Oil Sands

Oil sands are naturally occurring mixtures of sand or clay, water and an extremely dense and viscous form of petroleum called bitumen. They are found in large amounts in many countries throughout the world, but are found in extremely large quantities in Canada and Venezuela. These have recently been considered to be part of the world's oil reserves as higher oil prices and new technology enable them to be profitably extracted and upgraded to usable products.

Oil sand is often referred to as non-conventional oil or crude bitumen, in order to distinguish the bitumen and synthetic oil extracted from oil sands from the free-flowing hydrocarbon mixtures known as crude oil traditionally produced from oil wells. The operation to recover bitumen comprises of three major steps; mining, extraction and upgrading.

If the oil sands are close to the surface extraction is possible by surface mining using shovel and truck operations. After excavation, hot water and caustic soda (NaOH) is added to the sand, and the resulting slurry is piped to the extraction plant. These pipelines can be 10s km in length. Deeper deposits of oil sands are recovered by the use of steam injection techniques which enable the oil sand to flow.

At the extraction plant the slurry is agitated and the bitumen froth is skimmed from the top. The spent sand and other materials are then returned to the mine, which is eventually reclaimed. Further treatment of the bitumen froth removes residual water and fine solids. The purpose of upgrading is to convert the bitumen, a viscous tar like material, into a high quality, low sulphur content crude oil by fluid coking, hydroprocessing, hydrotreating and reblending.

Measurement is a key challenge given the complex, and multi-phase nature, of oil-sands and its derivatives. Process tomography can deliver valuable information for a variety of processes:

• Flow characterisation - the flow characteristics of oil sands is very different to conventional crude oil and the m3000 dual-modality Electrical Resistance Tomography and Electrical Capacitance Tomography offer the potential to visualise the flow patterns of these complex multi-phase systems
• Separation of multiphase components. Electrical tomography has been demonstrated to identify the interfaces during the settling of bitumen emulsion and aliphatic solvents

Benefits

Improved understanding of the flow characteristics of oil sands will aid the development of flow models leading to capital cost savings and when designing lengthy pipelines from the mine to the processing plant and reduced energy costs in their operation.