Preface

Despite the clamor for reduced dependency on fossil fuels, the demand for hydrocarbonbased energy is on the rise. Consequently, the strain on oil and gas reservoirs is greater than ever before. This has also drawn more attention to unconventional reservoirs, making it exigent for further innovations in producing hydrocarbon formations. This book introduces an array of cutting-edge strategies for the exploitation of depleted and unconventional reservoirs. It provides some insights pertaining to interactions between formation in situ and injected fluids and rock constituents under extreme underground conditions. In addition, it presents a novel model for gas flow, pertinent to understanding flow mechanisms in the shale rock matrix.

In tandem with the evolution of the petroleum industry, there have been major advancements in the range of stimulation methods for the production of reservoirs. Chapter 1 is a breakdown of the different types of hard-to-produce rock formations and the corresponding diversity of stimulation techniques appropriate for their production. Furthermore, the chapter describes the multiplicity of fracturing fluid systems and the associated influencing factors, which are instrumental to the successful execution of many stimulation operations. This is then focalised on shale reservoirs in Chapter 2, which casts a spotlight on the fracturing mechanisms and evolvement in fracturing technologies applied in shale gas formations. In Chapter 3, a case is presented that supports the extended application of hydraulic fracturing techniques in the measurement of in situ stresses in porous and fractured rocks. This approach promises better results at deep subsurface levels in comparison to antecedent techniques. Chapter 4 demonstrates formation-proppant contact behavior and its impact on the conductivity of shale reservoirs following the creation of hydraulic fracture networks with the aid of a model that analyzes contact characteristics of proppant embedment. Chapter 5 is a detailed review of the interactions between formation/hydraulic fracturing fluids and clay minerals in shale formations, with an emphasis on geomechanical and geochemical feedback. Chapter 6 presents a nanoscale model to investigate the gas flow mechanisms of shale reservoirs. The chapter also explores upscaling techniques used to translate results from the proposed model and laboratory-scale experiments to field-scale representations.

The state-of-the-art techniques and procedures exhibited in this book are yet another indication of the pool of resounding efforts to harness unconventional hydrocarbon resources more effectively. Applications of the proposed methods are not limited to the scenarios presented; it is possible to extend them to a broader ambit of underground conditions, provided the constraints are recognised.

> **Dr. Kenneth Imo-Imo Israel Eshiet** Faculty of Science Engineering, University of Wolverhampton, Wolverhampton, United Kingdom

**Rouzbeh G. Moghanloo** University of Oklahoma, Oklahoma, United States of America

Section 1
