Application of Computational Fluid Dynamics for Investigation the Effect of the Hole Cleaning Parameters in Inclined and Horizontal Wells

The increasing global demand has prompted the development of more innovative ways to enhance the drilling of oil wells at lower costs, and avoid operational problems that affect the speed of drilling oil wells. The numerical cuttings trajectories simulation has been done to include the effect of cuttings collisions using commercial ANSYS FLUENT 2019 R3 CFD software. The (Eulerian-Eulerian) model was used to verify the cuts transport behavior due to the existence of liquid and solid phases. In this simulation, the mind transport rate is checked by changing the operational parameters which including (drilling mud flow rate and temperature, cuttings size, inclination, drill pipe rotation and eccentricity). The results show that the high degree of agreement was observed between the numerical results with experimental studied by the researcher Yaacob, indicating the CFD analysis system's dependability and capacity to mimic the drilling operation. The use of (Eulerian-Eulerian) model is found reliable in interpreting the phenomena of multiphase flow for understanding the mechanism of influence of parameters associated with the process of drilling oil wells on the lifting capacity. Increasing the flow velocity of the drilling mud transforms the flow pattern from laminar to turbulent, and the latter is one of the desired flow patterns during the flow that enable to


Introduction
When employing the directional and horizontal oil well drilling methods, focused on investigating difficulties cleaning the bottom of the well and transporting the cutting to the surface has recently grown. Cleaning the well during the drilling process is one of the most important elements determining the cost, time, and quality of drilling oil wells. Cleaning effectively entails bringing the cutting to the well's surface as rapidly as feasible. Numerical computations and methodologies have been extensively employed by numerous academics to solve many of the drilling fluid flow difficulties, as well as their link to cutting transport under different operating situations. Based on mechanical theory and a three-layer method, developed a mathematical model to describe cutting particle movement in the annular flow during horizontal drilling. The model was solved numerically using MATLAB computer methods. In a concentric ring, the model helps assess the performance of irregular-shaped cuts. An annular size, cut size and shape, rate of penetration (ROP), and drilling fluid rheology influence have been properly modelled. The drilling fluid viscosity, cuttings size, and ring size all influenced the transportation operations. Among other characteristics impacting transportation, penetration rate had the least influence. It has also been shown that the mathematical model may be used to plan or study the 18 transport process of cuttings in horizontal wells [1]. Used continuity equations, Navier-Stoke, and the force law to describe non-Newtonian fluids to convey cuts to the well surface. FLUENT software was used to simulate. Three kinds of drilling mud were used in the studies. A drilling location in Sudan provided the feeding conditions and cutting size. The influence of cuttings shape was tested at (600-900) GPM and cuttings size (2.54, 4.45, and 7) mm.
The findings revealed that fine clippings are the easiest to raise and clean the well. The best cleaning results were observed while drilling at 30 degrees and using an 800 GPM flow rate [2].
Simulated the influence of many settings on the ability to move items to the well surface.
A simulated well with a depth of 2000 m and a diameter of 380 mm was built with a 200 mm spinning inner tube. The GAMBIT 2.4.6 application was used to construct the mesh and send it to ANSYS (FLUENT). The suggested approach uses a distinct phase model to track cutting travel. Along with three drilling fluids, the influence of flow, cutting size, shape, and eccentricity of the rotating tube on cutting components was explored. To validate the simulation technique, the results were compared to earlier operations.
The findings demonstrated that turbulence in the drilling fluid helps circulate the ring and raise the cut. The findings also show that tiny particles and spheres are the simplest to clean [3].
Simulated drilling fluid flow numerically using a multi-phase Euler model. The most essential characteristics impacting cuttings layer development are flow rate, hoof slope, and rotation speed. The drill pipe was simulated at an inclination of 45-90 degrees and a rotation speed of 80-240 rpm with a flow rate of 30-50 L/s. This rotation increases cutting transmission and assists in disperse cuttings asymmetrically during runoff. The impact of rotating the drill pipe is strong when the drilling fluid flow rate is low or medium [4].
Simulated drilling mud behavior and cuttings transport efficiency using the Fluent CFD software suite. The current study focused on centric and eccentric rings and the parameters of the drilling mud. The simulation model was compared to earlier experimental investigations for verification and demonstrated an error rate of 8%, indicating that employing simulation software (CFD) to represent physical variables of drilling fluids is reliable. Cuttings transport rate rises with rheological properties and flow rate of drilling mud. The cutting ratio falls from (0-45) degrees further from the head. From 0-120 rpm, the cutting transmission rate improves from 72-79 percent [5].
Offered a numerical investigation of the influence of drill pipe rotation on the efficiency of conveying cuttings to the well surface in horizontal drilling. A numerical simulation was run on (ANSYS 15.0 CFX). The program's correctness was confirmed by comparing the cut concentrations and pressure losses at (0 and 60) rpm for the hoof tube to earlier operations.
Numerical and experimental findings agreed well, with an agreement rate of around 12%.
Increasing the burring tube rotation speed from 0 to 120 rpm reduced the cutting concentration by 84.3 percent with a loss of pressure at 2.43 m/s. When the flow rate is large, the influence of the drill pipe rotation is minor [6].
Drilling mud flow via a spinning inner ring was analyzed. The influence of several parameters on cuttings transport efficiency was evaluated, including drill pipe rotation speed, drilling mud flow rate and type, and cuttings concentration inside the test loop. The data were evaluated to explain the mixture's pressure drop, slip velocity, and kinetic energy distribution inside the test ring. Used (ANSYS CFX-15) software to simulate a multi-phase liquid (Eulerian-Eulerian) model.
The particle size ranged from 90 to 270 microns, and their concentration ranged from 10% to 40%. The k-epsilon model was selected to apply with existing experimental data. The findings indicated that as particle size grew, flow pressure loss increased. Reducing the cutting focus helps decrease pressure loss [8]. Used a numerical model to solve liquid and solid flow equations (cuttings). The (Eulerian-Eulerian) model was adopted to predict particle behavior during flow.
The degree of convergence was verified by comparing numerical findings to experimental data.
Flow rate, pipe rotation, slope, and cutting size were all tested extensively. The findings indicated that cuttings transfer efficiency reduces between 45-60 degrees. Increasing burr rotation and flow velocity also improves cleaning efficiency [9].
Employed a (k-e) turbulent model and a multiphase (Eulerian-Eulerian) model to describe threephase flow inside a concentric ring. To verify the numerical simulation, the results were compared to earlier operations. These included drill pipe rotation, water and air flow rate, cutting size and inclination. The findings revealed that rotating the drill pipe between (0-75) rpm reduces cuttings concentration, whereas rotating between (75-125) rpm increases cuttings concentration. The rotation of the drill pipe has a stronger impact on little particles than big items.
The concentration within the well rises with increasing air flow, reduced inclination, and drill pipe rotation [10]. ANSYS FLUENT 17.1 was used to evaluate two-phase flow in a well loop.
These factors included drill pipe deviation, tilt, rotation, rate of penetration (ROP), and drilling fluid rheology. Particle motion was modelled using an Eulerian-Eulerian multi-phase tracking model. The numerical model was validated by comparing simulation results to experimental data (error rate less than 11 percent). The findings indicated that the drilling fluid velocity, pipe inclination, and deflection are the most important elements affecting cuttings transit efficiency [11].
Employed a simulation software to explore parameter effects on cutting transport. The drilling fluid type, cutting density, and concentration ratio were studied using fluent software. The findings revealed that increasing the drilling fluid density lowered cuttings concentration in the test tube by 32.9 percent while decreasing pressure. Increasing the cuttings density from the operational density increases the cuttings concentration within the ring by 200 percent [12].
It is feasible to tailor the drilling fluid density to the cuttings density. The influence of flow rate, inclination, rotation of the drill pipe and drilling fluid viscosity on cuttings uplift. To verify the numerical model's accuracy. The findings converged well with earlier experimental data. The findings revealed that increasing flow rate helps minimize cutting layer thickness. Another finding is that transporting cuttings at an angle of (35-65) degrees is the most problematic.
Changing the drill pipe's rotation speed has no impact on transferring cuttings [13].
Simulated cutting transport using CFD-DEM (CFD-DEM). The drag force, lift, and pressure gradient associated with two-phase flow were utilized. The model investigates cuttings collision and transmission, as well as cuttings bed mechanics. Drilling fluid velocity, inclination, and rotation were examined. The findings demonstrated that when the drill pipe rotates, a layer of cuttings forms inside the inner walls of the ring, which thickens with decreasing flow velocity.
After the drill pipe's rotation speed reaches the crucial speed for high flow rate, no more rotational contribution is made. When the hoof slope is 40 degrees, rotating the drill pipe helps minimize cutting thickness [14].
Employed computational fluid dynamics (CFD) to solve multi-phase flow issues. The influence of (the drilling fluid rheology, drill pipe rotation, flow rate, cuttings density, shape and focus) on the efficiency of lifting cuttings in vertical wells. Multi-phase liquid flow was simulated using concentration, flow rate, and pressure gradient were studied. The study's findings validated the suggested simulation model and demonstrated its use in many applications, including oil and gas [16]. Simulated the effect of nanoparticles on drilling fluid performance. Used computational fluid dynamics (CFD) to deal with multi-phase flows and flow issues. The influence of drilling fluid rheology, flow rate, cuttings density, shape, and concentration on drilling fluid efficiency was examined. The findings demonstrated that adding nanoparticles to the drilling fluid increased its rheological characteristics and hence its capacity to clean the well [17].
Used a concentric pipe to dig a horizontal well. (CFD) is used to solve two-phase flow equations with solid particles (cuttings). A horizontal ring with 1.9 in inner and 2 in outer diameter was created. Several models were used to determine the hydrodynamic inlet length, which came out to 40 ft. The findings demonstrated that the drill pipe's rotation encourages solid particle movement and slows their sliding. Increasing the drilling mud flow rate reduces the influence of bore tube rotation [18].
Although extensive research has been carried out for studies over the past few years on the topics of cuttings transport and hole cleaning, there is a need for further study to verify the impact of operational parameters accompanying the drilling process of oil wells and to determine the most influential on the ability of drilling mud to transport pieces. There is also a limited understanding of the impact of operational parameters on the ability of drilling mud to transport pieces in directional and horizontal wells. The effect of high drilling mud temperature on the lifting capacity of the shale blocks has rarely been studied despite the high temperature during the drilling process. The current study includes determining the extent to which most operating parameters affect the lifting capacity and what is the effect of each parameter on the other in vertical, horizontal and directional wells. Also, verifying the accuracy of using CFD programs to simulate the oil well drilling process. One of the novelties in this study is the containment of particle collisions in order to develop a more accurate physics-based numerical model of particle flow in a rotating system.

Drilling Liquid Conservation Equations [19].
 For the liquid phase, the continuity equation is as follows: In general, is a function of the rate of deformation tensor's three invariants, and is a function of the shear rate's function: The consistency factor (K) is equal to the power-law index (n). When n 1¼, the rheological characteristics of the fluid are separated into two halves, it is a Newton fluid. When n > 1, it is shear thickening fluid, and when n 1, it is shear thinning fluid.

Cuttings Phase Conservation Equations [19].
 Cutting phase's mass conservation equation is represented as:

Coefficient of Interphase Momentum Transport [19].
The (Huilin-Gidaspow) drag correlation may be used to determine the drag force between drilling mud and cuttings.

( ) ( )
In the cuttings phase, the Reynolds number is defined as:

Model Geometry
The flow geometry was assumed to be an annulus formed by two cylinders. The inner and outer cylinders, respectively, depict the drill pipe and borehole. Drilling fluid is pumped into the drill

Independent Study of Computational Meshes and Grids.
In all flow configurations, both dynamic and static hexagonal meshes were used. At the inlet and outflow borders, edge scaling and face meshing techniques were used to provide a high resolution capable of recording boundary circumstances. It was critical to maintain a high degree of orthogonally and minimal skewnes in the mesh; hence, the number of exterior pipe divisions was equal to the number of internal pipe divisions. To establish the optimal number of elements required to provide an accurate solution while using the fewest computer resources possible, a grid size independence research was performed on all pipe eccentricities evaluated Figure (2). As seen in Figure (3), the concentric flow arrangement needs more elements than the eccentric annuli to provide an independent solution regardless of the grid size.

Study Summarizes
The stages of study that followed to conduct the study begins after completing all of the requirements related to CFD programs that have been clarified in the current study body. The study is summarized by examining the factors that affect the cutting transport represented by

Numerical Results
The advent of computational fluid dynamics (CFD) and its ability to simulate experimental aspects of numerous studies has provided an unprecedented and unparalleled opportunity to    using other parameters that help solve this problem associated with the eccentricity of the drill pipe.

Conclusions
1-There is a clear convergence in the numerical results with experimental studied by the researcher [20] with the error rate (7%). A good agreement was obtained which indicates the reliability and ability of the CFD analysis system to simulate the drilling process.