Fractures are a universal element in sedimentary rock layers, so much that they are virtually omnipresent in outcrops of sedimentary rocks. Think of all the outcrops of sedimentary rocks that you have ever seen and try to recall a layer that was completely unfractured, with the possible exception of extremely ductile rock, such as salt or certain shales, you will not be able to recall any unfractured rocks simply because they do not exist. Further, it has been demonstrated over and over again that the vast majority of fractures observed in outcrop are not solely the result of surface conditions. In other words, the fractures seen in outcrop also exist in the subsurface. Therefore, it follows that hydrocarbon reservoirs in sedimentary rock all contain fractures and most of them are fractured enough to be treated as fractured reservoirs. <...>

Progradation of Atchafalaya Delta, one of the most dynamic geological events of the century, has produced a sizable new sand body on the Louisiana coast. Evolution of depositional environments in Atchafalaya Bay has been determined from analysis of sediment cores and bathymetric surveys. Use of X-ray radiography has made possible recognition of a number of subenvironments within major environments. Atchafalaya Delta exhibits all the sedimentary environments recorded in earlier Mississippi delta lobes. However, excellent stratigraphic control and current knowledge of the processes of deposition in Atchafalaya Bay make it possible to better link process-response in this than in other Mississippi subdeltas. In contrast to the modem Mississippi subdelta, the Atchafalaya should prograde more rapidly, form thinner sand bodies, and eventually cover a wider area, much like the Lafourche, St. Bernard, and Teche delta lobes. <...>

This is a book on the geology of hydrocarbon reservoirs in carbonate rocks. Although it is written for petroleum geologists, geophysicists, and engineers, it can be useful as a reference for hydrogeologists and environmental geologists because reservoirs and aquifers differ only in the fl uids they contain. Environmental geoscientists interested in contaminant transport or hazardous waste disposal also need to know about porosity (capacity to store) and permeability (capacity to fl ow) of subsurface formations.

Depth imaging is changing the face of seismic technology. First and foremost, depth imaging greatly extends our ability to image geologic structure. This is true not only for highly complex structures such as thrust imbricates and subsalt structures, but also for subtle structural plays like fault shadows. In fact, since the late 1980’s, almost all structural play exploration has been stalled at the frontier where time imaging is no longer effective. In the 1990’s depth imaging has taken us through this frontier and is renewing many of these structural plays.

The series of articles on Facies Models in Geoscience Canada was initiated by editor Gerard V. Middleton, partly in response to a suggestion from Erich Dimroth that "brief, well-written, concise articles, outlining the techniques of rock interpretation, and the concepts and criteria for regional evaluation would be an enormous help to the general purpose field geologist”. Each author was asked to prepare a review that covered the basic ideas, without unnecessary jargon, in terms that the student or "general purpose field geologist” could understand. Most of the illustrations in the articles have been prepared with this objective in mind.

Deltaic depositional facies result from interacting dynamic physical processes (wave energy, tidal action, climate, etc.) which modify and disperse riverborne elastics. Since ancient times, river deltas have been of fundamental importance to civilization. Owing to their early significance as agricultural lands, deltas received considerable attention from scholars such as Homer, Herodotus, Plato, and Aristotle. More recently, subsurface deltaic facies have played a paramount role in accommodating the world's energy needs; ancient deltaic sediments have provided source beds and reservoirs for a large percentage of the known petroleum reserves. The facies relationships and mechanisms responsible for development and distribution of deltaic sand bodies must be understood before they can be explored efficiently. <...>

The clay minerals are small hydrous layer silicates and are part of the phyllosilicate family. As discussed in Chapter 11, many of the hydrous layer silicates in clays, muds, soils, shales, slates, etc. are coarser than clay (< 2 or < 4 pm). Primarily for this reason I have suggested (Weaver, 1980) using the term physil, which has no size connotation, to refer to the low-temperature ( 5 400°C) hydrous layer silicates.

Clays are one of the most important groups of minerals that destroy permeability in sandstones, but they also react with drilling and completion fluids and induce fine-particle migrationduring hydrocarbon production. They are a very complex family of minerals that commonly are mutually intergrown and contain a wide range of solid solutions and form by a wide range of processes. They form under a wide diversity of pressure and temperature conditions, as well as rock and fluid compositional conditions.

In 1984, I had had the chance to join the organic geochemistry group of Prof. Dr. D. Welte at the Institute for Petroleum and Organic Geochemistry, KFA Jtilich, where my first encounter with organic geochemistry took place. There, I learned - as marine geologist - to talk to and work with geochemists and to understand the importance of multidisciplinary cooperation. For this possibility, I gratefully thank Prof. Welte as well as Dr. J. Rullk6tter.