An Investigation Into Practical Removal of Downhole Paraffin by Thermal Methods and Chemical Solvents
- T.J. Straub (Amoco Production Co.) | S.W. Autry (U. of Tulsa) | G.E. King (Amoco Production Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Production Operations Symposium, 13-14 March, Oklahoma City, Oklahoma
- Publication Date
- Document Type
- Conference Paper
- 1989. Society of Petroleum Engineers
- 5.4.6 Thermal Methods, 5.2.1 Phase Behavior and PVT Measurements, 3.1.1 Beam and related pumping techniques, 4.2 Pipelines, Flowlines and Risers, 4.3.4 Scale, 2.4.3 Sand/Solids Control, 1.8 Formation Damage, 4.3.3 Aspaltenes, 4.2.3 Materials and Corrosion, 4.1.5 Processing Equipment, 4.1.2 Separation and Treating
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One of the most recurrent problem in the oil-field is the removal of paraffin deposited on down-hole equipment and near-wellbore. Several field experiments were conducted to evaluate the effect of hot oiling for either the removal or redeposition of paraffin downhole. Laboratory work is presented paraffin downhole. Laboratory work is presented that suggests the use of hot solvents has the greatest potential benefit. Means of conventional field application are limited, and nonconventional means are discussed.
The treatment of paraffin waxes within the oil-field is generally directed towards two goals: (1) removal or inhibition of deposits within the formation or on the formation face and (2) the removal or inhibition of paraffin from surface and downhole tubulars and equipment, which impedes the flow of produced fluids. The most common forms of treatment can be divided into three categories: thermal, chemical, or mechanical, with some methods using a combination of these means.
Paraffin Description Paraffin Description Paraffins are composed of carbon and hydrogen atoms with formulas of C18H38 to C70H172. Although usually straight chain, they can also be branched. Paraffin is commonly associated with organics such Paraffin is commonly associated with organics such as oil and asphaltenes and inorganics such as sand, rust, iron sulfide, and scale. The location of the deposit are dependent upon the cloud point (the lowest temperature at which the first paraffin is precipitated), an available surface and/or loss of precipitated), an available surface and/or loss of gas or light ends by a drop in pressure. While the paraffin is in solution, the oil may be Newtonian, paraffin is in solution, the oil may be Newtonian, but as paraffin particles begin to precipitate, the oil may become thixotropic. The composition of paraffin deposits may vary enormously, even in the paraffin deposits may vary enormously, even in the same field. Samples of paraffin from different depths in the same well have different peak carbon chain numbers, indicating a stepwise precipitation.
In addition to properties that relate to the specific paraffin and produced wellstream, the mechanism of paraffin deposition is a function of pressure and temperature. In general, lower pressures pressure and temperature. In general, lower pressures increase the cloud point temperature. The range of cloud point temperatures of many paraffin crudes is such that paraffin may precipitate on the formation face and within the formation during the normal pressure depletion encountered over the well life. The reduction in producing rate may in practice be incorrectly attributed totally to depletion, when in fact, it is largely due to reduction in completion efficiency.
It is the relationship between temperature and paraffin cloud point and solubility that is the paraffin cloud point and solubility that is the basis for one of the most universal methods of removing paraffin deposits from downhole tubulars and piping equipment; hot oiling. In many producing areas, particularly in rod pump systems, it is common practice to periodically treat with heated lease crude (sometimes in conjunction with paraffin treating chemicals) to melt and solubilize paraffin wax deposits. The most common method is to pump the heated crude down the tubing - casing annulus, which transmits heat through the tubing string to melt wax deposits on the tubing wall and rods. The solubilized paraffin is returned to the surface with the rest of the liquid wellstream.
It has previously been postulated that the practice of hot oiling to remove paraffin wax practice of hot oiling to remove paraffin wax deposits on downhole equipment and tubulars could lead to chronic near-wellbore formation damage with the redepositing of waxes removed uphole and those waxes originally contained in the load oil.
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