Buzzard Field Research Articles

The Buzzard Field, Blocks 19/5a, 19/10a, 20/1 and 20/6a, UK North Sea

Abstract The Buzzard Field remains the largest UK Continental Shelf oil discovery in the last 25 years. The field is located in the Outer Moray Firth of the North Sea and comprises stacked Upper Jurassic turbidite reservoirs of Late Kimmeridgian–Mid Volgian age, encased within Kimmeridge Clay Formation mudstones. The stratigraphic trap is produced by pinchout of the reservoir layers to the north, west and south. Production commenced in January 2007 and the field has subsequently produced 52% over the estimated reserves at commencement of development, surpassing initial performance expectations. Phase I drilling was completed in 2014 with 38 wells drilled from 36 platform slots. Platform drilling recommenced in 2018, followed in 2019 by Phase II drilling from a new northern manifold location. The evolution of the depositional model has been a key aspect of field development. Integration of production surveillance and dynamic data identified shortcomings in the appraisal depositional model. A sedimentological study based on core reinterpretation created an updated depositional model, which was then integrated with seismic and production data. The new depositional model is better able to explain non-uniform water sweep in the field resulting from a more complex sandbody architecture of stacked channels prograding over underlying lobes.

The Golden Eagle, Peregrine and Solitaire fields, Blocks 14/26a and 20/01, UK North Sea

Abstract The Golden Eagle Field is located 18 km north of the Buzzard Field in the Moray Firth, and consists of oil accumulations in the Lower Cretaceous Punt and Upper Jurassic Burns Sandstone members. The development area comprises three fields, Golden Eagle, Peregrine and Solitaire, but up to 90% of the oil-in-place and ultimate recovery are in Golden Eagle. The two satellite fields are primarily structural closures, while the Golden Eagle Field reservoirs have a major element of stratigraphic pinchout. Production commenced in October 2014 and approximately 140 MMbbl of recoverable oil is anticipated over its field life from the 19 development wells (14 producers and 5 injectors) that form the initial development phase. Production performance to date has exceeded expectations, aided through the use of completions that provide zonal control of the reservoir units which has successfully supported reservoir management and improved sweep efficiency. A number of significant lessons have been learned during the early stages of the field life from the integration of dynamic data (real-time downhole fibre-optic reservoir monitoring instruments, inter- and intra-well tracers, and well interference tests) and seismic data improvements (post-start-up acquisition of high-density ocean-bottom node seismic and depth-conversion improvements).

Economic threshold of CO2-EOR and CO2 storage in the North Sea: A case study of the Claymore, Scott and Buzzard oil fields

CO2-enhanced oil recovery in the North Sea can provide additional oil revenues, prolong the productive lifetime of oil fields, and potentially catalyse the large-scale deployment of CO2 geological storage. Under the current low oil prices, around and below 50 €/bbl, the investment is more difficult to justify. Here we show three case studies for the Claymore, Scott and Buzzard fields offshore of Scotland. A techno-economic assessment is made with the PSS IV simulator considering a low oil price scenario, market uncertainties and geological uncertainty. Stochastic parameters and project flexibility are used to simulate realistic project decisions. The Modified Internal Rate of Return (MIRR) is introduced as a performance indicator in combination with hurdle rate scenarios of 10, 11 and 12% for risk compensation. The possibility of continuing the storage of CO2 after oil production has stopped is considered, and reservoir uncertainty is introduced as stochastic parameters defining the EOR production profile. In terms of total value and development probability, the Buzzard field has the highest potential for a successful CO2-EOR project in all of the simulated scenarios, followed by Claymore and Scott. When compensating for field size, the Buzzard field still has the highest value per barrel of additionally produced oil, but the Scott field has a higher efficiency compared to Claymore. With an increase of the hurdle rate, the probability on investment in CO2-EOR decreases, but the probability on a profitable project increases. It also becomes more likely that if an EOR project is started, it will be followed by a CO2 storage phase. A hurdle rate of 12% even completely offsets the financial risk under the simulated conditions.

The Buzzard Field: anatomy of the reservoir from appraisal to production

Abstract The Buzzard oil field in the Outer Moray Firth, Central North Sea was discovered in 2001 and rapidly appraised during 2001–2002. Pre-production development drilling began in 2005 and the field was brought on stream in January 2007 by operator Nexen Petroleum UK Ltd. The Buzzard reservoir consists of Upper Jurassic deep marine turbidites within the Kimmeridge Clay Formation. Sands were derived from the shelf to the west and the resulting mass flow deposits were contained within a fault-bounded basin, whose margins were prone to mass wastage. The deposits pinchout to the west and thicken eastwards into the basin and hydrocarbon source kitchen. Following appraisal drilling, the high net-to-gross reservoir was interpreted as well connected. Interbedded shale layers were thought unlikely to control flow through the reservoir. However, a biostratigraphic review indicated that a consistent biostratigraphic event, indicative of reworking, could be identified field-wide. This shale layer is interpreted as a large-scale, muddy slump, extensive enough to form a significant vertical barrier to flow. Subsequent production data, modelling and chemostratigraphy studies suggest greater subdivision and vertical baffling within the main reservoir. Interpretation of these data has led to a move away from early models of Buzzard as a tank-like reservoir to a model dominated by compensationally stacked lobes, where hydraulic flow is influenced by sand body geometry and extensive shales. A comprehensive understanding of the Buzzard Field has only been possible through full integration of core, log and dynamic data, benefiting from a high density of well control, an extensive data acquisition programme and early reservoir monitoring. Ongoing reservoir management, involving continuous update of both the geological and dynamic models in response to new data, has enabled an evolving understanding of the Buzzard reservoirs, and placed the operator in an excellent position to proactively address future development challenges.

Nexen's Buzzard to Fly with Fourth Platform

Canada's Nexen is pushing ahead with the next phase in the development of its Buzzard field in the UK sector of the North Sea, with a plan to install a new hydrogen sulfide (H2S) treatment platform due to get into full swing this year. The new "crude-sweetening" platform will be installed as part of the Buzzard Enhancement Project on the 600 million bbl field, which straddles two licenses—P.986 (Blocks 19/10 and 20/6) and P.928(S) (Blocks 19/5a and 20/1S). Buzzard is the largest discovery on the UK Continental Shelf (UKCS) in more than a decade and has been developed with three bridge-linked platforms, soon to become four when the new platform is fully installed in 2010. The field is operated by Nexen with 43.2% interest, and partners include Petro-Canada 29.9%, BG Group 21.7%, Dyas UK 2.6%, and Oranje-Nassau 2.6%. The field was discovered in the Outer Moray Firth in May 2001 with the 20/6-3 exploration well, which hit a 400 ft oil column and was flow tested at 6,547 BOPD of 32ºAPI crude oil. Construction work on the development was completed in 2006 and first oil flowed in January 2007. Peter Addy, Nexen's Project Director for Buzzard, said that production is currently running at 210,000–215,000 BOPD and 30 MMcf/D of gas through 14 production wells with a further 12 producers planned. Reservoir pressure is currently sustained by water injection. The John Shaw semisubmersible and the Transocean Galaxy III jackup rigs have carried out the development drilling program on the wells that feed into the Buzzard processing complex. The production platform receives multiphase reservoir fluids through the bridge-linked wellhead platform and processes them to separate crude oil, gas, and water. Oil is then exported through an 18-in., 30-km pipeline, tieing-in subsea to the Forties Pipeline System. From there it is sent on through the onshore section of the pipeline system to Kinneil, crude oil stabilization terminal on the Firth of Forth in Scotland, for further processing and export by tanker. Gas is exported by a 10-in., 29-km line to the Captain T point on the UK Frigg gas pipeline.

The geological exploration techniques applied by BG in evaluation of the Buzzard Field prior to discovery

Abstract Substantial technical studies were undertaken by BG in the exploration effort which preceded the discovery of the Buzzard oil field. These studies were of value in forming BG’s perception of prospect risk and reward and confirming the company’s commitment to drill the prospect. Studies ranged from standard evaluation techniques to application of cutting edge technology of the time to innovative applications of software to address specific uncertainties or risks. BG perceived the prospect to be of moderate to high value, with a substantial upside reward, and since acquisition of 3D seismic to have moderate risk. This perception derived from several factors that may be peculiar to this particular prospect: • an existing well with an oil accumulation, located down dip, proving a migration path from oil mature source and the presence of thick sandstone units of excellent reservoir quality, logged and cored • tectonic tilting had both accentuated trap relief significantly increasing trap volume, and aided migration direction • the abundance of offset well data allowing an understanding of basin history and a robust geological model Furthermore the BG evaluation benefited from: • involvement of in-house specialists in sedimentology, basin analysis and geophysical modelling • application of the findings of research projects at Edinburgh and Leeds Universities in the fields of Moray Firth structural development and Turbidite Sedimentation respectively

The Buzzard Field

The Buzzard Field is one of the largest fields to be discovered on the United Kingdom Continental Shelf in the last 25 years; it has a current reserves estimate of over 400 × 10 6 BBL. It lies some 50 km northeast of the Scottish mainland and 20 km west of the Ettrick Field in a water depth of 300 ft. The Buzzard Field was discovered in May 2001 by well 20/6-3. This well encountered high quality 32° API oil trapped within a latest Oxfordian to Early Volgian age reservoir informally defined here as the Buzzard Sandstone Member. The side-track penetrated an oil–water contact at 9194 ft TVDSS, establishing a minimum hydrocarbon column of 750ft. The field was the subject of an appraisal programme in late 2001 and early 2002, with eight wells and side-tracks drilled to define the field extent. These wells, coupled with a continual improvement in the quality of the seismic data, have helped to reduce the uncertainty associated with estimates of the STOIIP and reservoir geometry. The trapping mechanism for the field involves a complex stratigraphic pinchout of reservoir sands within shales of the Kimmeridge Clay Formation. This is combined with a downthrown faulted closure against Palaeozoic rocks. The Buzzard Sandstone Member comprises base of slope, submarine gravity flow sands with excellent porosity and permeability characteristics.