The “steam chamber” is formed when steam is pumped through the horizontal injection well and proceeds out the perforations in the well’s casing into the oil sands reservoir. The steam heats a growing zone around the injection well, from where the warmed and therefore less viscous bitumen begins to drain downward to the producing well. The more symmetrical this steam chamber forms around a given well pair – known as “steam conformance” – the more efficient will be that well pair’s production and the greater will be the ultimate resource recovery from that section of the reservoir.
The Clearwater Project design includes a greater than normal amount of reservoir monitoring, both within the reservoir and at ground level. This is being done to help achieve efficient low-pressure operations through well-formed steam chambers, and to maximize public safety by providing early warning of any anomalies in the steam’s behaviour.
The monitoring system will include vertical observation wells drilled into the heated portion of the reservoir, as well as an extensive array of 155 tiltmeters that can detect minute movements just below ground level, in real time, that are indicative of what the steam is doing in the reservoir. The tiltmeters will be bolstered by 36 satellite reflectors.
The tiltmeter array is a new approach for the Alberta oil sands. It has been applied successfully to an enhanced oil recovery project in the United States. AOS expects the tiltmeters to be helpful in guiding the operations team in fine-tuning the steam’s operating pressure and formation of the steam chamber.
To provide further subsurface detail, AOS will also consider applying so-called “4D” seismic, which consists of successive 3D seismic surveys over time, as well as instrumentation placed along the horizontal wellbores.
Through this methodology, AOS expects to optimize steam conformance along the horizontal wellbores, gaining high well productivity and resource recovery, and maximizing public safety.