Page 10 - Geology and Geochemistry of Oil and Gas

ix

PREFACE

The progress in the oil and gas industry is related closely to the acceleration of
discovery rates, exploration, development, and production of hydrocarbon resourc-
es. Exploration, development, and production of hydrocarbon resources must be
based on reliable information, which helps to predict subsurface conditions and
properties of oil- and gas-bearing formations.
Main oil and gas reserves are found in sedimentary basins composed of ter-
rigenous (siliciclastic), carbonate, and, sometimes, volcanic or volcaniclastic rocks.
Preservation of high reservoir pressure and good properties of reservoir rocks and
seals (caprocks) in these basins depends greatly on their origin and further evolution.
The process of sedimentation, and the following processes of diagenesis (i.e., phys-
ical, chemical and biochemical processes, which occur in the sediments after sed-
imentation and through lithification at near-surface temperature and pressure) and
catagenesis (or epigenesis) (i.e., physical and chemical processes, which occur in the
sedimentary rocks at high temperatures and pressures after lithification and up to
metamorphism), cause alterations, which may enable one to predict oil and gas
potential.
Considering an interest demonstrated by petroleum geologists and reservoir en-
gineers, this book discusses the major theoretical and practical problems of petro-
leum geology and geochemistry as they are viewed at the end of the 20th century and
the beginning of the 21st century. The treatment of the material is non-uniform in
the sense that the accepted scientific concepts are treated cursorily, just to maintain
the completeness and continuity of the story, whereas the disputable and innovative
issues are handled in more detail. The discussion is conducted from a position of
the science of petroleum geology, geochemistry, and other related disciplines. For
instance, in describing oil-bearing sequences, the main brunt is on depositional
environments and such features as reservoir and fluid-sealing properties.
A considerable attention is devoted to the transformations within the rock–
water–organic matter system of the Earth’s crust with changes in the subsurface
temperature and pressure. New reservoir and accumulation types are identified and
their exploration/development features are defined.
A variety of common reservoir engineering problems can be solved during field
development and production by the integration of geological, geochemical, and en-
gineering studies. For example, such studies can identify reservoir compartment-
alization, allocate commingled production, identify completion problems (such as
tubing leaks or poor casing cementing jobs), predict fluid properties (viscosity, den-
sity) prior to production tests, characterize induced fracture geometry, monitor the
waterflood process and water encroachment, or explain the causes of produced sludge.