Appendix A Denmark
Guidelines for Well Abandonment
“A Guide to Hydrocarbon Licences in Denmark” (DEA, 2007) contains the section “Guidelines for Drilling - Exploration” which was published in 1988 and revised in 2005. The latter section contains guidelines for well abandonment. This appendix presents an overview of these guidelines1:
- Normally, an exploration well shall be abandoned permanently when drilling operations as well as relevant logging and test production have been carried out. Under special circumstances the DEA may permit a well to be abandoned temporarily without permanent plugging. To obtain such permission the Licensee must submit an application indicating how and when the well is to be abandoned permanently or operations will be resumed. Furthermore, the application must describe the responsibility and supervision situation during the temporary abandonment.
- Application for permission to stop operations and to plug (permanently or temporarily) and abandon a well, shall together with a copy of essential logs and other relevant documentation material, if any, be available to the DEA at least 24 hours before estimated commencement of the actual abandonment activities. In the application the Licensee shall give the reasons for the planned plugging and specify how the plugging will take place and how the plugs will be checked. The well site condition after the abandonment and procedures for verification of this must be stated.
- In cases where the well is uncased opposite permeable zones, plugging shall be carried out so that there can be no flow of fluid through the hole (normally by cementing at least 50 m below and above the individual zones).
- Where there is an open hole below the deepest casing, a cement plug shall be placed in such a manner that it extends at least 50 m above and below the casing shoe. The top of the cement plug shall be located by load testing. Where the condition of the formation makes cementing difficult, a mechanical plug may be positioned in the casing, within 50 m from the shoe as an alternative to the cement plug below the shoe. In addition, a cement plug, at least 50 m long shall be placed on top of this plug. The performed plugging of the open hole section shall be pressure tested for sufficient time and with enough differential pressure to detect a possible leak or mechanical failure of the plug.
- Perforated zones must be plugged with cement so that no fluid flow to or from the well is possible. Where possible perforated intervals shall be isolated with cement plugs through the individual perforated zones and with 50 m long cement plugs below the lowermost perforation and above the uppermost perforation. Alternatively the perforated zones can be isolated by a combination of a mechanical plug squeeze cementing of the perforations and cement plugging above the mechanical plug.
- If a liner has been used, a cement plug shall be placed in such a manner that the plug extends 50 m above and below the point of suspension. Alternatively a mechanical plug followed by a 50 m long cement plug can be set just above the liner hanger. The top of the plug shall be located by load testing and the plug shall be pressure tested as specified in item 4.
- In the innermost casing a cement plug must be placed from the shoe depth of the previous casing and 100 m up.
- It must be ensured that no communication from down hole formation to the sea-bed/surface via any casing annulus is possible.
- A cement plug, at least 100 m long, shall be placed near the surface.
- The total weight of the cement plugs in the well and the weight of the fluid between the plugs shall ensure that as a minimum the system is in balance with any pressure which may develop in the borehole.
- When a well is abandoned the original state of the well site shall be re-established. Reasonable departure from this requirement may be approved by the DEA (approval by other authorities may also be necessary). When abandoning a well, the condition of the well site shall be verified. Obtained documentation shall be submitted to the DEA.
1 DISCLAIMER: The English version of this document is an unofficial translation. In case of discrepancy, the original Danish text shall prevail.