Numerical modeling on air injection in a light oil reservoir: Recovery mechanism and scheme optimization

Abstract

Air injection in light oil reservoirs is a promising enhanced oil recovery (EOR) method because of its wide availability, low cost, and ability to stimulate subterranean oil combustion. However, oil recovery mechanisms and physical processes for air injection in conventional light oil reservoirs are still not well understood. An improved understanding of air injection mechanism in conventional light oil reservoirs is provided in this paper. We use the reservoir simulation approach to study air injection in a light oil reservoir. Effects of O 2 mole concentration, activation energy, intake air temperature, geological structure and development scheme on the well performance of air injection are examined. The driving mechanism of thermal effect is revealed through the observation of oil rate fluctuating and dynamic temperature distribution. We present the evidence of the "bulldozing effect (or pore blocking)" for air injection in a light oil reservoir which shows the sudden decrease of gas relative permeability. The effect has the potential of redirecting gas flow to improve sweep efficiency. Analysis of influence factors from this work indicates that the oil recovery factor is sensitive to O 2 content in air and geological structure of the reservoir. The performance with gas injected updip is better than that downdip. It is insensitive to intake air temperature or activation energy in the reaction scheme favoring a generation of more H 2 O, insoluble CO and CH 4 .

Enhanced oil recovery mechanism of low oxygen air injection in high water cut reservoir

“…Some people tend to use ''bulldozing effect'' to describe the hypothesis. As Jia and Sheng (2016) have verified that temporary pore blocking can redirect gas flow, which can improve volumetric sweep efficiency. Moreover, it has the potential of delaying gas breakthrough due to this gas moving frontal ''self-adjustment.''…”

“…In addition, we have proved the evidence of the ''bulldozing effect (or pore blocking)'' for air injection in light oil reservoirs, which has the potential of redirecting gas flow to improve sweep efficiency (Jia and Sheng 2016). In recent years, low oxygen air injection has been proposed in China in order to replace the conventional air injection from the considerations of the risk reduction and pipeline corrosion.…”

Crude Oil Oxidation in an Air Injection Based Enhanced Oil Recovery Process: Chemical Reaction Mechanism and Catalysis

“…Zhao et al reported that saturates and asphaltenes showed the highest heat release in LTO and HTO, respectively. There are some other findings related to SARA fractions’ oxidation; for instance, resins and asphaltenes showed a similar HTO path because of their similar structures; saturates and aromatics directly influenced whether self-ignition occurred or not for light crude oil; and asphaltenes played a predominant role in determining the HTO kinetics and contributed largely to coke formation. , …”

Catalytic Effect of Cobalt Additive on the Low Temperature Oxidation Characteristics of Changqing Tight Oil and Its SARA Fractions

“…Air flooding is a cost-effective technique for exploiting oil reservoirs, which is remarkably effective for tight oil reservoirs and conventional reservoirs in the late stage of waterflooding [1][2][3][4]. Recently, there have seen numerous researches and field pilots for air flooding in the North Sea [5,6], Indonesia [7,8], Argentina [9], Buffalo Red River Unit (BRRU) [10], West Hackberry [11,12], Coral Creek [13], Ekofisk [6,14], Buffalo [15,16], and Horse Creek oilfields [17] with good performance.…”