Introduction

Hydrocarbons(oil and gas) are found in the pore spaces of sedimentary geologic formations (reservoir rocks).  Once an oil or gas reservoir is discovered and assessed, production engineers begin the task of maximizing the amount of oil or gas that can ultimately be recovered from it. Some reservoir rocks may allow the oil and gas to move freely, making it easier to recover. Other reservoirs do not part with the oil and gas easily and require special technique to move the oil or gas from the pore spaces in the reservoir rock to a producing well. Even with today’s technology, in some reservoirs more than two-thirds of the oil in the reservoir may not be recoverable.
Optimum production of oil from an oil reservoir is the main objective or target of the operators of an oil well in order to meet up with the growing demands of the crude oil. The efficient production of fluids from a reservoir depends on the maintenance of the pressure draw down between the reservoir and the well bore which is the driving force or energy that forces the reservoir fluid (oil) from the reservoir into the wellbore.