The success of drilling operations is heavily dependent on the drilling fluid. Drilling fluids cool down and lubricate the drill bit, remove cuttings, prevent formation damage, suspend cuttings and also cake off the permeable formation, thus retarding the passage of fluid into the formation. Typical micro or macro sized loss circulation materials (LCM) show limited success, especially in formations dominated by micropores, due to their relatively large sizes. In the current work, a new class of nanoparticle (NP) loss circulation materials has been developed. Two different approaches of NP formation and addition to oil-based drilling fluid have been tested. All NPs were prepared in-house either within the oil-based drilling fluid (in-situ), or within an aqueous phase (ex-situ), which was eventually blended with the drilling fluid. Under low pressure low temperature API standard test, more than 70% reduction in fluid loss was achieved in the presence of NPs compared to only 9% reduction in the presence of typical LCMs. The filter cake developed during the NP-based drilling fluid filtration was thin, which implies high potential for reducing the differential pressure sticking problem and formation damage while drilling. Moreover, at the level of NPs added, there was no material impact on drilling fluid viscosity and the fluid maintained its stability for more than 6 weeks.

Nwaoji, C. O. (2012). Wellbore Strengthening-Nano-Particle Drilling Fluid Experimental Design Using Hydraulic Fracture Apparatus (Unpublished master's thesis).

Development of new exploration, drilling and completion technologies in the past two decades have led to the opening of new plays in North America targeting unconventional resources. Lots of innovative drilling fluids have been developed and applied in the drilling and completion engineering. The demands encountered drilling highly deviated wells include the effective control of torque and drag. Therefore one of the applications of the innovative drilling fluids is to lower friction coefficient between drillstring and wellbore, which will reduce the drag and make it possible to drill longer horizontal or extended distances during horizontal or extended reach wells. This paper first briefly introduces the problems from the drag when drilling horizontal or extended reach wells, calculation of torque and drag with analytical models and the shortcomings of those models. Then addresses how the lower friction coefficient from the innovative fluid will bring benefit to the horizontal or extended reach drilling, where finite element method (FEM) is introduced to analyze the interaction between the wellbore and drillstring. Finally three case studies are detailed and results are also analyzed. The three examples are calculating the drag and torque along the entire drillstring, comparing the drag and torque with different friction coefficients with constant torque, buoyancy and downhole weight on bit, and obtaining the increment of horizontal section when using the innovative drilling fluid. The tension or compression force distribution along the entire drillstring is clearly shown through graphs or plotting. The results and analysis with FEM show that the low friction coefficient from the innovative drilling fluid has a great benefit in horizontal or extended reach drilling, increasing the current rig and equipment reach limit substantially. The analysis method presented in this paper can provide a solid base for drilling engineers so that they can accurately estimate the extended reach with this new drilling fluid. It will improve the drilling efficiency and reduce the total cost, especially in unconventional well drilling in that less and longer wells can be used to drain the reservoirs.

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