7" Monobore Completion Design for Qatar's Offshore North Field

Abstract

Abstract Producing gas from the Khuff formation in Qatar's offshore North Field presents several completion design challenges. The North Field Khuff formation is a competent limestone / dolomite that is estimated to contain a GIIP of 504 x 1012 scf (504 TCF), which makes it the largest single accumulation of natural gas in the world. The North Field Khuff gas contains hydrogen sulfide and carbon dioxide concentrations of approximately 5,000 ppm and 2.5 mole percent, respectively. Initial condensate yields exceed 40 bbl/MMscf. For design purposes, brine water production was taken into account when making the metallurgical choices for the completion equipment. The producing interval, Khuff K-4 at a datum of 9,400 ft. subsea has a bottom hole temperature of 222°F, and an initial shut-in bottom hole pressure of 5,265 psi. Actual well deviations range from vertical to slightly over 60° from vertical, but all completion equipment was designed and tested to function properly in horizontal wells. The monobore completions have also been designed to accommodate high rate and high volume HCI acid stimulations that are performed during initial completions, and that may be needed throughout the life of the field. Qatar's North Field monobore completions have been designed to accommodate all of the above well conditions under all expected wellbore load cases, while providing years of trouble free service. This paper describes the wellbore and equipment design concepts utilized, the equipment innovations made, the equipment installation philosophy and results, and the equipment performance realized to date for the monobore completions in Qatar's offshore North Field.