Performing an underreamed gravel pack in a hot, overpressured reservoir is difficult. Underreaming fluid must be non-damaging, provide hole stability and cleaning, and generate a filter cake that can be removed. The gravel pack must be designed to minimize filter cake removal and gravel/formation sand intermixing. Successful underreamed gravel packs have been accomplished in normal pressure environments, but they have not been attempted in overpressured environments because of the associated difficulties.
This paper describes:
Displacement procedures used to clean the casing and procedures used to clean the casing and protect the open hole,
Non-damaging protect the open hole,
Non-damaging underreaming fluid system which meets drilling and completion requirements,
Gravel pack design that minimizes gravel/formation sand intermixing,
Post gravel pack acid stimulation to remove the underreaming-fluid filter cake,
Gravel pack log, and
Well performance. pack log, and
Minimizing formation damage while underreaming and gravel packing a hot, overpressured reservoir requires careful planning and execution. The following planning and execution. The following factors must be considered. The open hole must be protected from incompatible fluids, foreign solids and extreme pressure differentials during displacements. The underreaming fluid must maintain well control, control fluid loss, have adequate carrying capacity, be non-damaging, provide hole stability and generate a filter cake that can be removed. Gravel pack/formation sand intermixing must be minimized during gravel pack pumping operations. Post-gravel pack removal of the salt filter cake pack removal of the salt filter cake (generated by the underreaming fluid) is essential.
This paper describes the techniques used to successfully underream and gravel pack a hot, overpressured reservoir in the pack a hot, overpressured reservoir in the Gulf of Mexico. A custom blend of ZnBr and sized salt was used for underreaming. Removal of the salt filter cake from the open hole sand face was accomplished by employing a 4-stage post-gravel pack acid treatment.
The well is located approximately 116-miles (187-km) offshore from Cameron, Louisiana, in 342-ft. (104-m) of water. Reservoir characteristics included a 15.0 lbm/gal (1.9 g/cm) pore pressure, 180 deg. F (82 deg. C) bottom hole temperature and 400 millidarcies permeability. Deviation through the 180-ft (55-m) sand was 47 deg. The 7-in. (178-mm) casing liner was set at 12,721-ft (3877-m) near the gas/oil contact. The oil bearing portion of the zone was to be underreamed and gravel packed, leaving the gas cap for a later recompletion.