To address the challenge of inadequate structural strength in the spatial framework of oil-based drilling and completion fluids under ultra-high temperatures and extended durations,which leads to poor solid phase carrying and suspension capabilities,two key materials were developed:an amphiphilic multiblock polymer viscosifier(HT-TQ)and an oil-soluble small molecule gelling agent(HT-CB).HT-TQ effectively enhances the yield point and low shear rate viscosity of the base emulsion,while HT-CB significantly improves the static yield point.Sepiolite fibers were selected as suspension enhancers,which,in synergy with HT-TQ and HT-CB,further improve the rheological properties of the emulsion after ultra-high temperature rolling and strengthen the spatial framework structure.Using these three suspension stabilizing materials as the core,optimal additives were selected to construct a highly stable oil-based drilling fluid system suitable for ultra-high temperatures.This system withstands temperatures up to 240℃,maintains a viscosity retention rate greater than 78%after five days of continuous ultra-high temperature rolling,with a yield point greater than 5 Pa and LSYP greater than 3 Pa,and exhibits excellent rheological properties under high temperature and high pressure.Additionally,by using compounded barite as a weighting material,a stable oil-based completion fluid system was developed,which withstands temperatures up to 240℃and remains homogeneous without hard settling after ten days of static exposure to ultra-high temperatures,with a settlement degree less than 1.2 N.These research findings provide technical support for efficient drilling and completion fluids in deep and ultra-deep oil and gas reservoirs.
High temperature resistanceOil-based drilling fluidOil-based completing fluidSuspension stabilitySynergistic effect
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