TABLE OF CONTENTS In this chapter, the basic properties of sedimentary rocks are discussed: their texture (grain size), sedimentary structures, and composition. We need to be able to recognize and characterize these features in cores and borehole-image logs of reservoir formations, so that we can use them to predict the reservoir's external geometry and internal architecture, the reservoir rock's orientation and trend, and potential interactions between reservoir fluids and reservoir rock. The subject of rock properties is very comprehensive, and this chapter will simply introduce the subject. For a more in-depth treatment, the reader is referred to numerous textbooks on the subject.
The Glossary of Geology (Bates and Jackson, 1980) defines sediment as: Solid fragmental material that originates from weathering of rocks and is transported or deposited by air, water, or ice, OR that accumulates by other natural agents, such as chemical precipitation from solution or secretion by organisms, and that forms in layers on the Earth's surface at ordinary temperatures in a loose, unconsolidated form. Sedimentary rock is defined as: A rock resulting from the consolidation of loose sediment that has accumulated in layers.
From this classification, three groups of sediments and sedimentary rocks can be defined: siliciclastic material (fragmental materials that originate from weathering), biogenic material (material originating from secretion by organisms), and chemical material (material produced by chemical precipitation).
The origins, formative processes, and depositional environments of sediments are shown schematically in Fig. 3.1. Sandstones and shales (and conglomerates)...
