Reservior characterization of West Waha and Worsham-Bayer Fields (PDF)

Master's Thesis from the year 2010 in the subject Geography / Earth Science - Geology, Mineralogy, Soil Science, grade: 700, University of Ibadan, language: English, abstract: West Waha and Worsham-Bayer fields are located in the Southeastern Delaware Basin, West Texas. For several decades, these fields have been experiencing problem of low natural gas recovery in contrast to their large estimated reserves. This study involved the integration of interpreted three data sets namely; 10 well logs, 20-sq- miles 3D seismic and production data. The principal objectives for this study were to determine the impact of thin-beds on reservoir petrophysical analysis and to assess the impact of estimated recoverable reserve on the interpreted reservoirs (R1 [Lower Ordovician Ellenburger group], R2 [Silurian Fusselman formation], R3 [Devonian Thirtyone Formation] and R4 [Undifferentiated Mississippian Limestone].
Reservoir characterization method employed were: well log correlation, petrophysical analysis to calculate porosity and Movable Hydrocarbon Index (MHI), reservoir attribute analysis for thickness estimation, seismic-to- well ties to detect the reservoirs of interest, fault mapping, 3D seismic interpretation, generation of time-depth structure maps for prospect mapping, volumetric analysis for recoverable reserve estimation and production record interpretation.
Well log correlation revealed complex thrust faulting, structural rotation and left- lateral strike-slip which serves as major traps in some areas of the fields. The reservoirs were thickening to Northeastern direction towards Texas arch and thinning Northwestern and the log motifs depict carbonate depositional environment type. The mean porosities for R1, R2, R3 and R4 reservoirs are 23.7%, 16.3%, 26.1% and 26.0% respectively, while the fields' mean porosity value is 23.1% showing excellent porosity value for natural gas flow. Wells 29, 36, 37 and 38 have MHI of >20%. R1 reservoir had the highest thickness value (146 ft) at well log 29. F1 and F2 are major faults and F3, F4, F5, F6, F7 and F8 and F9 are minor faults. F3, F2, F4, F5, F6, F7 and F8 dip north, while F1, F3 and F9 dip south. The total Gas in place (BScf) and the total Recoverable reserve (Tcf) calculated were 359.73 and 636.62 respectively. Production records interpretation showed decrease in reservoirs' productivity as a result of decline in the natural pressure of the reservoirs. From analysis results, it was deducted that the thin beds positively impact the reservoir petrophysics and the calculated recoverable reserve also impact reserve.