BP low sality EOR to bring 6% additional oil recovery
BP and its partners ConocoPhillips, Chevron and Shell presented at the British Science Festival in Aberdeen a new technology to significantly improve the enhanced oil recovery (EOR) technology by water injection.
Based on the principle of low salinity water injection, BP deployes this new technology for the first time at large scale in the offshore Clair Ridge enhanced oil recovery project.
BP measured the low salinity effect for the first time in Alaska on the Endicott field in 2008.
In the this northern region, the sea water has naturally a low salinity.
In these natural conditions, a low salinity water was injected by a test well in Endicott oil field and revealed unexpected high rate of oil recovery.
The conventional technique of water injection for the enhanced oil recovery is to create a waterflooding across the reservoir to sweep the oil and gas trapped within the grains of the rock toward the producing wells.
With the depletion of the field, the natural pressure of the reservoir is declining and reduces the effects of the waterflooding.
A reservoir is made of layers and sandstone where the oil and gas is naturally enclosed in the pores of the rock.
These pores contain clays bounding the oil molecules and preventing them to move even under the pressure of the waterflooding.
The low salinity water reduces the ionic concentration of the water and facilitates the oil to flow.
The oil molecules and the clay particles are linked by bridges of divalent cations.
The high ionic concentration of the salty water generates electric forces on the divalent cations bridges compressing the oil molecules against the clay particles.
With less ionic concentration, the low salinity water reduces these forces and facilitates the sweeping effect break these bridges and release the oil molecules to flow out of the pores towards the producing wells.
BP to deploy the low salinity EOR in Clair Rigde
BP and its partners ConocoPhillips, Chevron and Shell made the final investment decisions (FID) for Clair Ridge Development in October 2011.
According to BP’s estimations Clair Ridge to contain 640 million barrels of recoverable reserves.
With this new EOR technology BP expects to reach and extract significant oil reserves stocked further deep in the rocks far below the seabed impossible to remove otherwise.
For this specific application BP has allocated $120 million as part of the Clair Ridge project capital expenditure to desalinate water.
The purpose of this water desalination unit is to produce the low salinity water required for the injection in the reservoir.
On Clair Bridge, the desalination unit will have a capacity of 145,000 b/d of sea water.
So the investment in the desalination unit represents less than 2% of the project costs but will generate more than 6% of additional production.
Clair Ridge is expected to produce 120,000 b/d of crude oil and to start operations in 2016.
After Clair Bridge, BP is planning to use the low salinity EOR technology for the Mad Dog Phase 2 in the Gulf of Mexico.
In Mad Dog Phase 2, the desalination unit will have a capacity of 250,000 barrel per day of sea water treatment.
With 60% of its oil production using conventional sea water injection, BP calculated that the full implementation of the low salinity enhanced oil recovery technology could increase BP’s oil recovery by 700 million barrels of oil equivalent (boe).