Optimized fast drilling technology for Yadavaran Oilfield of Iran

Yadavaran Oilfield of Iran has complex geologic conditions; it is a carbonate reservoir with high temperature and high pressure and multiple pressure systems, and contains acidic gases like high concentrations of hydrogen sulfide, carbon dioxide, etc. Five exploration wells with depths of 4 500-5 000 m were drilled from 2001 to 2003, which all experienced outstanding issues of low rate of penetration, mud loss, differential sticking, heavy oil influx, etc. These wells were drilled with long drilling period, and so safe and fast drilling faced great challenge. This paper has analyzed the difficulties in drilling and completion operations and the application scheme of optimized fast drilling technology in the field, including pressure detection technique in limestone formation, non-permeate anti-sticking drilling fluid technology, highly efficient rock breaking and parameters optimization, heavy oil layer drilling technology, etc. These solutions were fully utilized in casing program, bit selection, rate of penetration improvement and drilling fluids, etc., and have achieved remarkable economic benefit with average rate of penetration up by over 40%.