Drilling Fluids Challenges in Successful Drilling of Gotnia Formation in the State of Kuwait
M.J. Al-Saeedi, D. Al-Enezi and M. Sounderrajan
Event name: IPTC 2013: International Petroleum Technology Conference
Session: WELL CONSTRUCTION: CEMENTING AND DRILLING FLUIDS SUMMARY
Publication date: 26 March 2013
Info: Extended abstract, PDF ( 2.72Mb )
Price: € 20
Drilling the Gotnia formation in Kuwait has long been a drilling fluids challenge due to its sharp contrast in lithology of salt/anhydrite interfaces. Presence of this salt layer below 13,000 ft. with a thickness of 700-1,200 ft. in deep wells makes this formation more plastic in nature due to high pressure and temperature. There is a fine line between kicks and total loses in this fractured formation. Hole instability, stuck pipe, total loss, well control, acid gases and H2S are frequent problems while drilling this section. High pore pressures exist, requiring mud weights ranging between 18.5-21.5 ppg. With this mud weight range in salt drilling, there are limited options available with the drilling fluid to ensure bore hole stability. Drilling fluids design, loss control and well control are massive tasks. Mud weight management with the knowledge of formation stresses, maintaining lowest possible rheology and managing the salt dissolution to avoid well bore closure/instability are key factors in avoiding complications in these deep wells. OBM is utilized to drill this formation due to the insolubility of salt in oil. Historically, this formation was drilled with lower oil/water ratios resulting in high rheology along with higher mud weights causing frequent mud losses and stuck pipes. Maintaining high oil/water ratio helped to overcome the problems associated with rheology and hydraulics. Salt rapidly reduces electrical stability and oil wettability in OBM. Emulsion stability was increased as a precaution to the extremely fine particles created through salt re-crystallization which has detrimental effect on stability. Fresh water in the water phase helps to minimize salt saturation and crystallization. This paper describes the drilling fluids challenges faced while drilling the Gotnia formation and the progress zade over the years to drill this formation successfully.