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Copyright of Journal of Engineering Research is the property of Sultan Qaboos University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Drilling in high-temperature wells may worsen the flocculation of water-based bentonite suspension (BN-WBM), particularly when common drilling fluid contaminants like calcium cation (Ca2+) and sodium cation (Na+) are present. High concentrations of these cations can adversely affect drilling fluid rheology, filtration, and density. This can result in poor well control, pipe entrapment, poor hole cleaning, and prolonged inactivity, making drilling unprofitable. Therefore, this study examined how well CaCl2 and NaCl work with Nano-HAp to control the viscosity and filtration of BN-WBM at 25, 120, 150, 180, and 210 °C. The salt cation's (Ca2+/Na+) adverse effects on BN-WBMs and Nano-HAp's salt-tolerant activities were also shown. Adding 0.5 wt% Nano-HAp reduced the BN-salt-contaminated mud viscosity, shear stress, and fluid loss at all temperatures (25–210 °C). Salt screening demonstrated that Nano-HAp adsorbed onto the BN platelets' positive edge and negative face surfaces and protected the BN ion-sensitive regions. This prevented Ca2+ and Na+ from damaging the plate-like structure of the BN. When Nano-HAp is added to BN-CaCl2-contaminated WBM at 210 °C, the amount of fluid lost drops by 59%, from 192 to 79 mL, and the viscosity drops from 26.23 to 10.67 mPa s. In BN-NaCl-contaminated WBM, Nano-HAp reduced the viscosity from 20.82 to 8.91 mPa s and fluid loss from 169 to 73 mL by 57%. This study demonstrated that the drilling fluids performed efficiently with 0.5 wt% Nano-HAp. This study also reveals that Nano-HAp increases BN-WBM's salt and temperature resistance and efficiency in high-salinity, high-temperature settings. [ABSTRACT FROM AUTHOR]

[Display omitted] • An n-HAp additive for drilling fluid was developed and compared with some selected NPs. • Sandstone particles of 0.80–3.60 mm diameters were simulated using a customized field-oriented flow loop. • n-HAp outperformed CuO-NP, MgO-NP, Al 2 O 3 -NP, and SiO 2 -based drilling muds in cutting removal. • n-HAp increased the CTR by 28–38.6%, while the NPs caused a 2.8–23.5% increase. • Eccentric pipe at 55°-inclinations resulted in the lowest CTR compared to other hole angles. According to oilfield drilling records, improper transport of rock cuttings caused by eccentricity has led to some serious problems, such as mechanical pipe sticking, high fluid loss, and borehole expansion, which have reduced the total economic advantages associated with the well. These problems are common in directional drilling due to the substantial reduction of annular flow velocity from the narrow annulus, necessitating the need for high-functional drilling fluid components like nanoparticles (NPs). This study evaluated the performance of hydroxyapatite nanoparticles treated with sodium dodecyl sulphate (n-HAp) on the cuttings lifting ratio (CTR) of water-based mud (WBM). The rheological and filtration properties as well as the CTR performance of the designed n-HAp were compared with those of cupric oxide (CuO), nanosilica (SiO 2), alumina (Al 2 O 3), and magnesium oxide (MgO) NPs. The fluid systems lifted 0.80–3.60 mm sandstone particles through pipe angles of 0°, 55°, and 90°. Other wellbore variables investigated include annular fluid velocities of 1.5, 2.5, and 3.5 m/s, pipe eccentricity (e = 0, 0.5, and 1.0), and 0.4, 0.8, 1.2, 1.6, and 2.0 g concentrations of n-HAp. At the same 2.0 g concentration, the findings demonstrate that n-HAp performed better in cuttings removal than each of the NPs. At a 1000 s−1 shear rate, the NPs-based fluid systems increased the viscosity of the WBM (0.166 Pa. s) by 10–87 %, while the n-HAp concentration increased it by 168 %. Also, using 2.0 g concentration, the n-HAp and the NPs decreased the fluid loss of the WBM from 9.4 mL to 5.4 mL and 8.2–4.8 mL, respectively. With n-HAp, the CTR of the WBM increased the most, by 28–38.6 %, and CuO-NP (14.6–23.5 %) came next, followed by Al 2 O 3 (9.3–18.9 %), SiO 2 (5.0–13.4 %), and MgO-NP (2.8–7.7 %). Increasing eccentricity reduced the CTR of all the mud systems at all hole angles. Drilling through a 55°-pipe angle at 3.5 m/s resulted in the lowest CTR, and the obtained CTR related to this pipe angle is 58–75 % (e = 0), 53–70 % (e = 0.5), and 52–67 % (e = 1.0). These results are important for managing the drilling muds and optimizing drilling operations because they provide insight into the effect of pipe eccentricity on CTR. [ABSTRACT FROM AUTHOR]

The drilling for hydrocarbons from oil and gas wells requires efficient drilling fluid and cutting-edge drilling technology. Furthermore, the removal of rock cuttings from oil and gas wells while drilling is a vital task of the drilling fluid, particularly in large-angle wells and long-range drillings. The rock cuttings if not transported to the surface effectively can result in severe costly drilling problems of drag and torque, pipe sticking, faster bit damage, etc. This research suggests a new method that applies polypropylene beads (PP) and silica nanoparticle (NS) treated by sodium carbonate (Na 2 CO 3) to enhance the cuttings transport efficiency (CTE) of water-based mud (WBM). Tests were carried out in laboratory-scale cuttings lifting rig simulator equipped with a 20-ft. Long annulus, a 2.75-in. ID outer acrylic pipe, and an inner drill pipe of 1.05-in. OD. Six different 10 ppg weighted mud samples were formulated and coded mud nos. 1–6 using PP beads and Na 2 CO 3 treated NS concentrations. Four cuttings sizes in the range between 0.4 and 4.0 mm at various hole angles (0°, 30°, 60°, and 90°) without pipe rotation were evaluated using a constant flow rate of 5.13 L/s. The results of rheological characterization using Herschel-Buckley model showed that all the mud systems are shear-thinning as the flow behaviour index ranged between 0.50 and 0.60. The fluid consistency parameter of the WBM indicates that the addition of PP beads and NS concentrations decreases the viscosity of the WBM. Also, the viscosity, yield point, gel strength, and filtration parameters of the WBM were decreased when the PP beads and NS concentrations were introduced before and after thermal aging experiments. This interprets the thinning nature of the mud systems. However, when these products were applied to lift cuttings to the surface, the lifted cuttings increased. The optimum mud system using Bingham plastic expression was found at mud no. 6 (BM-PP8-NS1) containing apparent viscosity of 30.5 cP at a shear rate of 1022 s⁻1, plastic viscosity of 13 cP and a yield point of 35 lb/100 ft2 at 78 °F. Cuttings size and hole angles seem to wield significant influence on CTE as the smallest cuttings (0.4–1.4 mm) were easier to be lifted in the vertical hole (0° angle), while the largest ones (2.8–4.0 mm) were the most lifted in the horizontal section (90° angle). The findings of this study can help for a better understanding of the mud performance of PP beads and Na 2 CO 3 dispersed NS mixture for cuttings transport in a wellbore. • Polypropylene beads (PP) and treated nanosilica (NS) showed promising rheology in water-based muds (WBMs). • The NS with PP beads provides desirable properties with improved efficiencies. • The PP beads and NS have significant enhancing impacts on the cuttings transport capacity of the WBM system. • WBMs with PP beads and treated NS showed a thinning property suitable for enhanced cuttings transport. [ABSTRACT FROM AUTHOR]

The experience acquired in the field showed that poor cuttings transportation results in several drilling problems, such as pipe sticking, undue torque and drag, hole–pack off, or lower than projected drilling performance. In this study, complex water–based mud (WBM) formulated with polypropylene–nanosilica composite (PP–SiO 2 NC) and partially hydrolyzed polyacrylamide (PHPA), a drag–reducing agent were used to examine cuttings transferring efficiencies (CTEs). The examination focused on the impact of diameters of cuttings (between 0.50 and 4.00 mm), hole angles (45, 60, 75, 90°), mud velocities (between 0.457 and 1.80 m/s) and different concentrations (0.4, 0.5, 0.8 and 1.2 ppb) of PP–SiO 2 NC and PHPA. A field–oriented cuttings transport flow loop of dimensions (69.85 mm × 26.67 mm, 6.07 m–long annulus) was constructed to determine the CTEs of the drilling muds. Results showed that smallest cuttings were easiest to remove when mud velocities of 0.457, 0.630, 0.823 and 0.960 m/s were used, but when the velocity increased to 1.80 m/s, the transport of largest cuttings became the easiest. Results also confirmed that PP–SiO 2 NC muds are more capable of transferring cuttings than PHPA mud samples with or without pipe rotation speed due to increased colloidal forces that increase the interaction between cuttings and PP–SiO₂ NC particles. Rotation of drill pipe and an increase in mud velocity will effectively increase the drag effects, which will lead to increased CTE. Hole angle 45° was the most difficult inclination in the cuttings transport process due to the higher settling tendency of cuttings on the low side of the hole. The application of complex WBM with PP–SiO 2 NC showed promising attributes in a cuttings transport process. • A water–based mud (WBM) containing polypropylene–nanosilica composite (PP–SiO 2 NC) was formulated. • The properties of WBM with PP–SiO 2 NC was compared with those of partially hydrolyzed polyacrylamide (PHPA). • WBM with PP–SiO 2 NC showed better performance in modifying rheology and controlling filtration properties than PHPA muds. • WBM with PP–SiO 2 NC are more capable of transferring cuttings than the PHPA with or without pipe rotation. • The transport of smaller cuttings is relatively simplified and require less mud velocity compared to larger cuttings. [ABSTRACT FROM AUTHOR]