Offshore staff
ABERDEEN, UK -- Baker Hughes has deployed its Reservoir Navigation Services equipment spread in a recent heavy-oil appraisal well in the UK northern North Sea.
Xcite Energy Resources operates the Bentley field, which was discovered in 1977, 160 km (99 mi) east of the Shetland Islands in 113 m (370 ft) water depth. The field contains an estimated 700 MMbbl of heavy (10-12° API) viscous oil within a four-way dip closure at the Upper Palaeocene Dornoch sandstone reservoir.
As there was little usable offset data available on the Dornoch formation’s unconsolidated sands, XER asked Baker Hughes to provide the RNS service and also a method to locate a casing point based on old logging-while-drilling (LWD) measurements and to provide a competent casing shoe in the base of the overlying Balder formation.
“To determine if this was feasible, we reviewed the offset well data and, based on the limited LWD measurements we had been given, this was not possible,” said Baker’s David Holbrough, senior supervisor and U.K. RNS focal point.
“However, because the RNS procedure is primarily geared toward optimizing well placement in highly deviated and horizontal holes, we felt that our RNS offering would be of great benefit to ensure that the horizontal side track was placed in the most productive region of the reservoir with the maximum net-to-gross sand and the maximum net-to-gross oil pay.”
Baker Hughes says the RNS and AziTrak deep azimuthal resistivity tools have proven effective in heavy oil fields in the central and northern North Sea in several infill drilling programs.
“The work scope for the well and its side track was an initial deviated pilot hole to provide data to ensure that the top reservoir depth uncertainty was minimized and that the reservoir geology was understood,” said Alex Fraser, RNS supervisor, U.K. operations.
“Also, it was to allow the optimum positioning of the horizontal side track across the structure and to provide reservoir and fluid information to enable subsequent interpretation of the flow test and preparation for a future development.”
Using the RNS and AziTrak tools, Baker Hughes successfully drilled 555 m (1,823 ft) of 100% net-to-gross sand.
“From reservoir entry to total depth, the well was exclusively drilled in sand with 100% oil-pay,” Fraser adds. “Eighty-four percent of the reservoir section was drilled within 12 ft (3.6 m) of the top reservoir boundary, maximizing standoff to the oil/water contact and minimizing attic oil above the wellpath.
“We landed horizontally in the best quality reservoir zone, delivering an average 32% porosity compared to an average 27.5% in the pilot hole, demonstrating a higher than predicted top reservoir at pilot and side track reservoir entry points, and delivering information on depth and morphology of top reservoir along the horizontal section.”
Holbrough added that real-time geosteering decisions were made based on the newly available interface between the RNS software and the Dynamic Graphics† CoViz 4D visualization suite. “Data can be accurately visualized in 3D space allowing for a high degree of confidence when making important azimuthal steering decisions to minimize attic oil.
“Integration of the RNS interpretation and distance to bed calculations facilitated the construction of 2D minimum tension grids, the results of which accurately depicted the morphology, orientation, and position of the reservoir roof and were used to update the 3D earth model post-well.”
Baker Hughes made available its BEACON collaboration facility in Aberdeen to bring all the well’s decision makers together in one location.
Although Xcite had anticipated production of 1,500-2,400 b/d, the well tested at a surface-constrained 2,900 b/d, with assistance from an electrical submersible pumping system. This program helped prove the commerciality of the Bentley field, which is now moving towards a first- stage development.
05/27/2011
