Through tubing reentry drilling (3 5/8") operations were first commenced in Saudi Arabia in 2008. Since then the application has proven to be an efficient and reservoir friendly method of reentry drilling. Old vertical and sometimes deviated candidate wells are screened and worked over by setting a through tubing whipstock in the 4½", 5½" and 7" casings then exiting in a 3 5/8" hole size. A curve section is then drilled at 20° to 35°/100 ft build up rate (BUR) and subsequently, lateral sections of 2,000 to 3,000 ft are drilled in the reservoir.

Despite the good learning curve, certain technical challenges are limiting the operating envelope of 3 5/8" through tubing re-entry drilling (TTRD). Some of these challenges are: surface setup and pressure deployment, inefficient tool face control, vibration, releasing a stuck bottom-hole assembly (BHA), etc. Other challenges related to drilling sandstone reservoirs.

Keeping these challenges in mind, Saudi Aramco and Schlumberger (SLB) embarked on a project to develop a new drilling system, which would prevent and mitigate the risks highlighted above and allow safe application of 3 5/8" TTRD to areas and fields where it was previously not practicable. This new drilling system was successfully deployed to the field in June 2012.

The paper will cover some of the key features of the new drilling system, which were proven during the first job.