Abstract
Due to gravity, drilling cuttings are easily accumulated in an inclined well section, ultimately forming a cuttings bed, which places the drill pipe under strong friction torque. In severe cases, this can cause dragging, stuck drills, and broken drill tools. Because conventional drilling fluids are difficult to prevent the formation of cuttings in inclined well sections, a method of carrying cuttings with the pulsed drilling fluid to improve wellbore cleanness is proposed. Experiments and numerical simulations are conducted to investigate the effects of cuttings bed transport velocity, cuttings size, cuttings height, drill pipe rotation speed, cuttings bed mass, and roughness height. The optimal pulse parameters are determined per their respective impact on cuttings transport concerning varied periods, amplitudes, and duty cycles of the pulsed drilling fluid. Compared to cuttings transport under the conventional drilling fluid flow rate, the pulsed drilling fluid produces the turbulent dissipation rate, increases cuttings transport velocity, and thus improves the wellbore clearance rate.
Highlights
Energies 2021, 14, 2141. https://The transport of cuttings in an inclined well section with a small borewell is a major challenge in drilling applications
Yu et al (2007) [8] found that the height of the cuttings bed sharply increases upon a certain drill pipe eccentricity; the torque increases at this point, resulting in an increased likelihood that the drill will stick
Ofei et al (2014) [19] used the computational fluid dynamics (CFD) method to analyze the effects of various fluid velocities and inner/outer pipe diameter ratios on solid–liquid flow pressure loss and cuttings density
Summary
The transport of cuttings in an inclined well section with a small borewell is a major challenge in drilling applications. Ofei et al (2014) [19] used the computational fluid dynamics (CFD) method to analyze the effects of various fluid velocities and inner/outer pipe diameter ratios on solid–liquid flow pressure loss and cuttings density Their results indicated that reliable CFD simulations accurately reflect complex, real-world oil and gas drilling operations. The pulsed jet generator modulates the conventional continuous flow of drilling fluid through the drill bit into a pulsed flow, forming a pulsed jet at the nozzle outlet and generating hydraulic pulses, cavitation erosion, and local negative pressure at the bottom of the well This approach enhances the flow field at the bottom of the well, improves purification capacity, and helps break down rock material, enhancing ROP and improving cuttings transport efficiency [27,28,29,30]. The results of this work may have guiding significance for the further research and development of pulsed drilling fluid cuttings conveying tools
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