In 1984, Texaco initiated a field test of multizone thermal recovery with dually-completed injection wells. With a single tubing string and packer, a concentric injection arrangement was implemented. Hot water was injected down the tubing into a previously-steamflooded sand, while high-quality steam was injected down the tubing-casing annulus into an overlying active steamflood zone. While both floods have demonstrated favorable production behavior, the heat transfer between the tubing and annulus has had a major impact on the planned injection strategy, with indications that the "hot waterflood" has actually been a low to mid-quality steamflood for most of its project life. Furthermore, regional gravity drainage has unexpectedly been a dominant recovery mechanism in the lower zone, creating regions of distinct production characteristics within the project area.

This paper analyzes the field results from the first 2-1/2 years of the dual injection project and discusses the identified recovery mechanisms in addition to the heat transfer consequences of dual steam/hot water injection.

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