About This Item
- Full text of this item is not available.
- Abstract PDFAbstract PDF(no subscription required)
Share This Item
The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Slime, Sand, and Shells: Lacustrine Hydrocarbon Play Elements Within
a Continental-Environment Phase Stability Framework
By
ExxonMobil Upstream
Research Company
Lake basin
types have characteristic associations and distributions
of hydrocarbon source, reservoir and seal strata. These
differences arise mainly from distinct histories of lake hydrology,
which control the evolution of lake water chemistry, the nature
and stability of food webs and clastic sediment supply rates.
Hydrocarbon sources are influenced strongly by these controls
on the ecosystem and reservoir- and seal-prone strata are linked
to these controls through the timing of clastic sediment supply
relative to lake level and the influence of water chemistry on the
dominant lithology (e.g., clastic, carbonate, evaporite).
The strong genetic association of play elements
requires an integrated approach to
prediction, which is facilitated by expanding
the lake-basin
-type diagram (Carroll and
Bohacs, 1995, 1999) to a full continental-environment
phase stability framework. This
framework places fluvial, floodplain, coal,
aeolian and the three lake-
basin
-type strata
into relative stability fields, constrained by
their inter-related controls: the rate of potential accommodation
relative to supply rates of sediment and of water. The phase
trajectory of
basin
evolution determines the proportion of each
lake
basin
type in the resultant strata. This approach helps
explain why all lake basins do not contain the full suite of lake
basin
types and how the fill of a chain of ancient lakes may
be genetically related. One can predict phase trajectories in a
forward sense from estimates of
basin
subsidence, paleoclimate
and sediment yield, or one can reconstruct phase trajectories
from relative thicknesses and areal extents of each continental
environment stratal package: thick underfilled lake packages
point to dominant control of potential accommodation rates
whereas thin underfilled lake packages indicate dominant
control of supply rates of sediment plus water.
Associated fluvial styles among the lake basin
types appear to vary
systematically, with perennial, high-sinuosity streams in over-
filled, intermittent to perennial low-sinuosity streams in balanced
fill and a wide range from ephemeral sheetflood/braided streams
to perennial high-sinuosity streams in underfilled lake basins.
Lateral distributions of reservoir-prone strata also vary significantly among lake
basin
types and lake shoreline shapes
encompass a richer diversity than typically seen in marine
settings: shorelines tend to be more highly constructive and
dispersive in more persistently closed hydrologic basins.
Fundamental changes in shoreline type and
lake character between highstands and lowstands
may even obviate the application of
Walther's Law for predicting lateral distributions,
especially in underfilled lake basins.
Ultimate reservoir quality may be related to
phase trajectory through the diagenetic effects
of fluctuating groundwater tables. Each lake-
basin
type has a characteristic history of
groundwater level changes, recorded in recurring
associations of paleosol types and ichnofossil assemblages:
histosols and shallow single-tier burrows, tracks and trails in over-
filled, vertisols and multi-tier, moderate depth insect burrows in
balanced fill, and aridisols and entisols with multi-tier, multiple-generation,
relatively deep burrows in underfilled lake basins.
Observations indicate that these associations of hydrocarbon play elements occur in a wide variety of tectonic settings and ages, from continental rift to convergent foreland basins of Cambrian to recent age. Continued success in economic discovery and efficient recovery of hydrocarbons depend upon continued testing and elaboration of these concepts and a deeper understanding of the essential processes controlling deposition of lacustrine strata.
End_of_Record - Last_Page 21---------------