Hydrocarbon Play Assessment of “Oswil” Field, Onshore Niger Delta Region

Osisanya W. O. (Department of Physics, University of Benin, Benin City, Edo state, Nigeria)
Alile O. M. (Department of Physics, University of Benin, Benin City, Edo state, Nigeria)
Eze S. U. (Department of Marine Geology, Nigeria Maritime University, Okerenkoko, Delta State)
Ibitoye T. A. (Department of Petroleum Engineering and Geosciences, Petroleum Training Institute, Effurun, Nigeria)
Oyanameh O. E. (Department of Earth Science, Anchor University, Lagos, Nigeria)


Hydrocarbon play assessment of any field involves the evaluation of theproduction capacity of hydrocarbon reservoir unit in the field. This involvesdetail study of the reservoir petrophysical properties and geological interpretation of structures suitable for hydrocarbon accumulation in the field as observed from seismic reflection images. This study details the assessment of hydrocarbon play in OSWIL field onshore in Niger Delta, with the intent of appraising its productivity using a combination of seismic, well logs,petrophysical parameters and volumetric estimation using proven techniques which involves an integrated methodology. Two reservoir windows “R1” and “R2” were defined from five wells OSWIL-02, 04, 06, 07 and 12. The top and base of each reservoir window was delineated from the wells.Structural interpretation for inline 6975 revealed two horizons (X and Y) and eight faults labelled (F1, F2, F6, F8, F10, F16, F17 and F18). Fivefaults (F1, F6, F10, F17 and F18) were identified as synthetic faults and dipbasin wards while three faults (F2, F8 and F16) were identified as antitheticfaults and dips landwards. Time-depth structural map at top of reservoirsR1 and R2 revealed structural highs and closures. These observations arecharacteristics of growth structures (faults) which depicts the tectonic styleof the Niger Delta. Results of petrophysical evaluation for reservoirs “R1”and “R2” across the five wells were analysed. For reservoir “R1” effectiveporosity values of 27%, 26%, 23%, 20% and 22% were obtained for wellsOSWIL-04, 12, 07, 06 and 02 respectively with an average of 23.6%, whilefor reservoir “R2” effective porosity values of 26%, 22%, 21%, 24% and23% for wells OSWIL-04, 12, 07, 06 and 02 were obtained respectivelywith an average of 23.2%. This porosity values correspond with the alreadyestablished porosity range of 28-32% within the Agbada formation of theNiger Delta. Permeability index of the order (K > 100mD) were obtainedfor both reservoirs across the five wells and is rated very good. Hydrocarbon saturation (Shc) across the five wells averages at 61.6% for reservoir“R1” and 67.4% for reservoir “R2”. Result of petrophysical model for porosity, permeability and water saturation reveal that the reservoir system in R1 and R2 is fault assisted and fluid flow within both reservoirs is aided bypresence of effective porosity and faulting. Volumetric estimation for bothreservoirs showed that reservoir R1 contains an estimate of 455 × 106 STBof hydrocarbon in place, while reservoir R2 contains an estimate of 683 ×106 STB of hydrocarbon in place. These findings impact positively on hydrocarbon production in the field and affirm that the two reservoirs R1 andR2 are highly prospective.


Seismic;Well logs;Petrophysical parameters;Hydrocarbon play;Structural interpretation;Niger Delta

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