Morvin Hydrocarbon Discovery Offshore Mid-Norway: Exploration and Field Development in A High Pressure - High Temperature Realm

Alf Ryseth¹, Kjell Martin Edin², Bjarte Moltu², Sigurd Hansen², Jan Ove Hansen², et al.
¹Statoil ASA, Harstad, Norway
²Statoil ASA,

Prior to the Lavrans and Kristin discoveries (1994 – 1997), the high pressure – high temperature area in the western Halten Terrace offshore mid-Norway, was regarded as a high-risk area, due to inferred seal failure and poor reservoir quality seen in the first exploration wells. The present paper will review some challenges and opportunities in the area, with particular emphasis on the Morvin discovery (2001), which contains an estimated recoverable volume of about 9 MSm³ light oil. The field will be discussed by its structure, trapping mechanisms and reservoir architecture, with comments on the planned production strategy.
Regionally, Middle Jurassic sandstones (Ile- and Garn fms.) form laterally persistent, high-quality reservoirs of tidal and shallow marine origin. However, overburden exceeding 4,5 km to the west is associated with reservoir temperature and pressure above 160 °C and 700 Bars, respectively. Particularly, the high temperature causes significant precipitation of quartz cement and severe loss of porosity, unless inhibited by grain-coating chlorite preserving anomalous reservoir properties.
The Morvin structure was originally considered as favourable for preservation of reservoir properties. However, two wells now confirm extensive quartz cementation in all reservoirs, reducing porosity to an average of 6 – 8 % throughout. Accordingly the field's production potential represents a key uncertainty, although core data and production tests indicate permeability in the 10 – 100 mD range, apparently maintained by large grain size and favourable packing.
Accordingly, it seems possible that the field can be produced, through a tie-in of hydrocarbons to adjacent infrastructure. Furthermore, a successful development is important for further exploration in the area, which is bound to target still deeper Jurassic structures.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece