Catching Thieves in the Oil Sands

Oil sands reservoirs may experience “thief zones” — areas above or below the oil zones that “steal” energy and pressure. During production, if steam goes into those areas, it can reduce reservoir pressure and temperature and inhibit production. Since increased steam injection is then required to maintain pressure, temperature and oil production, thief zones result in increased GHG emissions and decreased production.

A 2017 pilot project in Canada tested the effectiveness of coinjecting a non-condensable gas (NCG), such as methane, with steam to create an insulating blanket that reduces potential thermal and pressure losses in the steam chamber. Initial results have demonstrated a 20–25% reduction in GHG emissions intensity, improved cost competitiveness, and promising economic returns. With a short development lead time, NCG is less expensive than other competing technology options, with similar GHG reduction benefits. We are now extending this NCG coinjection technology to thief zone management.

We plan to collaborate with Emissions Reduction Alberta, a government organization that helps accelerate commercial development by co-funding innovative technology projects, to continue work on 12 additional well pairs at Surmont 2 in 2018. Advanced monitoring equipment (such as 4-D seismic surveys and surveillance wells in the thief zone) will observe and differentiate the complex multi-phase interaction. Additional data will be collected at the wellhead and downhole to monitor temperature, pressure and flow rates. Nearby observation wells will also monitor methane concentration, detect chemical tracers and water quality. Data will be combined to develop a better understanding of the subsurface processes and benefits of the co-injection of NCG.