Investigation of magnetite-based invert emulsion mud at high pressure high temperature

The weighting agents in drilling fluids are functioned to obtain the required density to control the oil and gas wells throughout the drilling operations. The operational and technical challenges in high-pressure high-temperature (HP/HT) wells necessitate using efficient weighting materials with higher specific gravity. This work introduced and thoroughly investigated the invert emulsion mud weighted using the magnetite (Fe₃O₄) for HP/HT applications. As the barite is commonly used, it was employed in field mud formulation as a base mud for comparison. The particles of both barite and magnetite were firstly characterized to address their mineralogical and textural features. Then laboratory experiments were conducted to study the density, emulsion stability, sag performance, rheology, viscoelastic behavior, and filtration properties for the formulated muds. The acquired results confirmed the ability of magnetite to produce heavier mud with density of 14.9 ppg comparing to 14.5 ppg with barite, which indicates the ability to obtain the required density with less amount of solids content. However, the emulsion stability with magnetite was reduced to 421 V comparing to 900 V in barite mud, which requires further investigation. The static and dynamic sag tests indicated that the magnetite solved the barite incorporated sagging issue with sag tendency within the recommended safe range. Moreover, the magnetite resulted flat rheology, 26% improvement in yield point, and preferable viscoelastic behavior indicating better hole cleaning. The filtration properties of magnetite-based mud were superior comparing to the barite fluid with 29% reduction in filtrate volume and less filter cake’s thickness and weight by 16%. This work contributes to improve and economize the drilling cost and time by formulating stabilized and distinguished performance drilling mud using applicable magnetite weighting agent at HP/HT.