TY - THES

T1 - Evaluation and comparison of drilling parameters and hardware used to improve cuttings transport and limit the thickness of cuttings accumulations in high angle and horizontal well bore sections

AU - Sonwa Lontsi, Tresor

N1 - embargoed until null

PY - 2008

Y1 - 2008

N2 - The increase in the demand of energy worldwide has resulted in the expansion of the drilling activities, particularly in deviated and extended reach wells. One of the major challenge while drilling these type of wells is the transport of cuttings in inclined section of the annulus when angle exceeds 30° (degrees) of inclination. Inefficient hole cleaning will cause cuttings bed formation, which if not handle lead to problems such as premature bit wear, high torque and drag, high non-productive time and drilling cost, stuck pipe, lost of the well. In the inclined wells, cuttings settle vertically due to the gravitational force, but the fluid velocity has a reduced vertical component. Drilled cuttings settle than quickly in the low side of annulus and have less distance to travel before they hit the borehole wall. Here the velocities are negligible and particles tend to deposit in the annulus leading to the formation of cuttings bed. The first approach when faced with such a situation is to optimize the controllable drilling parameters such as flow rate or annular velocity, wellbore inclination, mud properties, drill string rotation and rate of penetration. It is showed in this work that for the same drilling condition, the directional wells require significantly higher flow rate which is the most important operating parameter than the vertical ones in order to remove or prevent the cuttings bed formation. However for many cases the required flow rates are not always practically achievable due to pump limitations and borehole washouts. The positive effect of drill pipe rotation on the cuttings transport is not always applicable because of the sliding mode while drilling which make things more complex. Theoretically, the rate of penetration is usually kept on the highest possible value mostly because of economics reasons The second part of this thesis deals with the economic evaluation and performance analysis of wells drilled with specific drill strings components such as Hydroclean (HDP) in comparison to the Standard Drill Pipe (SDP). Two sections, 12 1/4" and 8 1/2" of three wells (well P, well G, well H) drilled with SDP and one well C drilled with HDP were analyzed. The result led to the conclusion that with good drilling practice and HDP, the drilling time and cost in deviated wells can be reduced but not for all the wells. Alternative mechanical cuttings removal aids such as Cuttings Bed Impellers, Helical Drill Pipe and their characteristics were also highlighted in this work.

AB - The increase in the demand of energy worldwide has resulted in the expansion of the drilling activities, particularly in deviated and extended reach wells. One of the major challenge while drilling these type of wells is the transport of cuttings in inclined section of the annulus when angle exceeds 30° (degrees) of inclination. Inefficient hole cleaning will cause cuttings bed formation, which if not handle lead to problems such as premature bit wear, high torque and drag, high non-productive time and drilling cost, stuck pipe, lost of the well. In the inclined wells, cuttings settle vertically due to the gravitational force, but the fluid velocity has a reduced vertical component. Drilled cuttings settle than quickly in the low side of annulus and have less distance to travel before they hit the borehole wall. Here the velocities are negligible and particles tend to deposit in the annulus leading to the formation of cuttings bed. The first approach when faced with such a situation is to optimize the controllable drilling parameters such as flow rate or annular velocity, wellbore inclination, mud properties, drill string rotation and rate of penetration. It is showed in this work that for the same drilling condition, the directional wells require significantly higher flow rate which is the most important operating parameter than the vertical ones in order to remove or prevent the cuttings bed formation. However for many cases the required flow rates are not always practically achievable due to pump limitations and borehole washouts. The positive effect of drill pipe rotation on the cuttings transport is not always applicable because of the sliding mode while drilling which make things more complex. Theoretically, the rate of penetration is usually kept on the highest possible value mostly because of economics reasons The second part of this thesis deals with the economic evaluation and performance analysis of wells drilled with specific drill strings components such as Hydroclean (HDP) in comparison to the Standard Drill Pipe (SDP). Two sections, 12 1/4" and 8 1/2" of three wells (well P, well G, well H) drilled with SDP and one well C drilled with HDP were analyzed. The result led to the conclusion that with good drilling practice and HDP, the drilling time and cost in deviated wells can be reduced but not for all the wells. Alternative mechanical cuttings removal aids such as Cuttings Bed Impellers, Helical Drill Pipe and their characteristics were also highlighted in this work.

KW - Bohrklein Bohrkleintransport Bohrkleinablagerung geneigte Bohrabschnitte horizontale Bohrabschnitte Pumprate Bohrstrang Hydroclean

KW - Cuttings Cuttingstransport Cuttings bed deviated wells horizontal wells minimum flow rate drill pipe Hydroclean

M3 - Master's Thesis

ER -