Study On The Synthesis Of Sulphate Scale Dissolving Agent And The Scale Dissolving Effect

In the process of oilfield water injection development,scaling is easily caused due to the incompatibility of injected water and formation water and changes in reservoir environment.On the one hand,the deposited inorganic scale can block the pores of the formation and reduce the permeability of the reservoir;on the other hand,it adheres to the wall of the wellbore and the gathering pipeline,which increases the flow hindrance of the crude oil,reduces the oil production rate and shortens the equipment service life.The types of inorganic scales commonly found in oil fields are mainly carbonate scales and sulfate scales.Carbonate scales are easily dissolved in acid and are removed;while sulfate scales are insoluble in strong acids and are extremely difficult to remove.Therefore,it is of practical significance to carry out research on the synthesis of new high-efficiency scale dissolving agent for sulfate scales.Based on the condensation reaction principle,a new high-efficiency scale dissolving agent TTHA was obtained by triggering condensation under NaOH and heating conditions.The results showed that the experimental time was 10 hours,the temperature was 65℃,and the ratio of materials was n(CICH2COONa):n(C6H18N4):n(NaOH)=6:1:6.5.The yield rate is as high as 92.31%.When the concentration is 0.10mol/L and the solution pH=10,the scale-dissolving rate of TTHA to SrSO4,CaSO4,BaSO4 and other scales is 63.67%,67.89%and 60.34%,respectively.In order to improve the scale-dissolving effect,it overcomes the shortcomings that the scale-dissolving effect of the single scale dissolving agent on the sulfate scale is not ideal,this paper also synthesizes a polymer dispersant JTGN by opening and grafting PSI,adding to-S03H and-COOH.By increasing the contact area of the scale dissolving agent with the scale in the solution,which is to achieve the purpose of improving the scale-dissolving effect.When the addition amount is 0.6 mol/L,the suspension rate of the sulfate reaches the maximum value of 69.71%.According to the optimization of the scale dissolving agent formulation,the formulation of HJZB:the Scale-dissolving main agent,TTHA,0.10 mol/L;dispersant,JTGN,0.6 mot/L;the solubilizer formula ZA:n(甲醇钠):n(NaOH)=7:3,the addition amount is 1.2 mol/L;the surfactant formulation KJ:MAPK,0.05 mol/L.Under the optimal scale-dissolving conditions,when the temperature is 80℃,the concentration is 0.5mol/L,and the time is 24h,the dissolution rate is as high as 90.54%.Based on the water analysis data in YC oilfield,the scaling prediction and dynamic scale-dissolving effect analysis were carried out.When the mixing ratio of the injected water to the formation water is 6:4,the amount of sulfate scale is max,and its value is 3648.31 mg/L.Screening experiment of concentration of ale-dissolving HJZB was carried out,under the mixing ratio with the largest amount of sulfate scale.The results show that the damage rate of the scaled core permeability decreased from 45.78%to 3.04%,when HJZB with the concentration of 0.5mol/L is driven.Therefore,the HJZB has a good scale-dissolving effect.