Clean Technology 2011
V. Mostafavi, M.Z. Ferdous, G. Hareland, M. Husein
University of Calgary, CA
nanofluid, drilling, plug, circulation loss, invert emulsion, mechanical strength, resiliency, fluid loss
Nano-fluids have recently attracted attention in the petroleum industry as potential solutions to several shortcomings of conventional drilling fluids. Drilling fluid is in charge of numerous functions during the drilling operation including transport of cuttings to the surface, maintaining the wellbore pressure and stability, lubrication and cooling of the drill bit and isolation of formation fluids by forming a filter cake around the borehole. Most troublesome drilling issues are directly or indirectly triggered by fluid related problems including loss of drilling fluid and wellbore instability. Circulation loss which is defined as the gradual or accidental loss of drilling fluid to formation voids is one of the most well-known drilling problems which may lead to increased costs and time required to reach the drilling target depth, loss of pressure control, increased safety concerns on the rigs, contamination of water beds as well as several other consequences. A large amount of capital and time has been spent on development of new Lost Circulation Materials (LCMs) and technologies to plug the openings in the wellbores with various levels of success. The key to experience a “fluid loss free” drilling operation lies within the ability to build a firm and high strength plug over the fractures and other types of “thief zones” to maintain the fluid level in the borehole. An extensive collaborative research program at the University of Calgary has led to development of a profound understanding of the sealing mechanisms and reliable analytical models based on a wide range of experimental work. The research also aimed at developing a new class of highly specialized nanoparticle based drilling fluids with superior ability to plug the pore throat of the formation and prevent fluid loss while drilling. Application of nano calcium carbonate and nano iron hydroxide were considered in the drilling fluid to fill the gaps between larger particles forming the plug. Nano materials are capable of reducing the permeability and the porosity of the media and increase its yield point and mechanical strength. Filtration and rheology tests performed on nano-fluids unveiled the significant capabilities of nano calcium carbonate to increase the consistency and sealing capabilities of the filter cakes. The behavior of nanoparticles in invert (water/oil) emulsion drilling fluids was investigated. Iron hydroxide nanoparticles were prepared in invert (water/oil) emulsion drilling fluids by reaction with FeCl3 and NaOH at room temperature. The nanoparticles were characterized using analytical tools such as X-ray diffraction and transmission electron microscopy. Presence of iron hydroxide nanoparticles in invert emulsion drilling fluid substantially reduced the fluid loss. A separate series of resiliency and triaxial tests showed the significantly improved mechanical strength of the samples which contained nano particles. The tests also showed a remarkable impact of nanoparticles on the mechanical strength of the filter cakes. This paper shows an optimum composition of the particles can be obtained to maximize the desired capabilities of the nano-fluids while minimizing the costs.