This paper covers the drill cuttings reinjection engineering and operating techniques utilized by British Gas and Apollo Services, on the three year Tunisian Miskar project off the coast of Sfax, Tunisia. At the time of this writing, British Gas has completed the subsea template phase, including the drilling and cuttings injection on 9 wells. A platform was installed in the last quarter of 1994 and the second drilling phase of this project began in March of 1995. A total of 11 or more wells are planned over a 3 year period.
Environmental regulations prohibited the dumping of oil based mud in the sea. Thus, if British Gas wanted the high penetration rates and, limited hole problems achieved by utilizing low cost, natural oil based mud, then cuttings reinjection presented the cost effective alternative.
All waste, from 8 wells, has been successfully pumped down three of the annuli with great success. Insignificant downtime has been experienced due to the injection process, even at instantaneous penetration rates in excess of 200 meters per hour on 12 1/4 inch hole. The CRI contractor rigged up and operated, with one man per 12 hour tower, the cuttings transfer system, the cuttings grinding/slurrification system and the triplex pump cuttings injection system. Over 2000 meters of limestone/claystone was encountered in each well while drilling and injecting successfully, (in the frac mode), into an impermeable claystone formation.
Addressed in this paper are:
Well Planning with information on template drilling as it relates to cuttings reinjection.
Injection well disposal design and planning, including multiple well casing points, for development drilling while producing.
Requirements for surface equipment, personnel and commissioning.
Field Results and Data with adjustments for unplanned events.
Economics of CRI and natural oil base verses synthetic (psuedo) oil mud.
Conclusions and recommendations for future work.