Abstract
In the drilling of horizontal wells, the drill cuttings tend to settle down on the low side of the annulus due to gravity and form a stationary bed, which results in hole cleaning problems. In this paper, a novel type of drillpipe with an elliptical shape was proposed to alleviate inadequate hole cleaning during the drilling of horizontal wells. A three-dimensional computational fluid dynamic (CFD) Eulerian-Eulerian approach with the Realizable k-ɛ turbulence model was developed to predict the solid–liquid two-phase flow in the annular space. Numerical examples were given to investigate the influence of different parameters on cuttings’ transport behavior, and the elliptical drillpipe was compared with the circular drillpipe. The annular cuttings concentration, annular pressure drop, and hole cleaning efficiency were evaluated. The numerical results clarify the potential of the elliptical drillpipe to enhance the hole cleaning efficiency without significantly increasing the annular pressure drop. Due to the swirl flow and secondary flow caused by the rotation of the curvature wall, the swaying phenomenon of drill cuttings’ distribution along the rotation direction of drillpipe was observed and enhanced the cuttings transport ability. Using the elliptical drillpipe as a joint-type tool can improve hole cleaning performance. Under the optimum conditions applied in this study, the hole cleaning efficiency increased by nearly 18%.
Highlights
With the rapid development of the world economy, energy demands are increasing
When the rotational speed was 50 rpm, in the ranges of rate of penetration (ROP) used in the simulation, the hole cleaning effect of the elliptical drillpipe with minimum ROP and maximum ROP increased by 6.2 and 10.2%, respectively
It explains the fact that when the value of ROP is considerable, maintaining the elliptical drillpipe at a higher rotational speed will have a better hole cleaning performance
Summary
With the rapid development of the world economy, energy demands are increasing. Oil and gas are still vital energy resources to ensure human survival and development over a sufficiently long time [1,2]. Among many variables that affect the ability of cutting transportation, it is considered that the annular fluid velocity and the rheological properties of drilling fluid are the most effective drilling parameter to prevent the development of the cuttings’ bed [17,18] Drilling parameters, such as flow rate and rheological properties, are limited by hydraulic conditions and cannot be changed at will. The validated simulation model was further extended, and the effects of ROP, rotational speed, axis ratio, eccentricity, and pitch length ratio on the cuttings’ transport behavior with an elliptical drillpipe were investigated, and paved an avenue toward using hole cleaning in the drilling of horizontal wells in petroleum engineering [28]. Annulus length (L), mm Wellbore diameter (Dwb), mm Drillpipe diameter (Dpipe), mm Minor axis (b) (equal to Dpipe), mm Major to minor axis ratio (a/b)
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