Applicable scope of oxygen-reduced air flooding and the limit of oxygen content

Abstract

The mechanisms of oxygen-reduced air flooding (ORAF) and the explosion limit and the corrosion control approaches were studied based on the pilots of oxygen-reduced air flooding (ORAF) in the Dagang, Changqing and Daqing oil fields in China. On the foundation of indoor investigations and pilots, the explosion limits, oxygen reduction limits and corrosion control approaches were clarified. When the temperature of reservoir is equal to and higher than 120 °C, there is a violent reaction between oxygen and crude oil, that means the effect of low temperature oxidation would be fully taken use of to enhance oil recovery by air flooding directly; nitrogen dominated immiscible flooding with oxygen-reduced air should be applied in cases where reservoir temperature is below 120 °C with little oxygen consumption and little heat generated. The oxygen-reduced air flooding is suitable for 3 types of reservoirs: low permeability reservoir, water flooding development reservoir of high water-cut and high temperature and high salinity reservoir. In the process of development, in order to ensure safety, the oxygen reduction limits should be controlled fewer than 10%, while oxygen-reduced air can obviously reduce the corrosion rate of pipes; The surface pipelines and injection wells don't need to consider about oxygen corrosion with no water, special materials and structure of pipe or corrosion inhibitor can be applied to the surface pipelines and injection wellbores with water. Air/oxygen-reduced air is a low-cost displacement medium and it could be applied in many special conditions of low permeability reservoir for energy supplement, huff and puff and displacement, that means oxygen-reduced air flooding has become the most potential strategic technology in 20 years.