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Remedial treatment for asphaltene precipitation
Asphaltene precipitation and its subsequent deposition in the wellbore and near-well region are detrimental to oil production. The most effective preventive method is to operate at conditions outside the asphaltene precipitation envelope (APE) (see Asphaltene precipitation). This is not always possible because of the large drawdown in the vicinity of the wellbore, which lowers the reservoir pressure below the onset pressure. For precipitation in the wellbore, mechanical methods, such as rod and wireline scrapers, can be used to remove asphaltene deposits. Although these methods provide good cleaning and minimal formation damage, their application is limited to the wellbore and does not resolve the problem associated with near-wellbore formation plugging.
Solvents
Because the solubility of asphaltene increases with an increase in aromatic contents, solvents such as xylene and toluene commonly are used to dissolve asphaltene deposits in both the wellbore and formation. Stricter regulations governing disposals, volatile-emission limits, and flammability concerns have made the use of xylene and toluene less attractive, and alternate solvents have been investigated.[1] Cosolvents for asphaltene removal also have been studied.[2] Cosolvents are xylene-enriched materials with water-wetting properties that use moderate-length carbon-chain alcohols. Production restoration is comparable to that obtained with xylene, but the treatment lasts longer (average of 6 to 8 months). Polymeric dispersants also have been used as alternatives to aromatic solvents.[3] These dispersants inhibit the deposition of asphaltene by breaking the precipitate into smaller particle sizes, which can remain in suspension in the oil phase. Solubility parameter models have been used to evaluate and screen solvents and inhibitors.[1][3] Jamaluddin et al.[4] performed experiments that showed that deasphaltened oil is a strong solvent for asphaltene because of its native resin and aromatic contents; however, the cost of producing large amounts of deasphaltened oil to be used as solvent is not viable economically.
References
- ↑ 1.0 1.1 Samuelson, M.L. 1992. Alternatives to Aromatics for Solvency of Organic Deposits. Presented at the SPE Formation Damage Control Symposium, Lafayette, Louisiana, USA, 26-27 February. SPE-23816-MS. http://dx.doi.org/10.2118/23816-MS
- ↑ Trbovich, M.G. and King, G.E. 1991. Asphaltene Deposit Removal: Long-Lasting Treatment With a Co-Solvent. Presented at the SPE International Symposium on Oilfield Chemistry, Anaheim, California, USA, 20-22 February. SPE-21038-MS. http://dx.doi.org/10.2118/21038-MS
- ↑ 3.0 3.1 Bouts, M.N., Wiersma, R.J., Muijs, H.M. et al. 1995. An Evaluation of New Aspaltene Inhibitors; Laboratory Study and Field Testing. J Pet Technol 47 (9): 782-787. SPE-28991-PA. http://dx.doi.org/10.2118/28991-PA
- ↑ Jamaluddin, A.K.M., Nazarko, T.W., Sills, S. et al. 1996. Deasphalted Oil: A Natural Asphaltene Solvent. SPE Prod & Fac 11 (3): 161–165. SPE-28994-PA. http://dx.doi.org/10.2118/28994-PA
Noteworthy papers in OnePetro
Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read
1. A Novel Way to Treat Asphaltene Deposition Problems Found in Oil Production Allenson, Stephan J., Nalco/Exxon Energy Chemicals L.P., Walsh, Marjorie A., Nalco/Exxon Energy Chemicals L.P. 37286-MS SPE Conference Paper - 1997
2. Application of Emulsion Viscosity Reducers to Lower Produced Fluid Viscosity Allenson, Stephan John, Nalco Company, Yen, Andrew T., Nalco Company, Lang, Frank, Nalco Company 22443-MS OTC Conference Paper - 2011
External links
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See also
Formation damage from paraffins and asphaltenes