Developing Nanocomposite Gels from Biopolymers for Leakage Control inOil and Gas Wells

摘要

Crosslinked polymer gels have been widely used to overcome water and gas coning problem in thepetroleum industry.Recently,nanoparticles are identified to have a potential of reinforcing the polymer gelsystems by improving physical bonding and heat transfer properties in the gel structure.In this study,silicondioxide and aluminium oxide nanoparticles were introduced to xanthan gum polymers that were crosslinkedby chromium (III) acetate,to create polymeric nanocomposite gels with higher shear strengths.The gelationtime and gel strength have been selected as main parameters to evaluate the effect of nanoparticle types andconcentrations on the nanocomposite gels performance.The gelation time is measured until the onset ofgelation or the moment when apparent viscosity starts to increase at 60°C.The gel strength is represented bythe storage modulus (G') after 24 hours of gelation at 60°C.Both parameters were measured by a rheometer,through constant shear rate and oscillatory tests respectively.The addition of 1000 and 10000 ppm of silicon dioxide (SiO2) nanoparticles into a solution of 6000 ppmxanthan gum polymers that are crosslinked with 50000 ppm chromium (III) acetate caused insignificantchanges in gelation time.Similar result was also reported when 1000 and 10000 ppm of aluminium oxide(Al2O3) nanoparticles was introduced into the polymer system.This suggests that when SiO2 and Al2O3nanoparticles are introduced to xanthan/chromium (III) Acetate system for field application,no additiveswould be required to prolong or shorten gelation time to counter the nanoparticles addition.To analysethe gel strengths,the results from the oscillatory test were averaged throughout the frequency range,andit was shown that the addition of SiO2 nanoparticles decreases the average storage modulus from 75.1 Pawithout nanoparticles,to 72.3 Pa at the nanoparticles concentration of 1000 ppm.However,the averagestorage modulus increased to 83.0 Pa and 94.7 Pa at higher nanoparticles SiO2 concentrations of 5000 ppmand 10000 ppm.The same trend was observed for the nanocomposite gels that were produced by Al2O3nanoparticles.Similarly,the storage modulus decreased initially to 70.8 Pa at the concentration of 1000ppm,then it increased to 89.9 Pa and 109.4 Pa at nanoparticles concentrations of 5000 pm and 10000 ppm,respectively.Hence,the nanoparticle-enhanced biopolymer gels showed insignificant changes of gelationtime,and at the same time,they demonstrated up to 45% improvements in the gel strength properties whenthe nanoparticles concentration is higher than 5000 ppm.In conclusion,the nanocomposite gels demonstrated reinforced bonding properties and showed highergel strengths that can make them good candidates for leakage prevention from gas wells and blocking ofwater encroachments from aquifers into the wells.