Study On Preparation And Drag Reduction Ability Of Nano Drag Reducing Agent For Oilfield Exploitation

With the continuous decline of conventional oil and gas resources,the development of low-permeability reservoirs has become a top priority for oilfield exploitation.The problems of difficult water injection and high pressure under-injection in such reservoirs are the key issues that need to be solved urgently at present.After nanomaterials have been gradually applied to composite materials,coatings,rubber,and drug carriers in recent years,they are also receiving more and more attention as an emerging trend in oilfield extraction.In this paper,a hydrophobic graft-modified graphene oxide nano drug reducing agent was prepared by adjusting the oxidation conditions of graphene oxide and its dampening ability was investigated.The details of the study are as follows.(1)Graphene oxide was prepared by the modified Hummers method and characterized by FT-IR,XRD,AFM,SEM,BET,XPS,particle size analysis,and wettability analysis.The effects of three factors,namely the amount of potassium permanganate for the first stage of oxidation,the temperature and duration of the second stage of oxidation,on the content of graphene oxide functional groups during the preparation process were also investigated.The final preparation conditions were determined as 3 g of potassium permanganate,the second stage oxidation temperature was 35 °C and the duration was 4 h.The results were also characterized by FT-IR,XRD,XPS,and particle size analysis to draw conclusions.The increase of potassium permanganate dosage leads to the increase of hydroxyl and epoxy groups.The higher the temperature or longer the duration of the second stage of oxidation,the more easily the epoxy group is reduced or broken to hydroxyl group thus leading to its decrease,the hydroxyl group content tends to be stable,and the carboxyl group content is on the rise.(2)Three modifiers were selected to hydrophobically modify graphene oxide to obtain octadecanol-modified graphene oxide(A-M-GO),KH550-modified graphene oxide(550-M-GO)and octadecyltrimethoxysilane modified graphene oxide(O-M-GO),and A-M-GO,550-M-GO and O-M-GO were preferentially selected by FT-IR,XRD and buckling capacity analysis.The most suitable nano drug reducing agent was selected as O-M-GO,which was successfully grafted onto graphene oxide by SEM and BET characterization,and its transformation from hydrophilic to hydrophobic was confirmed from the microscopic perspective.(3)The conditions for O-M-GO to achieve the best drag reduction effect in pressure reduction and injection were investigated.The carbon chain length of the drug reducing agent,the injection volume plug volume,the adsorption time on the core surface,the flow rate of water drive injection,the dispersion concentration of O-M-GO and the dispersion reagent were varied.The results showed that the carbon chain length of trimethoxysilane should reach18 before the nano drug reducing agent can have the effect of drag reduction.When the injection section plug volume was 3 PV,adsorption time was 1 h,water drive flow rate was0.5 m L/min,and dispersion concentration in diesel was 50 mg/L,the pressure of the subsequent water drive was reduced by 14.21%,and the core permeability was 1.166 times of that before the injection of O-M-GO.