Development and Application of Unique Natural Solvents for Treating Paraffin and Asphaltene Related Problems
- S.R. King (AMSOL Corporation) | C.R. Cotney (C.R.C. Consulting)
- Document ID
- Society of Petroleum Engineers
- SPE Mid-Continent Gas Symposium, 28-30 April, Amarillo, Texas
- Publication Date
- Document Type
- Conference Paper
- 1996. Society of Petroleum Engineers
- 1.6 Drilling Operations, 3.2.4 Acidising, 5.2 Reservoir Fluid Dynamics, 4.1.2 Separation and Treating, 4.3.4 Scale, 4.1.5 Processing Equipment, 2.7.1 Completion Fluids, 3 Production and Well Operations, 4.3.3 Aspaltenes, 5.2.1 Phase Behavior and PVT Measurements, 1.8 Formation Damage
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Paraffin and asphaltene related problems including solid deposits, stabilization of emulsions and sludge production continue to plague the oil and gas industry. Condensates and refined aromatic solvents are popular treatments for dissolving and/or, controlling paraffin and asphaltene related problems. These treating fluids are typically used as a quick fix with little regard for, formation damage consequences and long term effectiveness.
Testing, blending and refining of unique condensate feedstocks has resulted in unique natural multi-component hydrocarbon solvents. These unique solvents will dissolve a broad carbon number spectrum of organic deposits and keep them in solution under extreme conditions. These natural solvents maximize solvency, demulsifying properties and natural wettability tendencies without the addition of chemical additives. These natural solvents offer economic alternatives and enhancement to common treatment practices including condensate treatments, hot oiling, chemical treatments, stimulation and production treatments.
Thermodynamic changes during production, storage, transportation and refining of crude oil can adversely affect the chemical equilibrium resulting in physical changes. Localized changes include those resulting from drilling, stimulation and workover procedures. These changes often induce paraffin crystallization and/or asphaltene flocculation and precipitation. Problems occur when these organic solids adhere to the formation or mechanical surfaces reducing production.
Historically, research and development has been directed toward inhibiting paraffin and asphaltene precipitation. Blended solvents, as well as chemicals, are crude oil specific and will not work in all oils. Compatibility with the formation, reservoir fluids and treating fluids must be considered. Little attention has been given to developing multi-component hydrocarbon solvents with high multi- aromatic content. This is due to single component expense and strict regulations governing handling and disposal of single component aromatic solvents.
Typically, the introduction of incompatible fluids, gasses and chemicals into the reservoir is the main cause of damage and the resulting production loss. Almost any chemical or physical change in equilibrium can cause organic deposition and reduce permeability. Although a number of chemical and physical events can change the equilibrium, the most common are categorized as follows: (1) Cold fluids can precipitate paraffins. This occurs when the oil is cooled below the cloud point In some instances there is insufficient formation temperature to dissolve the precipitated paraffin. (2) An acidic shift in pH can cause asphaltene precipitation and sludging. This typically occurs during acid treatments and when CO2 combines with formation water in CO2 floods. (3) Strongly charged chemicals may change natural wettability. As a rule, strongly cationic chemicals tend to oil wet a sandstone and strongly anionic chemicals tend to oil wet a carbonate formation. Exceptions to the rule are dependent on pH. (4) Pressure drops and the resulting shear and temperature drop. (5) The introduction of heated oil to dissolve deposits is known to cause formation damage.
Quite often the formation of deposits, sludge, and formation damage are labeled as a paraffin or asphaltene problem. However, deposits can contain resins, gums, crude oil, water and inorganic matter in addition to paraffin and asphaltenes.
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