The StatoilHydro bitumen reserves will be recovered using steam assisted gravity drainage (SAGD), which involves steam injection into horizontal wells drilled into the reserves to reduce viscosity and allow the water/bitumen emulsion to be pumped to the surface for processing.
The design ratio of steam to oil is typically three barrels of steam (water equivalent) for every barrel of bitumen recovered. The water recovered with the bitumen, termed "produced water," will be recycled, and only the water left in the bitumen reservoir, and process purges and losses are lost from the system. Concentrated waste brine, containing 32,000 to 48,000 mg/L total dissolved solids, will be bled from the process to purge the reuse system of concentrating salts which enter the system with the bitumen and the make-up waters. This brine will be pumped into brackish aquifers for disposal. More than 90% of the produced water returned to the surface will be treated and reused.
There are no large surface water sources (lakes or rivers) in the vicinity of the project and surface water is therefore not available for use. The water management strategy for the make-up water for the process is based on groundwater from deep aquifers (more than 300 metres). Based on extensive mapping and exploratory drilling and testing, the only confirmed brackish source is in contact with the recoverable reserves. In order to use this source for make-up and not upset the pressure balance of the resource, an equal amount of water is injected in a separate well system for disposal as is withdrawn for make-up. This concept is termed "push pull". The remainder of the make-up water requirements will have to be produced from a non-saline aquifer.
The water management strategy for the SAGD development is, however, still evolving. Eleven exploratory water wells were drilled and tested in the first quarter of 2008, and this programme identified the majority of the non-saline groundwater make-up resources required for the first two developments. In the coming drilling season, the focus of the work is on exploring and proving brackish water sources to substitute some of the non-saline supply, and to try to find deep saline disposal zones for disposal of the concentrated waste stream. The regulatory agencies are being kept informed about developments and are supportive of the investigations and water strategy development.
In parallel, emerging technology processes to reduce steam requirement have been studied, and one process in particular, "solvent co-injection", shows promise as a way of reducing steam requirements by 10 to 25%.
