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--- wellsite_biosteer [20/03/2023 16:18] – created mike_gss
+++ wellsite_biosteer [21/03/2023 13:15] (current) – mike_gss
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 //The basic components of a horizontal production well. With greater familiarity of the field, fewer (if any) pilot holes may be needed.//
+**Joanne Field (UK North Sea) “Chasing the Reservoir”**
+In the structurally complex Joanne Field of the UK North Sea, Holmes (1999) demonstrated that close analysis of the section reveals in situ claystone layers above and below the reservoir sand unit (which in itself is relatively unfossiliferous) which are separated by limestones containing re-worked older microfossils. Each unit can be fingerprinted by its specific type of in situ or re-worked component. A “combined biozonation” of in situ and re-worked forms can be constructed for the succession.
+During the drilling phase it can be seen that the well bore exited the reservoir on several occasions and that the wellsite biostratigraphic determinations allowed the well trajectory to be adjusted in order to re-acquire the reservoir as quickly as possible. In this very complex reservoir setting the well bore did not remain within the reservoir for very long before the next exit, however, the total percentage of borehole length within the reservoir by the time TD was reached was still very much more than was expected than by drilling //without// the use of wellsite biostratigraphy.
+{{:wellsite06.jpg?nolink|}}
+//Biozonation and events used on the Joanne Field (Holmes, 1999). The zones comprised intervals of in situ and reworked microfossils, each having slightly different compositions to allow correct identification.//
+{{:wellsite07.jpg?nolink|}}
+{{:wellsite08.jpg?nolink|}}
+//Two wells illustrating the complexity of the Joanne Field and the well trajectories "biosteered" to maximise exposure to the reservoir interval. Biostratigraphy allowed to quick return to the reservoir after frequent exits due to dip changes or structural features such as faults.//
+Because wellsite biostratigraphy was shown to be an effective tool at maximising reservoir exposure, the production strategy for the field was changed from plans to drill 16 conventional wells, to 9 “horizontal” wells resulting in an overall estimated saving of $12 million.