Stratigraphic traps have been expected in the Natih Formation in North Oman based on geological understanding and indications from Top Natih seismic amplitude. Recently the presence of commercially recoverable oil in a stratigraphic trap has been demonstrated by a dedicated exploration and appraisal campaign. This is the first hydrocarbon discovery in stratigraphic trapping configuration in PDO's Block 6.
In 2008 well N1 was drilled based on 2D seismic for a deeper gas target and found 15m of pay in the shallow Natih A. A new 3D wide azimuth (WAZ) seismic was acquired in 2011-2012 over the area where the well is located. The detailed interpretation of the Top Natih carbonate on the new seismic revealed an amplitude anomaly in spite of the absence of any apparent structural closure. Well N1 sits within this anomaly and the HC-water contact interpreted from well logs roughly coincides with the northern edge of the amplitude anomaly. Further analysis of the seismic and well data led to the identification and interpretation of an intra Natih A reflector with a pinch-out towards the south coinciding with the southern edge of the amplitude anomaly.
Seismic inversion supported by QI modeling was fundamental for the evaluation and appraisal of this non-conventional discovery and supported the search for subtle traps over the whole area of good quality seismic. Impedance volumes and map extractions from the volumes indicate high porosity areas which cannot be identified in a similar way on seismic amplitude maps. The volumes and maps were used to select well locations in the appraisal campaign and have also significantly impacted in-place volumes. The data led as well to the identification of a number of additional subtle trap leads in this area in North Oman and supports the concept of porosity preservation by early HC charge.