Preparation And Performance Research Of Downhole Control-release Corrosion And Scale Inhibitors

Most of the oil fields in China have been entered the middle and late stage of production,and a large amount of water injection is needed to stabilize the pressure of reservoir.During the crude oil production process,due to the change of pressure,temperature,scaling ions and other factors in the produced fluid,the scale is formed in many location of oil field pipelines and equipment,resulting in the decreasing of the efficiency of oil production and water injection,which generates a lot of economic losses and safety hazards,seriously endangering the normal exploitation of oil fields.In this paper,to predict the scaling tendency of produced liquid,the water quality of the produced fluids from two oil wells was analyzed.The results demonstrated that the oilfield produced fluids had serious scaling tendency.In order to alleviate the problem of corrosion and scaling of the oil field,phosphate glass was used as a control-release material,and other metal oxides were added into reacted and clarified under high temperature conditions to obtain a water treatment agent which could be slowly released in the produced fluid of oilfield and play the role of corrosion and scale inhibition.Referring to the relevant literature,the technical conditions for sample preparation process and formula of the control-release corrosion and scale inhibitor sample were optimized by experiments.On the basis of the phosphate glass composed of40Na₂O·60P₂O₅,an appropriate amount of additives was added to enhance its chemical stability,a programmed heating process was adopted to make the scale inhibitor material melt at 900℃and clarify at 1200℃.Finally,some molded samples of control-release type of anti-corrosion scale inhibitor were prepared.From evaluating results,it was known that the dissolution rate of the sample in deionized water at 50°C was 7.14 mg·cm^-2·d^-1,and the release period was more than 600 days.When the sample concentration in the produced fluid was 25 mg·L^-1,the scale inhibition rate was more than 90%and the corrosion inhibition rate was 50.4%at 50℃.Since the control-release corrosion and scale inhibitor proposed by this work had a certain ability to adapt to the change of environmental factors,such as temperature and p H,it is expected to be used in corrosion and scale inhibition of other water system.Compared with the scale inhibitor currently being used in oil fields,the control-release scale inhibitor which was developed by this work has the advantages of lower cost,better effect,longer release period and automatic dosing,and there is no residue and toxic side effects after the dissolution.The service life and dissolution rate of it could be designed according to the process requirements,and it is not necessary to set up the additional injection equipment for the control-release corrosion and scale inhibitor prepared by this work.All the characteristics of the control-release corrosion and scale inhibitor prepared by this work could reduce the equipment investment and operating cost of targeted oil field.It is expected to be popularized to oilfields.