Well-site biostratigraphy of Danish horizontal wells

Abstract

Abstract The number of horizontal and subhorizontal wells drilled has significantly increased over the last decade, especially during the last five years, and the use of horizontal wells in oil-field production and development is now routine. In 1987 Maersk Olie and Gas AS drilled the first horizontal well on the Dan Field. Since that time biostratigraphers at Robertson Research International Limited have been involved in Maersk’s pioneering work on the development of steering techniques for horizontal wells in the Danish sector of the North Sea. Well-site biostratigraphy has been successfully used to aid in the steering of these horizontal wells. The background studies leading to the erection of highly detailed local biozonal schemes capable of detecting changes over vertical distances as little as 1 foot are described. The logistics of how well-site biostratigraphy is carried out at the well site is explained. In addition to Dan, well-site biostratigraphy has been successfully applied to development wells from several other Danish North Sea carbonate fields operated by Maersk Olie og Gas AS on behalf of the Danish Underground Consortium (a joint venture between Shell, Texaco and AP Møller). These fields include Harald, Kraka, Gorm, Roar, Skjold, Svend, Tyra and Valdemar. Over 100 wells from Danish fields have to date been effectively steered using high-resolution biostratigraphy. Vertical targets of 10–20 feet or less have been successfully followed over distances of several thousand feet.