Laboratory Investigation on the Feasibility of Light-Oil Autoignition for Application of the High-Pressure Air Injection (HPAI) Process

Abstract

Whether thermal effects have a contribution on oil recovery mechanisms in the high-pressure air injection (HPAI) process in a light-oil reservoir has confused many people over several decades. The argument is due to the lack of convictive evidence from both direct laboratory and simulation studies. This paper is the prelusion for the subsequent study for a better understanding of the influence of thermal effects on oil production. In a previous study, thermogravimetry/differential thermogravimetry (TG/DTG) and differential thermal analysis (DTA) tests were employed to investigate the kinetic parameters and exothermic behavior of Keke Ya light crude oil (Tarim Basin, China) and oil + cuttings, showing that Keke Ya light crude oil as well as oil + cuttings exhibited very low activation energy and favorable exothermic behavior. In this study, we develop a thermal effect monitoring device, which is similar to the isothermal oxidation tube, and we have detected the obvious exothermic phenomenon of Keke Ya light crude oil in porous media in the isothermal aging test at reservoir conditions (80 °C and 16.7 MPa). The witness of the combustion (or high-temperature) process is exhibited, which is expressed in specific characteristics made up of the self-heating behavior, low hydrogen/carbon (H/C) ratio of 1.50 from gas composition analysis, and generated precipitation coverings (halite crystalloid) in the core section surface through scanning electron microscopy (SEM) analysis. This study provides new insight that thermal effects should exist during the light-oil isothermal aging process in porous media and proposes a laboratory analysis method to understand the feasibility of light-oil autoignition at the oil-bearing reservoir during application of HPAI.