Extending thermal stability of calcium carbonate pills using sepiolite drilling fluid

The aim is to investigate the plugging ability of sepiolite clay water base drilling fluids over a wide range of high permeable zones at high temperature and high pressure conditions. The special emphasis of this study is to extend the usage of loss preventer material (LPM) as a component of fresh water sepiolite base mud that has never been investigated for this purpose before. The rheology and loss tests at 27−204 °C and 2070 or 6895 kPa revealed that the sepiolite drilling mud shows good rheology and high solid suspension capability at all temperatures except 149 °C, and low loss circulation at high temperature and high pressure. The Permeability Plugging Apparatus (PPA) experiment, in which the 10−90 µm permeable ceramic plate was simulated as formation, showed that the sepiolite drilling mud without CaCO₃ can not plug the pores, while the sepiolite drilling mud with CaCO₃ can plug the pores quickly and keep the CaCO₃ particles suspended even at high temperature (up to 193 °C). The PPA experiment results were proved by the analysis using SEM and ideal packing theory.