Laboratory Investigations of CO2 Near-miscible Application in Arbuckle Reservoir

Abstract

Carbon dioxide (CO 2 ) is a proven enhanced oil recovery technology. However, many reservoirs are located at shallow depths or geologic conditions such that CO 2 can not be injected at pressures above the MMP. CO 2 injection is usually not considered as an enhanced oil recovery process in these reservoirs. When CO 2 is injected below the MMP, displacement efficiency decreases as a result of the loss of miscibility. Near miscible displacement has sometimes been referred to as the process occurring between immiscible and miscible pressures, but has never been clearly defined. This paper describes laboratory study of CO 2 near miscible displacement in an Arbuckle reservoir in Kansas.Phase behavior studies between CO 2 and Arbuckle crude oil were carried out to define near miscible conditions at reservoir conditions. Swelling/extraction tests combined with slim-tube experiments were interpreted to identify the mass transfer mechanisms at near miscible condition. A phase behavior model was developed to match PVT data and MMP in the slim-tube experiment. Good agreement was obtained between simulated and observed data from slim-tube experiments. Core flooding tests were conducted to evaluate oil recovery at near miscible condition at which pressure varies from 1350 psi (MMP) to 1150 psi. Recovery of over 50% of the waterflood residual oil saturation was observed when CO 2 was used to displace Arbuckle oil from Berea, Baker dolomite and Arbuckle dolomite cores.At near miscible conditions, extraction appears to be the primary mechanism for mass transfer between hydrocarbon components and CO 2 . However, the reduction of oil viscosity by a factor of five occurred when CO 2 dissolved in the oil. This suggests that some of the additional oil recovery may be attributed to reduction of the mobility ratio between CO 2 and resident oil.

Determination of Minimum Miscibility Pressure of Crude Oil–CO2 System by Oil Swelling/Extraction Test

“…This results in yielding three discrete phases including gaseous CO 2 -rich phase, liquid CO 2 -rich phase and oil phase. [21] Since CO 2 capability to extract hydrocarbon components from the oil phase increases at higher pressures, the volume of the oil shrinks and the oil swelling factor declines.…”

CO2 Near-Miscible Flooding for Tight Oil Exploitation

“…For oil with API greater than 30, the bubble point pressure is related to the solution gas ratio R s as given by the following equation, 20 and the solution gas-oil ratio increases as the bubble point pressure increases: (4) where P b is the bubble point pressure in psi, ␥ gc is the gas specific gravity, R s is the solution gas-oil ratio in scf/STB, T is temperature in°F, and a, b, c and d are constants.…”

“…4,5,6 Laboratory studies and field pilots show that oil recovery can also be high in a near-miscible region. 4,[7][8][9][10][11][12] After water breakthrough in a producer, CO 2 injection can still extract oil even at a very high water cut. 4 Displacements of oil by CO 2 can develop miscibility through extraction of light hydrocarbon components into a CO 2 -rich phase.…”

“…4,[7][8][9][10][11][12] After water breakthrough in a producer, CO 2 injection can still extract oil even at a very high water cut. 4 Displacements of oil by CO 2 can develop miscibility through extraction of light hydrocarbon components into a CO 2 -rich phase. 13 There will be a great change in gas oil relative permeability when interfacial tension drops to 0.04 mN/m by CO 2 miscible flooding.…”

CO2 Minimum Miscible Pressure MMP Estimation using Multiple Linear Regression MLR Technique

“…Carbon dioxide (CO 2 ) can sometimes be used to enhance the displacement of oil from a reservoir (L. H. Bui, 2010). Carbon dioxide flooding is commonly used to recover oil from reservoirs in which the initial pressure has been depleted through primary production and possibly water-flooding (Orr et al, 1982).…”