Study On Chemical Cleaning Of Barium Sulfate Scale

After entering Water injection development of oil and gas field, due to the change of conditions such as pressure, temperature, the thermodynamic instability and chemical incompatibility of water, Often cause formation, wellbore oil Wells and water injection oil casing, ground equipment and gathering line in scale, bring huge losses to the production. Oil spilling caused by pipeline scaling corrosion perforation, causes irreversible damage to the environment. Because of the inompatibility of injection water(with rich SO42-) and formation water (with rich Ba2+、Sr2+), scaling happened in formation and wells. Formation scaling makes water injection efficiency reduced, energy consumption increased water injection system. Because the increase of pressure and reservoir pressure recovery is slow, resulting in low productivity and liquid production decline. A lot of scale in perforating gun and Diu-gun cause oil wells can not work normally and shutdown overhaul, resulting in serious economic loss.At present, a lot of methods can be used for oilfield descaling, mainly including the mechanical scale cleaning, physical and chemical scale removal. Chemical scale dissolving often used to remove carbonate scale, iron scale, sulfide scale and other commonly scale, and has very good effect. But, when dealing with barium sulfate and strontium sulfate scale, general chemistry reagents exist descaling ability problems such as weak, slow speed of dissolving scale. If you can not quickly and effectively remove the scale, which not only can not solve the base problem of oil field scaling, and anti-drain liquid can also cause damage and threats to the environment. Therefore developing a dissolving scale ability strong, dosage, descaling fast speed scale remover is very necessary. After analyzing the causes and descaling mechanism of fouling, explore the essence of chemical dissolving scale, according to the theory of solubility product undissolved sulfate, complex theory and soluble complexing constant scale dynamic mechanism three aspects as the breakthrough point, to guide the development of NA-2 scale remover, aimed at resolving the low efficiency of sulfate scale descaling and a long time of descaling.EDTA has been choosed as main dissoving reagent of NA-2 because its high chelating ability with Ba2+ and Sr2+, and low molecular weight polyacrylic acid potassium been choosed as auxiliary agent due to its high dispersion. With acrylic acid as monomer, using aqueous solution polymerization to synthesize a series of low molecular weight polyacrylic acid potassium. The synthesis condition was optimized by orthogonal test, obtained the best synthesis process, and the infrared spectrum analysis was carried out on the product Will synthesize a series of potassium polyacrylate and descaling main agent EDTA distribution experiment, optimal concentration of potassium polyacrylate added. To prevent cleaner equipment corrosion of the pipes, screening of different kinds of corrosion inhibitors, and get the optimum inhibitor and its quantity. Examines the dissolving scale temperature, dissolving scale time, pH, salt content, the study of the influence factors, such as iron, get the best solution scale and condition of its descaling, at the same time get a lot of basic experiment data. NA-2 under the condition of temperature 90℃, pH12 has the best effect of descaling, of WeiZhou X oilfield scale in 24 hours dissolution rate is as high as 90.7%, than the domestic existing descaling descaling time required to shorten, descaling rate is greatly increased. Also has carried on the NA-2 compatibility, thermal stability, biological toxicity, environmental damage test and analysis.Through a large number of tests, developed NA-2 scale dissover which with high scale descaling rate, short scale removing time and so on. NA-2 can meet the needs of oil field to remove barium strontium sulfate scale, and its superiorities of good compatibility and thermal stability, the slight equipment corrosion makes the descaling agent is suitable for application in oilfield. It’s large practical significance and value that NA-2 solve the descaling problem, decrease the economic loss, reduce the risk of environmental damage, control the environmental damage before its happened.