Geoscientists and reservoir engineers are very well acquainted with the terms "net-to-gross (NTG)" and "petrophysical cut-offs" or just "cut-offs". The significance of these terms is ultimately to define productive zones in the reservoir for hydrocarbon exploitation. However, there has been marked misunderstanding surrounding the usage of the term, net-to-gross and implicitly, the derivation of cut-offs which are limiting values used in expressing the net-to-gross ratio. While the geologist may be concerned with the pay for evaluating hydrocarbon-in-place and the ultimately the estimation of economically producible reserves, the simulation engineer is more concerned with fluid flow for pressure support in the reservoir. The significance of this paper is to consider the different cut-offs selection methods, the varying interpretation of net-to-gross ratios and the implications inherent in such methods. A case study from a field in the Niger Delta is also carried out to reveal the impact of such selection criteria especially in rocks with congenital weak hydraulic properties which cannot be excluded at geologic correlation stage. The effect of cut-off parameters on oil-initially-in-place (OIIP) calculation was also investigated and a sensitivity analysis carried out on the petrophysical parameters to reveal the impact of the dynamically conditioned cut-offs selection on the petrofacies. Multiple Monte Carlo realizations were also employed to obtain probabilistic OIIP estimates rather than a single deterministic result. Introduction Over the decades, the term net-to-gross and by extension, cut-offs have been extensively used in the oil industry especially by petrophysicists, reservoir geologists, and reservoir/simulation engineers. It is a basic reservoir parameter used for solving various problems ranging from OIIP calculations to reservoir flow simulation as one among several other variables to determine and predict reservoir performance. However there has been a great deal of confusion arising from the ways these parameters are defined, derived, and used. The fact actually is that it actually depends on the professionals involved, the circumstance of their usage, and the intended deliverables. Therefore, there have been no clear-cut definitions for these terms since most investigators do not explain the methodology involved in arriving at their own results. These have led to errors in areas of volumetric calculations, recovery factor calculations, welltest interpretations, stimulation design, and equity determination among others.

There have been many different aims, relevance and results justifying single well study. Yet little or none has been said about its relevance in production enhancement. Single well modeling is the act of using numerical reservoir simulation equation to study well performance. It is very insightful in evaluating completion strategy, study coning/cusping behavior, well reserves, and relative permeability pseudo-functions for wells in full field models, complex pressure transient data analysis and well economics. This paper presents the applications of single well modeling in productivity enhancement. The productivity of a well is going to be modeled by using the numerical simulation equations coupled with well production parameters. A combination of several production strategies will be evaluated. Having matched the well model, the combination and strategy that gives the optimum production from the well is to be recommended. The advantage of this is that it couples the reservoir conditions, near wellbore fluid distribution, near wellbore reservoir description, production mechanism with completion strategy to predict well performance. The matched model with a level of uniqueness can predict the well performance to an acceptable level of accuracy. The challenge of handling excess water production and its impact on the overall well productivity can met through Single Well Numerical Modeling. Single well modeling can be used to determine the optimum well operation and production approach. The result of the numerical modeling indicates that Single Well modeling is a powerful tool for production enhancement. In water cusping cases, the best strategy for maximum recovery from the well is to avoid early water breakthrough. Re-perforation is not the best economic solution for a well experiencing water cusping. It is a good practice to numerically simulate a well to determine its cone and cusp free rate prior to production. This will aid to archive maximum recovery from the well. Single Well modeling is a good tool for Well economic analysis. A case study of two wells that penetrated a Niger Delta reservoir will be used. History The case wells are located in OSY reservoir. The reservoir first came on stream in July 1980 through Well A.