Extreme Fast Track: Combined Subsea HPHT Horizontal Production and Exploration Well

Abstract

The last well on the Morvin subsea High Pressure High Temperature (HPHT) field, located offshore Norway, was a combined production and exploration well. This well had as objective to drill through two known producing reservoirs and then continue drilling whilst dropping into two deeper and unexplored reservoirs. Drilling conditions on Morvin are very tough due to extremely hard and abrasive sandstone formations combined with long horizontal reservoir sections with temperatures of up to 167° C. Neighbouring wells had been on production for several months causing depletion in the upper formations. This depletion had to be carefully monitored and managed to prevent any losses/well control scenarios. In order to prove the reservoir fluid system in the exploration part of the well several operations were conducted. These consisted of, amongst others: extensive logging, coring, pressure points and a newly developed formation sampling tool. The results were used to adjust the well path and to decide whether the new formations would be completed, or cemented back. An HPHT oil and water tracer system was developed to be installed in the completion. The specially developed tracer technology enables the localisation of any possible water or oil producing formations. In addition, blank pipe combined with openhole swell packers were installed between the different formations for zonal isolation. Wireline conveyed bridge plugs give the possibility to plug water produsing zones back. This paper describes the strategy which was followed, together with the technology that was used, to prove the reservoir fluid system in the exploration part of the well. After assessing all data it was decided to complete both exploration formations. The well was successfully put in production 5 weeks after the exploration part was finished making this an extreme fast track project.