Study On Application Of Cellulose Nanofibril In Oil Exploration

Cellulose nanofibril(CNF),as a natural,renewable and nano-sized nano-fiber,has the characteristics of high strength,large specific surface area,high reaction activity,and the CNF hydrogel has good fluid property at ambient temperature.The cellulose nano fibril(CNF)hydrogels prepared by Tempo-oxidation has excellent physical and chemical properties,but the CNF hydrogels show poor colloid stability in high temperature and high salinity environment,therefore,it is of great significance to give CNF the ability of salt resistance and temperature resistance and expanding their application in the drilling engineering.The purpose of this paper is to use CNF as substrate,through salt tolerance and thermal stability modification of CNF and cross-linking salt tolerance monomer with cellulose nanofibril,a novel oil field chemical with salt tolerance and thermal stability was prepared.The salt tolerance and thermal stability of modified or crosslinked cellulose nano fibril hydrogels were characterized,and the potential value of its application in petroleum exploitation was discussed.The main research contents and results are as follows:1.Poor colloid stability of cellulose nano fibril(CNF)hydrogels at high temperature and high salinity can severely limit their industrial applications.Cellulose nano fibril hydrogels with improved salt tolerance and thermal stability was attained by simultaneous grafting of N,N-Dimethylacrylamide(DMA)and Butyl Acrylate(BA)onto the CNF surface based on the ceric ammonium nitrate-induced radical polymerization.The modified and original CNF samples were characterized by FT-IR,FBRM and rheological measurements.The FBRM results showed that the maximum salinity(NaCl)the CNF hydrogels can withstand increased from 1%to 8%after the simultaneous grafting of DMA(2g/L)and BA(3g/L).Moreover,rheological analysis results showed that the modified CNF hydrogels exhibited a much improved long-term thermal stability and a“salt-thickening”effect.2.The poor salt tolerance,thermal stability,and environmental performance of petrochemicals can severely limit their applications in drilling engineering.Cellulose nano fibril-based hydrogels with improved salt tolerance and thermal stability were prepared,and their filtration performance was evaluated.The hydrogels were prepared through the simultaneous grafting of 2-acrylamido-2-methylpropane sulfonic acid(AMPS)and butyl acrylate(BA)onto the CNF surface through ceric ammoniumnitrate-induced radical polymerization.The modified and original CNF samples were characterized using Fourier Transform infrared spectroscopy(FT-IR)and rheological measurements.The FT-IR results showed that both AMPS and BA were grafted orito the CNF backbone,affirming the successful preparation of the grafted CNFs.The rheological analysis results showed that the modified CNF hydrogels exhibited significantly improved salt tolerance,thermal stability,and“salt-thickening”effect.Moreover,the results of the fluid loss test showed that the modified CNF hydrogels exhibited a much better fluid loss control than the original CNF hydrogels.In addition,after adding 2%modified CNF hydrogels as a filtrate reducer in the drilling fluids prepared with a 6%combined salt solution,the filtrate loss was significantly reduced even after aging for 72 h at 160?.3.Ionic-covalent cross-linked poly-2-acrylamido-2-methylpropane sulfonic acid(AMPS)-N,N-Dimethylacrylamide(DMA)-cellulose nanofibril(CNF)-Fe3+(PADC-Fe3+)hydrogels were synthesized by immersing CNF reinforced covalent poly-AMPS-DMA(PAD)composite hydrogels into ferric chloride aqueous solution.To produce PADC-Fe3+polymer with different CNF contents,CNF loadings of 5-20%were explored.The UV-spectroscopy analysis demonstrated the occurrence of CNF coalescence and optimized the 10%CNF loading to produce PADC-0.1-Fe3+with the highest absorbance.Compared to copolymers(PAD or PADC-0.1)prepared without CNF or Fe3+,the synthesized PADC-0.1-Fe3+ showed much better tolerance to salt,telperature,and shear.After adding synthesized PADC-0.1-Fe3+ as a filtrate reducer into the drilling fluids prepared with fresh water and 4%sodium chloride,the filtrate loss was significantly reduced even at an elevated temperature of 200 ?.Additionally,the addition of PADC-0.1-Fe3+ also increased the portion of fine bentonite particles in the drilling fluid.4.The copolymer was first synthesized from 2-acrylamido-2-methylpropane sulfonic acid(AMPS),N,N-dimethylacrylamide(DMA)and 2-Hydroxyethyl acrylate(HEA)by UV-induced polymerization.Subsequently,cellulose nano fibril(CNF)hydrogels were introduced into the copolymer through ironic crosslinking between ferric ions and carboxylate groups as well as sulfonic acid groups to produce a drilling fluid filtrate reducer The salt tolerance and thermal stability of the synthesized copolymers were investigated.Results showed that the optimum HEA dosage was 5%(relate to total mass of AMPS and DMA).In addition,the fluid loss test showed that after the addition of the copolymer PADHC-Fe3+-3,the salt tolerance(maximum tolerance of NaCl is 26.5 wt%,maximum tolerance of combined salts are 32 wt%)and thermal stability(maximum tolerance of temperature is 200?)of the drilling fluid were significantly improved,The SEM images indicated that after the addition of PADHC-Fe3+-3,the filter cake becomes denser.