L. B. Magoon, W. G. Dow
Sedimentary basins,
petroleum
systems, plays, and prospects may be viewed as
separate levels of investigation, all of which are needed to understand the
genesis and habitat of hydrocarbons. Sedimentary basin investigations emphasize
the overall stratigraphic and structural evolution of sedimentary rocks.
Petroleum
system
studies describe and map the genetic relationship between a pod
of active source rock and the resulting discovered oil and gas accumulations.
Investigations of plays describe the present-day geological similarity of a
series of present day traps, and studies of prospects describe an individual
present day trap. The sedimentary basin and
petroleum
system
occur in nature
regardless of economics. However, the play and prospect exist only when
undiscovered co mercial accumulations of
petroleum
are thought to Occur.
A
petroleum
system
encompasses a pod of active source rock and all
genetically related oil and gas. Additionally, a
petroleum
system
includes all
the essential elements and processes that are needed for oil and gas
accumulations to exist. The essential elements are the source rock, reservoir
rock, seal rock, and overburden rock, and the processes include trap formation
and the generation-migration-accumulation of
petroleum
. All essential elements
must be placed in time and space such that the processes required to form a
petroleum
accumulation can occur. Characterization Of
petroleum
systems include
the procedures to identify, characterize, name and determine the levels of
certainty.
The
petroleum
system
has a stratigraphic, geographic, and temporal extent.
The
system
name combines the names of the source rock and the major reservoir
rock and also expresses a level of certainty-known, hypothetical, and
speculative. For example, the Mandal-Ekofisk(!)
petroleum
system
. Four figures
and a table that best depict the geographic, stratigraphic, and temporal
evolution of the
petroleum
system
include a burial history chart to establish
the critical moment for the
system
, a map and cross section drawn at the
critical moment, an events chart to summarize the formation and history of the
petroleum
system
, and a table of related accumulations. The
petroleum
system
concept is used to investigate discovered hydrocarbon accumulations and as a
basis for proposing plays and prospe ts.
AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995