Design and Implementation of a Successful Vertical Tertiary Hydrocarbon Miscible Flood

Abstract

Abstract Tertiary hydrocarbon miscible flooding is an important enhanced oil recovery process for revitalizing mature, waterflooded, carbonate reservoirs. Over the last 16 years Husky Oil has developed extensive expertise in successfully applying tertiary vertical gravity-stabilized hydrocarbon miscible floods in the Rainbow Basin, Alberta. The combined incremental oil reserves of four major tertiary miscible floods (Keg River B, F, and South E and G pools) are expected to be 25 ? 106 m3. This paper presents the design, operation, and three-year actual field performance of a vertical tertiary hydrocarbon miscible flood in the northwest lobe of the Rainbow Keg River F pool. Oil production from the northwest lobe has improved significantly, from less than 100 m3/cd during the first few months of miscible flooding to more than 200 m3/cd over the past year. This paper discusses major design factors and a sound corresponding operating strategy that have ultimately resulted in the technical and economical success of the vertical tertiary miscible flood scheme. These factors include:Selection of a minimum operating pressureOptimal solvent compositionSolvent slug sizeCritical frontal advancement rate, andProper placement of solvent slug. Introduction Tertiary hydrocarbon miscible flooding is an important enhanced oil recovery (EOR) process for revitalizing mature, water-flooded, carbonate reservoirs. Husky Oil Operations Limited, over the last 16 years, has developed extensive expertise in successfully applying tertiary vertical gravity-stabilized hydrocarbon miscible floods in the Rainbow Basin in Northwest Alberta. The combined incremental oil reserves of four major tertiary miscible floods (Keg River B, F, and South E and G pools) due to tertiary miscible flooding are expected to be 25 ? 106 m3. Applicability of a tertiary hydrocarbon miscible flood has been evaluated and found to be technically feasible and economically attractive for the Rainbow Keg River (RKR) F pool. The tertiary miscible scheme was proposed to be implemented first in the northwest lobe of RKR F pool, since this region is more geologically and structurally isolated and has the thickest remaining oil bank among the lobes of F pool (Figure 1). Expansion to the restof the pool would be considered when more NGL becomes available. This paper presents the design, operation, and three-year actual field performance of a successful vertical tertiary hydrocarbon miscible flood in the northwest lobe of Rainbow Keg River F pool. FIGURE 1: Rainbow Keg River F Pool structure map. Available In Full Paper. Reservoir Depletion History As was discovered in March 1966, Rainbow Keg River F pool had four separate gas caps and one continuous oil zone. The original gas-oil contacts were all at about 1,310 m sub-sea (mSS), and the oil-water contact (OWC) was at 1,408 mSS, giving an oil zone thickness of 98 m, containing up to 40 E6 m3 of original oil in place (OOIP). The oil had a density of 654 kg/m3, a viscosity of 0.268 cp and was saturated at reservoir conditions of 87 °CDATA[C and 17,457 kPag.