Nano-materials Application In Drilling Fluid System

Drilling fluids used while drilling unconventional reservoirs draw attention from whole wide world recently.The major concern is the swelling of shales(hole stability).The swelling of shales results in strength loss,wellbore collapse,dispersion of shale cuttings and at times loss of the well.Wellbore instability problems may occur during drilling process when shales are exposed to drilling fluids,which result in high drilling costs.Due to the limited functional ability of conventional additives and the size effect of the materials,conventional water-based drilling fluid systems with macro or micro material-based additives,are not usually successful in solving instability problems.This wellbore instability problem can be best solved by selection of excellent smart drilling fluids.Nanoparticles can physically plug the nano-sized pore throats of shale and prevent water intrusion into them;thus prevent shale swelling.The purpose of this thesis was to develop smart drilling fluids using nano materials.Rheology,pH,filtration and lubrication coefficient tests were carried out to evaluate the smart drilling fluids as a preliminary selection.Two rock samples were tested against the formulated smart fluids with nano materials.The first was man-made gunk squeeze and the second was shale cuttings from rig site in Abu Dhabi.The rocks were characterized by scanning electronic microscope(SEM).All selected smart drilling fluids were tested against gunk squeeze and shale cutting rock samples.Dispersion tests,rock-swelling tests and barite sag tests were performed.After comparing all the test results,the conventional inhibited potassium chloride drilling fluid system with 0.2 gram Nano-silica Aerosil 90 was the best formulation.The use of this formulation resulted in thin,tight,and well textured mud cake.Mud cake thickness was reduced a lot after adding nano materials.Out of the six smart drilling fluids used for the dispersion tests and rock-swelling tests,the best fluid was the one with Nano-silica Aerosil 90.The barite sag tests also indicated the fluid to be good for cutting suspension.No sedimentation was observed after monitoring for three days,which indicated a good cleaning efficiency.The rheology and filtration properties of smart drilling fluid system remained stable under static condition after three days of aging.After necessary tests on rig site,smart drilling fluid system can be applied into practice.