Research And Application Of Controlled-Releasing Solid Inhibitors For Corrosion, Scale And Paraffin In Oil Wells

Paraffin deposition, scaling and corrosion in oil production system are common problems. Paraffin and scale in oil well pipelines can plug the pipes, causing oil and gas production to decline. Corrosion can accelerate devices failure, reducing devices life. All these seriously affect the normal operation of oil wells and bring great damages to production of crude oil. At present, the generally used method of intermittent agent injection in oilfield has many drawbacks, such as heavy workload of dosing, excessive agent, complicated dosing devices, and short period of effective protection etc.Addressing these problems of current dosing method, this paper discusses a new advanced technology of solid paraffin, scale and corrosion inhibition in oil wells. By considering a variety of paraffin inhibitors, scale inhibitors and corrosion inhibitors, implementing a series of indoor experiments of paraffin, scale and corrosion inhibition, employing injection molding technology and cement forming process, two types of trinary solid inhibitors, i.e. oil-soluble ones and water-soluble ones, are developed and studied.By means of 58# paraffin control ratio determination experiments in kerosene, it was obtained that optimum formula of paraffin inhibitor (wt) is 60%EVA,30%LDPE, and 10% CAA. Based on this optimum formula, the compound doses got paraffin control ratio of over 60%. In accordance with this formula, using injection molding technology, we made the oil-soluble solid paraffin inhibitor. Through dissolution rate tests, using period in kerosene could reach 90-120 days. When applied on-site, according to different water content of oil wells, the actual effective duration may increase 1 to 3 times.Taking advantage of porous fumed silica’s adsorption properties, we transformed the liquid paraffin inhibitor, scale inhibitor and corrosion inhibitor into solid powders. Fumed silica adsorption ratios to liquid paraffin inhibitor, scale inhibitor, corrosion inhibitor are 1:4,1:10, and 1:4.Water-soluble trinary solid inhibitors are formed from cement and those inhibitors, and the optimum formula is as follows:60 portions of cement,40 portions of solid inhibitors,35-75 portions of water, whose releasing rate is controlled by adding epoxy resin. The preparation process of cement forming is simple, and we can make individual solid inhibitor or flexiblely mix two or three kinds of inhibitors together, according to actual situations of oil wells.The trinary solid inhibitors are in line with the current direction of oil field chemicals-"one agent with more functions ". They can replace the existing wellhead dosing technology, because of their simple structure, convenience to use, long validity, energy saving, cost-effective and other advantageous features.