Estimation of "Very-Difficult-to-Identify" Data for Hole Cleaning, Cuttings Transport and Pressure Drop Estimation in Directional and Horizontal Drilling

Abstract

As the inclination of a wellbore increases, cuttings start having a tendency to accumulate in the lower section of the wellbore, and develop a cuttings bed. This developed bed causes a reduction in the flow area, an increase in the friction between the drillstring and the wellbore, leading to an increase in torque, decrease in force transfer to the bit, and lose control on the bottomhole pressure. Finally, drilling rate decreases. Estimation of total concentration inside the wellbore is not an easy task. Moreover, moving cuttings and fluid dragging them to move have different relative velocities inside the wellbore, causing variations in pressure drop. Although there are many attempts to estimate the cuttings concentration and slip between the cuttings and the fluid using mechanistic models and empirical correlations, the performances are limited either with the strong assumptions made, or the experimental facility capabilities. This study aims to determine some of the very-difficult-toidentify data for estimating total pressure drop and total cuttings concentration inside the wellbore. Extensive experimental work has been conducted using a cuttings flow loop at horizontal and inclined wellbores. Tests have been conducted using water to simulate low viscosity fluids. Data has been collected for a wide range of flow rates, cuttings injection rates and pipe rotation speeds. All experiments have been recorded using a high-speed digital camera. Images have been processed using special algorithms, and volumetric distributions of cuttings and fluid can be identified very accurately. By comparing consecutive images, very valuable information has been collected about the accumulated cuttings amount, concentration of moving particles, their relative transport velocities, slip velocity between the phases, the friction factor on the stationary bed, etc. Since the images are digital, information collected is converted into numerical values, and semi-empirical equations are developed as a function of known drilling parameters. The obtained information is tested in simple mechanistic models for estimating pressure drop inside a wellbore with the presence of cuttings, and the performance of the model is tested by comparing the results with the measured ones. It is observed that, after supplying the very-difficult-to-identify information to the mechanistic model, the performance of the mechanistic model improved very significantly. The information provided will improve the design of long extended reach wells while estimating hydraulic requirements, and make it possible to have a better understanding of what is really happening inside the wellbore.

Numerical modeling and simulation of drilling cutting transport in horizontal wells

“…In this modeling, fluid and drilling cuttings are considered as continuous phase and non-continuous phase, respectively. Comparison between CFD-DEM model by Akhshik et al (2015) and CFD model by Ozbayoglu et al (2010) and also, mathematical equations by Yu et al (2007) showed that CFD-DEM modeling has a better performance in modeling of cutting transport. Zhu et al (2013) studied the cutting transport in horizontal wells by CFD modeling and Navier-Stokes equations and showed that the amount of formed cuttings considerably decreased by increasing fluid velocity.…”

“…Efficient wellbore cleaning is an important goal in a drilling operation especially in horizontal and deviated wells since it can prevent problems such as stuck pipe, lost circulation, high torque and drag, loss of control on density ECDs, and finally it can reduce the cost of the drilling operations (Ozbayoglu et al 2003). Some of affective parameters on wellbore cleaning have been studied by some researchers experimentally (Tomren et al 1986;Yu et al 2004;Ford et al 1990;Hareland et al 1993;Okrajni and Azar 1986;Sifferman and Becker 1992;Hussaini and Azar 1983) and by modeling approach (Nguyen and Rahman 1998;Wazed 2002;Akhshik et al 2015;Zhu et al 2013).…”

Evaluation of Annular Pressure Losses while Casing Drilling

“…Smaller cutting size or casing wear is attributed to the eccentric configuration of Casing in the wellbore (Fontenot et al 2004). Ozbayoglu et al, (2010), and Osgouei (2010) measured some data for estimating total pressure drop and cuttings concentration in narrow eccentric horizontal and inclined annuli from cuttings transport experiment. Results from their study indicate that drillpipe rotation speed does not have significant influence on pressure drop for constant rate of penetration (ROP) and flow rate.…”

Simulation on Cuttings Transport with Drillpipe Rotation in Highly-Inclined Well Section

“…Many models to calculate cuttings bed height and minimum mud rate have been established. Part of these models are theoretical, including steady models [1,2,3,4] and unsteady models [5,6,7,8], and the rest are experimental [9,10,11]. The influence rules of different factors on cuttings transport have been studied deeply except the drill pipe rotation because the pipe rotation can make the two-phase flow in annular become more complicated and difficult to solve.…”