Using Repeat Microgravity Measurements to Track Reinjection in Liquid-Dominated Fields

Abstract

The gravitational effect of reinjection will generally depend on the mass of water reinjected and on the conditions of the reservoir near where the water is introduced.
If the reinjected water is introduced directly into a steam zone, and the temperature in the zone is not sufficient to cause significant amounts of boiling to occur, the reinjected water will start to resaturate the zone. Reinjection directly into a two-phase zone (overlying a single-phase deep liquid zone) will produce gravity effects similar to those for reinjection directly into a steam zone except that, with the presence of more liquid already in the pores, less mass will be required to saturate the pores and hence there will be smaller density changes.
If the water is reinjected into a single-phase liquid zone at a relatively shallow depth beneath the two-phase zone then the water displaces some (or all) of the water in the pores near the well upwards, causing the lower part of the two-phase zone near the reinjection well to be resaturated, and thus the deep liquid level to be raised.