Summary: This paper was prepared for presentation at the 2005 SPE Technical Symposium of Saudi
Arabia Section held in Dhahran, Saudi Arabia, 14-16 May 2005.
This paper was selected for presentation by the Technical Symposium Program Committee
following review of information contained in full manuscript submitted by the author(s).
Contents of the paper, as presented, have not been reviewed by the Society of Petroleum
Engineers and are subject to correction by the author(s). The material, as presented, does not
necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members.
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
mechanism 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