Controls On Soap Scale Formation, Including Naphthenate Soaps - Drivers And Mitigation

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSoap deposits, which can manifest as emulsion soaps (carboxylates) or hard deposits (naphthenates), are an increasingly recognized cause of some unique flow assurance and crude marketing problems in oilfield processes. This paper illustrates the physical and chemical drivers for the generation of soap scales in a number of differing and challenging production system environments. Mitigation options for the successful treatment of soap scales are also discussed. Where possible, data presented in this paper are taken from field trials in order to illustrate these drivers and the impact of successful mitigation strategies.An understanding of the key fluid characteristics allows prescreening of fluids from new field developments that are likely to develop naphthenate/soap deposits and allows diagnosis of the likely soap scaling problems. The critical fluid characteristics required for the generation of naphthenate soaps are different from those required for generation of carboxylate soaps. An empirical approach to predicting the degree of risk for soap generation, based on oil and produced water properties, can be adopted, although there are knowledge and data gaps that increase the uncertainty of this approach.Physical parameters, such as pressure, are known to influence soap generation. However, other physical parameters that are key in the design and operation of an oil-field process can also influence the soap severity. These parameters include temperature, shear, electrostatic fields, water cut and fluidfluid incompatibility; examples of each are discussed. This information can be used in the design stages of an oil-field process where engineers must think beyond the conventional process designs.Despite the fact that the impact of a soap problem can be considerably reduced by adjustment of physical design and operating parameters, chemicals are usually required to provide complete mitigation of soap. Chemical mitigation (acid and non-acid) guidelines are discussed with field examples and the need for a chemical management and monitoring programme.

Characterization of Sodium Emulsion Soaps Formed from Production Fluids of Kutei Basin, Indonesia

“…In practice, in the field, Kutei Basin oils rarely precipitate asphaltenes in production well tubing, unless spiked with condensate streams or if gas lift and/or gas injection in wells is utilized. Generally, asphaltenes can act as emulsion stabilizing agents in the separator fluids. , They can plug oil strainers and heaters/exchangers and will gravity-segregate out in oil storage tanks to form bottom tarry sludges. Although Kutei Basin oils contain significant amounts of linear fatty carboxylic acids (C 20 −C 37 ), often in concentrations of tens to hundreds of ppm of acid, which are part of the soap formation reaction, some also contain minor amounts of ARN acid; i.e., cyclic acids known for creating calcium naphthenate soaps, but not necessarily involved in creating linear acid soaps.…”

“…Among the most challenging and potentially devastating forms of flow assurance problems faced by many oilfield operators today are a class of deposit-forming materials known as soaps. Two main types of soaps can form in production fluids: calcium naphthenate scales, which can manifest as in situ sticky or hardened deposits, and sodium emulsion soaps, which can create severe oil dehydration problems and lead to excessive slop oil/sludge volumes at crude-oil terminals. This paper concentrates on the latter type of soap, the sodium emulsion soap, which is common to fluids produced from the Kutei Basin of East Kalimantan, Indonesia (see Figure ) and forms the main focus of this paper.…”

“…Since 2001, many papers have been published that detail the different types of production processing problems caused by oilfield soaps, and discuss the various methods used for soap mitigation and control. ,− An important area of interest is the source of these soaps, which is thought to be precursor organic acids in crude oils. An understanding of the source rocks that generate oils prone to forming soap emulsions would be beneficial, as would an understanding of how different oils yield different soap types.…”

“…The calcium naphthenate type of soap is usually quite viscous within separators. When subjected to a shutdown of surface equipment, cooling, and exposure to air, calcium naphthenates harden. ,,, Calcium naphthenate scales have been reported in produced oils of the North Sea, West Africa, the NW Shelf in Australia, Bohai Bay in China, and the Gulf of Mexico. , …”

Interfacial Films of Calcium Naphthenate: Influence of Polycardanol Structures

“…This looks like a very simple and efficient solution. However, there is an important drawback: the quantity of acid needed to reach the desired pH can be too large, resulting in severe corrosion and logistic problems. − So, the use of noncorrosive treatments that are able to effectively control the calcium naphthenate deposition has emerged as the best solution. Different authors have proposed the use of molecules with a different structure, and combinations of these, to inhibit calcium naphthenate formation. − Two main action mechanisms have been suggested.…”