Bitumen in oil sands is extra heavy crude oil. Bitumen's API gravity is between 8 and 12 and its viscosity is from 100, 000mPa·s to 8, 000, 000mPa·s. Bitumen has no mobility at the original reservoir temperature (10°C). In order to reduce its viscosity, thermal method should be applied to recover the bitumen.
Bitumen-in-place in Alberta of Canada is estimated to be about 1 .7 trillion barrel and bitumen is expected to be an important energy source in the near future.
Steam Assisted Gravity Drainage (SAGD) method is new promising technology for bitumen recovery. Twin horizontal wells are drilled to apply the SAGD method.