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.

The influence of a slope break on turbidite deposits: An experimental investigation

“…If sandy deposits downstream of a slope break are connected to the updip slope sands, potential hydrocarbons leak through those connections. In contrast, a system with slope-detached sand sedimentation may result in the formation of sealed reservoirs (Doré and Robbins, 2005;Ray et al, 2010). The estimation of the bypass-slope criterion and the comparison with the actual upper slope in a slope-break system provides a rough assessment of the likelihood of whether or not deposits drape the upper slope.…”

“…Sediment deposits in slope-break systems can serve as potential reservoirs for hydrocarbons (Pettingill, 2004;Weimer and Slatt, 2004;Zou et al, 2015). The likelihood of forming a sealed reservoir depends on the proximal termination point of the sediment bodies, like those seen in the Buzzard Field (Doré and Robbins, 2005;Ray et al, 2010). The location of the point where the current transitions from bypass to depositional conditions is here termed up-dip pinch-out (UDPO).…”

Understanding Oil and Gas Shows and Seals in the Search for Hydrocarbons

“…STOIIP estimate is 1.4BBO, making it a world-class giant field discovery (Ray et al 2010). The trap is a combination of fault closures on the north and south and stratigraphic closure to the west.…”

“…One of the largest discoveries globally made in the last 15 years was that of the Buzzard Field in the North Sea (Carstens 2005;Ray et al 2010;Robbins and Dore 2005). The prospective acreage block was acquired by Amoco in the late 1995, in partnership with British Gas.…”

Stratigraphic reservoir compartmentalization: causes, recognition, and implications for the geological storage of carbon dioxide

“…In the Upper Jurassic turbidites of the Buzzard Field, North Sea, stratigraphic compartmentalization was identified shortly after production began by pressure-time analyses of pressure monitoring wells adjacent to a production well (Ray et al 2010). These data showed that, after water injection began, pressure declined in three wells but increased in a fourth.…”