Development and Application of Micro-Nano Organic Plugging Agent for Ultra-Deep Well Drilling Fluids

An ultra-high temperature micro-nano organic plugging agent TSF is developed through a two-step reaction (pre-hydrolysis followed by free radical polymerization) with organic hydrolysable monomers and polymerization monomers such as AMPS, DMAA and BA. Thermogravimetric (TG) analysis shows that the initial thermal decomposition temperature of TSF is 240℃, indicating that TSF has excellent thermal stability. Before and after aging at 220℃, the particle sizes of TSF remain between 342 nm and 825 nm, indicating that TSF has dispersion stability. TSF has a glass transition temperature of 192℃, and can transform from the glassy state to the viscoelastic rubbery state, meaning that it has both plugging capacity through deformation and borehole wall strengthening capacity through adhesion. At 4% TSF treatment, a base drilling fluid, after aging at 220℃ for 16 hours, can have its HTHP filter loss reduced by 43.1%, and have its HTHP filter losses tested on 5 μm and 10 μm ceramic sand discs reduced by 37.1% and 34.5%, respectively. These data show that TSF has excellent filtration control capacity through plugging. At 220℃, TSF produces no H2S, indicating that TSF has good safety performance at ultra-high temperatures. After aging at 220℃, the drilling fluid produced mud cakes whose permeability was reduced by 50.8%. Borehole wall strengthening effect through adhesion of TSF can increase the compressive strengths of core columns by 12.6-17 times, showing that TSF can enhance its ability to plug the fractures in the formations in ultra-deep wells through self-adaptability and to strengthen the borehole wall. These characteristics of TSF have been successfully applied in drilling the ultra-deep well A.