Optimization of hole cleaning in horizontal and inclined wellbores: A study with computational fluid dynamics

Abstract

The issues related to hole cleaning have long been stressed as being most noticeable and aggravating in horizontal or inclined wellbores; where cuttings accumulation on the low annular side of the wellbore lead to reduced flow and drilling complications. Experimental studies, mechanistic models, and field practices have attempted to address these issues but have failed in completely solving the problem. Considering the lack of matching results, limiting assumptions, and lack of general applicability, the question of efficient hole cleaning is still of concern. The main objective is to generate correlations and matrix tables pertaining to the optimization of various parameters including flow rates, pipe, cuttings, and fluid characteristics. Correlations for critical velocity and critical pressure gradient that could be used for field applications were developed through data analysis resulting from computational fluids dynamics simulations. A new, thorough investigation on level of turbulent flow for efficient hole cleaning in horizontal/inclined wellbores is conducted through a study of the behavioral pattern of the Reynold's number as a function of the critical velocity and critical pressure gradient. A Reynold's number matrix table is produced that could be used to define and tailor specific level of turbulent flows in the most uncommon field applications. Cutting density of 112.4 lb/ft 3 , section pipe length of 16 ft, cutting size of 0.25 in, and inclination of 60° are pivotal points, above which significant flow requirements are needed for effective cleaning; whereas fluid viscosity of 50 cP, fluid density of 12.5 ppg, and diameter ratio (outer pipe to inner pipe) of 1.54 are pivotal points, below which significant flow requirements are needed. • Improvement on hole cleaning investigation methods in inclined wellbores with CFD. • Sensitivity analysis of cleaning variables with accent on level of turbulent flow. • Reynold's number has same trend as the critical velocity except with fluid density. • A matrix table with associated Reynold's number for specified cases was developed. • Correlations were developed for critical fluid velocity and critical pressure drop.