Abstract

We examine the nearly one-year history of a horizontal well equipped with three downhole valves to control production of three presumably distinct sand channels of the Ness formation in the Oseberg field. We present a modeling methodology to assess the impact of downhole flow control on production performance, and explain how this methodology addresses the problems of zonal allocation and valve settings selection.

Introduction

Oseberg is an offshore field in the Norwegian sector of the North Sea and is operated by Norsk Hydro. Pressure maintenance is ensured by re-injection of associated gas and imported gas from the nearby Troll field. In addition, sea water injection takes place in some parts of the field. Peak production reached around 510,000 bopd in 1993–94, with the Oseberg Field Centre (OFC) and Oseberg C (OSC) platform contributing 360,000 and 150,000 bopd respectively. Current production (May 2001) from both platforms is about 210,000 bopd. Most producers have experienced gas breakthrough, and oil production is now limited by gas handling capacity. Field production has been essentially from the Oseberg formation, though Tarbert and Ness are also hydrocarbon bearing. Ness is a sequence of channel sands embedded in non-reservoir facies, and is the object of active development. There are currently (May 2001) six dedicated Ness wells, i.e. two at OSC (C-16, C-19) and four at OFC (B-27B, B-21B, B-29B, B-38B). Four of these wells (B-21B, B-29B, B-38B and C-19) are equipped with an 'intelligent' completion. We examine in this paper the performance of well 30/9-B-38B, which is the last well drilled exclusively in Ness and has now been producing for one year. The performance of the first well with an 'intelligent' completion has been reported elsewhere (Ref. 1); the wells with fuller instrumentation have recently come on stream.

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