Abstract
Porosity indicates the potentiality or fluid storage capacity of a reservoir or rock. It is the first of the two essential attributes of a reservoir. Permeability is a parameter for the recovery of hydrocarbon from the reservoir, it is required for proper reservoir evaluation, as it aids in the estimation of how much fluid can produced from the reservoir. The aim of this study is to determine porosity-permeability correlation with pressure and depth in part of Niger Delta basin using well log data. A suite of geophysical well logs comprising of gamma ray, neutron, density, spontaneous potential and sonic logs from four oil wells were used in the study. Porosity values were estimated from well log data, while permeability and pressure values were determined using empirical relations with respect to specific depth in the wells. The results of this work show that three reservoirs (reservoir sands) were identified and correlated across the four wells, each reservoir sand unit spread across the wells and differs in thickness ranging from 8ft to 155ft, with some unit occurring at greater depth than their corresponding unit.The lithostratigraphic correlation section of the wells revealed a sand – shale sequence which is a characteristic of a typical Niger Delta formation. The average porosity, permeability, pressure and depth values for the four wells range from 0.001 to 0.309, 34.999mD to 306.360mD, 61926.863psi to 109928.054psi and 3000ft to 4450ft respectively. The analysis of the wells show that wells OTIG9 and OTIG11 have better reservoirs indicating high potentiality and productivity due to their more porous and permeable nature, reflecting well sorted coarse grained sandstone and linearity in the relationship between porosity, permeability, pressure and depth. The reservoir of well OTIG7 is the least porous but most permeable, thus is highly productive but less potential. The reservoir of OTIG2 has moderate potentiality and good productivity, hence is said to have average production capacity. The results of this work can be used as an evaluation tool for reservoir engineering activities, structural engineering, well stability analysis, blowout and lost circulation prevention.
Highlights
The measure of the void space in a rock is defined as its porosity, while the measure of the ability of the rock to transmit fluid is its permeability
5.6 Porosity – Pressure Correlation. It is observed from figure 11 – 14 which shows the Porosity and overburden pressure relationship that Porosity decreases with increase in overburden pressure
There is a normal porosity decrease as depth increases due to the effect of compaction resulting from weight of overlying rocks
Summary
The measure of the void space in a rock is defined as its porosity, while the measure of the ability of the rock to transmit fluid is its permeability. The knowledge of these two parameters is essential before questions concerning types of fluid, amount of fluid, rate of fluid flow and fluid recovery estimates can be answered (Djebbar and Erle, 2004). Porosity is the capacity of a reservoir rock to contain hydrocarbon (Tarek, 2006). This implies that it is a measurement of the
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