Mechanistic Study of Gravity-Assisted CO2 Flooding
- D.L. Tiffin (Amoco Production Co.) | V.J. Kremesec Jr. (Amoco Production Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- May 1988
- Document Type
- Journal Paper
- 524 - 532
- 1988. Society of Petroleum Engineers
- 5.4 Enhanced Recovery, 5.5 Reservoir Simulation, 4.1.2 Separation and Treating, 2.4.3 Sand/Solids Control, 5.4.2 Gas Injection Methods, 4.3.4 Scale, 4.6 Natural Gas, 1.6.9 Coring, Fishing, 4.1.5 Processing Equipment, 5.4.9 Miscible Methods, 5.2.1 Phase Behavior and PVT Measurements, 5.2 Reservoir Fluid Dynamics
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A series of gravity-assisted vertical core displacements of contact-miscible and multiple-contact-miscible C02/recombined-crude-oil systems was conducted and simulated. Gravity-assisted displacements offer the advantages of eliminating gravity tongues and stabilizing viscous fingers. Although the process has been used successfully in the field, a mechanistic laboratory and modeling study of gravity-assisted multiple-contact-miscible C02 flooding has not been described previously. The results from this experimental and computer modeling study elucidate the complex mechanisms acting in gravity-assisted C02 flooding. Component transfer, as occurs in multiple-contact-miscible processes, can strongly affect flood-front stability. In general, better performance is obtained from vertically downward displacements than from comparable displacements in horizontal cores. Miscibility develops at the same pressure in vertical floods and in a much shorter core length. It was further demonstrated that displacement efficiency increases at conditions where mixing of CO, and oi is minimized. Excellent simulation of experimental recoveries and rates were obtained with a compositional simulator in a one-dimensional (ID) mode.
The use of C02 or enriched gas in gravity-assisted floods has been very successful on a field scale. High recovery of oil in place is projected from the rich-gas miscible flood at Wizard Lake. In projected from the rich-gas miscible flood at Wizard Lake. In spite of a few operational problems, Perry reports good results from the C02 gravity-assisted flood at Weeks Island. Gravity-assisted C02 floods are also planned or underway at Bay St. Elaine, Timbalier Bay, and other locations.
Vertical floods offer the advantage that at low enough displacement rates, gravity forces (which segregate the less dense gas from the more dense oil) can dominate the viscous forces (which can create instability by causing the gas to finger into and through the oil) to give a stable flood front. Stable flood fronts can result in minimal solvent requirement and excellent displacement efficiency. Although many authors have recognized the advantages of vertical miscible gravity-assisted core floods, this is the first mechanistic study of vertical displacements that reports measurements of density and compositional behavior for C02 multiple-contact-miscible processes. The purposes of this work were to determine whether the current stability criteria apply to the C02 process; to provide basic design data for gravity-assisted CO, flooding; and to test the ability or to find methods to simulate the process. This work also contributes to our understanding of the viscous and gravity forces acting in laboratory high-pressure C02/crude-oil core displacements.
|File Size||673 KB||Number of Pages||9|