Measurement and calculation of polymeric scale inhibitor concentration in water

Abstract

Mineral scale deposition is a well-known problem within the oil and gas industry. Scaling leads to tubing diameter reduction, failure of well equipment, reduction of heater-treaters performance, severe corrosion of tubing and piping internal surface, etc. One of the most widely used methods of scale prevention in oil and gas industry is application of scale inhibitors. A large class of scale inhibitors is presented by reagents with polymers as an active base, the so-called polymeric scale inhibitors. For the successful application of any scale inhibitor, the concentration of applied regents in water phase of an oil production system shall be monitored. However, there is no standard method for analysis of polymeric scale inhibitor concentration in the water phase of oil and gas production systems. Using of energy-dispersive X-ray fluorescence analysis, CHNS-analysis, IR-spectroscopy, pyrolytic chromatography mass spectrometry, low-resolution chromato-mass spectrometry and high performance liquid chromatography, the composition of SCW85370 scale inhibitor (SI) was studied. It was found that scale inhibitor consists of a high molecular sulphated poly acrylic acid. A method for analysis of SCW85370 concentration in water was developed. The lower detection limit of the method does not exceed 3 mg/dm3. Practical results obtained using this method are provided. A formula for calculation of scale inhibitor concentration in formation water produced after scale inhibitor squeeze into formation is proposed. The formula allows the SI concentration to be calculated at any point of time using following data: volume of SI solution squeezed, volume of water squeezed, well water flow rate. It is shown that experimental data is well characterized by the suggested formula.