An Integrated Approach to Volume of Shale Analysis: Niger Delta Example, Orire Field

Abstract

An integrated approach for the estimation of volume of shale from a suite of logs comprising the gamma ray, neutron-density combination, resistivity, combination of different methods (total) was carried in an Old Niger Delta Field called Orire with a view to ascertaining the reservoir quality and mapping reservoir bodies for further petrophysical analysis. The volume of shale (Vsh) calculation based on naturally occurring gamma ray frequently overestimates shale volume when encounters radioactive sand as sand appears shaly. In this situation, a Vsh calculation from neutron-density data yields a more accurate shale volume but in the presence of gas or light hydrocarbon, this approach is less accurate. The deficiency in this method is now addressed by Vsh calculation from the resistivity data. To avoid overestimation or underestimation of shale volume from any of the methods, the three methods were integrated to obtain Vsh total which finds the minimum value of all the methods. This approach distinguishes properly permeable bed (sand) from non-permeable bed (shale). Also from this method, the depositional environment was easily inferred.