The Monterey Formation of California: New Research Directions
The Miocene Monterey Formation is an exceedingly
heterogeneous, biogenic-rich (siliceous, calcareous and carbonaceous) deposit
and only a minor fraction of its volume would be considered a true
“shale”. It is California’s primary petroleum source rock and
an important “conventional” reservoir in many areas, primarily
exploiting naturally fractured rocks. Recently, due to its great thickness,
broad areal extent and organic-richness, the Monterey was recently estimated to
hold more than half of all the recoverable shale oil resources in the lower 48
states. This significance raises the following fundamental and applied research
questions: How much of the Monterey’s varied lithostratigraphy reflects
global vs. local environmental conditions? How do facies in the formation vary
laterally? How does porosity and permeability vary with diagenetic setting and
timing - not just silica phase and composition? How does diagenesis
and
deformation vary with
depositional
environment
, primary composition and
structural setting?
As part of the CSU Long Beach Monterey and Related
Sedimentary rocks (MARS) Project, we are investigating stratigraphic,
geochemical, diagenetic, and structural aspects of this important formation
with the following goals: Refine the chronostratigraphy lithostratigraphy for
the Monterey Formation of the San Joaquin Basin, applying chemostratigraphic,
cyclostratigraphic and tephrochonologic methods. Investigate compositional
variability in facies of the "Nodular Shale" or "Black
Shale" of the Los Angeles Basin. Characterize Monterey lithologies and
microfacies petrographically, including unusually porous diagenetic siliceous
rocks. Investigate variability in genus-level composition of diatomite related
to depositional
environments and the
influence
of diatom assemblage on physical
properties and diagenetic potential. Study mechanical stratigraphy in different lithologies and stratal architectures and their
influence
on fracture
development in the Monterey Formation. Develop a genetic model of lithologic
composition and cyclicity that can be predictive of mechanical stratigraphy and
fracturability in different lithofacies. Hopefully, wih success in these
endeavors, the Monterey Formation, with its varied composition and stratigraphic character, can serve as a valuable analog for other
“shale” and non-conventional resource plays.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California