GYDA: Recovery of Difficult Reserves by Flexible Development and Conventional Reservoir Management

Abstract

Gyda is a 200MMstb field, located in the North Sea Central Trough, offshore Norway. The field was discovered in 1980, and first oil was produced in 1990. It is one of the deepest, hottest and poorest quality oilfields in the North Sea. The structurally complex field contains three different fluid types, and the crude is asphaltene rich. The shallow marine sandstone reservoir is gently dipping, wedge-shaped, with an oil column of 500m. The field receives no aquifer support and is being developed by waterflood. The connate water/injection water mix has a severe scaling tendency.Development of the field is set against a background of tight cost control within the industry generally, and within the Operating company in particular. With six wells drilled per year, a current offtake rate of 70Mstbpd, and areas of the field showing early mature performance, the challenge is to maintain production whilst keeping costs low. The development is therefore managed by maintaining maximum flexibility in drilling locations, sequence and well use, by use of appropriate technology, and by the innovative use of conventional techniques to exploit the field's characteristics. This paper describes: 1. reservoir complexity; 2. the technologies employed to meet the reservoir management challenges; 3. development philosophy; 4. field management history; and 5. value generation.

Analysis of Mineral Reactions Occurring in the Gyda Field Under Seawater Injection with the Help of Geochemical Non-Isothermal Model and Produced Water Data

“…When the production of oil began in July 1990, it was known to be the deepest, hottest and lowest permeability oilfield in the North Sea at that time (Rothwell et al, 1993). Peak oil production of 20,100 m3/day was achieved during 1993.…”

“…(Figure 2) The Crest was initially developed in the early 1990s, and high water-cut have been observed at most of the wells in the Crest and down-dip areas, but there is still high potential for oil production in the Gyda south area (Rothwell et al, 1993).…”

The Development of a Scale Management and Monitoring Program for a High-Temperature Oil Field During the Production-Decline Phase of the Life Cycle

“…1), and production has demonstrated that communication in some reservoir layers is good. Nevertheless, several distinct field compartments are defined from pressure data, and geochemical data from Gyda South indicate that sealing faults controlled the filling and cementation history 1 .…”

“…Gyda is currently operated by Talisman-Energy Norge A/S (61 %) on behalf of DONG (34 %) and Norske AEDC A/S (5 %). It was originally operated by BP Norway Ltd., and when it came on stream in July 1990, it was the deepest, hottest and lowest permeability oilfield in the North Sea 1 .…”

“…There are 32 well slots of which currently 15 are for producers with a further 10 wells dedicated to water injection. From the outset it was recognised by BP that the formation water / injection water mix would lead to a severe scaling tendency 1 . The current operator, Talisman, have sought to review the scale management process to ensure that any lessons that can be learned from analysis of the earlier stages of production may be applied to ensuring effective scale control to the end of the field life cycle.…”