Research On Chemical Cleaning Technology For Strontium Barium Scale In Oil And Gas Fields

In the process of oilfield development,water flooding is an important means to maintain or restore reservoir pressure,improve reservoir production speed and recovery efficiency.However,in this process,when injected water is incompatible with formation water,scaling ions in water from different sources will precipitate when they reach supersaturation.With the increase of precipitated crystals,the impurities carried in the water,such as gum,asphaltene and sediment,fill in the meantime,inlaid with each other,and gradually form a solid,hard layered scale.Among them,barium sulfate/strontium scale has a very dense structure,low solubility,and is not easily soluble in acids,alkalis and organic solvents.Therefore,the removal of this type of scale has become a major technical problem in the oilfield development process.In this paper,chemical descaling technology is adopted.Firstly,a chelating main agent is selected,and then different auxiliaries are added to improve the descaling ability by utilizing their synergies,synergies and modifications.The main research results are as follows:(1)An efficient barium sulfate/strontium descaling agent was obtained by the combination of single factor and orthogonal experiment.The formula was 10%DTPA+6%salicylic acid+0.2%Tween-80+300 mg/L potassium polyacrylate+10%potassium carbonate.(2)Barium sulfate,strontium sulfate powder and actual scale samples were used to evaluate the formula properties of scale removal agent,and the influencing factors of scale removal effect were studied.The results show that the best descaling effect is achieved when the temperature is 80℃,pH is 12 and descaling time is 24 h.Under these conditions,the descaling rates of barium sulfate,strontium sulfate and actual scale samples are 84.43%,84.02%and 66.12%,respectively.(3)It is found that the addition of sodium chloride and potassium chloride can inhibit the scale removal rate of barium sulfate,strontium sulfate and scale samples to some extent,and the inhibition effect of sodium chloride on scale removal is much stronger than that of potassium chloride.The effect of removing scale can be improved by stirring and reducing the surface area of scale block.(4)Through the evaluation results,it is found that the formula of scale removal agent screened in this paper has the advantages of high scale removal efficiency,good thermal stability,good compatibility with formation water and seawater and low corrosion rate.In addition,it also has some advantages in terms of cost.