2-D Pore-Scale Experimental Investigations of Asphaltene Deposition and Heavy Oil Recovery by CO₂ Flooding

Abstract

To understand the pore-scale processes of asphaltene deposition during heavy oil recovery by CO2 flooding, a series of microscopic flooding experiments were conducted in two-dimensional models under high-temperature (80 °C) and high-pressure (2, 6, and 10 MPa) conditions. Two different heavy oils, AZ-4 and KD-9 (with viscosities of 7754 and 19 290 mPa·s, respectively, at 80 °C), were used. In these samples, up to 95% and 85% of oil viscosity reduction, respectively, could be achieved by CO2 dissolution. During CO2 flooding in the microscopic models, with increasing fluid pressure (6 and 10 MPa) and CO2 concentrations (60–80 mol %), both the covered area (17–38%) and the sizes of the deposited particles (up to 200 μm) became larger. At 6 MPa, a dynamic between between dissolution and precipitation was observed in large pores (with diameters of >350 μm). According to the solvent dissolution test (heptane and toluene), the deposited solids comprise both asphaltene and alkane components. Between AZ-4 and KD-9, higher resin/asphaltene ratios tend to reduce asphaltene deposition during the dissolution of CO2 by stabilizing the solubility of asphaltene in crude oil. In addition, although permeability decreased (up to 15%) with increasing pressure (2–10 MPa) and CO2 concentrations (25–70 mol %), the oil recovery mostly increased (up to 88.6% with AZ-4). The only decrease in oil recovery occurred with KD-9, which decreased from 64.7% (6 MPa, with a CO2 concentration of 69.7%) to 56.1% under 10 MPa and considerably high CO2 concentrations (79.7 mol %). Compared with the light oil system, the tested heavy oil shows considerably improved recovery and less asphaltene deposition during high-concentration CO2 flooding. Therefore, although CO2 miscibility can hardly be achieved in heavy oil reservoirs, CO2 is of great interest due to its high solubility in heavy oil and significant oil viscosity reduction.

Studying key processes related to CO2 underground storage at the pore scale using high pressure micromodels

“…236 The latest developments among the microfluidic approaches include the study of the combined application of CO 2 storage and oil recovery processes. [237][238][239] Understand microbial behavior deep underground gives insights to the bioplugging mechanisms leading to significant changes within the porous media, such as the reduction of the porosity and the permeability. 240,241 Engineering bioplugging has been used for several industrial applications (e.g.…”

CO2 Miscible Flooding for Enhanced Oil Recovery

“…Improvement of oil recovery occurs through different techniques, one of which is CO 2 flooding in low permeable and light-oil reservoirs [35,36], as it can increase recovery factor from 10 to 20% [37]. Moreover, it reduces atmospheric gas emissions through CO 2 storage [38].…”

“…It is estimated that there is the potential to recover 24 billion barrels of additional oil in the North Sea using the CO 2 -EOR process. About 60 active miscible CO 2 projects were in operation in the United States in 1996, whereas in Canada, hydrocarbon miscible floods reach nearly 40 active projects [35,65] where 128 projects contributed about 126 million tons of oil [66], applied through carbonate and sandstone reservoirs with a percentage of5 5a n d3 7 %r e s p e c t i v e l y ,w h i l et h eo t h e r6 % were implemented in tripolite reservoirs [67]. The range of porosity is from 4 to 29.5% with a permeability of 100 mD.…”

Novel Insights into the Pore-Scale Mechanism of Low Salinity Water Injection and the Improvements on Oil Recovery

“…Furthermore, we aim to demonstrate the actual mechanism of LSWI in porous media by performing several Micromodel experiments. Micromodel experiments have been given tremendous attention since they can provide direct evidence of phenomena taking place between different phases at a porous medium. ,,,, They have been used to provide valuable information about the flow of emulsion in porous media, − heavy oil recovery, − CO 2 injection, , carbonated water injection, , water alternate gas injection (WAG), and low salinity water. ,,,, …”