One of the extensive problems in oil industry is enhancing the process of oil extraction in arduous geological and technological conditions. This is due to the assumption of most of the high-yield oil fields of the country in late stage development and the growing proportion of hard to recover reserves to their total (Guskova et al., 2011). This mechanism of oil extractions becomes significantly convoluted because of high water cut production wellbore and formation of organic and inorganic deposits.
Water factor is a fundamental part in the development and exploration of oil fields. Due to the process of flooding, formation of scale initiates. Scale, formed at the down hole equipment, results in reduction in productivity, costly workover, premature failure of the pumping equipment, thus deteriorating the economic indices of diverse oil and gas firms. Scale is an assemblage of hard, inorganic crystals that cake perforations, casing, production tubing and restricts fluid flow. In USA, productivity of oil wells has been estimated to be declined due to scale formation in production tubing.
High pressure flat fan atomizers can provide a possible solution to the problem of scale formation and has significant advantages over other conventional methods. The overall aim of this research study is to investigate the characteristics of a flat fan nozzle system and critically analyze its effect on scale removal. This study proposes a new technique to address the problem and lay the foundations for a methodology of descaling in oil and gas wells. It furnishes a basic introduction to scale detected in various oil field operations and sources of scale formation. It also provides a synopsis of the schematic design of the apparatus which utilizes high pressure water atomizers with high impact force for scale removal and highlights the results and analysis obtained through calculation of spray impact (theoretical).
Keywords: Descaling, Atomizers, Scale Formation
The fundamental objective of oil industry implicates increasing efficiency during oil extraction. A key step in this direction is associated with dealing with the complications of scale formation in the course of well operation. Scale cake build up are commonly observed in perforations, production tubing, pumps, valves, casing and downhole completion equipment which results in wellbore clogging and restricts flow of fluid. Primary elements of deposits in oil field includes CaCO3 (Calcium Carbonate), CaSO4 (Calcium Sulphate) and BaSO4 (Barium Sulphate). Pure scale is rarely found in deposits in oil wells. It generally comprises of an amalgamation of various inorganic compounds mixed with corrosion products, sand particles, and few are coated with substances like asphalt, resin and paraffin. (Mackay et al., 2003; Moghadasi et al., 2003a).
Scales are commonly formed in three patterns:
• Thin incrustation/Loose flakes
• Stratified form
• Crystal form.
Loose flakes or thin incrustation holds a permeable and loose geometry and hence are easily removed. Gypsum creating layers of crystals and bunching of slivers are classified under stratified form which fills the entire section of pipe (Bayona, 1993; Andersen et al., 2000; Paulo et al., 2001). Barite and Anhydrites forms dense, solid and impermeable crystal structures.
Radioactive salts of Barium found across mineralized produced water in oil fields are highly compact and most hard to out scale. Concentration of this mineralized water ranges from 0.15 gpl to 0.5 gpl. Barium Sulphate (BaSO4) are formed due to existence of lower concentrations of sulphate ions and thus, solubility of these scale is low.
Petroleum industry approximately spends $1,000,000 every year on problems of scale deposition depending on the plant size and it is a major cause for decline in production worldwide (Mackay, 2003). Methods for treating these problems have been limited and lately inefficient. Scale formation must be followed by a competent and productive removal technique. Presently available techniques of scale removal include mechanical and chemical approaches, depending on scale location and physical properties of respective scales.