Canadian oil sands in the province of Alberta are a hydrocarbon source for North America. By the year 2015, the oil sands will be producing in excess of 3 million barrels/day of crude oil. A number of companies operate Upgraders that convert the bitumen that is extracted from the oil sands into light sweet crude oil. Steam is required to heat utilities at the Upgrader facility.
In one major oil sands extraction site, well water is being used as feed water for the boilers producing this steam. Reverse Osmosis (RO) systems were designed and installed to produce high quality water required for this application. The pretreatment system was designed with conventional multimedia technology. The RO system required feed water with silt density index (SDI) of 3 or less. Due to ineffectiveness of the conventional pretreatment system, the SDI of the RO feed water was in the range of 12-20. This resulted in severe fouling of the RO membranes and production losses.
In order to optimize the performance of the RO membrane system, a pressurized microfiltration membrane system was delivered and commissioned within 5 days to replace the existing pre-treatment system. The new unit contained an automated PVDF hollow fiber microfiltration membrane system mounted in a trailer. SDI values in the range of 1.0-2.5 were immediately observed in the feed water to the RO system. The end user has enjoyed significant cost savings and ease of operation as a result of this innovative technology. This paper describes the details of the installation and the superior performance data gathered at the end user site.
A. Oil Sands Deposits.
The Oil and Gas Journal has reported nearly 175 billion barrels of reserves from oil sands in Alberta, Canada in 2005, (1) making it one of the largest oil reserves in the world. They are located in three distinct areas in northern Alberta—the largest deposits are along the Athabasca River and there are smaller deposits in Cold Lake and Peace River. Current production of approximately 1 million bbl/day of crude oil from bitumen is predicted to increase to over 3 millon bbl/day by Y2015. With oil prices now in excess of $80/bbl, there are nearly 100 oil sands projects totaling about $100 billion in capital investment. Tax incentives are no longer necessary to encourage oil sands investments.
B. Extraction Methods.
Currently, two-thirds of the bitumen output is produced by strip mining (2) and a quarter by in-situ methods such as Steam Assisted Gravity Drainage (SAGD). But since 80% of the recoverable bitumen is buried too deep for strip mining, the in-situ methods are expected to dominate the scene in the coming years. In the SAGD process, two horizontal wells are drilled into the oil sands, one near the bottom of the formation and another one, typically 5 meters above it. These wells can extend up to a kilometer in all directions. Steam is injected into the upper well. The heat decreases the viscosity of the bitumen, which allows it to flow into the lower well, from where it is produced.