Effect of six kinds of scale inhibitors on calcium carbonate precipitation in high salinity wastewater at high temperatures

Precipitation of calcium carbonate （CaCOs） scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect of six kinds of commercial scale inhibitors and screened out the best one （scale inhibitor SQ-1211） to investigate its scale inhibition performance in highly saline conditions at high temperature through static scale inhibition tests. The influences of scale inhibitor dosage, temperature, heating time and pH on the inhibition efficiency of the optimal scale inhibitor were investigated. The morphologies and crystal structures of the precipitates were characterized by Scanning Electron Microscopy and X-ray Diffraction analysis. Results showed that the scale inhibition efficiency of the optimal scale inhibitor decreased with the increase of the reaction temperature. When the concentration of Ca^2＋ was 1600 mg/L, the scale inhibition rate could reach 90.7% at 80℃ at pH 8. The optimal scale inhibitor could effectively retard scaling at high temperature. In the presence of the optimal scale inhibitor, the main crystal structure of CaCOs changed from calcite to aragonite.

Corrosion Inhibition of a Green Scale Inhibitor Polyepoxysuccinic Acid

The corrosion inhibition of a green scale inhibitor, polyepoxysuccinic acid (PESA) was studied based on dynamic tests. It is found that when PESA is used alone, it had good corrosion inhibition. So, PESA should be included in the category of corrosion inhibitors. It is not only a kind of green scale inhibitor, but also a green corrosion inhibitor. The synergistic effect between PESA and Zn2+ or sodium gluconate is poor. However, the synergistic effect among PESA, Zn2+ and sodium gluconate is excellent, and the corrosion inhibition efficiency for carbon steel is higher than 99%. Further study of corrosion inhibition mechanism reveals that corrosion inhibition of PESA is not affected by carboxyl group, but by the oxygen atom inserted. The existence of oxygen atom in PESA molecular structure makes it easy to form stable chelate with pentacyclic structure.

The state of the art in scale inhibitor squeeze treatment

The mechanistic understanding of the reactions that govern the inhibitor retention and release,modeling,and the state-ofthe-art innovation in squeeze treatment are reviewed.The retention and release are governed by(1)the amount of calcite that can dissolve prior to inhibitor-induced surface poisoning;(2)calcite surface poisoning after^20 molecular layers of surface coverage by the adsorbed inhibitors to retard further calcite dissolution;(3)less base,CO3^2-,is released into the aqueous solution;(4)formation of the more acidic inhibitor precipitates;(5)phase transformation and maturation of the more acidic inhibitor precipitates;and(6)dissolution of the less soluble crystalline inhibitor precipitates.The trend to advance squeeze technologies is through(1)enhancing scale inhibitor retention,(2)optimizing the delivery of scale inhibitors to the target zone,and(3)improving monitoring methods.Lastly,a prototype yardstick for measuring the squeeze performance is used to compare the squeeze life of 17 actual squeeze treatments.Even though the various squeeze treatments appear to be different.all published squeeze durations can be rated based on the normalized squeeze life per unit mass of inhibitors.

Laboratory investigation of a new scale inhibitor for preventing calcium carbonate precipitation in oil reservoirs and production equipment

The formation of mineral scale is a complex problem during the oilfield operations. Scale inhibitors are widely used to prevent salt precipitation within reservoirs, in downhole equipment, and in production facilities. The scale inhibitors not only must have high effectiveness to prevent scale formation, but also have good adsorption- desorption characteristics, which determine the operation duration of the scale inhibitors. This work is focused on the development of a new scale inhibitor for preventing cal- cium carbonate formation in three different synthetic for- mation waters. Scale inhibition efficiency, optical density of the solution, induction time of calcium carbonate for- mation, corrosion activity, and adsorption-desorption ability were investigated for the developed scale inhibitor. The optimum concentration of hydrochloric acid in the inhibitor was determined by surface tension measurement on the boundary layer between oil and the aqueous scale inhibitor solution. The results show that the optimum mass percentage of 5 % hydrochloric acid solution in the inhi- bitor was in the range of 8 % to 10 %. The new scale inhibitor had high efficiency at a concentration of 30 mg/L. The results indicate that the induction period for calcium carbonate nucleation in the presence of the new inhibitor was about 3.5 times longer than the value in the absence of the inhibitors. During the desorption process at reservoir conditions, the number of pore volumes injected into the carbonate core for the developed inhibitor was significantly greater than the volume of a tested industrial inhibitor, showing better adsorption/desorption capacity.

A dynamic method for experimental assessment of scale inhibitor efficiency in oil recovery process by water flooding

Scale formation due to the mixing of injection water with formation water causes formation damage and reduction in petroleum production.By using scale inhibitors,scale formation/scaling could be prevented.In this work,static experiments were performed with rapid controlled precipitation tests,which were undertaken using three different scale inhibitors namely Falat scale inhibitor,Scahib 760 scale inhibitor and Scahib 780 scale inhibitor.Results show that parameters such as temperature and pH have significant effects on scale inhibitor efficiency.In this study,at pH of 7.8e9 it was found that an increase in pH can lead to a decrease in SI efficiency.In addition,acquired data shows that Falat scale inhibitor is more efficient at 45
C but scale inhibitors(Scahib 760,780)have better efficiencies at 25
C.SEM tests were performed to find structure deformation and morphology of precipitation crystals,which indicated that scale inhibitor can have various effects on crystal's shapes.Finally,dynamic tests were performed with coreflood equipment that indicated higher recovery by using the scale inhibitors.The dynamic tests results show that the recovery factor in the presence of Scahib 760 scale inhibitor is about 58%and breakthrough time is 2099(sec).In the absence of scale inhibitor,the recovery factor is about 52%and breakthrough time is 2720(sec).

The study of a highly efficient and environment-friendly scale inhibitor for calcium carbonate scale in oil fields

A highly efficient and environment-friendly scale inhibitor(MA-VA-VS)was synthesized via free radical solution polymerization method,where maleic anhydride(MA),vinyl acetate(VA)and vinyl sulfonate(VS)acted as monomers,while ammonium persulfate was used as initiator.The inhibition performance and the structure as well as properties was characterized using static jar measurement and dynamic test,Fourier transform infrared spectroscopy and thermogravimetric analysis.The surface morphology and composition of scale formed in the solution were examined using scanning electron microscopy and Xray diffraction,respectively.The binding energies of inhibitor with calcite(104)face were calculated using Materials Studio 2017(MS)at 323 K.The results show that the inhibition efficiency gradually increases with increasing inhibitor concentration.While as the Ca2þconcentration increases,the efficiency first increases and then decreases.With the increase in temperature or pH,the efficiency generally decreases.It is confirmed that the inhibition efficiency can reach 91.4%when 150 mg/L MA-VA-VS is used in a flow condition.Both the calculated binding energy and inhibition performance evaluation results demonstrate that the scale inhibition performance of MA-VA-VS is better than a commercial scale inhibitor(HPMA).The excellent inhibition performance of this inhibitor is due to its chelation and dispersion properties.