The Petrophysical Evaluation and Depositional Environment of Harrison 1 Well Using Core Data and Wireline Logs

Abstract

A comprehensive petrophysical evaluation is essential to optimise development and production in complex environments in different prolific regions including West Africa. In this study petrophysical parameters in the Harrison 1 well, central Niger Delta were carefully evaluated using cores and wireline logs zones of hydrocarbon saturation were deduced using a combination of conventional logs including Gamma ray, Resistivity (Schlumberger’s platform Express-Array induction tool (PEX-AIH) and Neutron/density combination log.

Cored interval ranged from 11915ftah to 12005ftah within which several analyses were carried out to deduce lithofacies, environment of deposition and prospective reservoirs for hydrocarbon. Reservoirs are located between 11933-11952ftah, 11960-11965ftah, 11975 -12005ftah. These reservoirs have excellent porosity values (though permeability decreased with depth because of increased clay content), low water saturation percentage (? 20%), high hydrocarbon saturation (?80%), favourable values of ROS and MOS.

The depositional model comprises a prograding shoreface deposit which passes upward into stacks of channel deposits characterised by features typical of estuarine setting. Studies of Hydrocarbon fill using cores from Harrison 1 well under UV-light reflected recognisable fluorescing unit between  11956-12005ftah stratigraphic interval and a non-fluorescing unit between 11915 – 11955ftah meaning these intervals contains oil and gas , however  gas -oil ratio of 45:55 affirms the gas prone nature of the reservoirs within the interval of study.

Keywords: Conventional logs, hydrocarbon saturation, reservoir, ROS, MOS, UV-light, water saturation.