ABSTRACT
The 15/9 Gamma gas field lies in the central North Sea midway between Norway and the United Kingdom. The field was discovered in 1981 and, by mid-1982, 3 additional confirmation wells had been completed. The reservoir is provided by a complex of Paleocene submarine-fan sandstones. The sandstones decrease in thickness across the field from 150 m (492 ft) in the northwest to less than 58 m (164 ft) in the southeast. The sandstones pinch out entirely a few kilometers beyond the field. The volume of gas in place is on the order of 65 × 109 m3 (2.3 tcf). The trap in the Paleocene sandstones is interpreted as being formed by a mid-Tertiary compressive phase which reactivated preexisting basement faults. Detailed structural analysis suggests that WNW-ESE-trending faults have suffered repeated strike-slip offset associated with Jurassic transtension and mid-Cretaceous and middle Tertiary transpreariou. The writers surest that the WNW-ESEtrending basement faults represent a northwestward continuation of the Tornqist line, a fundamental fracture zone bounding the East European-Scandinavian platform, which had previously been considered as terminating at the line of the Oslo graben, about 250 km (155 mi) to the southeast.
