Abstract
A new development well in the Halfdan Field, well HBB-05, was selected as a candidate for the first Multilateral Completion Stimulation Technology (MCST) installation in the Danish sector of the North Sea. Placed in a thinner part of the Ekofisk formation it was important that the well didn't communicate with the underlying Tor formation, which would reduce the recovery from both reservoirs. An alternative completion was sought that would enhance reservoir contact, while protecting reserves.
Halfdan is a laterally extensive field and comprises a high porosity (25% - 35%), low permeability (0.5 mD – 5 mD) chalk reservoir of Maastrichtian (Upper Cretaceous) and Danian (0.1-1mD) (Lower Paleocene) age. The main field, located within the Maastrichtian Tor formation, is developed with long horizontal wells of 10,000 ft - 15,000 ft reservoir sections drilled in a parallel pattern of alternating oil production and water injection wells spaced 600 ft apart.
A multizone MCST was placed in a thin, layered chalk aiming for an increased effective well bore radius. The well consisted of a 4-½" liner with a new record number of subs placed in one well; 56 MCST subs. Each sub contained four needles at 90 degrees phasing capable of penetrating up to 40 ft. into the reservoir. The subs were placed in the distal 3,000ft horizontal section, beyond the reach of coiled tubing. The liner was installed on a work string starting at 16,820 ft.
First time usage of MCST offshore Denmark creates a potential game changer for carbonate reservoir productivity enhancement. Production improvement over conventional stimulation methods where the following challenges may be addressed: –Thin, layered chalk–Need for increased wellbore radius–Extended reach reservoir sections–Beyond the reach of coiled tubing