Prospectus re Admission to the Official List - Heritage Oil

RPS EnergyHeritage Oil – Competent Persons ReportFigure 28: RPS Top Reservoir Depth Map, Block 122FEB200803432250The maximum size of the structures in Block 1 range from 5 to 69 sq km. Heritage mapping is based on astrong reflector which they interpret, based on seismic facies, to be the top of a sandy sequence. Theinterpretation of this unit is very robust as the seismic quality is very good. Heritage has identifiedamplitude anomalies at the crest of structures throughout the block which could be indicative ofhydrocarbon fill although the anomalies do not cover the entire area of the larger prospects. The concernthat any oil might be biodegraded due to the very shallow reservoir depth is partly allayed by the presenceof relatively light oil in the Paraa oil seep (Section 5.3).As in Block 3A, Heritage has used time structure maps to determine the extent of prospects and areas forvolumes. RPS has re-gridded the mapped horizons and depth converted them using average velocitiescalculated from the time-depth relationship seen at Kingfisher-1.It is stressed that prior to the completion of the ongoing seismic programmes, large areas of both blocks,particularly the north of Block 1A are still relatively unexplored, although high resolution satellite data isunderstood to show the presence of some potentially interesting structures.5.5. VolumetricsRPS has used area-depth curves calculated from the RPS depth maps which were produced by RPS foreach prospect at each reservoir horizon. RPS applied an uncertainty on possible leak point/spill points tothe prospects. For the P1/M6 cycle an appropriate range of gross reservoir thickness was taken from theKingfisher 1A well and a stacking factor of three was applied to calculate the volume in the Kingfisherdiscovery and the Kingfisher North prospect. For other P1/M6 prospects a range of stacking factorsbetween 2 and 4 was applied as there is uncertainty over continuity of the reservoir sands. The basal sandsare interpreted to be thicker alluvial to fluvial early syn-rift sediments. Consequently, RPS has assumed agreater range of thicknesses than the younger Pliocene sands.RPS undertook an independent petrophysical evaluation of the Kingfisher well. The results of thisevaluation have been used to constrain the range of N:G, porosity and S w values used in the Plioceneprospects along the basin margin. Lower average porosities were assumed in the deeper Pliocene leads andthe Miocene basal sands.110