Abstract
Unusual pressure was encountered while drilling through the Triassic lower Jilh formation in a wildcat. The well was one of the deep exploration wells for non-associated gas, in the northern fields, targeting the Permian Khuff and Pre-Khuff gas reservoirs. Mud weight was increased from 80-pcf (10.7 lb/gal) to 156-pcf (20.86 lb/gal) with barite. The drill-string became stuck against the formation above the high-pressure zone. A specially designed spotting fluid was used to disperse the wall cake and free the pipe. Well-killing operation continued with the drill-string inside the casing. Achieving higher mud densities required the use of hematite and phasing out the barite until the well was controlled with 162-pcf (21.66 lb/gal), which is the heaviest drilling mud ever used in Saudi Arabia’s oil fields.
Extensive laboratory work was carried out at the well site. The mud system formulation design was adjusted and maintenance treatment was carried out in timely manner. Drilling operations were commenced safely to the casing point where the temperature exceeded 300°F. Successful bit selection for this interval lead to a New World record run in rotating hours. A 9-5/8" liner was run and cemented with specially designed 170-pcf (22.73 lb/gal) cement slurry, which was also a challenge. The liner was extended to surface and cemented in two stages with 145-pcf (19.39 lb/gal) cement. This paper presents the laboratory data along with the field mud and cement formulations used.
