Research On Scaling Mechanism And Anti-scaling Measures Of Water Injection Wells In JD Oilfield

Water injection is an important way to maintain formation pressure and improve oil recovery in oilfield development.But in the process of water injection,there are scaling problems water injection wells in different degrees,wellbore scaling will lead to that the decline of effective internal diameter of pipe string,the decrease of fluid transportation efficiency,and increased development cost,which greatly affected the normal production of oilfields.Because of many influence factors of water injection wellbore scaling,and the complex of scaling situation,which is difficult to accurately predict wellbore scaling.Therefore,based on the injection water data of JD oilfield in this paper,by means of combination scaling theory predictions and laboratory experiments,the research is carried out from three aspects:the scaling mechanism of water injection wellbore,the synthesis and performance of scale inhibitor,and the evaluation of scale inhibition effect of water injection wellbore,the mainly obtain cognitions are as follows.(1)The effects of temperature,pressure and pH value on scaling type and quantity of water injection wellbore were clarified through the study of scaling theoretical prediction and experiments.The results indicated that the major water injection wellbore scaling is formed with calcium carbonate in JD oilfield.Temperature and pH value are the main factors affecting the wellbore scaling and the less effect of pressure.(2)For the major scaling types of water injection wellbore in JD oilfield,the synthesis reaction scheme of scale inhibitor was optimized.A scale inhibitor named MASE was developed by maleic anhydride,methyl acrylate and sodium 3-allyloxy-2-hydroxy-l-propane sulfonate as monomers,water as the solvent and ammonium persulfate as initiator,which was applied to the injection wellbore scaling types in JD oilfield.The reaction conditions of scale inhibitor were optimized by single factor and orthogonal experiment methods,the best scale inhibition effect of the scale inhibitor and high scale inhibition rate of 92.52%when m(maleic anhydride):m(methyl acrylate):m(sodium 3-allyloxy-2-hydroxy-l-propane sulfonate)=6:1:0.8,the polymerization temperature is 80?,the reaction time is 3.5h,the amount of initiator is 6%of the total monomer and the initiator dropping time is 50min.Infrared spectroscopy analysis showed that the inhibitor MASE contains carboxyl group,ether group,ester group and sulfonic acid functional groups,etc.,which can be complexed with calcium ion to achieve the goal of scale inhibition.(3)The scale inhibition effect of scale Inhibitors MASE and DTPMPA on C3-4?C3-9 wells under different influencing factors was evaluated.The experimental datas indicated that the scale inhibition rate of the C3-4?C3-9 wells more than 90%when the concentration of scale inhibitor MASE is 80mg/L.With the increase of temperature,the scale inhibition rate increased firstly and then decreased.With the increase of pH value,the scale inhibition rate increased firstly and then decreased,and the scale inhibition effect is the best when the pH value is 7.Pressure has little effect on the scale inhibition effect of scale inhibitors.With increasing salinity,the scale inhibition rate increased firstly and then decreased slowly.Compared with scale inhibitor DTPMPA,the scale inhibitor MASE has the advantages of low dosage,high scale inhibition rate,good thermal stability and high salinity resistance.(4)Based on the above study results,the type of scale inhibitor suitable for JD oilfield water injection wellbores is MASE,and the optimal concentration of scale inhibitor is 80mg/L,which provides scale inhibition scheme for JD oilfield water injection wellbore.