Composition Of Scale Inhibitors Used In High Tempreture And Study Of Inhibition Mechanism

At home and abroad, oil displacement by gas injection which can enhance the oil recovery is the main direction of the tertiary oil recovery. Injecting high pressurized CO2 will increase the danger of corrosion and scaling occurred in the produced water. Chemical methods are widely applied to control scaling because of their perfect anti-scaling efficiency and high pertinence. Considering the produced water quality in the oil displacement by carbon dioxide injection and the operating conditions in Jilin Oilfield,an inhibitor of high temperature was composited, which could also disperse the corrosion products effectively. The mechanism of scale inhibition was explored to supply theoretical and technical support to solve the problem happened in the process of oil displacement by gas injectionBased on the national standard method, the efficiency of 1-hydroxyextylidene-1,1-di- phosphonic Acid (HEDP), Amino trimextylene phosphonic acid(ATMP), hydroxypropyl methacrylate(HPMA), ethylene diaminete tratetramethylene phosphonic sodium (EDTMP), 2-Acrylamide-2-methyl- propanesulfonic acid(AMPS), 2-phosphonobutane-1, 2, 4-tri- carboxylic acid(PBTCA) and phytic acid in the simulated produced water was evaluated by static-method, bubbling method and critical supersaturation ratio method. The anti-scaling efficiency of PBTCA,HEDP and ATMP is proved to be better in the produced water in the oil displacement by carbon dioxide injection. Compared with other dispersants, peregal and eunatrol performed well in the experiment of dispersing ferric oxide and calcium carbonate.The orthogonal experiments of compositing HEDP, PBTCA, ATMP, peregal and eunatrol were done. The result showed that the optical concentration of HEDP, peregal and eunatrol was separately 2mg/L, 1mg/L and 1mg/L, when the composition could achieve high anti-scaling efficiency in low dosage.Scanning electron microscopy was applied to study the inhibition mechanism. The results were as follows:In synthetic water deoxidized by nitrogen, the scaling deposits without scale inhibitors were out of order and plate like, but they are composited by small calcite crystals; the growth of crystals was prohibited by HEDP and in PBTCA solution crystals are spherical and porous.In synthetic water deoxidized by carbon dioxide, the scaling deposits without scale inhibitors were big bulk crystals; the shape of calcium carbonate crystals was changed and the fouling products were loose in PBTCA solution; spherical calcium carbonate crystals were stable in HEDP solution, which hindered the crystals depositing on the metal surface. The mixture of scale inhitors, peregal and eunatrol could prevent the growth of crystals and make the white disk-shaped materials exist steadily, which may be the unstable state of crystals.In addition,the surface free energy of HEDP, PBTCA and ATMP solution was used to explain the reason why the efficiency of the scale inhibitors was good or bad.