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Alkaline Surfactant Polymer Flooding |
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The average worldwide oil recovery factor is about 22%. It is proven that this factor could be increased in more than two times. One of the enhanced oil recovery methods is implementation of alkaline-surfactant-polymer (ASP) technology.
The purpose of the alkaline-surfactant-polymer technology is to produce additional oil by reducing the oil saturation that remains trapped in the rock pores after a conventional waterflood.
The fields produced by SPD have insufficient natural energy in the reservoir to achieve good oil recovery and therefore a waterflood is implemented to improve this recovery. Water is injected over a regular pattern of injectors to drive oil towards a pattern of producers, therefore improving the recovery compared to leaving the reservoir produced without any pressure support.
ASP flooding goes a step further to improve the oil recovery. ASP technology combines interfacial tension reducing chemicals (alkali and surfactant) with a mobility control chemical (polymer). The three chemicals are pushed into the reservoir through the water injectors. The interfacial tension reducing chemicals minimise the capillary forces that trap waterflood residual oil in the small rock pores, while the mobility control chemical improves the volumetric sweep of the waterflood and microscopic oil displacement efficiency. The combined effect of the alkali and surfactant is to mobilise previously trapped oil and the polymer helps the subsequent waterflood to displace this new mobile oil out from a larger area than previously contacted by the conventional waterflood.
In practice a large slug of previously immobile oil forms as the ASP flood moves through the rock and once it reaches the producers it is recognised by a reduction in the fraction of water produced by the wells, while gross production remains relatively unchanged.
SPD is funding research work to optimise the ASP chemical cocktail as it depends on composition of the oil, formation water and rock mineralogy. This requires laboratory phase behaviour experiments followed by small scale ASP flooding conducted on rock cored from the subsurface reservoir. This allows the researchers to tune the chemical mixture and make a prediction of potential additional recovery. The next step is to develop a computer simulation, which approximates the phase behaviour and displacement efficiency in the coreflood trials. This simulation is upscaled to reservoir dimensions in order to predict what could happen when ASP is implemented in the field.
SPD is preparing the first of a small scale ASP pilot to be conducted in the West Salym Field. The pilot will help to improve the chemical cocktail and highlight operational and technical issues that may arise if expanded to a larger part of the field. The reservoir simulator is further tuned after the trial so that production and recovery improvement can be predicted to support investment decisions on a field scale.
By estimates, the size of the prize for SPD can be more than 250 mln bbl of additional oil in the next 30 years. |
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INFORMATION |
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Copyright © 2004 Salym Petroleum Development N. V.
// Russia, 31, Novinsky blvd, Moscow,
Tel.: +7 (495) 518-97-20,
Email: info@spdnv.ru |
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