Development And Application Of Temperature Resistant Cellulose In Environmental Water Based Drilling Fluid

With the continuous increase requirements about environmental protection in gas exploration and development in China,the higher requirements have been put forward for drilling fluids that not only meet the demanding geological conditions for drilling but also have environmental protection performance.Therefore,the paper aimed at the research status about the application of cellulose fluid loss control agents in drilling fluids.Through the graft modification and other means,the original salt-resistant calcium-reducing ability of cellulose fluid loss agents was kept with the temperature resistance ability improved,which met the requirements of environmental protection.The main contents of the paper were as follows:The carboxymethyl cellulose was selected as raw material in this paper.Under the initiation of ceric ammonium nitrate initiator,non-ionic monomer AM,anion monomer AMPS and cationic monomer METAC were grafted,and a new type of modified cellulose fluid loss agent was developed.The optimal synthesis conditions were determined as follows:reaction temperature was 45°C,reaction time was 4h,initiator dosage was 0.3%of the monomer,pH value was 7.0,monomer ratio was AM:AMPS:METAC=2:1:1.The intrinsic viscosity and the viscosity average molecular weight determine that the synthesized product was a macromolecule polymer.The infrared spectroscopy showed that there were three characteristic peaks in the grafted cellulose,and it was proved that the preparation process conditions were correct.According to the basic performance test of modified cellulose in drilling fluids,it was proved that the newly-developed fluid loss additive had good anti-temperature?150°C?,anti-salt?30%NaCl?anti-calcium?1.5%CaCl₂?and strong inhibitory capacity,which were better than the current domestic similar products.Through the analyses of the adsorption capacity test,particle size distribution test,cake permeability and compressibility test,it was showed that the modified cellulose fluid loss additive had the strong adsorption on clay particles and could significantly improve the particle size distribution and mud cake quality in the drilling fluid.The experimental results of Zeta potential and particle size test showed that the Zeta potential and median particle diameter gradually decreased with the increase of the modified cellulose fluid loss additive concentration.When the addition amount was 1%,the Zeta potential value was-48.82 mV,which achieved the purpose to reduce the filtration amount and make the system stabile.The developed modified cellulose fluid loss additive was used as the key additive.Through the optimization of the compatibility with other additives,the environment-friendly water-based drilling fluid system was built.The system had the good temperature resistance and heat resistance?resistance to 150°C and stable at 140°C for 32 hours?,good resistance to salt?20%NaCl?and calcium?2%CaCl₂?good dirty-soil resistance?8%?.It had the good inhibition?the expansion rate is 9.1%and the recovery rate is 93.9%?,lubricity,anti-dirty-soil pollution and environmental performance?BOD5/COD is 31.5%?.