| In the water injection of development process in oilfield, scaling is a common phenomenon, which will be acceletated with the change of the formation pressure, temperature or the water composition. The scale included calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate and so on is always found in underground reservoirs, producing well hole and ground gathering pipeline. Among these scales, the calcium carbonate and calcium sulfate is the most common scale depositions in oilfield production wells and surface facilities. And it can be deposited all along the water paths from injectors through the reservoir to the surface equipment, so this make the anti-scaling technology become more difficult, also the damage which the calcium carbonate causes is bigger. At present, among all the scale inhibition measures, the most common and effective method is using chemical scale inhibitor. Although there are many varieties of scale inhibitor, some problems still exist, because the metal ions contained in the oil field sewage concentration is much higher than metal ion concentration in the circulating cooling water, in view of the specific oil field water scale environment, there is no better solution, especially the scaling water of higher calcium ions concentration and composite scaling water.The purpose of this study is to synthesize a polymer for inhibiting calcium scale which has good inhibition effect and to research its scale inhibition performance, so that make it suitable for the water of relatively high calcium ions concentration(Ca2+>3000mg/L), further more the other better special barium strontium scale inhibitors should be optimized, also the two scale inhibitors are mixed, and hopes that their synergies can improve the scale inhibitor effect for composite scale, so to optimize the suitable formula system for different characteristic oilfield waters.This research synthesized the polyepoxysuccinic acid (ESA), and further synthesized the polymer for inhibiting calcium scale with polyepoxysuccinic acid (ESA) and allyl sulfonate (SAS) as the monomers, and the optimum synthesis conditions of ESA/SAS copolymerization were determined by the orthogonal experiment, so the best reaction conditions were followed as2:1of the monomer ratio(ESA:SAS),4%of initiator(ammonium persulfate),5hours of the reaction time and90℃of the temperature. IR spectra analysis shown that the optimization copolymer under the optimal synthesis parameters was the target product, then it was named as CX-3.The CX-3’s scale inhibition effect was also studied in different water condition, the result found that its scale inhibition rate was88.76%for inhibiting calcium carbonate at the dosage of40mg/L, and was89.95%for calcium sulfate scale, also the result indicated that the effect resisting barium sulfate/strontium sulfate was poorer. At the same dosage of40mg/L, the CX-3’s scale inhibition rate was97.30%for the single calcium scale water (Ca2+:1650mg/L), the effect was better which compared with the other calcium scale inhibitor used commonly (PESA, AA/MA, AA/AMPS).Considering the practice of oilfield, CX-3was used in different oil field water, at the dosage of100mg/L, the scale inhibition performance was better for output water in Shengli oilfield Chunliang C26-08well, the rate for inhibiting calcium magnesium scales and barium strontium scales were96.00%and80.20%respectively, which demanded the scale inhibition rate was greater than80%. However, the effect was poorer for inhibiting barium strontium scale in formation water of Weizhou oilfield, which was located in the west the Nanhai Sea, in view of this, it should be compounded with the other barium strontium scale inhibitor together to increase the inhibition efficiency.In order to choose which scale inhibitor had the best effect for barium sulfate and strontium sulfate scale, the scale inhibition effect of AA/MA/MAC, AD304, TH607B and the other two scale inhibitors (provided with Shanxi Ande and Shangdong Taihe Water Treatment Co., Ltd) were compared in this paper. Comparison found that the CT-3was best for compounding with CX-3. And the compounded scale inhibitor with the mass ratio1:1of CX-3and CT-3had the best scale inhibition effect on calcium magnesium scale and barium strontium scale, the rate were96.00%and80.20%respectively,so it was named as FH-11with the optimal mass ratio. The best dosage of the complex was also obtained which was100mg/L, the effect met use requirement of oil field.The performance for restraining composite scale in the simulated formation water of Weizhou oilfield was also discussed, the results confirmed that the FH-11had a better performance than the single corrosion inhibitors, that further affirmed that the synergies was existed between CX-3and CT-3, in addition, the scale inhibition effect was significantly enhanced with the dosage increasing.Considering the practice of oilfield, the scale inhibition effect of compound scale inhibitor FH-11was studied, that in different oil field water quality (①Weizhou oilfield of the west of South China Sea high carbonate high barium and strontium formation water;②C26-08well of Shengli Chunliang oilfield high carbonate low barium and strontium formation water;③C47-5well of Shengli Chunliang oilfield low carbonate low barium and strontium formation water;④C3-4well of Qinghai Qigequan oilfield low carbonate high barium and strontium formation water), the results shown that the rate of FH-11for resisting calcium magnesium scale and barium strontium scale could all be above80%, so it had good adaptability for the four water, that indicated the FH-11could be available for different water. As well as, the comparison between FH-11and the four industrial scale inhibitor (AD304, TH607B, scale inhibitor of Shanxi and Shangdong Taihe corrosion scale inhibitor) indicated that FH-11had excellent performance. The scale inhibition rate were all above80%, whatever for calcium magnesium scale and barium strontium scale. In spite the effect was not as good as TH607B, it didn’t contain phosphorus and had no pollution to the environment. |
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