| As the alkalescent ASP used and developed in Daqing oil field, the scale is becoming one of the major problems to affected oilfield production efficiency. Gathering system is the core of ground facilities, its good condition is the key to guarantee the oilfield production efficiency. Scale on gathering line can make higher fluid resistance, higher energy consumption, and even block the line. So it is significance for the alkalescent ASP flooding to study the law of the scale formation、scale inhibitor and scale eliminator. The main research contents and conclusions are as follows:1. Using ICP and titration techniques analyzed the water from produced liquid and furnace of alkalescent ASP, the average of pH was 8.25, concentrated in7.75~8.75. The ions which are formations of scale were Ca2+, Mg2+, Ba2+ and CO32-. The average concentration of Ca2+, CO32-, HCO3- were 47.95mg/L, 215.95mg/L and 2602.09mg/L respectively. To forecast trend of scaling of water by saturation index(SI) and stability index(SAI) showed that the water quality has obvious trend of scaling. Using XRF, XRD and SEM techniques analyzed the component of scale, more than 50% that was CaCO3, which was calcite.2.To study the influence degree of pH, temperature, concentration of polyacrylamide,salinity and proportion of hot-water by simulative water. The experimental results showed that Ca2+ and Ba2+ were priority to scaling, Mg2+ was not scaling. The concentration of Ca2+ was much higher than Ba2+, so it was representative to study scaling of Ca2+ in weak base ASP flooding. The pH and temperature of system would promote systematic scaling degree. When pH<8.25, the scaling rate was slowly; pH>8.25, the amount of scale increased rapidly, to take scale prevention method was necessary. When temperature was less than 45℃ scaling rate was slowly, the temperature more than 45℃, the scaling rate increased gradually. The temperature of hot-water pipe was about 60℃, some measures should be taken to prevent scaling. pH was greater influence of scaling than the temperature. PAM, petroleum sodium sulfonate and salinity have inhibitory effect on fouling, polyacrylamide was the main factor to inhibited scaling. The hot-water proportion had great influence to temperature and little influence to constituents, high proportion of hot-water would promote systematic scaling.3. The ternary copolymer scale inhibitor MA-AM-SAS was synthesized by maleic anhydride(MA), acrylamide(AM) and sodium allylsulfonate(SAS) as monomers,H2O2-NaH2PO2 was the initiator, and the performance of inhibitor was evaluated. The results showed that the optimum synthesis conditions was that, n(MA): n(AM) : n(SAS) : n(NaH2PO2) = 1:0.5:0.2:0.6, H2O2 was 20% of all monomers mass, the time of dropping of H2O2 was 50 min, reaction temperature was 105℃, reaction time was 3h. MA-AM-SAS antiscale agent made good performance in high temperature, high alkali, when the concentration of Ca2+ was 140mg/L, MA-AM-SAS still had excellent antiscaling performance.When the concentration of anti-scaling agent was used in produced fluid was 40mg/L, the inhibit rate was more than 90%, and MA-AM-SAS had great synergy with demulsifier.4. The cabonate scale eliminator contained 20% of chelating agent DA, 0.2% of penetrating agent AE-2 and 3% of dispersant F-1. The best conditions of descaling was that,temperature was 55℃, concentration of eliminator was 50%, descaling time was above 16 h.Experiments showed that the scale removal rate was above 90%. The corrosion rate of Descaling agent for A3 steel was 0.0042g/(m2·h). |
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