Anti-ultra-high Temperature Suspension Stabilizer HPAS for Oil-based Drilling and Completion Fluid and Its Mechanism of Action

Aiming at the problem that the suspension stability of oil-based drilling and completion fluid was difficult to maintain at high temperature above 240℃, based on the principle of enhancing colloidal stability by space grid structure, a strong hydrophobic suspension stabilizer HPAS was developed by using sepiolite fiber and n-octyltriethoxysilane as raw materials and organic modification after hydrochloric acid treatment. The monomer was characterized by infrared spectroscopy, thermogravimetric analysis, particle size analysis and surface wettability, which proved that the modification was successful. A set of high density oil base drilling fluid based on HPAS had good performance after aging at 260℃, its AV and PV were maintained at about 33 mPa·s and 27 mPa·s, the dynamic shear force was maintained above 4 Pa, E_S was higher than 800 V, the FL_HTHP was controlled below 5 mL, and the mud cake thickness was less than 2 mm. Through the settlement stability evaluation, it was found that there was no hard sink at 240℃ for 7 days, and the open tank state was that the glass rod fell freely and touched the bottom easily, which met the requirements of field application. In addition, the system maintained YP above 4.5 Pa in the temperature and pressure range of 65-240℃ and normal pressure −190 MPa, which ensured the good suspension stability and cuttings carrying capacity of the system. It provided technical support for the further application of oil-based drilling and completion fluid in deep wells, ultra-deep wells and 10,000 meters deep wells.