DONG Energy is involved in drilling of exploration, appraisal and production wells – from planning to execution and documentation.
Since water depths and reservoir conditions vary from licence to licence, exploration, development and production of oil and natural gas often require different techniques. We are not only involved in many standard drilling operations of exploration wells – we are also capable undertaking more advanced drilling operations required because of scarce resources and consequently, the resources become harder to reach.
Under-balanced drilling (UBD) is a special drilling technique used for drilling oil and natural gas wells. The method requires special equipment, expertise and personnel. We have experience with UBD from the South Arne field located in the western part of the Danish sector of the North Sea. During UBD, the pressure in the well is lower than the liquid pressure at the location where drilling takes place. As the well is drilled, the oil and natural gas flow into the well and to the surface.
This is the opposite of a ’normal’ situation where the pressure in the well is kept at a higher level than the pressure in the formation to avoid occurrence of hydrocarbons in the well. UBD is a more complicated but lucrative drilling technique and it is required for further development of the South Arne field.
We have achieved good results from horizontal drilling in in the North Sea; eg the South Arne field, the Siri area and in the Trym and Oselvar fields. In the Siri field, this has helped extend the life of the reservoir because we are able to drill longer reservoir sections in each well. It enables us to make connections to more hydrocarbon pockets than we were able to using vertical drilling.
High pressure, high temperature
We have drilled in reservoirs with high temperatures and very high formation temperatures several times (HPHT), eg in the Hejre field in the Danish sector of the North Sea close to the Norwegian/Danish demarcation line. It is technically challenging to drill under these conditions, but it is necessary to enhance our reserves in area where we operate at present, and it will prepare us for future challenging operator tasks.
Deep sea drilling
Since 2000, we have undertaken deep sea drilling and drilling in the arctic regions in several of our licences. This means that we drill further out at sea and drill deeper into the seabed to enter concealed oil and natural gas pockets.
Deep sea drilling is more complicated and time-consuming than drilling standard wells, because equipment must be installed on the seabed, and in these areas the current is stronger and the weather conditions are more extreme.
DONG Energy is one of the leading energy groups in Northern Europe. Our business is based on procuring, producing, distributing and trading in energy and related products in Northern Europe.