Abstract: In view of problems such as wellbore instability,lost circulation,and reservoir damage in the Linxing-Shenfu Block tight gas reservoirs,which are caused by strong water sensitivity of mud shale,well-developed microfractures,low porosity and low permeability,and poor pore-throat connectivity,the concept of "dual hydrophobic-oleophobic inhibition plus film-forming plugging" was proposed.A weakly crosslinked superamphiphobic polymer inhibitor for drilling fluids and an amphiphilic polymer film-forming plugging agent were developed,and together with a fluid-loss reducer,flow-pattern regulator,and lubricant,a superamphiphobic strong-plugging water-based drilling fluid system was constructed.The results show that this system can effectively regulate the surface electrical properties of bentonite,inhibit clay hydration and dispersion,and enhance the stability of particle aggregation.After aging at 200 ℃,it still exhibits good rheological stability and fluid-loss control capability,with both API fluid loss and high-temperature high-pressure fluid loss below 5.0 mL.It also shows excellent plugging,lubrication,and reservoir-protection performance,with primary and secondary rolling recovery rates of 98.6% and 94.5% respectively,and a permeability recovery rate of 92.5%.Field application demonstrates that,compared with a conventional polymer drilling fluid,the superamphiphobic strong-plugging water-based drilling fluid increases the average rate of penetration by 23.9%,shortens the drilling cycle by 9.6 days,and reduces the average hole enlargement rate by 46.4%,with smooth drilling-fluid operations throughout.This system can effectively solve the problems of wellbore instability,difficulty in plugging microfractures,and reservoir protection in the Linxing-Shenfu Block,and can provide a reference for safe and efficient drilling in similar tight reservoirs.

Key words: superamphiphobic, strong plugging, water-based drilling fluid, tight reservoir, Linxing-Shenfu Block