Volume 55

Effects of Thermal Accumulation Along the Path of Oxygen-Reduced Air Flooding on Pore Utilization Characteristics in Low-Permeability Reservoirs LI Qihang, LI Yiqiang, YAN Zhiqian, WANG Wenxu, CAO Jinxin, ZHANG Yaqian, TANG Xuechen, SONG Tao, LIU Zheyu

Abstract

The thermal accumulation caused by low-temperature oxidation(LTO) reactions in the formation significantly impacts the progression of these reactions. To clarify the blocking pattern of pores due to the deposition of heavy components generated by crude oil oxidation during the thermal accumulation process, this study employed serial core displacement and nuclear magnetic resonance (NMR) scanning experiments. It investigated the effect of thermal accumulation on the distribution pattern of residual oil in the core. Additionally, chromatographic experiments were used to explore the degree of crude oil oxidation and the pattern of oxygen consumption along the path under different thermal accumulation conditions. The results of the core displacement experiments show that as the temperature increases, the amount of heavy components produced by oxidation increases, and the degree of oxygen consumption per unit volume of the formation also increases. The oxygen consumption after core displacement is 16.92% at 89℃, 29.78% at 100℃, and 51.2% at 120℃. The results of NMR scanning indicate that the heavy components produced by oxidation can block the dominant airflow channels and increase the gas sweep range. The recovery rates at 89℃, 100℃, and 120℃ are 51.27%, 58.62%, and 59.37%, respectively. The recovery rates for pores smaller than 0.05μm are 0.9%, 0.95%, and 0.96%, while the recovery rates for pores larger than 0.48μm are 47.34%, 53.57%, and 54.29%, respectively. This paper can provide theoretical guidance for improving recovery efficiency through oxygen-reduced air flooding.

Keywords reduced-oxygen air flooding，low-temperature oxidation(LTO)，enhance oil recovery (EOR)，thermal accumulation