(659k) High-Pressure High-Temperature Carbo Dioxide Interaction with Crude Oil and Its Impact on Asphaltene Deposition in Micro and Nano Pores: An Experimental Study

Gas Enhanced Oil Recovery (GEOR) is one of the most applied EOR methods to increase oil recovery. One of the most investigated gases due to its several advantageous properties is Carbon Dioxide. During its interaction with the crude oil, Carbon Dioxide can induce asphaltene deposition which may result in severe formation damage. This research investigates asphaltene deposition during Carbon Dioxide injection in both micro and nanopores and compares the severity of damage caused in both pore sizes.

Methodology

A specially designed filtration vessel was used to conduct all the experiments. Crude oil with viscosity of 32, 18 and 5.7 cp were used to investigate the impact of varying oil viscosity. The impact of varying filter membrane pores size, using 5 microns, and 100, 50, and 10 nanometers, Carbon Dioxide injection pressure using 2200, 1500, and 500 psi, and temperature using 80, 50, and 30 ⁰C was investigated. The filtration experiments were conducted using 50 ml of crude oil for each experiment. Carbon Dioxide was injected until no oil production was observed.

Results

The Carbon Dioxide injected was in the supercritical phase during all experiments. When varying the filter membrane pore size, it was found that as the pore size decreased, the asphaltene pore plugging increased significantly, and the rate at which the crude oil protruded through the filter membrane decreased at an extremely faster rate compared to the larger pore sizes. At 2200 psi, the Carbon Dioxide was completely miscible with the oil. This resulted in a larger asphaltene pore plugging compared to the smaller pressures. This could be due to the miscibility of the Carbon Dioxide which resulted in asphaltene instability, where pore plugging reached 87.34%. Increasing the temperature resulted in a larger asphaltene instability, which was evident from the 67.18% pore plugging recorded at 150 ⁰C, compared to the 49.88% at 50 ⁰C. The oil with the highest viscosity had the highest initial asphaltene concentration, 5.73%, while the lowest viscosity oil has the lowest asphaltene concentration, 0.82%. This asphaltene concentration resulted in a very low pore plugging percentage using the 18 cp oil, reaching only 27.06%, whereas the pore plugging reached 54.12% when using the 32 cp oil.

Novel Information

This research investigates asphaltene deposition during Carbon Dioxide injection in both nano and micro sized pores in order to study and compare the impact of asphaltene damage in both pores sizes. This research will help highlight the severity of asphaltene damage, especially in nano pores, mainly present in unconventional reservoirs. By studying the impact of different factors on asphaltene formation damage, asphaltene deposition may be avoided in future applications of Carbon Dioxide injection.