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The Carbonate Analogs Through Time (CATT) Hypothesis – A Systematic and Predictive Look at Phanerozoic Carbonate Reservoirs:
Extended Abstract*
By
James R. Markello1, Richard B. Koepnick2, and Lowell E. Waite3
Search and Discovery Article #40185 (2006)
Posted February 6, 2006
*Editorial Note: Modified from extended abstract prepared for presentation at
AAPG Annual Convention,
1ExxonMobil Upstream Research Company, Houston, TX ([email protected])
2Qatar Petroleum, Doha, Qatar ([email protected])
3Pioneer Natural Resources USA, Inc., Dallas, TX ([email protected])
Introduction
The Carbonate Analogs Through Time (CATT) Hypothesis defines an approach for
developing systematic evaluations and predictive models of Phanerozoic carbonate
systems and reservoirs for use in upstream exploration, development, and
production businesses. Three applications are illustrated in this extended
abstract: 1. age-based pattern development, 2. comparative reservoir analysis,
and 3. 
analog
selection.
Exploration
geoscientists employ a host of established and successful concepts, tools, and
data to develop predictive models for field/reservoir occurrence and quality.
However, as exploration successes decrease, alternative approaches are needed to
refresh the exploration mindset. We present the CATT approach as a hypothesis
and as an alternative mindset for carbonate reservoir exploration. The geologic
age-based concepts and products provide thought-provoking perspectives on known
carbonate reservoir occurrences and offer a different way of thinking about
predicting where undiscovered carbonate reservoirs may exist. At the very least,
our Carbonate Analogs Through Time hypothesis provides a framework or context
within which to insightfully and schematically organize all of the concepts,
facts, and carbonate reservoir case studies/examples one encounters throughout a
career, and it can be used as an approach for comparative analysis of systems.
Reservoir engineers require detailed geologic-based reservoir parameters for
simulations of reservoir/field performance. Such simulations form the bases for
field development/depletion plans that invoke huge capital and operating
expenses. Thus, it is imperative to provide the best possible input to
simulation so that capex and opex investments are optimal. Typically, the input,
if not derived directly from data collected within a field under development,
has been gathered or derived from “analog” fields. Thus, choosing the most
appropriate analog is a critical task. We contend that the CATT approach
provides the conceptual basis for choosing the most appropriate analogs.
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CATT HypothesisThe CATT hypothesis simply stated is: “Insightful, high-confidence, age-specific predictive models for carbonate systems and reservoir occurrence, composition, stratal attributes, and reservoir properties can be developed by summing the ambient conditions of the carbonate processes and Earth processes at any geologic age.” We term these models age-sensitive patterns or themes.
The hypothesis is built upon the cumulative body of knowledge that demonstrates carbonate and Earth processes have differentially varied throughout Phanerozoic time. These carbonate and Earth processes include: 1) ecologic, oceanographic, sedimentologic process-based controls on carbonate-factory development; 2) stratigraphic and accommodation-process-based controls on carbonate stratal architecture; 3) secular trends of evolution, grain mineralogy, tectonics, climate, eustasy, ocean circulation, and ocean chemistry; 4) the stratigraphic hierarchy and the constraint that first- and second-order Phanerozoic stratigraphic successions (Sloss Sequences) are age-fixed in geologic time (mybp). Two key products of this research are: 1) a poster compilation of secular varying geologic controls synchronized to the time-scale (Figure 1) and 2) a global atlas containing 29 present-day and paleogeographic map pairs with details of known Phanerozoic carbonate systems/reservoirs with age-based carbonate themes (Figure 2).
Age-Based Pattern DevelopmentAn example of developing an “age-sensitive pattern” or “time-based theme” is when the map-view configuration and spatial relationships of carbonate systems depicted on a paleogeographic map are convolved with the ambient states of the carbonate and earth processes for that time period (Figure 3). In this case, the key carbonate systems/reservoirs that form the basis for this time-based theme are in the Ellenberger Formation of West Texas. Articulation or characterization of the theme can be made with simple declarative statements that capture key system and/or reservoir attributes (Figure 3 bullet points). The validation of this age-sensitive pattern or theme is whether other coeval carbonate systems that formed on the other margins of Laurentia, Baltica, and Siberia can be characterized similarly.
Comparative Reservoir AnalysisSometimes there are significant differences between carbonate systems and reservoirs within a geologic time period or age. We propose that the CATT Hypothesis and the Atlas products (paleogeographic, paleoclimate and paleo-oceanographic maps) provide an approach for comparative analysis between systems within a geologic age that gives meaningful understanding for the causes of the differences. Since 2003, we have developed additional maps of paleoclimate and paleo-oceanography based on recent publications from National Geographic for each of the 29 Phanerozoic time slices. These maps were empirically developed based on present-day trends. Another ExxonMobil in-house project completed parametric modeling of various time slices to evaluate these empirically-based maps. There is very good agreement, and this increases confidence for comparative analysis between coeval systems with dramatically different attributes. An interesting case in point is contrasting Late Jurassic systems/reservoirs of the Arabian Basin (Arab Formation fields) with those of the northern Gulf of Mexico (Smackover Formation Fields) (Figure 4). Many key attributes that control reservoir properties are compared between the examples.
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