Reservoir Potential Evaluation of the Middle Paleocene Lockhart Limestone of the Kohat Basin, Pakistan: Petrophysical Analyses

Abstract

The Lockhart Limestone is evaluated for its reservoir potential by utilizing wireline logs of Shakardara-01
well from Kohat Basin, Pakistan. The analyses showed 28.03% average volume of shale (Vsh), 25.57% average
neutron porosity (NPHI), 3.31% average effective porosity (PHIE), 76% average water saturation (Sw), and 24.10%
average hydrocarbon saturation (Sh) of the Lockhart Limestone in Shakardara-01 well. Based on variation in
petrophysical character, the reservoir units of the Lockhart Limestone are divided into three zones i.e., zone-1, zone-2
and zone-3. Out of these zones, zone-1 and zone-2 possess a poor reservoir potential for hydrocarbons as reflected by
very low effective porosity (1.40 and 2.02% respectively) and hydrocarbon saturation (15 and 5.20%), while zone-3 has
a moderate reservoir potential due to its moderate effective porosity (6.50%) and hydrocarbon saturation (52%)
respectively. Overall, the average effective porosity of 3.31% and hydrocarbon saturation of 24.10% as well as 28.03%
volume of shale indicated poor reservoir potential of the Lockhart Limestone. Lithologically, this formation is
dominated by limestone and shale interbeds in the Shakardara-01 well. Cross-plots of the petrophysical parameters
versus depth showed that the Lockhart Limestone is a poor to tight reservoir in Shakardara-01 well and can hardly
produce hydrocarbons under conventional drilling conditions.