Date of Award

Fall 11-22-1991

Document Type

Dissertation

Degree Name

Doctor of Engineering (DEng)

Department

Chemical Engineering

Abstract

A laboratory model was built and used in a study to investigate the parameters which influence the bottomhole cleaning of wellbores during continuous and intermittent flow. Two simulated drill bits capable of producing pulsed flow from which one was modified to produce continuous flow were used in the model. These simulated bits have the same geometry including diameter, which remained constant A dimensional analysis was throughout this research. conducted to determine combinations of variables for flow rate, cutting density, fluid density, stand—off distance, fluid plastic viscosity, yield point, drillpipe speed, bit diameter, nozzle diameter, hydraulic radius, inclination Several and initial height of cuttings. angle, dimensionless groups were evaluated in terms of their effect upon a dimensionless dependent variable named in this study as "fraction of cuttings removed, (Lc/Lci) The SAS program (Statistical Analysis System) was utilized for a regression analysis to further assess the experimental results. Three models, linear, semi—log, and log—log, vere analyzed. predicted values of ( Lc/Lci) obtained from the regression analysis were compared to the experimental results. Results were presented in tabular and graphical forms to permit a comparison of the parameters. Conclusions were drawn which could assist one in optimizing bottomhole cleaning, hence improving rate of penetration. These conclusions indicate that in both continuous and intermittent flow (Lc/Lci) was maximized by minimizing the stand-off distance, declined as the density of cuttings increased, decreased by a significant increase in size of the cuttings, increased by increasing flow rate, and increased as a result of increases in jet impact force and bit hydraulic horsepower. In virtually all of the experiments, intermittent flow resulted in more efficient bottomhole cleaning than did continuous flow.

Download

Share

COinS