# A Novel Efficient Borehole Cleaning Model for Optimizing Drilling Performance in Real Time
###### Abstract
A drilling fluid with an optimal mud rheology, including appropriate plastic viscosity (PV), point of yield (YP), and initial and ultimate strength of gelation (GI and GF), would considerably improve borehole cleaning [7; 15]. The proper removal of debris produced in drilling is key to ensuring thorough bottom borehole cleaning. The drill pipe must be rotated to switch the flow from a laminar flow regime to a turbulent one to improve the removal of drilling debris. As the drill string does not have an eccentric position in the vertical borehole segments of the wellbore, drill cuttings will be moved to the opposite wall of the wellbore. Considering that the velocity is highest at the center of a laminar flow pattern [16; 17; 18], it is advisable to rotate the drill string to move the drill cuttings into the center of the borehole, making it easier for the flow of fluid to lift them [1; 16; 19]. As an example, [PERSON] and [PERSON] found that pipe rotation initiates an unstable turbulent flow regime, taking the drill cuttings to the center of the borehole, thus allowing the annular velocity to lift them to the surface. An unstable turbulent flow regime can cause an increase in the shear stress applied on the surface of the drill cuttings. Shear stress will support the removal of drill cuttings [20]. According to Unegbu, the effect of drill pipe rotation on borehole cleaning is minimal in vertical wells, while it is significant in inclined wells. The rate of drilling has a significant bearing on the conveyance of cuttings and the cleaning of boreholes. As the volume load of drill cuttings in the annulus increases with an increasing drilling rate, the ROP must be controlled for the effective transfer of cuttings as well as the cleaning of boreholes. When drilling in a formation with a sticky and clay-like lithology, more drill cuttings produced in rapid drilling can lead to the accumulation of drill cuttings in the annulus and shale shakers [21]. If shale caving or shale sloughing is present in the formation, determining the cutting density, size, and shape will be extremely challenging, and it is not possible to establish these characteristics of drill cuttings with a level of precision that is acceptable. At the top of some wells, there exists a clay formation lithology, and these areas are notoriously sticky. As shale shakers are loaded with muddy cuttings, it is difficult to detect the size, shape, and density of each particle individually [2; 22]. When cleaning boreholes in sections that are deviated and horizontal, the angle of the borehole,the accumulated bed of cuttings, the rotation of the pipe, the quality of the mud, and the amount of time mud is circulated are the most critical aspects. The angle of inclination, accumulated beds of cuttings, pipe rotation, amount of time spent in circulation, properties of the mud, ROP, including the flow rate and annular velocity have an incredibly close relationship with each other which makes them significant components [1; 19; 23]. During directional drilling, cutting beds are generated as there is either very little or no rotation of the pipe. The most important parameters that lead to better removal of beds of cuttings are mud characteristics, flow rate, pipe rotation, and borehole angle. The erosion of beds of cuttings due to annular velocity of mud causes the size of a bed of cuttings to diminish linearly with respect to the flow rate [1; 19; 23]. Moreover, the high-velocity drilling fluid is often referred to as the conveyor belt. This is because the fluid functions like a conveyor belt on top of the borehole annulus, carrying the cuttings generated by the drill bit to the surface. The fluid is pumped down the drill string and out through the nozzles at the bottom of the drill bit, creating a turbulent flow that helps to break up and suspend the cuttings. The cuttings are then transported by the fluid to the surface [24]. More importantly, the angle, flow rate, RPM, and rheology of the drilling fluid have a role in determining the distance travelled on the conveyor belt.