Complete Paraffin Control in Petroleum Production

Abstract

The wax crystal modifiers are the only chemicals found thus far to solve irreversibly the paraffin control problem from the point of chemical contact down hole (or at the wellhead), through the tubing, through the flowlines and through the surface equipment, storage tanks, and pipelines. Introduction Paraffin control in domestic production costs the Paraffin control in domestic production costs the petroleum industry an estimated $4 1/2 to $5 minion petroleum industry an estimated $4 1/2 to $5 minion annually. These are direct costs that result from the periodic removal of accumulated crude paraffin by periodic removal of accumulated crude paraffin by various mechanical, thermal and chemical means. Not included in this cost estimate are production losses, increased horsepower requirements, damage or increased wear to equipment, and manpower attention. In the early 1930's Reistle reported deposits and accumulations of paraffin as a problem down hole on tubing, rods, and subsurface pumps, and above ground in valves, flowlines, separators, and storage tanks. None of the traditional or new remedies have been effective in resolving even moderately severe paraffin problems. The mechanical approach, which includes cutting, and running pigs and soluble plugs, merely allows the operator to live with the plugs, merely allows the operator to live with the problem a while longer, at best; and at worst, this problem a while longer, at best; and at worst, this approach adds greatly to his tank-bottoms problem. Some modest claims have been made for plastic pipe, but in the final analysis this approach has pipe, but in the final analysis this approach has not solved the paraffin problem. Most of these same considerations apply to the thermal treatmentshot oil, steam, and heaters. Heat alone merely moves the deposit from one location to another, which may or may not provide some advantage; moving the paraffin from inaccessible downhole sites to the paraffin from inaccessible downhole sites to the surface may be an obvious advantage, but it remains a flowline or tank-bottom problem. A far more serious factor is that extremely hot oil sometimes up to 300 degrees F can carry paraffin back into the formation, and the formation temperature generally is not high enough to allow it to go back into solution. Formation damage is the undesirable result. The primary interest has now centered on the chemical approach. Solvents are sometimes adequate if the problem is only minor; but for moderate to severe occurrences of paraffin the quantities of solvent required are usually prohibitive. Some of the best solvents, such as chlorinated hydrocarbons, carbon disulfide, and terpenes, are either frowned on or prohibited because of health hazards and refinery catalyst poisoning. Wetting agents and dispersants constitute the vast majority of "paraffin chemicals" offered and sometimes sold by the many suppliers scattered around the oil patch. In theory, the wetting agents are supposed to work much like plastic pipe: the chemical forms a film on the surface of the pipe: the chemical forms a film on the surface of the pipe to change the contact angle and thus to retard pipe to change the contact angle and thus to retard deposition. A good example is an ethoxylated alkylphenol, which recently enjoyed some commercial success. Without analyzing every product on the market we cannot say how many dispersants are available. For example, the wetting agent just mentioned is marketed as a "dispersant". The theory behind the dispersant approach is that certain chemicals will cause the crude paraffin molecules to repel each other as well as the metal surfaces, and thus the mechanism is more physical than chemical. JPT P. 1151