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Analysis of wellbore instability in vertical, directional, and horizontal wells using field data
 

Summary: Analysis of wellbore instability in vertical, directional,
and horizontal wells using field data
M.A. Mohiuddin, K. Khan, A. Abdulraheem , A. Al-Majed, M.R. Awal
Center for Petroleum and Minerals, Research Institute, King Fahd University of Petroleum and Minerals,
P.O. Box # 755, Dhahran - 31261, Saudi Arabia
Received 18 April 2005; accepted 26 April 2006
Abstract
An old offshore field produced using vertical and directional wells is being redeveloped by drilling horizontal wells. The
experience gained while drilling vertical and directional wells is not useful for drilling horizontal wells, as the failure rate is 1 in 3
holes. Quantification of drilling problems in sixty wells show that majority are tight holes. Stuck pipes and hole pack offs are also
significant in number. The major loss of productivity is due to stuck pipes. A preliminary study of shale in sections where problems
occur, show no chemical reactivity. Petrographic analysis confirmed the fissile and brittle nature of shale with presence of open,
partially healed microfractures and partings. Rock mechanical simulation predicted the safe mud weight window for horizontal
wells as 7690 PCF, depending on azimuth. However, all the horizontal wells analyzed in this study were drilled using the same
mud weight window. Therefore, field based parameters like initial mud weight used for drilling, mud weight increment and
problems per well were used to analyze wellbore instability, identify different instability mechanisms and design safe mud weight
window for drilling horizontal wells. These parameters were used first on the drilling data of vertical wells to develop the procedure
for the analysis of wellbore instability and identify the mechanisms of instability. The developed procedure was then applied to the
drilling data of directional wells to show the dependence of mud weight on the inclination and azimuth of the well. Finally, the
procedure was applied to horizontal wells data along with the concept of critical washouts to infer the safe mud weight window as

  

Source: Al-Majed, Abdulaziz Abdullah - Center for Petroleum and Minerals at the Research Institute & Department of Petroleum Engineering, King Fahd University of Petroleum and Minerals

 

Collections: Fossil Fuels