The Influence of Pressure on the Low Temperature Oxidation (LTO) of Heavy Oil During the High Pressure Air Injection(HPAI)Process in Tahe Oilfield

Abstract

Abstract With the decline of conventional oil production, developing and producing heavy oil resources efficiently are becoming more important. High pressure air injection (HPAI) is generally considered as an efficient method to drive the crude oil in light oil reservoir. But there is a debate about whether the released heat from oxidation reaction is able to activate the heavy oil effectively. Comparing to the in-situ combustion (ISC) technique, air injection without ignition will reduce the operation difficulty and eliminate the security risk. Thus studying the changing of the oil property in presence of injected air is the prerequisite to apply the HPAI technique in heavy oil reservoir. For this purpose, the constant temperature oxidation experiments have been carried to study the influence of pressure on heavy oil in the air injection process at reservoir condition of Tahe oilfield. The results showed that the pressure has obvious influence on the crude oil property. By the increment of pressure, the oxygen in the air presented a decreasing trend while the amount of carbon dioxide did not exhibit an increasing trend. The oxidation addition reaction dominated the reaction type. For the oil phase, the viscosity of the oxidized oil presented a slight decrease under relative low pressure condition. When the pressure reached 50MPa, the crude oil has transferred into coke completely. During the oxidation process, the property and amount of the coke directly related to the released heat amount in the high temperature oxidation (HTO) stage. According to the thermogravimetry (TG) and differential scanning calorimetry (DSC) results, the oxidized oil achieved lower HTO trigger temperature. So it is believed that the higher pressure has a positive influence on the coke deposit process. The formation of sufficient coke will bring the possibility for the application of HPAI technique in heavy oil reservoirs.