Application of Field Analogs in New Mexico to the Re-Interpretation of Some Niger Delta Shallow-Marine Hydrocarbon Reservoirs

Onyirioha, Reginald; Okeke, Genevieve; Combellas, Ricardo; Ajao, Oyekunle; Okafor, Chioma; Pichard, Frank

Field observation of clastic outcrops of the Upper Cretaceous Gallup, Dalton, and Hosta Sandstone Formations of southern San Juan Basin in New Mexico indicate that they are good analogs of the Tertiary Benin River, Dibi, Gbokoda, and adjacent shallow-marine hydrocarbon fields of the Niger Delta. These Upper Cretaceous outcrops which are deposited in predominantly wave-dominated shoreface environments are characterized by heterogeneous juxtaposition of tidal and fluvial distributary channel deposits. The association of shoreface and transgressive deposits in these sandstones are widely accompanied by extensive, poorly sorted, and highly cemented lag deposits which are potential baffles and seals with thicknesses ranging from a few inches to a couple of feet.

Commonly used lithostratigraphic correlation of sands in similar shallow-marine reservoirs often fail to distinguish the tidal and fluvial deposits laid accross shoreface facies during intervening episodes of transgression and regression, thereby missing potentially critical barriers or baffles and their direct impact on reservoir sweep efficiency. Such lithostratigraphic correlation of heterogenous shallow-marine facies successions might lead to wrong reservoir management assumptions such as inaccurate reservoir compartmentalization or to flawed secondary recovery strategies such as ineffective water injection.

Core descriptions, well logs, and seismic data are integrated to re-interpret some reservoirs in Gbokoda and Dibi Fields, Niger Delta, using analog outcrop models of the Cretacious clastic reservoir formations of the southern San Juan Basin.

The results will be used in the future to interpret other assets in similar shallow-marine environments of deposition which may not have as much data as Gbokoda and Dibi Fields.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013