Abstract: Quantitative Predictions of Petroleum Charge System Risk From an Integrated, Multidisciplinary Team Approach
TOBIN, RICK C., BRENDA L. CLAXTON, GORDON D. WOOD, and ZVI SOFER, Amoco Corporation
Technical risk analysis
of the petroleum charge system is a
two-step process involving: (1) quantitative and non-quantitative
predictions of risk components (source, expulsion, product type,
migration, timing, entrapment and porosity) and (2) estimates of
the degree of uncertainty (“chance of failure”) for each
component. The best predictions of risk components involve the
integration of multiple technologies, technical project planning,
and cooperative teamwork. Estimating the degree of uncertainty for
each risk component is also greatly enhanced by the use of
multidisciplinary evaluations, because they are constrained by a
wider variety of complementary data types, thereby increasing the
degree of confidence in the assignment of risk.
The interpretation of a basin's thermal evolution is
fundamental to predicting petroleum charge system risk because of
the effect on source rock maturation, hydrocarbon generation and
expulsion, migration and entrapment timing, hydrocarbon
preservational state and reservoir rock diagenesis and porosity
history. The most successful method of thermal history evaluation
utilizes a multidisciplinary team approach that includes
contributions from the geochemistry, petrology and paleontology
disciplines. Recommended analytical procedures that are included in
this evaluation are vitrinite reflectance, thermal alteration
index, conodont alteration index, Rock-Eval pyrolysis, biomarker
analysis
, apatite fission track
analysis
, fluid inclusion
petrography, inorganic thermochronology (Helium isotopes,
40Ar/39Ar, etc.) and illite crystallinity.
Resulting thermal data are then used in conjunction with structural
geology data and thermal modeling software to interpret thermal and
burial histories. Multidisciplinary maturity studies benefit from
improved reliability, greater cost effectiveness and wider
applicability (no age, lithology, or structural complexity
restrictions). In addition, these techniques provide accessory data
that are beneficial to the explorationist, such as source rock
geochemistry, kerogen identification, biostratigraphy,
paleoenvironmental
interpretation, diagenesis, migration and
timing, and the timing of heating and cooling events.
The conventional style of thermal history application generally
involves the calibration of computer modeling with basic organic
maturity data, stratigraphic and lithologic data, and wellbore
temperatures to yield an optimized burial and thermal history.
Thermal modeling results are usually focused on the interpretation
of source rock parameters only (generation/expulsion timing,
transformation ratios, etc.). In contrast, we advocate a redesigned
style of thermal history application that is an iterative
integration and interpretation process geared to address multiple
risk parameters. This process includes five stages: (1) technical
project planning to select the most appropriate mix of maturity
technologies, (2) independent maturity analyses to ensure unbiased
data generation and initial interpretations, (3) first-pass
integration of maturity datasets and development of preliminary
interpretations, (4) optimization of thermal modeling efforts with
the previously integrated maturity data in an iterative process
designed to provide an overall interpretation of thermal and burial
history, and (5) higher-level integration of thermal history
interpretations with related technical data sets (e.g., structural
geology, geophysics, log analysis
, etc.) to address other risk
parameters associated with all components of the petroleum charge
system (source quality, product type, reservoir quality and the
timing of expulsion, migration, re-migration, and entrapment).
Examples of successful integrated maturity studies are shown from
the USA, the Middle East, China, and the Baltic Sea.
AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah