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Reasons of scale formation in oil field

2016-05-25 23:00:07

        In the production process of oil field, the change of pressure and temperature or the incompatibility of water phase can cause scaling on the surface of formation, wellbore and pipeline, which will affect the production of crude oil. At present, many oil fields in our country have entered the high water cut stage, and the scaling problem has become more and more serious.

        There are two main reasons for scaling in oil field. One is formation water containing high concentrations of easy scaling salt ions, in the production process of pressure, the change of temperature and water content changed original chemical equilibrium and produce scale, mainly the scale composition is calcium carbonate, mixed with magnesium carbonate, calcium sulfate / magnesium, China's onshore oil field scale mostly by this. Two is two or more than two incompatible water mixing, scaling ion interaction and scale formation, the most common are barium sulfate and strontium sulfate scale. In particular, the formation water often contains barium strontium ions, while the seawater contains a large amount of sulfate ions, and both of them are mixed to produce the insoluble barium sulfate scale.
        In addition, oilfield scale reasons but also because some ion binding will form in the water insoluble and soluble and slightly soluble substances, these substances could easily become a accumulation of scale, namely the salt scale. Usually, this kind of scale is composed of carbonate and sulfate, typical of calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate and so on. This scale formation in general will experience a process of nucleation and growth, first a small amount of scale core on the pipe surface formation, adhesion, and more other fouling compounds around these core aggregation, become more large scale group. With water erosion, part of the scale has been obliterated, but other scale continues to generate, may end up blocking the pipes, with the increase of temperature, the insoluble or slightly soluble salt solubility decreased, more and more of the substance separated from water, become scale. In some pipes, when the temperature is higher than 60, there will be a significant scaling trend. The higher the temperature, the more serious the fouling tendency.
        The flow rate of water will obviously affect the trend of scaling. The water flow more relaxed, more stable scale core growth environment, with pipeline transportation medium velocity decreased, scale the probability increased gradually, the flow velocity and the flow direction suddenly change will exacerbate the scaling.


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