TABLE OF CONTENTS The petroleum geologist is largely concerned with exploring for crude oil and natural gas, and the major part of this book is devoted to this theme. Vast amounts of energy, however, are also locked up in what may loosely be described as nonconventional petroleum resources. These include gas hydrate, tar sands, oil shales, shale gas, and coal-bed methane. These reserves have been hard to unlock because the relatively low cost of producing petroleum from conventional sources has inhibited technological research into their extraction. An increase in the cost of producing conventional petroleum provides an incentive to develop methods of producing these nonconventional petroleum resources.
This chapter deals with the plastic and solid hydrocarbons (excluding coal), describing their composition, origin, and distribution, and briefly reviewing production processes. Gas hydrates are not discussed here because they were dealt with at some length in Chapter 2. Shale gas and coal-bed methane are also described in this chapter.
Plastic and solid hydrocarbons are common in sedimentary rocks of diverse ages in many parts of the world. They are distinct from crude oils, which are liquid at normal temperatures and pressures, although many of these hydrocarbons are viscous, and their viscosity decreases with increasing temperature. Figure 9.1 classifies the solid hydrocarbons.
Mankind s first exposure to hydrocarbons was from surface occurrences of solid and viscous tars rather than from liquid crude oil, which was...
