This paper presents the history of the development of an oil rim in a chalk gas field. In a low relief gas field, oil rim development is problematic because the proximity to fluid contacts leads to gas and water coning and a significantly decreased oil production. This problem has been reduced in Tyra by developing the oil rim with horizontal wells. The best oil wells are in areas where gas production is impaired by tight chalk immediately above the gas-oil contact, and where the oil rim Is thickest.

The field was initially developed as a gas field due to poor production tests of the oil rim during the appraisal of the field. An understanding of the distribution of oil led to the drilling of a successful oil rim well. The advent of horizontal drilling increased the scope for oil rim development and accelerated the drilling of oil rim wells. Extensive reservoir simulation work provided the reservoir management tool for the planning of an oil rim development under the constraint of a gas sales agreement. H has resulted in a plan for further development of the Tyra gas field. According to the plan additional gas Injection will in a period of seven years result in low net annual gas off-take from the Tyra gas production wells and the main production will instead come from horizontal wells in the oil-rim. During this time the majority of the oil reselrves will be produced.

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