WRRCTR No.108 Well Injection into a Two-Phase Flow Field: A Hele-Shaw Model Investigation

Abstract

A Hele-Shaw model was employed in conducting preliminary studies of waste water injection into a fresh-saline water system. Three different field conditions were simulated: injection under static conditions, injection into an ambient flow field without a fresh-saline water interface, and injection into an ambient flow field with a fresh saline water interface. Both single and double-well injections were studied for the latter case of injection in the presence of an interface. The density of the saline water was 1.026 g/cm^3 for the majority of the tests while that of the injected fluid was 1.0005 g/cm^3. The test results indicate that when injection is below the fresh saline water interface, the injected fluid, under the action of the buoyant forces, rises through a relatively narrow, vertical channel to the interface and then spreads laterally along that surface. The distance the injected fluid migrates upstream from the point of injection increases with the distance below the interface at which injection takes place. Consequently, injection at or above the interface appears to be preferable to injection below the interface from an economic as well as a pollution standpoint. The general behavior of the injected-ambient flow field as observed in the two-dimensional Hele-Shaw model is consistent with that observed in a three-dimensional, sand-filled, hydraulic model.