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The traditional way to mitigate loss circulation in drilling operations is to use preventative and curative materials. However, it is difficult to quantify the amount of materials from every possible combination to produce customized rheological properties. In this study, machine learning (ML) is used to develop a framework to identify material composition for loss circulation applications based on the desired rheological characteristics. The relation between the rheological properties and the mud components for polyacrylamide/polyethyleneimine (PAM/PEI)-based mud is assessed experimentally. Four different ML algorithms were implemented to model the rheological data for various mud components at different concentrations and testing conditions. These four algorithms include (a) k-Nearest Neighbor, (b) Random Forest, (c) Gradient Boosting, and (d) AdaBoosting. The Gradient Boosting model showed the highest accuracy (91 and 74% for plastic and apparent viscosity, respectively), which can be further used for hydraulic calculations. Overall, the experimental study presented in this paper, together with the proposed ML-based framework, adds valuable information to the design of PAM/PEI-based mud. The ML models allowed a wide range of rheology assessments for various drilling fluid formulations with a mean accuracy of up to 91%. The case study has shown that with the appropriate combination of materials, reasonable rheological properties could be achieved to prevent loss circulation by managing the equivalent circulating density (ECD). [ABSTRACT FROM AUTHOR]

Steelmaking is an energy-intensive process that generates considerable amounts of by-products and wastes, which often pose major environmental and economic challenges to the steel-making industry. One of these by-products is steel dust that is produced during the separation of impurities in the smelting and refining of metals in steel-making furnaces. In this study, electric arc furnace (EAF) dust has been evaluated as a potential, low-cost additive to increase the viscosity and weight of drilling muds. Currently, the cost of drilling operations typically accounts for 50 to 80% of the exploration costs and about 30 to 80% of the subsequent field development costs. Utilization of steelmaking waste in drilling fluids formulations is aimed to produce new and optimized water-based drilling formulations, which is expected to reduce the amount of bentonite and other viscosifier additives used in the drilling formulations. The results showed that in a typical water-based drilling fluid of 8.6 ppg (1030.51 kg/m3), the amount of standard drilling grade bentonite could be reduced by 30 wt.% with the addition of the proposed new additive to complete the required mud weight. The mixture proved to be stable with no phase separation. [ABSTRACT FROM AUTHOR]

Cuttings removal out of the wellbore represents a real barrier for successful drilling operations. The performance of hole cleaning is determined by several factors. The current article provides a theoretical study of the impact of three operational parameters on cuttings transport in non-Newtonian drilling fluids. Computational fluid dynamics (CFD) is used to study the effect of drill pipe rotation speed (from 0 to 200 rpm), inclination angle (0–90⁰), and pipe eccentricity (0–0.8) on the cuttings transport ratio (CTR), cuttings volume concentration (CVT), and pressure drop. Response surface methodology (RSM) is employed to explore the two-factor interactions and to optimize the parameters by minimizing the CVT while maximizing the CTR. RSM is also used to generate statistical models to correlate the impact of the aforementioned three factors to the hole cleaning performance (represented by CVT, CTR, and pressure drop). Results revealed that many interactions exist between the tested operational parameters. The drill pipe rotation has the dominant effect on the performance of cuttings transportation, with the effect are more pronounced for highly deviated and horizontal wells. The results indicate that there are only a few cases of inadequate hole cleaning that drill-pipe rotation cannot control, and those cases are associated with the operation in vertical wellbore sections. Less effective cuttings transportation (i.e lower CTR) was observed when the hole angle deviated from the vertical. In addition, a significantly higher CVT (up to 73%) was recorded for eccentric pipes as compared to the concentric cases, primarily due to the reduced fluid velocity in the narrow gap of the eccentric annulus. As far as the pressure drop is concerned, lower pressure loss was obtained at lower rotation speeds and higher angles of inclination from the vertical. As the drill pipe rotational speed increased, the pressure drop decreased slightly until a critical rotatory speed was reached, thereafter, the pressure drop increased markedly. This trend was similar for all pipe eccentricities at any inclination angles, however, the critical rotational speed at which the pressure loss started to increase was found to be dependent on both the inclination angle and eccentricity. Operating at low drill pipe rotation speeds in a concentric annulus is recommended for vertical wells while higher speeds are favorable for more effective cuttings transport in horizontal wells. The CFD simulation results have been validated against experimental measurements for single and multiphase flow for different cases with/without drill pipe rotation at various inclination angles for both Newtonian and Non-Newtonian fluids. • CFD simulations of cuttings transport in the non-Newtonian drilling fluid are conducted. • Eulerain Eulerian multiphase method is used to implent the CFD model. • The Impact of drill pipe rotation, inclination angle, and eccentricity is investigated. • Two faction interactions between parameters are considered by RSM. • Optimization studies are conducted for the vertical and horizontal wellbore sections. [ABSTRACT FROM AUTHOR]

The settling of drilling cuttings is important for the drilling and clean-out operations. The current article provides a Computational Fluid Dynamics (CFD) modeling study of particle settling behavior during the drilling operations, with a special focus on the impact of fluid rheology, flow regime, particle size and shape on the settling rate. The Eulerian-Lagrangian method are adopted to track particle trajectories in a shear-thinning fluid under quiescent conditions. The rheological properties of the drilling fluids are described by different rheological models. Settling of spherical and ellipsoidal cuttings, with various aspect ratios, is studied for particles with a diameter ranging between 2 and 6 mm. The settling behavior is predicted for particles with narrow (0.5–2 mm), medium (0.5–6 mm) and broad (0.5–10 mm) particle size distributions (PSD). Applying a non-Newtonian power-law model at low shear rates, where the fluid is in the Newtonian regime, resulted in 11–19% over-prediction of settling velocities as compared to the experimental data. On the other hand, ignoring the particle-induced shear rate by assuming a Newtonian fluid behavior in the transition regime showed 8–10% difference between the estimated and experimental settling rates. Therefore, the CFD computations of settling rates suggest that Cross and Carreau models provide more accurate predictions than a simple power-law model. The selection of the suitable rheological model is a key factor in predicting settling in drilling fluids. This is more important for small particles where the Newtonian behavior is dominant and particle-induced shear rate is low. Ellipsoidal cuttings exhibited significantly greater resistance to settling as compared to spherical particles, mainly due to the increased drag force. Further, the terminal settling velocity of ellipsoidal cuttings consistently increased with the particle aspect ratio. Cuttings with broad PSD showed ~32 times higher settling velocity than particles with narrow PSD. CFD results are validated with experimental measurements. Moreover, results for settling of non-spherical particles are validated with an empirical correlation. Agreement of experimental and theoretical predictions is observed when the fluid and flow regimes are well identified and described. Image 1 • Settling velocity of particles in Newtonian and non-Newtonian drilling fluids is predicted. • The Eulerian-Lagrangian method has been adopted to track particle trajectories in a shear-thinning fluid. • Simulation results have been validated with published experimental measurements. • The impact of cuttings aspect ratio on their settling behavior is investigated. • Average settling velocity of size distributed cuttings is also studied. [ABSTRACT FROM AUTHOR]

Horizontal wells provide high drainage area within the reservoirs. Advancements in horizontal drilling technologies are utilized to develop unconventional resources such as shale gas and coal bed methane. However, wellbore instability and difficulties in hole cleaning are combined with high-temperature high-pressure conditions in such sensitive formations. Inefficient cuttings removal out of the wellbore results in increasing drag and torque, pipe stuck and may induce lost circulation and consequently increases drilling non-productive time (NPT). Various drilling methods and hole cleaning technologies including downhole tools and complex fluid systems have been implemented to transport cuttings out of horizontal and highly deviated wellbore sections. This review explores the factors that lead to cuttings settling and resuspension in horizontal and deviated sections. Furthermore, it discusses various types of drilling sweeps and additives used with water, oil and gas based drilling fluids to improve the cuttings lifting efficiency in horizontal wells. Bio-based additives and nanomaterials used with unconventional reservoirs are also highlighted. Moreover, different methods used in drill cuttings removal are illustrated. Factors affecting the cuttings removal have also been evaluated and general guidelines for selecting additives and sweep fluids are established. Finally, the main laboratory techniques used to analyse cuttings settling behavior and fluid stability are presented. [ABSTRACT FROM AUTHOR]

The problem of lost circulation is a direct consequence of the presence of fractures or high permeability. Lost circulation material (LCM) is used to treat the loss that occurs or proactively strengthen the wellbore of the potential loss zones. The polyacrylamide (PAM)/Polyethylenimine (PEI) cross-linkable polymer gel is proven to work best in zone-sealing and plugging applications. In addition to their thermal stability, the fact that these gels are flexible gives them the advantage of deforming and sealing-off multiple and complex near wellbore fractures. The primary objective of this study is to investigate the gelation kinetics of the PAM/PEI cross-linkable polymer to be used in drilling fluids formulations to enhance wellbore stability and strength. Different combinations of polymers and crosslinkers were evaluated; potential polymers were screened for gelation kinetics and gel strength in typical drilling mud formulations. The gelation time of the polymer-based drilling mud formulation is determined in salt-free and in saline systems. The results on rheological properties and gelation kinetics were used to prepare a gelling mud formulation using PAM/PEI cross-linkable polymer as LCM. The produced gel was thermally stable under high-temperature-high-pressure reservoir conditions, which will result in enhanced wellbore strengthening. • Investigation of the gelation kinetics of the PAM/PEI cross-linkable polymer in drilling fluids. • Impact of different parameters on the strength of the PAM/PEI LCM gel. • Effect of temperature and retarder on the gelation process. • Investigation of the rheological properties of a polymer-based drilling fluid. • Treating lost circulation with PAM/PEI pill to increase the maximum sealing pressure. [ABSTRACT FROM AUTHOR]