| Serious scaling affected the produced safety in the gathering and transferring system in Jilin oilfield. Scaling of walls created technical problems, including impedance of heat transfer and energy expenditure. The water and scale sample from gathering and transferring system in Jilin oilfield were analyzed by EXD, XRD, SEM and AAS. The EDX results of scale sample showed that there were lots of Ca, O, C elements in scale sample, the XRD results of scale sample showed that scale sample mainly contained Ca CO3, a few fraction of Mg CO3 and(Ca Fe Si2O6). The SEM results of scale sample showed that scale sample had an obvious organics parcel characteristics. The p H values of water samples in gathering and transferring system were between 7.5 and 8.2. Compared to the source water’, the produced water and mineral water’ HCO3- ion content was higher. The Ca2+ ion content was up to 59.12 mg/L, Mg2+ ion content was up to 35.69 mg/L and there was a little Fe2+ ion and K+ ion. There was no CO32- ion.The scaling mechanisms in gathering and transferring system in Jilin oilfield were stated by chemical solubility products and chemical equations. Because the concentration products of carbonates in Jilin oilfield water samples were far greater than their solubility products, carbonates separated crystals out in quantity. The clay from injected water deposited on the surface of wall formed aluminosilicate scale. Corrosion on iron formed little iron scale. A large number of Ca2+ and HCO3- in gathering and transferring system in Jilin oilfield in Ca(HCO3)2 form, which were resolved at high temperature. In the balance process, the solubility of Ca(HCO3)2 was much higher than that of Ca CO3. When temperature increased, CO2 emitted and Ca CO3 precipitation emerged.The p H and temperature performances for Ca2+ and HCO3- ions in source water from 9 team, mineral water from 3 factory, the produced water from 10 team in east zone were studied. When p H value increased from 7.5 to 9, HCO3- ons contents decreased from 17.86 mg/L to 3.28 mg/L. With the increasing of p H value, water samples’ rate of loss of calcium increased and Ca CO3 deposited in quantity. From 15 ℃ to 45 ℃, Ca2+ ions contents decreased. The higher temperature was the faster Ca2+ ions contents decline speed was. At 15 ℃, HCO3- ions contents was essentially unchanged. At 30 ℃, HCO3- ions contents was declined a little. At 45 ℃, HCO3- ions contents was declined fast.To solve the scaling problems of industrial circulating cooling water system, we used maleic anhydride(MA) and acrylic acid(AA) as raw material to synthesize a kind of no phosphorus environment-friendly scale inhibitor-maleic anhydride-acrylic copolymer scale inhibitor in this paper. The reaction time, the reaction temperature, the amount of initiator and the initiator dropping time and other conditions of this synthesis inhibitor were studied by response surface methodology. On the basis of response surface model, optimum reaction time(2.06 h), optimum reaction temperature(80.75 ℃), optimum initiator dosage proportion was(8.24 %), and optimum initiator addition time(1.14 h) was obtained through the quadratic fit regression equation. The scale inhibition rate of this scale inhibitor synthesized under the optimal conditions was 99.03 %. The technical indexes of copolymer scale inhibitor were measured, its viscosity was 2745 m Pa?s, solids content was 39.57 %, and density was 1.6~1.7 g/m L. The corrosion inhibition performance of this scale inhibitor was also measured. When the inhibitor dosage is 60 mg/L, the corrosion inhibition rate was 61.69 %.This paper has studied the applicable conditions of copolymer scale inhibitors, including the dosage of copolymer scale inhibitor, suitable temperature and suitable p H. When the dosage of copolymer scale inhibitor was 60 mg/L, its inhibition rate was 97.89 %. When the temperature at 70 ℃, its inhibition rate was 98.07 %. When p H was 7, its inhibition rate was 97.67 %. At the same time, effect of scale inhibitor of synthesis was evaluated on the water samples of gathering and transferring system in Jilin oilfield, comprehensive inhibiting rate of scale inhibitor of synthesis reached over 90% at the amount between 10 and 40 mg/L.On the basis of analysis of water and scale samples from gathering and transferring system in Jilin oilfield, Ca CO3 scaling tendency of different water samples and mixing water samples were predicted by using Davis-Stiff Saturation Index and Ryznar Saturation Index. Calcium carbonate scale maximum amounts were calculated by using Maximum Stability Index. The results showed that source water did not readily form the scale. When temperature, p H and pressure changed, it showed a scaling tendency. The mineral water and produced water whose SAI were 4.63 to 5.38 showed a dramatically scaling tendency. The maximum amounts were 158.59 to 427.2 mg/L. When source water, mineral water and produced water were mixed, the scaling tendency became obvious and maximum amounts increased twice. |
