Detailed quantitative sequence stratigraphic interpretation for the characterization of Amangi field using seismic data and well logs
The sequence stratigraphy of Amangi field of the Niger Delta was studied using seismic data and well logs. The field is a structurally complex one and presents serious challenges to hydrocarbon exploration and production. The main objective of these analyses is to identify sand intervals using the available data. Well log data were used as additional tools to constrain the seismic correlations in order to solve the correlation problem. The well logs were evaluated for the field’s petrophysical properties by combining the gamma ray and resistivity logs to determine reservoir zones with considerable hydrocarbon saturation. Also, the relationship between some basic rock properties/attributes and litho-types were determined for the study area. Next, well-to-seismic ties were produced and two horizons were picked. Acoustic impedance inversion was also performed which revealed “hard sands” due to mixed lithologies (heterolithics). This made it difficult to discriminate the sands from shales in the P-impedance domain alone. So, progress was made to determine the net-to-gross of the field. The analysis revealed that these reservoirs have shaly sand with shale content of 10%, porosity averaging 21%, and hydrocarbon saturation of 90%. The result established a vertical stack of a series of reservoirs in an anticlinal structure of which the H1000 and H4000 stand out for their huge volumes of rich gas condensate accumulation. This discovery provoked the drive for the first phase of development of this field.
Keywords: stratigraphy, facies, net-to-gross, horizon, lithology, well-to-seismic tie, impedance