Steamdrive Direct Contact Steam Generation for SAGD

Abstract In recent years there has been a shift in the Steam Assisted Gravity Drainage (SAGD) steam generation technologies from the traditional Once Through Steam Generator (OTSG) and lime based water softening towards the use of an evaporator and industrial High Pressure (HP) steam boilers. As a result, the available steam temperature and pressure exceeds the steam temperature that is required for injection into the underground formation. This excess steam enthalpy is the driver behind the steam generation method to be proposed. The method described is a revolutionary process for generating additional steam from highly contaminated oily water with an option for zero liquid waste discharge. The industrial boiler superheated steam is used as the driving force for generating additional steam in a direct contact heat transfer with the contaminated water. Fine Tailings from tailing ponds can be also used. The presented technology generates a "tailor made" pressure and temperature steam, as required for injection into the underground oil bearing formation. This newly developed technology allows generation of additional lower temperature steam from waste water in a high efficiency energy process. The simulation results show that an additional 8% – 24% steam (on a mass basis) can be generated from highly contaminated oily water. The amount of additional steam generated increases with the temperature of the driving steam, and with the reduction of the pressure of the formation. For low pressure shallow formations, additional steam can be produced in comparison to deep, high pressure formations. Another option is to recycle a portion of the produced steam through a heater and use it as the driving steam, and by that minimizing the need for external steam as a heat energy source. A portion of the oil component in the water feed will be converted into hydrocarbon gas that is expected to show similar behavior to a solvent. Additional solvents can be added and injected with the steam to improve the oil recovery. The presented technology has a high thermal efficiency capable of consuming contaminated hot produced water, without the need to reduce their heat to allow effective water treatment. The technology "fits" in the gap between the HP superheated steam and the injection steam while allowing the producers to maximize the advantages and benefits from the use of evaporators and steam boilers for SAGD oil production and can convert the existence of oil contaminate within the feed water into an advantage by replacing the solvent. This steam generation direct contact facility can be located in close proximity to the SAGD pads to use the hot produced water and inject the produced steam into the injection wells.