Evaluation of Hydrocarbon Charge and Leakages using Chimney Cube: Examples from the Deep Offshore Niger Delta Basin, Nigeria

This research investigated hydrocarbon charge and leakages using chimney cube in Woda Oil Field, Western Offshore Niger Delta. The data sets used include well logs and 3D Post Stack Depth Migration (PSDM) seismic volume. The reservoir zone was identified, using well log data (gammaray, resistivity, and Vp sonic logs). The Chimney cubes generated from Supervised Neural Network (SNN) validated the identified chimney morphologies, gas zones and was overlain on interpreted reservoir surfaces D, G and I. Majority of the chimney morphologies identified are type I and II that nucleated in the lower part of the faulting system below the partially permeable portion of the fault planes and across the regional partially permeable barrier as revealed by thin fault likelihood attribute (TFLA) and fault polygons. Gas expulsion occurring along the lower portion of the complex faulting system may have preconfigured the spatial organization of the chimney morphologies. The anisotropic stress pattern around the tectonic and anisotropic polygonal faults coupled with the partially permeable faults may have determined the directions of long-term gas migration pathway and linear geometries of the chimney morphologies. Pockmarks formed above the chimney morphologies may have inherited the same linear planform geometry that recorded the timing of gas leakage and paleo-stress pattern of the study area and thus used as a tool to reconstruct the orientations of stress patterns in the sedimentary successions within the Woda oil field. The character of the chimneys and well log interpretation were used to evaluate the petroleum system in the study area.