Exploration Handbook | 23
» » To aid frontier play analysis by providing a framework for
assessing analogue basins and play types
» » To help evaluate the likely generation of hydrocarbons through
burial depth of source rocks and an assessment of thresholds,
such as the oil and gas windows
By: Emily Firth
» » As an input for basin modeling by providing information on
basin evolution and fill, including the depth of burial, thickness,
and lithology of play elements
WHAT ARE PLAY CROSS SECTIONS?
A play cross section, or schematic play concept diagram, is a simplified geological cross
section that illustrates the stratigraphic and structural context of one or several plays along a
particular transect. Resolution can vary, but representation is typically on the basin, field, or
prospect scale. The Z-axis is presented as either depth or seismically derived two-way travel
time.
Play cross sections can be depicted as simplistic cartoons, derived from a basic regional
understanding, in order to illustrate the presence or relationship of certain play elements.
More detailed transects are typically based on structures identified from seismic lines or
regional cross sections. A detailed depiction of the stratigraphy is made from well data,
chronostratigraphic charts, and gross depositional environment (GDE) maps.
An example of a highly simplified Neftex ® Insights Play Cross Section can be seen in Figure
1, illustrating play concepts within Cyprus and Lebanon.
» » To illustrate sequence stratigraphic concepts and highlight
the tectono-stratigraphic evolution, aiding prediction of
stratigraphy where data are sparse
“Play cross sections help
evaluate the likely generation
of hydrocarbons through
burial depth of source rocks
and an assessment of
thresholds, such as the oil
and gas windows”
BUILDING A PLAY CROSS SECTION
Play cross sections are built from a wide array of geological data
(Figure 2). There are no widely accepted standards for producing play
cross sections, but some of the data and concepts that can be used
in their construction are described in the following sections.
Basin Familiarization
East
I
C T UR A L O
R U
S T S M I C S E C T I O R
N
E I
L L S A N
W E A T I G R D
R
A P
T
H
O S
PO S I T
IO
S D E
O S N M E N T (G N A
R I R O
D
V
N
Pli Pl
Miocene
G
Oli
Eocene
Pale
Late Cretaceous
Neogene Q
IN
Paleogene
Early Cretaceous
M OD E L
B
Late Jurassic
Speculative source
S?
Cretaceous
R Reservoir S Source
I N
A S
Predominantly deep-marine carbonates
Basement
Salt
Predominantly shallow-marine carbonates
Predominantly deep-marine mudstones
Sand-rich clastic intervals
The first step is to familiarize yourself with the area of interest. What
exploration has occurred in the area, what was targeted, and was
there any success or failure? What data are available to improve the
understanding of the geology, and can they be used to construct
the play cross section? This will help when assessing what features
the play cross section should depict (i.e. dip or strike line) and the
resolution of the diagram, both geographically (e.g. basin, field, or lead)
and stratigraphically (e.g. bulk lithology or high-resolution facies).
West
» » To provide a framework for capturing available data and key
uncertainties within a basin
Figure 1 > A highly simplified example of a Neftex Insights Play Cross Section from Cyprus and Lebanon.
®
APPLICATIONS OF PLAY CROSS SECTIONS
J10 LST–J20 TST (181Ma)
» » To show the geographic and subsurface distribution of tested and untested plays
J80 TST (159.8 Ma)
50
Provides an understanding
of thermal regime
» » To illustrate play concepts as simple reservoir, charge, seal, and trap combinations
D Y
N A MIC M O
D
Provides age and
lithological constraint
Provides the structural
framework
P E R T I E
P R O
S
C K I C G E O C H E M A N
O N
I
A
FINAL PLAY CROSS SECTION
E O
Gives insight for infilling
stratigraphy
» » To highlight the approximate position, stratigraphic thickness, and depth of burial of key
play elements
100
Play cross sections have a number of different uses:
150
» » To help determine the prospectivity of an area by capturing proven play information, as
well as untested play potential
» » To provide rapid familiarization of a basin’s evolution, both structural and stratigraphic
» » To provide insight into potential risks associated with untested plays as a first pass
assessment on reservoir quality and charge
Establishes timing and context
of key tectonic events
Play Cross Sections — Visualizing Play
Concepts
Confirms petroleum
system elements
Figure 2 >The building blocks of a play cross section. The structural framework is provided by a seismic line. The stratigraphy is
filled in using well data and an understanding of the regional geology through gross depositional environment (GDE) maps and
chronostratigraphic charts. Where available, other data are incorporated to provide further constraint on the interpretation.
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