This article presents extensive analysis and review on recent developments in smart fluids as well as future opportunities of smart drilling fluids utilization in oil and gas well drilling while focusing on the following smart fluids: smart nanoparticles, electrorheological, magnetorheological, and viscoelastic surfactant (VES) fluids. The distinctive properties of nanoparticles such as tiny particle sizes, high specific surface area, mechanical strength, and thermal stability make them suitable for utilization in drilling fluids. In bentonite water-based drilling fluid systems, this review suggests that charged nanoparticles are capable of displacing exchangeable ions in between bentonite clay platelets, thereby forming intercalates which can interact with clay surfaces through electrostatic attraction or repulsion. In improving wellbore stability, it is presented in this review that nanoparticles are able to invade and plug ultratiny pore spaces in shale formations, thereby further enhancing shale formations’ mechanical strength and wellbore stability. According to this review, the magnitude of changes in properties of smart electrorheological and magnetorheological fluids largely depends on the intensity of applied electric and magnetic fields. The intensity of smart fluids properties alteration due to applied field would equally depend on wt.% concentration and chemical compositions of particles susceptible to electric and magnetic fields. Based on review carried out on VES smart fluids, attractive and repulsive forces in the smart VES fluids solution result in the formation of micelles which can cause changes in viscoelastic property of the formulated smart viscoelastic fluids. The more the concentration of charged ions in the base fluid which VES fluids come in contact with, the higher the viscoelasticity of the smart VES fluids. According to this review, utilization of smart materials in drilling fluids can result in meeting oil and gas well drilling technical challenges including enhancing wellbore stability, improving hole cleaning performance, lost circulation control, fluid loss control, enhancing rate of penetration, pressure drop control, and easing cutting carrying efficiency of drilling fluids. This review equally suggests that the utilization of smart fluids such as smart magnetorheological and electrorheological fluids would facilitate drilling automation and real-time data acquisition processes, which is the future technology in oil and gas drilling.

Summary Asphalt nanoparticles (ANs) were developed by synthesizing asphalt powders with chloroacetic acid (ClCH2COOH). The objective of this synthesis was to develop engineered ANs with a cationic point capable of adsorbing on the net negatively charged clay platelets, thereby improving drilling fluid functionality and pore-plugging performance, reducing shale dispersion, and ultimately enhancing shale stability. Tests carried out to study the performance of the synthesized ANs include particle size analysis, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy, drilling fluid rheology, and filtration rate and shale dispersion tests. FT-IR spectrum results confirming the occurrence of a chemical reaction between asphalt and ClCH2COOH showed a shift in NH vibration from 3,439.95 cm−1 (before synthesis) to 3,435.05 cm−1 (after synthesis). Based on particle size analysis, an average particle size diameter of 92.9 nm was observed, suggesting the tendency of ANs to invade and seal nanopore spaces. The shape of ANs ranged from spherical to irregular, because intercalated structures were observed from the scanning electron microscopic analysis on the interaction between ANs and sodium bentonite (Na-Bent). An increase in attracting force between the Na-Bent particles caused by the adsorption of ANs cationic point on bentonite clay particles led to an increase in drilling fluid rheological properties as the ANs %w/v increased. The drilling fluid filtration rate was, however, not significantly affected by the %w/v increase in ANs because results indicated slight decrease in fluid loss when compared with the base mud (BM). According to the shale dispersion test, the shale cuttings percentage recovery of the 2%w/v ANs sample was 76.5%, owing to the decrease in fluid-rock interaction caused by ionic adsorption and encapsulation of shale surfaces by the ANs. Experimental results from this investigation indicate that the likely mechanisms of the effect of ANs on shale formations would be sealing off nanopore spaces in formations because of its ultratiny particle size; adsorption of the net negatively charged shale cuttings by the ANs cationic point, thereby reducing drilling cuttings dispersion; and improving hole-cleaning performance due to its effect on the drilling fluid rheological properties.

The effect of corrosion inhibitor Benzotriazole on synthetic-based mud system was studied. Rheological performance of the benzotriazole enhanced synthetic-based fluid system was studied and compared against the base mud. To study its effect on dynamic wellbore conditions, different drilling fluid compositions were placed in a hot rolling oven for 16 hours at temperatures 150 °C and 170°C and the effect of temperature on mud properties were studied. Tests carried out include rheological test (before and after hot rolling), filtrate pH, lubricity test, and fluid loss test. The corrosion penetration rate was studied using the weight loss method. Based on experiment results, the synthetic-based mud system which comprised of benzotriazole displayed a reduction in coefficient of friction up to 95.93%. At ambient condition, optimal ratio of mineral oil:benzotriazole (M:B) which gives best lubricity performance on synthetic-based mud system is 80:20. This leads to improved corrosion inhibition and lubricity of the synthetic-based fluid by reducing the coefficient of friction up to 90.13%. Increased temperature led to further decrease in coefficient of friction with a % torque reduction of 95.93 displayed by the 80:20 ratio M:B mud composition at 170 °C. Significant alterations of the mud composition rheological and fluid loss parameters before and after exposure to high temperature in hot rolling oven were not observed. pH values were maintained ≥7 at the dynamic conditions highlighting solubility of the formulated fluid composition and absence of contaminants which can pose significant threats to the rates of corrosion in drill pipes. Increasing the concentration of Benzotriazole led to a reduction in corrosion rate. However, as the temperature effect increased, the corrosion rate elevated. Based on results from this investigation, it was concluded that Benzotriazole can be applied as a corrosion inhibitor in a synthetic-based drilling fluid system as an alternative corrosion inhibitor without significant alteration of the base mud properties. Benefits of this will be the optimization of extended reach well drilling operations due to excellent lubricity performance, corrosion rate reduction, compatibility with HPHT wellbore condition and fluid loss control.