSC) measurements and Accelerating Rate Calorimeter (ARC) for the studies. The combustion and kinetics of three (3) light crude oils obtained from Offshore of Newfoundland, Canada were precisely described by the methods. It was observed that the crude with the lowest API of 30.214 had the lowest enthalpy change of 10.9 J/g and the highest onset oxidation temperature of 220 oC, while the crude with the highest API gravity of 46.963 had the highest enthalpy of 24.6 J/g and the lowest onset oxidation temperature of 140 oC. Effect of 10% water saturation of one of the crude samples (Sample A) was studied and it was observed that there was increase in the onset oxidation temperature by 40 oC and lowering of the enthalpy change by 9 J/g. These findings provided evidence that the versatile Differential Scanning Calorimetry thermograms when coupled with kinetic simulation technique can yield reliable results with respect to oil recovery with high correlation coefficient (r > 0.9). This reliable information such as onset, peak and endset temperatures with their respective heat flow patterns, could then be used to provide precise thermo-kinetic parameters. Kinetic triplets such as activation energy, pre-exponential and the reaction model necessary for reservoir screening in an air injection EOR process can also be accurately determined. Mine tailings containing high pyrrhotite content were then used as catalyst to study its effect on the onset oxidation temperature of the crude oils using ARC. An amount of 20% tailings in crude oil lowered the average onset oxidation temperature from 148 oC to 116 oC. It also had the widest oxidation temperature range of 63 oC between the onset and endset temperature, as well as the highest pressure drop of 2.4 bar, which signifies high conversion in the crude oil oxidation reaction as well as production of miscible flue gas which favoured enhanced oil recovery process. Products of air combustion products in-situ was studied as an injectant in a light oil Nigerian reservoir using a simulated slim tube experiment and was observed than flue gas products from air oxidation at high temperature and pressure favoured enhanced oil recovery.