--> Abstract: Dan Field--Danish North Sea, by L. N. Jorgensen; #91004 (1991)

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Dan Field--Danish North Sea

JORGENSEN, LARS NYDAHL, Maersk Oil & Gas, Copenhagen, Denmark

The Dan field is a simple, salt-induced structural dome with the bulk of oil and gas trapped in low permeability chalk of Upper Cretaceous and Lower Paleocene age. Oil in place is in excess of 2 Bbbl.

Matrix permeabilities are generally less than 3 md. Permeability enhancement from natural fracturing as it is known from other chalk fields in the North Sea appears to be limited.

The lack of natural fracturing gave rise to rapid production decline in the wells drilled during the 1970s and early 1980s. Significant effort was continuously directed towards overcoming the lack of natural fracturing.

In 1987, the first horizontal well was drilled in the Dan field. This was to be the industry's first hydraulically fractured well. Since then, seven more horizontal wells with massive propped hydraulic fractures have been drilled in the field. The technique has more than doubled production per well, thereby proving to be viable for further development of the Dan field. Horizontal wells have recently successfully been placed in three other chalk fields in the Danish North Sea.

The introduction of horizontal wells has required strong geological participation in the well planning phase. In particular, determination of the orientation of the in-situ stress has been the subject of extensive investigation.

In the drilling phase, geological involvement has led to optimization of certain geological techniques, such as high-resolution biostratigraphy that is required to ensure correct stratigraphic placement of the individual well.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)