In 2006, Oilexco North Sea Limited developed the Brenda field in the Central North Sea. A total of over 8000 ft of horizontal section has been drilled in three horizontal production wells, all within Palaeocene-aged Balmoral turbidite sandstones below a Sele shale cap rock. To maximize reserves recovery, the horizontal drainholes not only had to cut as much of the good reservoir sand as possible, but as the Brenda field depends on water drive as its main production mechanism it was essential the wells were placed as close as possible to the top of the reservoir to ensure a greater long term field life and given the thin oil column, reduce the volume of attic oil. Generally the location of the top reservoir is visible on seismic but with significant sub-seismic variations in the top reservoir topography. Therefore to help optimal well placement, Oilexco used a new deep and directional LWD measurement in the Bottom Hole drilling Assembly in order to map the relative position of the drainhole to the overlying roof shales. As the reservoir top and internal shale layers were mapped, geosteering personnel had the ability to make changes to the directional plan to allow the well to be placed in the optimal location, at the top of the reservoir, often within 2 ft of the roof without reservoir exit.

The Brenda wells have proved to be well positioned using these new geosteering techniques. Initial flow testing of the wells was very positive with combined rates of over 26,400 BOPD with minimal reservoir drawdown. It is expected that the use of the new logging methods will result in more effective and uniform drainage of the Brenda reservoir sands, while minimizing the chance of premature water influx.

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