The effect of different phase zones distribution on the characteristics of oil production during CO2 flooding process

Title : The effect of different phase zones distribution on the characteristics of oil production during CO2 flooding process

Abstract:

Both laboratory tests and pilot wells have demonstrated the significant potential of CO₂ as an EOR medium. Due to the weak pressure conduction and mass transfer of the CO₂-oil system, multiple zones between the injection well and production well are generated in the ultra-low permeability reservoirs. This work aims to explore the characteristics of multiple zones and mechanisms of CO₂-EOR, combining the experimental results, core-scale, and field-scale simulation. Long core displacement experiments were conducted under different miscibility pressures with production gas assayed using gas chromatography. When the core-scale simulation matched with the experimental results, the four CO₂ fronts, which were used to distinguish different zones, were defined based on pressure, interfacial tension, and CO₂ concentration along the long core. The distribution of five zones was upscaled to the field-scale model after the history matching of pilot wells. The final step was to evaluate the value of the miscible zone range, utilization factor of CO₂ injection, oil recovery, and CO₂ storage efficiency during the CO₂ injection process. Results show that the boundary between the original oil zone and the oil transition zone exists at the CO₂ component front, where the CO₂ concentration is zero. Additionally, the location of the CO₂ component front does not overlap with the contact interface of CO₂-crude oil, meaning that the dissolution effect of CO₂ in the oil transition zone results in the CO₂ component front moving farther. Besides, when the formation pressure is higher than the minimum miscibility pressure (MMP), the distance between the CO₂ effective phase front and the CO₂ effective component front further expands as the pressure increases, enlarging the miscible zone range. The pressure accumulates around the injection well because of slow pressure conduction. When the average formation pressure reaches 1.1 MMP, the miscible zone range is enlarged by 2.7% higher than that of the near miscible flooding (0.92 MMP), leading to a higher rate of oil recovery by 8.6% and a utilization factor of CO₂ by 0.14t/t. An increment in pressure yields a slowing migration velocity of the CO₂ component front, therefore, the miscible flooding has a breakthrough time of 0.08 PV later, and the CO₂ storage efficiency of 1.4% higher than those of the near miscible flooding. It is for the first time that the range of five zones and the characteristics of four CO₂ fronts migration is assessed, furnishing an in-depth understanding of the complicated mechanisms and phase behavior in CO₂ EOR in the ultra-low permeability oil reservoir. This work contributes to providing significant information for designing an economic and environmental CO₂ flooding strategy and is significant in the improvement of oil recovery and the reduction of CO₂ emission.
 

 Audience Take Away: 

• This work contributes to providing significant information for designing an economic and environmental CO₂ flooding strategy and is significant in the improvement of oil recovery and the reduction of CO₂ emission
• This work explores the characteristics of multiple zones and mechanisms of CO2-EOR
• It is for the first time that the range of five zones and the characteristics of four CO₂ fronts migration is assessed.
• This work furnishes an in-depth understanding of the complicated mechanisms and phase behavior in CO₂ EOR in the ultra-low permeability oil reservoir
• This research could be used to expand other faculty research or teaching.

Biography:

Dr. Xiliang studied EOR at China university of petroleum Beijing in 2018. He joined the research group of Fellow of China academic of Engineering Yang Li at China university of petroleum Beijing. My research interests include CO₂-EOR and geological storage. As a researcher, I have published Chemical Engineering Journal, Applied Energy, Energy, Fuel, and Energy & Fuels. Besides, I have attended more than 10 projects entrusted by the National Natural Science Foundation of China, the National Key Basic Research Program, and oilfield enterprises and I have awarded 3 provincial level prizes.