Scale Formation In Petroleum Industry

The scale deposition may occur in oil well or reservoir in petroleum industry. The briefly review on scan formation and deposition in petroleum industry have been provided below:

Scale formation in reservoir:

Scale formation is a common issue in oil and gas industry and it usually occurs during water flooding processes. When the injected water is not compatible with the formation water, scale formation would occur. For example, seawaters are usually rich in anions such as sulfate and carbonate while formation waters are usually rich in cations such as barium and calcium. Mixing these waters may lead to mineral scale deposition such as barium sulfate and calcium carbonate. Other types of scaling which have been observed in oil fields include

Scale contributes to equipment wear and corrosion and flow restriction, thus resulting in a decrease in oil and gas production. Scale deposition results from the chemical treatment operations which are applied to maintain sustainable hydrocarbon production at oil, gas or gas condensate fields. Hydrocarbons coming out of a reservoir consist of hundreds of different components (N2, CO2, H2S, C1-C6, C7+, etc.) and may be present in a liquid (C5+) or gaseous form (C1-nC5). In addition water is usually associated to hydrocarbons coming out of reservoir, bringing within itself to the surface various dissolved compounds. The resulting composition of producing fluid will experience drop in pressure or a change in temperature, and some compounds may become more stable at solid state and will start to precipitate (Time, 2011). The precipitation of these solids occurs as a result of changes in the ionic composition, pH, pressure and temperature of the brine. When water flooding method is applied for enhance oil recovery, then the problem of scale may occur right from water injection facilities to the producing well, and generally scale can occur during and after injection operation in the injector wellbore, near the injection well bottom hole, in the reservoir between the injector

2009) and thus should be avoided completely in the oilfield industry. Common oilfield scales can be classified into “pH independent” and “pH sensitive” scales. The scaling tendency of sulphates (calcium sulphate, barite and celestite) and halite scales are not a strong function of brine pH. The carbonates (calcite, dolomite and siderite) and sulphide scales are acid soluble and their scaling tendencies are strongly influenced by the brine pH. The most common oilfield scales are listed in Table 1 (Kelland, 2009; Bin Merdah, 2008). These scales include sulfates such as calcium sulphate (anhydrite, gypsum), barium sulphate (barite), and strontium sulphate (celestite) and calcium carbonate. Other less common scales which have also been reported include iron oxides, iron sulfides and iron carbonate and calcium naphthenate scale from acidic