Induced multiphase flow behaviour effects in gas injection EOR projects

Document Type

Article

Publication Date

1-1-2002

Abstract

The recovery of oil by secondary waterfloods and tertiary miscible floods is significantly affected by the native wettability state of the reservoir. In gas injection EOR processes, the initial wettability state of the reservoir could be significantly altered due to mass transfer and phase behaviour interactions between the injected gas and the reservoir crude oil. This, in turn, would influence the water-oil and water-gas flow behaviour by altering their relative permeabilities. Should the reservoir engineer include these dynamic interactions and flow behaviour modifications in designing gas injection projects for optimum economic benefits? We seek to address this question by extending our understanding of the influence of the native wettability state on water-gas relative permeability by experimental measurements and by quantifying the effects of induced wettability and relative permeability changes on gas-flood design parameters. A sequence of coreflood steps was designed to mimic the field practices used in water-alternating-gas (WAG) injection projects. The sequence has been applied to two reservoir rock-fluids systems. Each sequence consists of four cycles of immiscible nitrogen floods in the core assembly at four different stages starting with clean core (unexposed to oil), core containing live-oil at waterflood-residual saturation, core subjected to a miscible flood, and the core after a repeat of the miscible flood. Both the rock-fluids systems studied indicate that the water-gas flow behaviour is modified due to the miscible displacement. These results, combined with the knowledge of our previous work on oil-water flow behaviour modifications, imply the need for a dynamic mode of miscible flood design that would incorporate the in situ rock-fluids interactions. The results of this experimental study and their impact on WAG ratio calculations are presented and discussed in the paper.

Publication Source (Journal or Book title)

Journal of Canadian Petroleum Technology

First Page

53

Last Page

60

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