Prospectus re Admission to the Official List - Heritage Oil

RPS EnergyHeritage Oil – Competent Persons ReportFigure 10: West Bukha 3D inline 112226FEB200822314633The Operator maps are based on a more simplistic approach to depth conversion than in previous studies,which used a complex interval velocity method for depth conversion as shallow salt was thought to impacton velocities. Despite this approach West Bukha-2 penetrated the reservoir some 80 m shallower thanpredicted which invalidated this method. The current maps are based on an average velocities for eachhorizon derived from well data. There is little variation in average velocities across the field, although aneastward decrease in average velocity is not supported by well data and velocities at the extreme west andeast of the model exceed the velocities in the wells although not markedly. RPS considers the depthconversion reasonable.A facies model has been developed by the Operator which has been reviewed by RPS and appearsreasonable. The Mauddud shows little variation in thickness across the field and the subunits are the samein all wells drilled in the field. All nine sub units across the field are carbonate platform facies. Correlationwith the Bukha filed shows that Mauddud sub-units 7, 8 and 9 are missing in Bukha which indicates theposition of the shelf is between West Bukha and Bukha. Correlation with Bukha and Tibat shows aback-stepping carbonate platform from the south east to north west during deposition of the Mauddud.Each well in the West Bukha Field has the same Mauddud sub-units, suggesting that West Bukha is thefinal carbonate platform and hence has a complete Mauddud section.The Mishrif varies considerably in thickness across the field with 3 sub- units present at West Bukha-2 andHenjam-1, whereas West Bukha-1 and Khasab-1 have only the deepest Mishrif-1 sub- unit. The Henjam-1and West Bukha-2 wells are interpreted to be on the carbonate platform during Mishrif deposition withWest Bukha-1 and Khasab-1 existing on the carbonate slope. Heritage has used an isopach thickness mapto determine the extent of the platform and the position of the slope. This is a reasonable approach asvariation in the thickness of the Mishrif is the predominant variable in the thickness of the Ilam-Nahr Umrisopach that was used to define the platform. This thickness variation is also visible on the seismic where asingle trough across the field at the Top Ilam becomes a trough-peak-trough to the north. Reservoir qualityand thickness are interpreted to improve to the north where the Mishrif is thickest. If this is the case, wellsdrilled to the SW of West Bukha-2 are unlikely to encounter the better carbonate platform facies and thereservoir will be similar to West Bukha-1.3.3.3. In Place VolumesRPS calculated in place volumes for the Mishrif/Mauddud and for the Thamama.85