“Being able to look around the well bore in a radius of 30 m enabled us to drill all four Duva production wells to the highest standards, maximising the length of reservoir penetrated and thus arriving at maximum flow rates,” says Steinar Meland, exploration and development director at Neptune Energy Norway.
Duva is the first development on the Norwegian Continental Shelf where all production wells were drilled using a cutting-edge Geosteering tool, developed by Schlumberger. This recently developed technology enables drillers and subsurface people to make real-time decisions with regards to the optimal direction of the drill bit, such that intra-reservoir barriers can either be avoided or effectively penetrated.
“Conventional Geosteering tools only allow to look both below and above the well bore, but the technology we used returns a full 3D image of the subsurface around the bit, resulting is less uncertainty with regards to optimal well trajectories,” Meland further emphasizes.
The sands of the Lower Cretaceous Agat Formation – the reservoir in the Duva field – consist of several turbidite lobes, separated by mudstones. It is these mudstones that can potentially cause issues, but when imaged correctly and drilled in the most efficient way, the detrimental effect of these barriers can be mitigated.
Above is an example of a Duva well where a slight deviation from the planned trajectory resulted in a much higher degree of reservoir penetration than in case of the original planned well path. The tool imaged the lateral termination of a lobe, but also pointed to a smaller oil-bearing reservoir body slightly deeper than the planned well path. “This allowed us to target this body, and subsequently move upwards again to join the original well path,” Meland illustrates.
Neptune (30% and operator) and partners Idemitsu Petroleum Norge (30%), PGNiG Upstream Norge (30%) and Sval Energi (10%) hope to produce 71 MMbo from the Duva field, which is the first development in Lower Cretaceous sandstones in the Norwegian North Sea. “This could be the beginning of more Agat projects,” says Meland: “We are looking at a couple of prospects to the north of Duva, where results from well 35/9-3 already suggest oil potential on the Agat Fm.
“We are eyeing two prospects in this area, named Ofelia and Hamlet (see map above), and aim to drill those in the foreseeable future,” says Meland. In other words, the Agat Fm is firm on the agenda!
HENK KOMBRINK
