The accumulations are stratigraphically, rather than structurally, trapped as the reservoir sands pinch out up-dip to shale.

Eleven gas and condensate bearing reservoir horizons have been identified to date, eight 'shallower' zones in the Lower Carboniferous (Visean) and three 'deeper' zones in the Lower Carboniferous (Tournasian).  The Visean reservoirs, which begin at a depth of approximately 4,700m, currently form the main gas and condensate bearing horizons and reach a gross thickness of 800m –1,000m within the field area.

To date, achieved flow rates in the Visean reservoirs have varied from 1.1 MMcf/d (31,000m³/d) to 7.4 MMcf/d (209,000m³/d).  The Tournasian reservoirs begin at a depth of approximately 5,800m.  These zones have a gross thickness of about 200m but have only been penetrated by five wells due to the depth limitations of the Soviet-era rigs previously used in these fields. Further, these zones are dry gas prone (i.e. have a low condensate content) and to date have only seen modest flow rates with the best achieved rate of approximately 2.9 MMcf/d (82,000m³/d).

Owing to the limitations of the previous wells, significant uncertainties exist as to the degree of sand distribution and gas water contact depth associated with the Tournasian reservoirs. These reservoirs present a key source of potential future upside, not currently included in the 2P reserves estimate of 169 MMboe (Ryder Scott, 2005).  Further potential exists in the lower carboniferous zone, located at depths of around 6,000m to 6,500m.  Exploration activity aimed at this horizon is not expected to commence until at least 2011.