Study On Scale Control Technology In Water Injection Development

With the acceleration of oil and natural gas recovery and water flooding going deep, water content in production fluid gets higher and higher. Scaling problems of oilfield wa-ter on normal production becomes more intensive. Based on the fluid analysis data of Jiudong Field, this paper conducted theoretical predictions and experimental researches on the scaling problem. The results indicated that the main scale type was calcium car-bonate, the most sensitive influence factors were mixing ratio, pH value and temperature, CO2content and salinity was less sensitive and pressure had relatively minor effects on scale.Selection experiments on scale inhibitors were conducted based on the scale type of Jiudong Field. The results showed when injection water and formation water was mixed at a ratio of2:8, TH-607B had the best inhibition effect; DTPMP was the best inhibitor with a ratio of4:6between production water and formation water; DTPMP was the also the best inhibitor when the ratio of injection water, production water and formation water was0.4:3.6:6. A conclusion could then be made on scale inhibition evaluation experiments: inhibition efficiency first came up and then declined as the inhibitor concentration in-creased; an increasing of temperature would decrease inhibition efficiency; pressure had relatively minor effects on inhibition; a neutral range of pH would induce the best inhibi-tion efficiency; an increasing of CO2content had a positive but relatively minor effect on inhibition; a5.5g/L salinity had the best inhibition efficiency. Through a comprehensive analysis based on the above results, specific scale inhibitor type and amount were selected to achieve best performance on waterflooding in Jiudong Field.To increase inhibition efficiency, this paper studied inhibition efficiency under dif-ferent ratios of inhibitor compound. The experimental results showed that under the con-dition of1:1ratio and80mg/L concentration, the inhibitor compounds TH-607B/DTPMP and TH-1/DTPMP were better than other compounds. The inhibition efficiency of com-pounds and single inhibitor varied similarly under different influencing factors, but com-pounds had better efficiency than single ones. Considering economic factors and opera-tional feasibilities, Jiudong Field should use inhibitor compounds as much as possible. This paper provided theoretical and experimental justifications for chemical scale inhibi-tion procedures in Jiudong Field.