Reservoir Management of Skjold: A Mature, Waterflooded, Fractured Chalk Field in the North Sea
- Jack Orman (Maersk Oil) | Andreas Harrer (HOT Engineering GmbH)
- Document ID
- Society of Petroleum Engineers
- SPE Europec featured at 79th EAGE Conference and Exhibition, 12-15 June, Paris, France
- Publication Date
- Document Type
- Conference Paper
- 2017. Society of Petroleum Engineers
- 5.2 Reservoir Fluid Dynamics, 3 Production and Well Operations, 4.6 Natural Gas, 5.5 Reservoir Simulation, 3.5 Well Intervention, 5 Reservoir Desciption & Dynamics, 5.4.1 Waterflooding, 5.7 Reserves Evaluation, 5.7.2 Recovery Factors, 3 Production and Well Operations, 5.4 Improved and Enhanced Recovery
- Fractured, Chalk, Waterflood, Mature, Reservoir Management
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- 188 since 2007
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Skjold is a mature, water flooded fractured chalk oilfield in the Danish North Sea. A satellite to the Gorm complex, it has been on production since 1982 and has produced 300 million stb of an estimated 790 million stb initially in place (38% recovery factor to date). The field is operated by water injection due to insufficient aquifer support. One major current challenge is that many of its wells produce at >95% water cut. The main reason is that a large proportion of the injected water is recycled through the same parts of the reservoir which are by now already well swept. These are often highly fractured areas of the field, connected via specific zones in the injection and production wells. The result is that large quantities of unproduced oil remain behind pipe at production wells.
A project called Skjold LTRO (Locate the Remaining Oil) was set up with the intention of identifying viable ways to increase the Skjold production and reserves. An initial data grounding exercise was undertaken where the rich Skjold static and dynamic dataset was thoroughly analysed. From this, significant insight was gained into how the Skjold reservoir is plumbed together. The natural progression was to integrate all the data and learnings, utilising the well-established platform of dynamic reservoir simulation. Concurrent data interpretation with permanent interaction across disciplines was key to arrive at a sound understanding of the complex fracture network which dominates Skjold reservoir fluid flow.
The work has led to the identification of multiple Skjold well intervention and water injection optimization opportunities: Throughout 2016, reduced water injection was trialled at specific Skjold wells. The trials have led to a sustained increase in field oil production potential of around 20%, as well as lowering operational expenditure (OPEX). A campaign of well interventions, based on the project learnings, has also been carried out in 2016. Finally, the project work has revealed that, several years prior to the end of field life, significant further value can potentially be added through completely shutting in the Skjold water injection, partly as a result of the pressure depletion leading to increased recovery from solution gas drive.
This paper describes how reservoir management is being approached for a late-life North Sea fractured chalk oilfield in a low oil price environment.
|File Size||1 MB||Number of Pages||13|