Geotrack International Pty Ltd (Melbourne, Vic),
Keiraville Konsultants Pty Ltd (Keiraville, Nsw), and
PetroConsult Pty Ltd (Melbourne, Vic)
the timing, distribution and origin of hydrocarbons in the Papuan Basin
and objectives of this study
perspective on the oil prospectivity of PNG
maturity, reservoir and the petroleum system
the importance and objectives of Basin Modelling
for this study
Konsultants Pty Ltd
Pty Ltd (www.petroconsult.com.au)
Constraining the timing, distribution
of hydrocarbons in the Papuan Basin
objectives of this study
This proposed study program is designed to answer specific
exploration questions that have long confronted explorationists working
the Papuan Basin, PNG. Fundamental exploration issues in the Fold Belt
and Foreland of PNG remain unresolved. These include:
Agreement on a unified tectono-stratigraphic framework for the Papuan
Basin encompassing both Foreland and Fold Belt regions.
The relative effects (structural and thermal) of major tectonic events
in the region.
Establishment of accurate thermal histories across the basin.
Evaluation of generation and charge history including local variances.
Determination of the type (oil versus gas) and relative volumes of
Effect of uplift, erosion and fresh water influx on hydrocarbon accumulations.
Recent drilling results and the extension of seismic
data in both the Foreland and Fold Belt make this an appropriate time
to re-evaluate the Papuan Basin in terms of the these issues. The timing
is also very opportune given that in the near future, companies will
have to make major decisions with respect to the future direction of
oil and gas exploration in PNG.
Answers to these questions necessarily require a multi-disciplinary
approach involving a strong, integrated group of people who have a long
working history in the region. Such is the motivation by which Geotrack
International, Keiraville Konsultants and PetroConsult have united to
target the following key issues in the Papuan Basin.
1. MATURATION, GENERATION AND FLUID MOVEMENT: THE NEED
FOR 2-D BASIN MODELLING: The use of multi-dimensional basin modelling
software such as PetroMod, is increasingly regarded as an important
component of exploration programs. While one-dimensional (1-D) models
have been used significantly in the past in PNG, they suffer from severe
inherent limitations, particularly in their failure to account for lateral
effects of temperature and pressure. They are also unable to account
for fluid movement important in both hydrocarbon maturation and migration.
1-D results can therefore be sometimes very misleading.
While many workers assume that the hydrocarbons in
the PNG Fold Belt were generated and emplaced prior to Late Tertiary
thrusting and formation of the Fold Belt, other evidence suggests synchronous
or even later generation and emplacement. Constrained answers to such
questions concerning the timing of source rock maturation, hydrocarbon
generation, oil versus gas and fluid migration questions are best answered
by detailed structural modeling involving sophisticated 2-D (or even
3-D) models tied into and constrained by existing well control.
2. IMPROVED RESOLUTION OF MULTIPLE EVENTS: Two major,
late phases (Late Cretaceous/ Tertiary and latest Tertiary) of structuring
affected the Papuan Basin. Although both events are considered important
to the origin of hydrocarbons in the Papuan Basin, the significance
of each is open to debate. While the Foreland and Fold Belt regions
were both affected, the relative and absolute magnitude of each event
varied across the regions. Understanding and measuring this variation
is vital to modelling of hydrocarbon generation and entrapment. Using
the latest AFTA technology, we will measure the timing and determine
the magnitude of these events across the Fold Belt and Foreland. This
will help constrain their effect on hydrocarbon generation and migration
allowing better basin models to be built and tested.
3. RIGOROUS ASSESSMENT OF MATURITY: As detailed in
the discussion presented in the following Section, there are numerous
apparent anomalies in the variation in maturity across the region. These
perceived problems are a consequence of multiple factors such as:
the poor quality of some maturity data,
unrecognised suppression and
complexities in the thermal history of the region.
A strategy to distinguish these factors and identify
the way for future exploration strategies in the region is an important
aim of this study.
The study objectives rely on the combined expertise
and experience of Keiraville Konsultants (experts in source rock characteristics
and maturity), Geotrack International (experts in measured thermal history),
and PetroConsult (experts in 2-D basin modelling). The project is designed
to provide constraints on the problems outlined above, and only when
taken together, will they allow a better understanding of petroleum
systems in the Papuan Basin. Such a project, bringing together world
experts in their own field to answer fundamental unresolved questions
in PNG, has not been attempted previously.
In the following Section, we provide some background
on the exploration history in the Fold Belt and Foreland of PNG. More
than an introduction, this background provides an important basis in
understanding why fundamental exploration questions remain unresolved
and uncertainty continues. The summary includes a discussion of the
elements of timing, structuring, source rock maturity, and migration,
thus demonstrating the need for an integrated approach in constraining
the problems outlined above. In addition, reference is made to some
of the more recent developments that make a reappraisal of these factors
on the oil prospectivity of PNG
The oil and natural gas industries in Papua New Guinea
have been characterised by a long period of exploration without any
commercial discoveries followed by the discovery of some small gas fields
in the 50s and then some gas and gas/condensate fields in the
60s. The first discovery of a significant oil accumulation at
Kutubu occurred in 1986.
Subsequent development saw Kutubu oil coming on-stream
on 28 October 1991 with the first export shipment taking place on 27
June 1992. Commercial production from Kutubu had been preceded by minor
gas and condensate production from Hides. Hides gas is used to generate
power for the nearby Porgera gold mine and the condensate is partially
refined giving a diesel fraction that is sold within the Papua New Guinea
The Kutubu discoveries were followed by the Gobe discoveries.
At this stage, oil was only known from the Fold Belt confined to a row
of structures running SW from Mananda to Gobe through the Agogo and
Hedinia/Iagifu fields. Until the Paua structure was drilled in 1995/96,
the structures lying to the NE of this belt were known only to contain
gas with some condensate. It appears that some companies had effectively
written off the terrain to the NE of the Mananda - Hedinia - Gobe trend
in terms of the existence of oil.
At Paua, a discovery of oil was made in the footwall
of the structure. This discovery was followed up by the drilling of
the Moran structure where the thrust sheet is present in a hanging wall
setting. Within Moran, a thick oil column is present, and unlike the
Kutubu fields, no gas cap is known. However, as at the Gobe field, cross
-faults have resulted in significant compartmentalisation. The Moran-4x
well showed the presence of oil within a different compartment at a
different pressure to those found in the initial discoveries. The oil
in Moran-4x also has a different API gravity to the oils in Moran-1x
and Moran-2x. More detailed information on oil chemistry differences
is not available at this stage. The pressure regime within Moran is
very different from that in the nearby Kutubu fields. Remarkably, pressures
are close to twice those in the Kutubu fields and formation pressures
are about 1000 psi higher than the pressure of the solution gas.
Two of the Moran wells have been placed on extended
well test through a connection to the Agogo Production Facility with
a short pipeline having a capacity of about 25,000 barrels per day.
These tests are likely to continue until the field is fully developed.
This may take some time due both to the complexity of the structure
and to the presence of oil within different permits: PDL2 (Moran-1X
and 2X) and PPL 138, and is also likely to be present within parts of
PPL 161. Extensive appraisal and unitization of the fields will be required.
Since 1986, exploration has largely focussed on the
Fold Belt, but some wells have been drilled within the Foreland Basin
to the SW and minor amounts of exploration has taken place within other
basins such as the North New Guinea Basin.
The oil discoveries have been restricted to the Fold
Belt and most of the gas discovered is also located within structures
in the Fold Belt. Smaller amounts of gas have been discovered within
the Foreland, including some discoveries in the offshore area within
the Gulf of Papua.
Early drilling within the Fold Belt was performed without
the availability of useable seismic. Targets were delineated largely
from field mapping followed by construction of structural sections.
Because of this difficult and imperfect method, a large number of wells
did not penetrate their intended targets. Two of the better known are
Gobe-1X which drilled too far off-structure intersecting the reservoir
below the oil/water contact, and Karius-1X which did not intersect reservoir
section in the hanging wall target. Lucky accidents have also occurred
as with the Paua discovery.
Recently however, resulting from developments in seismic
recording techniques in PNG, swath seismic lines have been recorded
down the valleys and dip lines directly across structures have become
available, dramatically improving the targeting of drilling.
rock maturity, reservoir and the petroleum system
Within humic coals, vitrinite reflectance has proved
a reliable indicator of rank. Coal scientists had generally used a number
of measures to assess rank, and therefore within the coal industry vitrinite
reflectance was used to assess rank - as opposed to being considered
a measure of rank. This lead to its use by the petroleum industry but
it has commonly been used as a measure of maturation rather than
as a property requiring interpretation.
Cook (in Hutton and Cook, 1980) of Keiraville Konsultants
drew attention to the probability that the vitrinite scales constructed
for marine sequences differ significantly from those based on humic
This has lead to a major emphasis on the importance
of what is termed vitrinite suppression. Such an approach is also over
A number of factors can complicate the use of vitrinite reflectance,
and these include:
Incorrect identification of other tissue types.
Vitrinite dominated by unusual tissue types.
Sedimentary, and more specifically, organic facies.
Interference effects of other macerals, especially alginite.
Impregnation with bitumen or oil.
Reworking of vitrinite so that the vitrinite reflectance is determined
by a previous thermal history.
Oxidation of vitrinite fragments, probably partial conversion to
Sediments deposited under marine conditions dominate
the sequence in the Papuan Basin, but the majority of the organic matter
is derived from higher plants. Sedimentary facies is generally an important
qualifier that should be applied to vitrinite reflectance data from
well sections in the Papuan Basin. Many of the plant fragments that
are preserved as vitrinite or vitrinite-like tissue include suberinite
or similar cortical tissues. Suberinite has much lower reflectances
compared with vitrinite. These two factors mean that much of the published
data understates the real level of maturation.
Careful attention to measurement can largely eliminate
the low-reflecting cortical tissues. An approximate correction can be
applied to allow for organic facies.
FAMM (fluorescence alteration of multiple macerals)
techniques have been applied to some samples from PNG. From the data
available to the investigators, the FAMM data are almost always higher
than conventional vitrinite reflectance data, in some cases markedly
so. The FAMM estimates of vitrinite reflectance effectively form an
upper boundary to maturation levels, and uncorrected vitrinite reflectance
data a lower boundary.
It is proposed that a small number of FAMM analyses
will be undertaken on samples assessed from conventional vitrinite reflectance
studies to be of critical importance in evaluating thermal histories.
Other properties that are sensitive to maturation levels
will also be used where appropriate.
It is considered that the proposed study will yield
high quality and consistent maturation data that can be fully integrated
with the AFTA results.
More about source rocks and reservoirs
The main hydrocarbon reserves found within the Fold
Belt have been within the Toro Sandstone. The Toro lies below the shale
dominated Ieru Formation and above the Imburu Formation. The Imburu
Formation is also dominated by shales but also contains a number of
important reservoir sandstones, such as the Digimu, Hedinia and Iagifu.
The Toro Sandstone is the main reservoir in the Kutubu fields but is
water wet at Gobe and there the Iagifu is the main reservoir unit.
The Alene Sandstone is present in some
areas above the Toro Sandstone and the Koi-Iange Sandstone is present
below the Imburu Formation.
In the Fold belt, vitrinite reflectance values near
the reservoir sections have commonly been reported as being in the range
0.45% to 0.55%, however, proprietary data suggests that values in the
range 0.55% to 0.65% are more representative. The organic matter within
the Ieru and Imburu Formations contains a marine element but is generally
dominated by organic matter of higher plant origin. Taking the facies
into account, maturation levels within the reservoir sections are most
accurately assessed as about 0.6% to 0.7%.
Lateral and vertical variations in maturation levels
within the reservoir section are not well understood. The general level
of maturation at Gobe appears to be similar to that in the Kutubu fields
even though the section at Iagifu is close to one km deeper than that
at Gobe. However, the intersections at Gobe tend to be slightly deeper
stratigraphically compared with the Kutubu data. Vertical vitrinite
reflectance gradients appear to be low with typical data sets showing
increases of less than 0.1% over intervals of about 600 m within the
Northeast of the Kutubu - Gobe trend within the higher
pressure regimes found in some of the thrust sheets lying further from
the front of the Fold Belt, maturation levels appear to be similar to
those in the Kutubu fields at similar depths.
In the northwest of the PNG Fold-Belt lower levels
of maturation at similar depths to those found in the Mananda - Kutubu
- Gobe trend occur, although a great distance away. Thus, on the basis
of limited data, it is difficult to know if the lower levels of maturation
there are due to lower cover or may also represent an element of lateral
variation. Even so, the data indicate that the section at the western
end of the Fold Belt has a similar assemblage of organic matter and
probably a similar thermal history to the sections in the main producing
areas to the SE.
Many of the samples examined contain small amounts
of reworked coals. Some of these have high rank and appear to be derived
from earlier sequences, but a high proportion shows vitrinite reflectances
close to those of the host rocks. The shales adjacent to the Toro and
Iagifu Sandstones appear to be marine in origin but were deposited close
to the shoreline. Additionally, proximity to a shoreline appears to
be persistent through a relatively thick sequence.
Within some overpressured zones, high levels of oil
saturation also occur. In these cases, the liptinite appears to have
been solubilised rather than to have enhanced fluorescence. There may
be a case for making a part of the study an integration of known pressure
data with the organic petrological characteristics. Although the early
oil discoveries within the Fold Belt were largely within the lower pressure
zones, most of the potential for additional discoveries appears to be
within the highly pressured parts of the system. A better understanding
of the effects of pressure on measures for maturation would be an important
potential spin-off from any study.
More about migration and physical processes in fluid transport
Conventional vitrinite reflectance data generally can
be used to support a local origin for the oil in the Fold Belt with
gas generated either much deeper within the section or to the NE where
higher levels of maturation are known. Further evidence for the possible
local sourcing of oil may be determined from the organic matter assemblages
within selected formations.
If it can be established that locally sampled horizons
are suitable sources for oil currently in place, then models involving
long-distance migration may require significant modification.
Within the Fold Belt, early assumptions appear to have
been that the GOR was at its lowest in the Mananda - Kutubu - Gobe trend
and that the amount of oil decreased in the thrust sheets NE of this
trend. It is clear that the terrain NE of the Fold Belt is of much higher
rank. Here units such as the Chime Shale are commonly anthracitic or
meta-anthracitic in rank. In contrast, studies on the thrust sheets
NE of Hides show no presence of high rank Mesozoic sections in outcrop.
One view on the origin of the hydrocarbons is that
they have been generated within sections of similar age to the reservoir
units, but of higher maturity lying to the NE of their present location.
This view has the GOR increasing to the NE and assumed that, with the
exception of the more distal belt containing the early oil discoveries,
that oil had been flushed by gas. The discovery of oil at the Moran
field would seem to discount this view. In addition, relatively long
distance migration implies the presence of carrier beds. The presumed
loss of the Toro reservoir to the NE of the producing fields suggests
the absence of effective carriers for hydrocarbon migration.
Most authors appear to assume that the oils were emplaced
prior to the development of the thrust sheets, possibly as early as
the late Cretaceous. Kreiger et al (1996, p. 407) suggest that
oil emplacement came before the establishment of the present hydrodynamic
flows and it is reasonable to suppose that these post-date the thrusting.
In the Foreland, a high proportion of wells have been
drilled within shallower parts of the section with many not well controlled
by seismic. The North Paibuna well, a deep test of the Foreland Basin
appears to have intersected some liquid hydrocarbons but the reservoir
was poorly developed. This well indicates that oil may be present within
some parts of the section in the Foreland.
The geological history in the Foreland is much less
complex than within the Fold Belt. However, a high proportion of Foreland
tests may have been too isolated from effective source areas to receive
Another important physical process possibly affecting
the distribution of hydrocarbons in the Papuan Basin is gas expansion.
The effects of gas expansion and gas/oil ratios due to uplift (or removal
of overburden) on an incipient oil trap cannot be ignored in modelling
the possible retention of oil legs in structures. Uplift and removal
of overburden leads to phase changes of the reservoired hydrocarbons.
Changes in the gas expansion factor results in an expansion of the gas
cap, a decrease in the gas/oil ratio, associated 'degassing' of the
oil leg leading to expansion of the gas cap and possible loss of the
Other features of the basin provide some insight to
the hydrodynamics of the Papuan Basin. The Toro Formation is a major
An analysis of the formation water systems in the Papuan
Basin was made by measuring hydraulic potential and formation water
salinity from wells (Kotaka, 1996). Regional water flow was interpreted
as fresh meteoric water entering the Toro Sandstone outcrops around
the Muller Anticline and the Lavani Valley northwest of the Fold Belt.
In the mountainous area of the northwestern part of the Fold Belt, the
hydraulic potential of formation water is 2,200-2,300 m. In the central
area of the Fold Belt, the hydraulic potentials are much lower at ~200-400
m while in Foreland areas they are below 100 m.
This active hydrodynamic regime has almost certainly
had, and still has an important effect on oil and gas distribution and
thermal modelling. This is particularly so across Highland areas of
the Fold Belt where potentiometric gradients and flow rates are significantly
higher than in the Foreland. High flow rates together with relative
differences in oil density and water salinity have the potential to
tilt oil/water contacts (gas/water contacts are little affected) leading
to spill of an oil column or complete flushing. This leads to questions
about the possible presence of tilted oil columns down-flank of structures
and the potential risk posed by hydrodynamic flushing of oil.
Little isotopic data supporting higher maturity of
gaseous hydrocarbons has been published. Waples and Wulff (Proc 3rd
PNG Petroleum Convention 1996, p417) have published data classifying
the oils from reservoirs and seeps on the basis of their chemistry.
They distinguished five main families and a number of sub-families within
this overall grouping. Families 1 and 2 are stated to indicate a Tertiary
origin but the occurrences of these generally lie well to the east of
the main producing areas. In the area where Family 1 is indicated, mature
Tertiary is known from the base of the Pale Scarp. In the Southern Highlands,
some of the Tertiary samples examined at Keiraville Konsultants from
the Highland have proved to be highly immature and are not considered
likely sources. Most of the commercial oils appear to have been derived
from Lower Cretaceous and Upper Jurassic sources on the basis of their
chemistry. This would be consistent with an origin from the shales close
to the reservoir horizons, but would also fit long distance migration.
The discovery of oil first at Paua and then at Moran
has shown that the early models with GOR increasing to the NE are not
correct. The presence of these oils and different pressure regimes at
the Moran, Makas and Beaver wells may have implications for the timing
of emplacement of the hydrocarbons.
Some of the recent unsuccessful wells within the Fold
Belt appear to have lacked viable reservoir as the Toro appears to lens
out to the E and NE of Kutubu. Within the Kutubu belt, meteoric waters
represent an additional complication. The absence of oil from the frontal
belt of structures could be due to flushing by meteoric waters.
The source potential of the sequences drilled within
the Foreland and Fold Belt provinces will be assessed largely on the
basis of organic petrology data, but other data types such as Rock-Eval
and pyrolysis will be used where appropriate. It is generally not possible
to study the source characteristics of sequences in possible source
areas under the long distance migration scenario. However, we do have
data on the characteristics of some of the possible source sequences
that could be invoked for long distance migration, except at much higher
current levels of maturation.
The general issue of source rock potential and oil
to source correlation falls outside the present studies but we are aware
of the significance of these issues as providing valuable input to the
studies that we are proposing and some of the data generated by the
study should add to information about source rock potential.
about the importance and objectives of Basin Modelling
More recently, improved seismic acquisition has led
to significant improvements in structural definition across both the
Fold Belt and Foreland regions. In addition, side-track drilling of
structures in the Fold Belt provides a much better understanding of
the structural geology and better control on structural modelling. Two-dimensional
modelling is also a vital aspect in evaluating petroleum systems.
Two general models have been proposed to explain the
generation and migration of hydrocarbons in the Papuan Fold Belt:
Model 1 (after Hill, 1991;
Earnshaw et al., 1993; Buchanan and Warburton, 1996) invokes an early,
main phase of hydrocarbon generation in the Late Cretaceous and Early
Tertiary. Maturation of Late Jurassic and Early Cretaceous source rocks
is thought to occur through depositional loading of Late Cretaceous
- Early Tertiary sediments and a possible increase in heat flow generally
associated with opening of the Coral Sea (the Coral Sea 'rift' event).
Migrating hydrocarbons were retained in pre-existing traps (e.g. tilted
fault blocks) associated with rifting and half-graben development. Generation
was curtailed in many areas with the onset of thermally driven regional
uplift and erosion also associated with Coral Sea 'rifting'. Oil was
retained in these traps until subsequent Plio-Pleistocene compressional
structuring in the Fold Belt caused the early traps to be re-mobilized
and in some cases spill with remigration into more recently formed traps.
In the Papuan Foreland Basin (which did not experience substantial structuring),
the hydrocarbons remained largely in the existing trapping situation
with gas an increasing generative product accompanying further subsidence
Model 2 (after Buck and Stone, 1991)
calls for much later maturation of source rocks with the predominance
of generation taking place in the Pliocene to Pleistocene. In the Foreland
Basin, maturation was caused by depositional loading of a thick Plio-Pleistocene
section. In the Fold Belt, maturation and consequent hydrocarbon generation
was confined to source rocks in synclinal areas and footwall locations
of thrust sheets. In these areas, source rocks are buried to varying
degrees by the combined overburden of pre-existing sediments and thrust
imbricates giving oil and gas products of variable maturities. Generation
and migration were largely synchronous with trap formation and many
kitchen areas are possibly generative present day. The model implies
multiple kitchen areas, each with its own, unique maturation, generation
and expulsion properties. In those areas of the Fold Belt that have
been uplifted and severely eroded, maturities are relict and reflect
the previous maximum burial depth. Even areas that have not been significantly
unroofed may not be presently generative due to overall cooling associated
with structuring over at least the last 4 Ma.
Model 1 has significant problems in trying to explain
the deposition and subsequent stripping of up to 2,000 m of Late Cretaceous
to Early Tertiary section across the Papuan Basin. The occurrence of
a major regional tectonic event involving significant structuring at
this time is not supported by seismic data across the Foreland Basin.
The wrench-related tectonism that characterizes the Coral Sea 'rift'
event, likely influenced structural development across the entire the
Papuan Basin (both present day Foreland and Fold Belt regions). Rather
than regionally near-uniform uplift across the basin, the combination
of transpression and transtension imposed by the wrenching was responsible
for significant but much more localised uplift and subsidence. The consequent
structuring is often very similar to rift-related tectonics on dip seismic
sections (and has been interpreted as such in the past).
Supporting, although not unequivocal evidence for Model
2 is provided by fluid inclusion and sandstone cementation studies.
These suggest that petroleum emplacement occurred during the latest
Tertiary and possibly through to Recent in some areas, synchronous or
post-dating thrusting and trap formation on the Fold Belt.
The main issue for basin modelling in the Papuan Basin,
is to ascertain the timing, magnitude and effect (local and regional)
of the two late phases of structuring and hence the validity or otherwise
of the two generative models. Solutions to these problems and a consequent
enhanced understanding of the petroleum systems that operated in the
Papuan Basin are best tackled through the construction of 2-D (or 3-D)
basin models. As discussed previously, multi-dimensional models have
significant advantages over 1-D models.
Petroleum generation, expulsion and migration are continuously
calculated along identified flow paths in 2-D models allowing much better
understanding of lateral variability. In addition, the simulation of
fluid flow (petroleum and water - not possible in 1-D models), enables
the effects of convective heat transport through the sequence to be
determined as well as providing a model of petroleum migration and accumulation
history through geologic time. Assessment of the additional affects
of hydrodynamics and local heating from igneous intrusions is also possible.
Simulation results can also be directly compared to fluid inclusion
and cementation studies. Other important physical processes must also
be included for any basin model to be useful in exploration.
An integrated basin model also needs to accurately
describe the pressure regime of sedimentary basins because pressure
gradients control the direction and intensity of fluid flow according
to Darcy's Law. The difference of the pore pressures of the fluid is
called the capillary pressure. It is used to derive the petroleum driving
forces of oil to water or gas to water. The petroleum moves from high
pore pressure regions to low pore pressure regions. Only modelling of
pore pressure in 2-D or 3-D can accurately account for the effects of
overpressuring, kerogen conversion on pore pressure, and fluid flow
due to lateral compaction.
Intrusions can have dramatic effects on palaeo- temperatures
and all thermally controlled values [e.g. calibration parameters]. Although
the duration of such events is relatively short, the extremely high
temperatures can trigger rapid chemical reactions in the near environment.
Such intrusions will be modelled and are known to be significant in
the Fold Belt area of Papua New Guinea. Both model output and experimental
data from samples will be evaluated to establish the nature and extent
of these effects. Contact alteration results in highly distinctive optical
properties and existing samples can be examined for evidence of contact
alteration. We will also try to target some sections where maturation
levels are high and attempt to determine if these result from regional
or contact coalification / maturation.
The decay of radioactive elements leads to significant
heat generation within the rock body. Such elements may be concentrated
in intrusive bodies.
Deterministic basin modelling necessarily offers a
definite value for a particular parameter in time and space as a result,
and not a range of values or value with error margins. However, sensitivity
analyses can define margins of error and are an integral part of the
basin modelling procedure, for example during the calibration.
A sensitivity analysis with the simulation program
is an efficient and quick method of defining error margins for any particular
parameter and range of input values.
Work program and deliverables
In addition to the collection of a range of selected
data sets (AFTA, VR, FAMM, fluid inclusions, Rock-Eval), the study will
require a number of seismic transects across the Foreland and Fold Belt.
Lines adequate for this purpose may be available in the published literature.
However, based on early indications, it is hoped that contributions
will be made by the participating companies. Collaboration between
the principal investigators and company personnel is an important aspect
of this study. There are mutual benefits to such interaction. Maximising
information exchange will ensure that:
The constructed models are based on a full account of all available
information (with proper quality control criteria).
Companies will have an opportunity to better familiarise themselves
with the methods used in this study (2D basin modelling, AFTA, source
rock analysis) and the quality of the data.
The extent of the success of this project will somewhat depend on the
active collaboration and participation from interested companies.
Quantitative models will initially focus on the Foreland
where the relatively less complicated structures together with the availability
of a more extensive seismic grid, will allow development of meaningful
2-D models. The structural complexity and poor seismic resolution through
the upper portion of the Fold Belt sequences introduce much uncertainty
and hence, construction of realistic physical models for the charge
history here are more difficult but not impossible. Modelling in the
Foreland relies on fewer assumptions and in this study, will be heavily
"data-driven" with strong emphasis on high data quality (AFTA,
fluid inclusion, VR, source rock, FAMM, structure, stratigraphy). All
data will be rigorously inspected before the data constraints are allowed
to be introduced to the basin models. In contrast, while modelling of
the Fold Belt will build from information gained from the Foreland,
it will necessarily be less rigorous. Objectives here will be targeted
more generally at understanding concepts (effects of pressure, long-distance
migration, source rock, diagenetic effects).
Identification of the seismic lines for this study
is currently underway; however, final selection of the precise lines
for this study will await further discussion with interested companies.
In addition to the wells included in Geotracks
previous work in the area (Geotrack Report #232), other key wells under
consideration for this study are:
Nomad, Cecelia, N. Paibuna, Moran, Beaver, Menga, Gobe,
Makas, Ketu Kiunga, Elevala, Koko, and Kimu (of course, sample availability
and well information may be subject to appropriate authority).
It is proposed that the study will proceed in four
phases with interim reports produced at the end of the first three phases
and made available to companies for discussion, with a final report
produced at the end of the fourth phase.
Compile and re-evaluate existing AFTA, VR, FAMM, fluid inclusion
and Rock-Eval data sets.
Acquire new AFTA and VR data at an additional 2-3 key Foreland wells.
Determine the structural and stratigraphic history at wells using
existing geological, basin modelling and seismic data sets.
Perform comprehensive basin modelling at key wells using well and
seismic data, incorporating new and re-evaluated maturity data.
Acquire additional maturity data if required and model.
Determine whether new maturity data and basin modelling is consistent
with ideas on structural and stratigraphic history at wells.
Modify structural and stratigraphic history if required.
Perform 2-D basin modelling in Foreland on 4-8 regional transects
incorporating knowledge on wells gained from Phase 3.
Extend 2-D basin modelling to Fold Belt using knowledge gained from
Phases 1 through 3 (additional AFTA and VR analyses may be required).
The final results will be provided to subscribing companies in a detailed
report. Issues highlighted in the margins of this report will be addressed
directly in the study using our integrated approach. In addition, the
following discussion sections will be provided in the final report:
(1) Re-evaluation of previous AFTA data using compositional control
(i.e., chlorine measurements and advanced algorithms) and interpretation
of new data by Geotrack International,
(2) Basin modelling results of 2-D modelling by Petroconsult,
Source rock maturation, analysis and discussion by Keiraville Konsultants,
Oral presentations to participating companies to report the main
modelling results and exploration implications, if desirable.
frame for this study
Commitments are sought immediately and work is anticipated
to begin on March 1st 1999. With sufficient pre-commitments, the project
will commence in two parallel stages: 1) selection of appropriate regional
seismic lines with industry participation, and 2) selection of samples
for source rock and maturity analysis (including, VR, FAMM, AFTA, Rock-Eval
and fluid inclusions). A final report will be delivered by the end of
November 1999, if pre-commitments are met by March 1st 1999, as anticipated.
Geotrack International references
Geotrack International Report #232, 1991, The Papuan Basin: Regional
thermal and maturation analysis incorporating AFTA of 27 wells,
A non-exclusive report, 319 pp.
Green P.F., Duddy I.R., Bray R.J. Green P.F., 1997, Variation in
thermal history styles around the Irish Sea and adjacent areas:
Implications for hydrocarbon occurrence and tectonic evolution.
In: Hardman M. Trueblood, S and Meadows, N. (eds)
The Irish Sea and Adjacent Basins. Geological Society of London
Green P.F., Duddy I.R. and Bray R.J. 1995. Applications of thermal
history reconstruction in inverted basins. In: Buchanan J.G.
and Buchanan, P.G (eds) Basin Inversion. Geological Society
of London Special Publication No. 83.
Duddy I.R., Green P.F., Bray R.J. and Hegarty, K.A. 1994, Recognition
of the thermal effects of fluid flow in sedimentarty basins. In
Geofluids: Origin, Migration and Evolution of Fluids in Sedimentary
Basins, Geol Soc Special Publication No 78.
Green P.F., Duddy I.R., Bray R.J. 1993. Early Tertiary heating
in Northwest England: fluids or burial (or both?). In Geofluids
'93: Contributions to an International Conference on fluid evolution,
migration and interaction in rocks. Parnell J., Ruffell A.H. and
Moles N.R. (eds) pp 119-123.
Duddy, I.R., Green, P.F., Hegarty, K.A. and Bray, R., 1991, Reconstruction
of thermal history in basin modelling using Apatite Fission Track
Analysis: what is really possible. Proceedings of the First Offshore
Australia Conference (Melbourne). III-49-III-61.
Arne, D.C., Green, P.F., and Duddy, I.R., 1990, Thermochronologic
constraints on the timing of Mississippi Valley-type ore formation
from apatite fission track analysis. Nucl. Tracks Radiat. Meas.
Kamp, P.J.J.and Green, P.F., 1990, Thermal and tectonic history
of selected Taranaki Basin (New Zealand) wells assessed by apatite
fission track analysis. AAPG Bulletin. 74, 1404-1419.
Green, P.F., Duddy, I.R., Laslett, G.M., Hegarty, K.A., Gleadow,
A.J.W. and Lovering, J.F., 1989b, Thermal annealing of fission tracks
in apatite 4. Quantitative modelling techniques and extension to
geological timescales. Chemical Geology (Isotope Geoscience Section),
Kamp, P.J.J., Green, P.F. and White, S.J., 1989, Fission track
analysis reveals character of collisional tectonics in New Zealand.
Tectonics, 8, 169-185.
Green P.F. and Duddy, I.R., 1988. Some comments on paleotemperature
determination from apatite fission track analysis. J. Petrol. Geol.,
Duddy, I.R., Green, P.F. and Laslett G.M., 1988, Thermal annealing
of fission tracks in apatite 3. Variable temperature behaviour.
Chemical Geology (Isotope Geoscience Section), 73, 25-38.
Green P.F., 1985b, A comparison of zeta calibration baselines in
zircon, sphene and apatate. Chem. Geol. (Isot. Geosci. Sect) 58,
Keiraville Konsultant references
Cook, A.C.; 1987: Source potential and maturation of hydrocarbon
source rocks in Indonesian sedimentary basins. Sixth Regional
Congress on Geology, Mineral and Hydrocarbon Resources of Southeast
Asia - Geosea VI, paper 16, pp. 1-42.
Cook, A.C.; 1991: Oil and gas prospects. Appendix B IN PAPUA
NEW GUINEA Economic Situation and Outlook International Development
Issues No. 16, Australian International Development Assistance Bureau,
Cook, A.C.; 1992: Environmental aspects of the mining and petroleum
industries in Papua New Guinea. Appendix B IN PAPUA NEW GUINEA
Economic Situation and Outlook. International Development Issues
No. 27, Australian International Development Assistance Bureau,
Cook, A.C.; 1992: Oil and gas prospects. Appendix C IN PAPUA
NEW GUINEA Economic Situation and Outlook. International Development
Issues No. 27, Australian International Development Assistance Bureau,
Cook, A. C., 1994. Oil and gas in Papua New Guinea. Appendix D
IN, Papua New Guinea - The Role of Government in Economic
Development, Australian Development Assistance Bureau, International
Development Issues No 33, 211-244.
Cook, A. C., 1996. Oil and gas in Papua New Guinea. Appendix D
IN, The Economy of Papua New Guinea 1996 Report, AusAID,
Australian Agency for International Development, International Development
Issues No 46, 173-202.
Cook, A.C., Davis, A., David, P., Depers, A.M., 1997. ICCP Accreditation
system for petrographic analyses. Proceedings of the New Zealand
Coal Conference, Wellington, October 1997.
Powell, T.G., Boreham, C.J., Smyth, M., Russel, N. and Cook, A.C.;
1991: Petroleum source rock assessment in non-marine sequences:
pyrolysis and petrographic analysis of Australian coals and carbonaceous
shales. Organic Geochemistry, 17, 3, 375-94.
Allen, P.A. and Allen, J.R., 1990: Basin analysis: principals and
applications. Blackwell Scientific Publications, Oxford, 451 pp.
Bracken, B.R. and Popek, J.P., 1995: Depositional interpretation
and reservoir quality assessment, Juha-2X, Juha-3X and Pnyang-2X
cores, Papua New Guinea.Reservoir Management Report for Chevron
Overseas Petroleum Inc, March 1995.
Buchanan, P.G. and Warburton, J., 1996: The influence of pre-existing
basin architecture in the development of the Papuan Fold and Thrust
Belt: implications for petroleum prospectivity. In: Buchanan,
P.G. (Ed.), Petroleum Exploration, Development and Production in
Papua New Guinea: Proceedings of the Third PNG Petroleum Convention,
Port Moresby, 9th-11th September, 1996.
Buck, S.P. and Stone, J.F., 1991: Source rock and basin modelling
study of PPL 93 plus addendum. Unpublished report for Mobil.
GSPNG Open File Rept. No. F1/R/92-249.
Cawley, S.J., 1991: Thermal modelling and phase prediction in the
Papuan Basin. Unpublished report for BP Petroleum, Technical
File Note: TFN 463, May 1991.
Cooper, G.T., Hill, K.C. and Baxter, K., 1996: Rifting in the Timor
Sea and New Guinea: a template for compressional forward modelling.
In: Buchanan, P.G. (Ed.), Petroleum Exploration, Development
and Production in Papua New Guinea: Proceedings of the Third
PNG Petroleum Convention, Port Moresby, 9th-11th
Earnshaw, J.P., Hogg, A.J.C., Oxtoby, N.H. and Crawley, S.J., 1993:
Petrographic and fluid inclusion evidence for the timing of diagenesis
and petroleum entrapment in the Papuan Basin. In: Carman,G.C.
and Carmen, Z. (Eds.), Petroleum Exploration, Development and Production
in Papua New Guinea: Proceedings of the Second PNG Petroleum
Convention, Port Moresby, 31st May 2nd
Hill, K.C., 1991: The structure of the Papuan Fold Belt, Papua
New Guinea. AAPG, V 75, No.5, p 857-872.
Hill, K.C. and Gleadow, A.J.W., 1990: Apatite fission track analysis
of the Papuan Basin. In: Carman, G.J. and Carman, Z. (Eds.):
Proceedings of the First PNG Petroleum Convention, Port Moresby,
Kotaka, T., 1996: Formation Water Systems in the Papuan Basin,
Papua New Guinea. Petroleum Exploration, Development and Production
in Papua New Guinea: Proceedings of the Third PNG Petroleum
Convention, Port Moresby, 9th - 11th September, 1996. Buchanan,
Krieger, F.W., 1996: Hydrocarbon and pore water migration in the
Papuan Basin PPL 101. Australian Petroleum Co-operative
Research Center confidential report No. 224, November, 1996
Krieger, F.W., Eadington, P.J. and Eisenberg, L.I., 1996: Rw, reserves
and timing of oil charge in the Papuan Fold Belt. In: Buchanan,
P.G. (Ed.), Petroleum Exploration, Development and Production in
Papua New Guinea: Proceedings of the Third PNG Petroleum Convention,
Port Moresby, 9th-11th September, 1996.
Lisk, M., Hamilton, J., Eadington, P. and Kotaka, T. 1993: Hydrocarbon
and pore water migration history in relation to diagenesis in the
Toro and Iagifu sandstones, S.E. Gobe-2. In: Carman, G.J.
and Carman, Z. (Eds.):Proceedings of the Second PNG Petroleum
Convention, Port Moresby, 31st May-2nd June,
Waples, D.W. and Wulff, K.J., 1996: Genetic classification and
exploration significance of oils and seeps of the Papuan Basin.
In: Buchanan, P.G. (Ed.), Petroleum Exploration, Development
and Production in Papua New Guinea: Proceedings of the Third
PNG Petroleum Convention, Port Moresby, 9th-11th
Geotrack International Pty Ltd
Geotrack is probably best known as the pioneer of the
AFTA technique (Apatite Fission Track Analysis) and while they continue
to be recognised as the world leader in this field, Geotrack has extended
its expertise to the broader field of basin modelling focussing on constrained
thermal histories. Using an appropriate mix of analyses, Geotrack routinely
provides reports that quantitatively constrain the timing and magnitude
of thermal episodes in an effort to resolve problems related to the
hydrocarbon generation and maturation history of a basin. AFTA offers
the potential for directly determining the timing of maximum paleotemperatures
and maximum maturity development in the section. Clearly the timing
of hydrocarbon generation with respect to trap formation is a key element
in exploration and not normally derived directly by conventional techniques.
Thus, Geotracks thermal history methods have proved to play a
key role in constraining the number of viable basin models for a basin.
Recognising the powerful and unique contribution of
AFTA, most of the world's major oil companies now use Geotrack's thermal
history techniques on a routine basis. Nevertheless, Geotrack continues
an exhaustive research program to further refine and improve the AFTA
technique. Since incorporation in 1987, Geotrack has completed more
than 700 proprietary studies and more than 35 regional basin studies
using AFTA as a cornerstone of the thermal history solution. Geotrack's
head office and laboratory are in Melbourne, Australia, while representative
technical and marketing offices are also located in London, Egypt and
Houston. The owners of Geotrack International Pty Ltd are Drs. Ian R.
Duddy and Paul F. Green.
Keiraville Konsultants Pty Ltd undertakes work in source
rock potential and maturity, organic geochemistry appraisals, coal and
coke petrology and economic assessments of mining and petroleum. The
majority of work relates to the petroleum industry and studies have
been undertaken in almost all petroleum provinces in the world for most
of the major international companies in the industry. The company is
a recognised authority on the measurement and use or vitrinite reflectance.
Dr Alan Cook, as Chair of Commission I within the International Committee
for Coal and Organic Petrology, has been a key figure in the establishment
of an International Accreditation system for vitrinite reflectance and
maceral composition measurements.
PetroConsult is an independent geoscience consultancy
that has gathered a substantial experience base, technical ability and
geographical coverage. This allows a full range of quality consultancy
services to be offered to clients including: prospect identification,
sequence and seismic stratigraphy, regional tectono-stratigraphic analysis,
petroleum charge evaluation and basin modelling. Based in Melbourne,
the company is well positioned to meet the needs of petroleum exploration
and production companies in New Zealand, Australia and South East Asia.
Company activity has included evaluation of exploration
areas covering the North West Shelf including the Dampier Sub-basin,
Browse Basin and Bonaparte Basin; Papua New Guinea; Otway Basin; onshore
Tasmania; and the Nam Con Son Basin offshore Vietnam. Further information
on the company can be found in PetroConsults internet web site
(www.petroconsult.com.au). The site also provides an extensive list
of other industry related web sites in Australia.
Please contact us with any technical or administrative enquiries. We
would be happy to answer any outstanding questions:
|Dr Ian Duddy
Geotrack International Pty Ltd
37 Melville Rd.
Brunswick West, VIC 3055
7 Dallas St.
Keiraville, NSW 2500
Geary or Ian Reid
PetroConsult Pty Ltd
21 Loraine Ave.
Box Hill North, VIC 3129