Formulation of New Drilling Fluids and Characterization in HPHT

During the well construction process, a properly designed and formulated drilling fluid is vital in order to successfully drill a well. In HPHT wells, both WBM and OBM properties are significantly affected, specially the rheological and physical properties. Alteration in fluid properties may cause; challenges with respect to maintain the annular pressure, higher potential for barite sagging, as well as poor hole cleaning. This thesis presents relevant drilling fluid literature study and basic theory for experimental work and simulation studies. Several different fluid systems, both water-based and oil-based, were formulated and characterized with respect to rheology, viscoelasticity, friction and barite sag. Additionally, performance simulation studies, including torque & drag and hydraulics, were performed with some of the best performing fluid systems. As thermal stability is critical for drilling fluids in order to maintain their physical properties and functions at any given wellbore environment, an optimized lignosulfonates-based flat rheology water-based drilling fluid was formulated. The best thermally stable WBM system was further modified by a MoS2-nanofluid. The application of the nanofluid enhanced the lubricity of the fluid system with a total of 40%, resulting in an 6.12% increase in expected maximum measured drilling depth. In HPHT environments, barite sag is considered one of the most prominent oil-based drilling fluid challenges, as OBMs tend to lose viscosity when heated. In order to avoid this problem, an effort was made to try to identify an anti-sagging agent. The experimental results showed that the application of 0.17 wt% of the polymer poly partial sodium salt increased the sag preventive properties of two different oil-based drilling fluid systems