Scale Inhibitors - Chemicals Services
During the production of crude hydrocarbons, water is co-produced with oil and gas; it needs to be separated from the oil and gas to allow the hydrocarbon meet the refinery specifications for export or sale.
As well as being a waste product, the produced water usually tends to precipitate inorganic salts during Production, due to modification of environmental conditions encountered as the fluids are extracted; this occurs due to the physical changes experienced by the water as it is produced into the well, is mixed with other fluids and passed through the separation train. The severity and type of scale(s) that occur depend upon the unique chemistry of the formation water and the physical processes of temperature and pressure change experienced during production and separation of the produced fluids.
The two most prevalent oilfield scales are calcium carbonate and barium sulphate. Most formation brines are saturated with respect to calcium carbonate due to the presence of an excess of the mineral in almost all reservoirs. Barium sulphate is commonly encountered when highly sulphated seawater or surface waters are injected into a reservoir to maintain pressure. Mixing with high barium formation waters can lead to rapid scaling due to the very low solubility of barium sulphate in water.
Unlike remedial treatment of calcium carbonate with acid, barium sulphate dissolver treatments are difficult to perform and seldom successful. Other common scales include strontium sulphate, Iron (II) carbonate and calcium sulphate. Other less common, or "exotic," scales include calcium phosphate, sodium chloride and the sulphides of zinc, iron and lead.
Supersaturation of brine to any particular inorganic salt creates the potential for precipitation, and if precipitation occurs, this scale can lead to problems with the well, either through impairment of reservoir productivity by restricting the fluid pathways in the near-well bore or by restricting fluid flow in the production tubulars and/or separators. In addition to restricted production, safety and operational concerns arise due to scaling of critical monitoring and safety equipment as well as the potential accumulation of low specific activity scales due to 'co-precipitation of radium sulphate.
A number of different approaches to tackling the problem of scale formation are employed in the field, preventative and remedial.
One of the most widely used preventative option is the continuous injection or squeeze treatment of chemical threshold scale inhibitors into the production and/or water injection system.
Scale inhibitors are typically either phosphorous containing molecules or water-soluble polymers. The method of action of scale inhibitors depends on type. It is thought that the phosphorous containing molecules bind to the crystal growth sites preventing further growth, allowing micro fine crystallites to be flushed from the system.
For the polymers, molecular adsorption onto the meta-stable crystallites destabilizes them back into solution and prevents the initial formation of scale. The performance and action of all scale inhibitors depend greatly upon the conditions of application, and it is suggested that scale inhibitors be screened under representative field conditions.
SAPESCO Chemical Solutions - SCS has developed a wide range of specialized Scale inhibitors that allow the treatment of all common scales in a range of production conditions we have assessed the performance of these products under a series of standard conditions to give indicative performance, as well as providing indicative physical property characteristics for these materials.
The product portfolio includes green products made using our patented hybrid technology platform. Accurate residual scale inhibitor detection methods for our scale inhibitor products are available. These methods use either ICP-AES or wet chemistry methods and have detection limits to a few parts per million.
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