Page 16 - Geology of Carbonate Reservoirs

PREFACE xiii

identified and ranked on their rock and reservoir properties, accurate maps, volu-
metric calculations, and economic forecasts can be made. Primary recovery methods
have produced only about one - third of the world ’ s original oil in place, leaving an
estimated 891 billion barrels or more (Ahlbrandt et al., 2005 ) . If unconventional

sources of oil and natural gas are included, the figure will be even larger. If reservoir
flow units could be mapped with a higher degree of precision than was available

previously, then a significant percentage of those 1 trillion barrels of remaining oil

could be within reach with novel methods of improved recovery. Knowing the size,
shape, and connectivity of flow units, secondary and tertiary recovery methods are

economically attractive, especially at current oil prices. This rings especially true
when one considers the extreme cost of deep water drilling and production, the risk
of geopolitical conflicts, and the risk of drilling dry holes as compared to extracting

bypassed hydrocarbons from proven fields. Also importantly, if hydrogeologists
have accurate maps of aquifer connectivity, their models for groundwater fl ow or
contaminant transport pathways will be greatly improved. If flow barriers were

more accurately mapped, site evaluation for dangerous waste disposal could be

improved significantly. These are only a few of the exciting reasons to learn more
about carbonate reservoirs and aquifers.
I would not have embarked on this project without the encouragement of the
graduate students who have taken my course on carbonate reservoirs over past
years and who have continually asked me to write a book for the course. Old friend
Robert Stanton read some of the early chapters and offered helpful comments. Rick
Major and P. M. (Mitch) Harris read early versions of the entire manuscript and
gave encouragement, guidance that kept me on track, and criticisms that greatly
improved the book.

Wayne M. Ahr
College Station, Texas
December 2007