两性离子聚合物改性纳米颗粒的抗钙封堵降滤失性能与机理OA北大核心

A high temperature calcium resistant plugging agent ZP-NPs has been developed based on the"anti-polyelectrolyte effect"theory to render water based drilling fluids high temperature stability,high calcium resistance and good plugging capacity.ZP-NPs is obtained by grafting zwitterionic polymer molecules onto the surfaces of nano silica.The microstructure of ZP-NPs was observed using infrared spectrum and electroscope,and the performance of ZP-NPs evaluated through dispersion test,filtration test and plugging test.It was found in these tests that ZP-NPs can stably disperse to nanoparticles/submicron particles for a long time in a high temperature high calcium chloride concentration(160℃,11%CaCl2)solution.A base slurry,after being contaminated by high concentration calcium ions,has a high temperature high pressure(160℃,3.5 MPa)filtration rate that does not exceed 20 mL,and the mud cakes obtained from the test are thin and tough.Fractures of 5 μm in width plugged by a bentonite slurry treated with ZP-NPs can stand pressures up to 5.5 MPa.The calcium resistant performance,plugging capacity and filtration control property of ZP-NPs were revealed through particle size analysis and EDS,and it was found that ZP-NPs has strong"anti-polyelectrolyte"effect;at high calcium concentrations,the particle sizes of ZP-NPs are still in nanometer size range,they can effectively shield the bentonite particles against the adsorption of calcium ions,thus maintaining the dispersion stability and excellent filtration control performance of a bentonite slurry at high calcium concentrations.This study provides a new theoretical and technical guidance for the development of new plugging agents with good calcium resistant capacity.