Near Miscible CO2

Near Miscible Application in Arbuckle Reservoir

Objective:

  • Determine the feasibility of using CO2 displacement at near miscible
    conditions to improve oil recovery with injection pressure below
    minimum miscibility pressure.
  • Develop appropriate plan for field test if the project shows that
    significant oil can be recovered by the CO2 process operating at near miscible conditions.


Why Near Miscible?

  • Many reservoirs are not considered for CO2 miscible flooding because
    the maximum reservoir pressure that can be attained is less than the
    minimum miscibility pressure (MMP).
  • Near miscible displacement refers to a process occurring at pressure
    slightly below MMP and is between immiscible and miscible.
  • Within the pressure range near miscible, significant oil recovery was
    observed in slim-tube experiments and to a lesser extent in the core tests.
  • Mechanisms in the displacement include extraction, oil swelling, oil
    viscosity reduction and favorable relative permeability as a result of
    reduction of interfacial tension between CO2 and oil.

General Information:

  • Oil Field: Ogallah Unit, Trego County, Kansas
  • Operator: Carmen Schmitt, Inc.
  • Formation: Arbuckle
  • Formation depth: 3950-4060 ft
  • Reservoir temperature: ~110 – 125 °F
  • Reservoir pressure: ~ 1150 psia
  • MMP: 1350- 1650 psig (110 -125 °F)
  • Oil API Gravity: 33.34


Laboratory Tests:

  • Oil characterization
  • Density, viscosity measurement
  • Swelling/Extraction test
  • Slim tube test
  • Core flood experiment


Simulation:

  • Phase behavior model
  • Geological model
  • Compositional reservoir model

Structure Top of Ogallah Unit

Cross Section

Incremental Oil Production at Well 3-2


Summary:

 

  • Properties of Ogallah unit oil produced from an Arbuckle reservoir in
    Kansas were determined at reservoir temperature from a series of phase behavior and slim-tube experiments where CO2 was dissolved in or used to displace the oil. The MMP at 110 ºF was 1350 psig. The MMP increased to 1650 psig when the temperature increased to 125 ºF.
  • At near miscible condition (pressure greater than 1100 psig), the oil
    viscosity was reduced by a factor of five due to the dissolution of carbon dioxide. Formation: Arbuckle
  • Recovery of more than 50% of the waterflood residual oil from Berea,
    Baker dolomite and Arbuckle reservoir rock was obtained when CO2 was
    injected at the current average reservoir pressure of 1150 psig, substantially
    less than the MMP (1350 psig).
  • Significant extraction of oil by CO2 started at pressure of 1150 psig which
    indicated that extraction/vaporization is the primary mechanism for oil
    recovery in the near miscible region from 1100 psig to 1350 psig at 110 ºF.
  • The simulation results indicate that near miscible displacement is
    achievable in lease 3 (E. A. Scott) at current reservoir operation pressure.
  • The incremental oil recovery generally increases with the injection
    pressure. The oil recovery efficiency was increased by 1.3 to 4.8% as a
    result of CO2 injection.