**Kenneth Imo-Imo Israel Eshiet PhD, CEng, MICE, FHEA**

Sustainable Energy Environmental and Educational Development (SEEED) Ltd, Sugarland, Texas, USA

**1**

Section 1

Introduction

Section 1 Introduction

**3**

**Chapter 1**

Reservoirs

**1. Introduction**

reservoir rocks.

etc.) and heavy oil reservoir rocks.

*Kenneth Imo-Imo Eshiet*

Introductory Chapter:

Developments in the Exploitation

of Unconventional Hydrocarbon

Hydrocarbon reservoirs contain fossil fuels and constitute a major proportion of sources of energy worldwide. In the past, extraction of oil and gas was mainly restricted to conventional reservoirs which underlie a sealing caprock or rock formation with lower permeability and consist of rock and fluid with characteristics that readily allow the flow of oil and gas into wellbores. These reservoirs are easily assessed and contain sufficient pressure such that the external and additional drive necessary to push the hydrocarbon fluids to the surface are not exigent. Conventional reservoirs are recognised by their structural layout, stratification and rock and fluid properties. Typically, they comprise three major parts: a cap rock, a source rock and a reservoir rock. The cap rock is the impermeable rock layer that seals the boundaries of the top and sides and entraps the hydrocarbons within the reservoir. Hydrocarbons are formed in the source rock (normally limestones or shales) which contains kerogen, an insoluble and solid organic matter. The reservoir rock is the permeable and porous layer containing hydrocarbon fluids generated in the source rock. Over a protracted period, oil and gas formed in source rocks migrate to reservoir rocks, a process that is essential for the existence and validity of

With the advent in advanced technology and increasing need for more and cleaner energy, oil and gas production has been extended to unconventional reservoirs. Generally, unconventional reservoirs are difficult to produce. They are mainly composed of very tight source rocks containing hydrocarbons that have not migrated to reservoir rocks. These ultra-tight source rocks are termed unconventional reservoirs. Fundamentally, unconventional and conventional reservoirs are differentiated based on the migration of hydrocarbons from source rocks. Conventional reservoirs are rock formations that are recipient of hydrocarbons from source rocks, while unconventional reservoirs are source rocks containing hydrocarbons that cannot be naturally released to reservoir rocks. Nonetheless, the term unconventional reservoirs broadly cover reservoir rocks which are problematic to produce, for instance, tight reservoir rocks (tight sandstones, tight limestone,

Artificial lift is a standard method of instigating flow from the reservoir through

the wellbore. This technique decreases the bottomhole pressure (BHP) while increasing the pressure in the reservoir, thereby raising the rate of well production. It is inevitably required at a certain time during the life of an oil/gas field due
