Flammability and Explosion Characteristics of Methane in Oxygen-Reduced Air and Its Application in Air Injection IOR Process

Abstract

Air injection into oil reservoirs has been widely applied in oilfields for improved oil recovery, while the safety of the process is of great concern due to the explosion of the mixtures of natural gas (mainly methane) and injected air at high pressure and high temperature. Oxygen-reduced air flooding (ORAF) has been proposed to eliminate the explosion risks. The combustion and flammability characteristics of methane–air mixtures at elevated pressure and temperature are also important for natural gas engines and air compressors. In this study, an experimental setup was used to measure the flammability limits and explosion energy of methane in oxygen-reduced air (ORA) at pressures up to 15 MPa and 373 K and compared with methane–air mixtures. The experimental results show that the flammability limits of methane in ORA can be significantly reduced or narrowed, which can reduce explosion risks. At high pressures, the low flammability limit of methane in ORA is reduced, and its upper flammability limit is increased, which follows a similar pattern with methane–air mixtures. The explosion energy of methane in ORA can be also greatly reduced due to the lack of oxygen. Finally, the explosion risks in applying the ORAF technique for improved oil recovery have been analyzed.

On the Second Explosion Limits of Hydrogen, Methane, Ethane, and Propane

“…Figure 6 shows the k PT as a function of the carbon number. Carbon number ranges of [0, 1], [1,2], and [2,3], respectively, represent fuel mixtures of H 2 /CH 4 (0…”

“…Therefore, the phenomenon of explosion has always been concerned by researchers owing to the explosion characteristics, 1 minimum ignition energy, 2 and flammability characteristics. 3 The explosion limits of a homogeneous fuel/oxidizer mixture that separates the explosive and nonexplosive regions are dominated by the competition of the radical producing and removing reactions, the result of which is pressure- and temperature-dependent. 4 As such, the explosion limit is typically characterized in the pressure–temperature parameter space and can be described by the pressure as a complex function of the system temperature.…”

“…Under certain conditions, the combustible mixture will explode in the processes of transportation, storage, mining, and utilization, resulting in a huge loss of life and property. Therefore, the phenomenon of explosion has always been concerned by researchers owing to the explosion characteristics, minimum ignition energy, and flammability characteristics . The explosion limits of a homogeneous fuel/oxidizer mixture that separates the explosive and nonexplosive regions are dominated by the competition of the radical producing and removing reactions, the result of which is pressure- and temperature-dependent .…”

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

“…Air injection based oil recovery processes include a big family of enhanced oil recovery (EOR) techniques, such as in situ combustion (ISC), high-pressure air injection (HPAI), air-foam flooding, and oxygen-reduced air injection. − For the latter two techniques, they barely take advantage of the oxidation reactions of crude oils and mostly use air as a gas source like other gas injection processes. ISC (also called fireflooding) usually refers to the air injection recovery process of bitumen and heavy oil, whereas HPAI is usually used for the description of air injection recovery for high API gravity oils and is sometimes also called air injection LTO or light oil air injection (LOAI). , In this work, we focus on mainly ISC and HPAI, where oxidation reactions govern the EOR process.…”

Identification of Gas Channeling and Construction of a Gel-Enhanced Foam Plugging System for Oxygen-Reduced Air Flooding in the Changqing Oilfield

“…In addition, to prevent explosions and ensure the safety and controllability of air flooding, light oil reservoirs are usually flooded with oxygen-reduced air. Oxygen-reduced air flooding (ORAF) is a development method in which deoxidized air whose volume ratio of oxygen is reduced to less than 10% is injected into oil reservoirs to displace crude oil by utilizing deoxidized air generation and pressurized injection systems [ 7 , 8 , 9 ]. Besides maintaining the reservoir pressure, the low-temperature oxidation heat generation, flue gas flooding, and swelling effect can be fully utilized to enhance oil recovery (EOR) during the ORAF process.…”