Key Suspension Materials and Ultra-High Temperature Long-term Stable Oil-Based Drilling and Completion Fluids

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.