Prospectus re Admission to the Official List - Heritage Oil

RPS EnergyHeritage Oil – Competent Persons Reportcore and it is therefore considered that the core did not suffer filtrate invasion in the volumes sampled forwater extraction, and no invasion corrections were applied.Values of R w were taken from the data supplied by Heritage where residual water was extracted from thecore and its resistivity determined. The average value from 8 samples reported was 0.277 Ohmm at 20 Cwith standard deviation of the mean of 0.012 Ohmm. Arps’ equation (8) was used to convert this to reservoirtemperatures. This resistivity represents an equivalent NaCl concentration of approximately 24,000 ppm.The result is in line with a previously reported salinity from well No. 14 which gave a value of 22,105 ppm.The ambient Archie Cementation exponent ‘‘m’’ and Saturation exponent ‘‘n’’ derived from P3 core were1.77 and 1.85, respectively. A produced water analysis was supplied by Heritage which was obtained bycentrifuging an oil sample from co-mingled production from Wells S226 and P3. The chemical analysisobtained a salinity of 49,454 ppm, which has an estimated R w of 0.143 Ohmm at 20 C.Because of the ambiguity in the results from the brine analyses, the 0.277 Ohmm R w at 20 C was used tocalculate saturations at the p90 level, and the 0.143 Ohmm R w at 20 was used to calculate saturations atthe p50 level.In the case of well P2ST, VSH was derived from the lower value from the density neutron cross plotmethod and a linear Gamma Ray VSH method derived from the Potassium and Thorium component ofthe gamma ray count. Parameters are presented in Table 1 in the Appendix. For well P3, shale volume wasdetermined from a density neutron crossplot using the parameters presented in Table 2 in the Appendix.For well P2ST, porosity was derived using the density neutron crossplot method In the case of well P3,porosity was derived for the LCa and LCb zones using the density neutron crossplot method. Porosity inLCc was derived from the density log. The parameters used in calculating porosity for both wells arepresented in Tables 1 & 2 in the Appendix.For both wells, total water saturation was calculated using the Archie equation (9) . Effective watersaturation was derived using the shaley sand ‘‘Indonesia’’ Equation of Poupon and Leveaux (10) . A CPI(for the p50 saturation case) from Well P3 is shown in Figure 15.Owing to the silty and thin bedded nature of parts of the reservoir, it is possible that thin beds are notbeing resolved fully by tool responses, and that the results of the interpretations have been influenced bysmoothed tool responses. A p50 case for water saturation has used an R w of 0.143 Ohm at 20 C. An R w of0.277 Ohm at 20 C has been used to construct saturations for the p90 case.(8) Arps, J.J. (1953) ‘‘The Effect of Temperature on the Density and Electrical Resistivity of Sodium Chloride Solutions’’Petroleum Transactions, AIME, Vol 198, 327-330.(9) Archie, G.E. ‘‘The Electrical Resistivity Log as an Aid in Determining Some Reservoir Characteristics’’. Petroleum Transactionsof the AIME 146 (1942).(10) A. Poupon, J, Leveaux ‘‘Evaluation of Water Saturation in Shaly Formations’’. SPWLA 12 th Annual Logging Symposium,May 2-5 1971.96