Predicting Petrophysical Properties Based on Conformance between Diagenetic Products and Depositional Textures
Lucia, F. Jerry1 (1) The
Carbonate reservoirs are a product of
depositional and diagenetic processes and rock
fabrics, which include the products of both processes, can be closely linked to
petrophysical properties. There is considerable
information on carbonate depositional facies that can
be used to predict patterns of sedimentary fabrics. Predicting the spatial
geometry of diagenetic products is more difficult
because it often involves the transport of material by fluid flow, and we are
poorly equipped to locate the source of the material or the direction of fluid
flow. Therefore, the most successful method for predicting spatial distribution
of diagenetic products is to relate them to
depositional facies. Accuracy in predicting the 3-D
distribution of diagenetic fabrics becomes a function
of the conformance between diagenetic products and
depositional textures.
The products of simple compaction,
cementation, and grain dissolution have the highest conformance to depositional
texture and are the most predictable. The pattern of dolostone
beds formed by hypersaline reflux can be predicted
using a prograding tidal-flat depositional model and
a density flow model, resulting in some conformance to depositional models.
However, predicting dolomite crystal size, which is critical to predicting flow
properties, is more difficult and often has poor conformance to depositional
textures. The products of late-formed dolostones
generally have poor conformance to depositional textures because the flow of
late dolomitizing water is typically controlled by
touching-vug pore systems and because the
hydrodynamics of the dolomitizing water is uncertain.
Diagenetic processes that produce touching-vug pore systems typically have the least conformance
between depositional textures and diagenetic products
because their geometry is typically controlled by paleogroundwater
systems.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California