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calculated to have been generated by the
Lower and Upper Bakken source rocks, with
200 BBOE from the Lower Bakken and 280
BBOE from the Upper Bakken (Figure 3).
These estimates are compared with published
values in Figure 4. They fall at the upper end of
those estimated by the USGS, and ~60% of
the ultimate volumes expelled as predicted by
Roller and Pepper (2018). This shows that the
Bakken Petroleum System is a highly effective
unconventional resource and is predicted to
have relatively negligible loss of hydrocarbons.
Volume of Generated
Hydrocarbons (MMBOE)
High
Low
© 2019 Halliburton
Application When Data are Sparse
Figure 3 > Volume of hydrocarbons generated from the Lower
and Upper Bakken source rocks.
The case study tested the workflow in a
data rich area. In data poor areas, such as
exploration frontiers, the workflow can be run
based on the application of assumptions for the
input data and maps, based on the prediction
of the depositional environment, source rock
type, and stratigraphic age. In these scenarios,
knowledge from analogues will have to be
leveraged.
Lower and Upper Bakken source rocks had
average original TOC values of 14.9 and 18.8
wt% and average original HI values of 320 and
395. These values are for the entirety of the
source rock, including immature areas — the
difference between present-day and original
TOC and HI values will be greater than these
averages imply where the source rocks are
mature to post-mature.
The source rock volume can be inferred from
the depositional environment and distribution of
organic rich sediments (as presented in Neftex
GDE maps) and through utilization of Neftex
Depth Analysis maps. Optimistic original TOC
and HI values can be assigned based on typical
The reduction in HI and TOC with maturity was
used to estimate the volume of hydrocarbons
generated at peak maturation (Figure 3). A total
volume of >480 BBOE of hydrocarbons was
Estimated
Volume (BBOE) Data Source
Lower and Upper Bakken source rocks
Hydrocarbons generated 484.3 Neftex ® Insights
Lower and Upper Bakken source rocks
Oil in-place 4 – 171.7 Neftex Insights
Lower and Upper Bakken source rocks
Hydrocarbons generated 10 – 400 USGS from Jin and
Sonnenberg (2013)
Bakken and Three Forks formations
Technically recoverable resource 7.38 USGS from Gaswirth and
Marra (2015)
Williston Basin, likely Bakken Formation sourced
Known recoverable reserves in discoveries 6.08 Lower and Upper Bakken source rocks
Ultimate expellable potential 814.0
Study Summary
®
Rystad Energy UCube,
version 2019-08-07
Roller and Pepper (2018)
© 2019 Halliburton
Figure 4 > Summary of the estimated generated hydrocarbon volumes, and the known oil reserves in the Bakken Petroleum
System, from this and published studies.
values associated with similar source rocks
and expected kerogen type. In the reverse
to the above case study, the present-day
TOC and HI values can then be calculated
by diminishing the values in areas where
the source rock is predicted to be mature or
post-mature. The maturity could be predicted
based on the depth of the source rock and the
application of modeled surface temperatures,
geothermal gradients, or heat flows. be determined and carried through to the
resulting volume calculated.
SUMMARY Cornford, C. 1998. Source rocks and hydrocarbons of the
North Sea. In K.W. Glennie (Eds.), Petroleum Geology of the
North Sea – Basic concepts and recent advances 4th edition,
p. 376-462. (XURBB_453032).
The workflow and case study presented here
demonstrate how widely available organic
geochemical and geological data can be used
in a series of calculations to estimate the
volume of hydrocarbons generated and the
amount of in-place petroleum preserved in
accumulations. The workflow, or aspects of it,
can be followed at any point in the exploration
or appraisal process. It can be followed in data
rich scenarios through the utilization of the
standardized Neftex databases, compiled from
public domain data, and in data poor scenarios
where assumptions for the input data have
to be made. Predictions and analogues, such
as those presented in products in the Neftex
portfolio, may be used for this process.
Estimation of the volumes generated and
those likely preserved enables the ranking of
basins in terms of their petroleum potential.
This increases understanding of the factors
that affect the estimation of volume of
hydrocarbons generated, and the associated
risks.
A crucial aspect of the workflow is the
restoration of TOC and HI to original, pre-
maturation values across the entirety of the
source rock extent. This is a key value of
the workflow and it is recommended that
it be considered in any workflow requiring
assessment of source rock hydrocarbon
generative potential.
Going forward, it is suggested that a simple
workflow be defined to better predict the
preservation and retention of hydrocarbons
without the need to build a 3D basin model;
particularly, in conventional systems where
losses are generally large. The case study
highlights that the estimated volumes carry
a large degree of uncertainty; therefore,
an error range on the data inputs should
ACKNOWLEDGMENTS
The author would like to thank Alex Bromhead,
Christine Yallup, and Thomas Butt for their
contribution in the development of the
workflow, and Lawrie Cowliff and Daniel Slidel
for their support and input into the project.
REFERENCES
Gaswirth, S.B. and K.R. Marra 2015. U.S. Geological
Survey 2013 assessment of undiscovered resources in the
Bakken and Three Forks Formations of the U.S. Williston
Basin Province. AAPG Bulletin, v. 99, no. 4, p. 639-660.
(XURBB_571096).
Jin, H. and S.A. Sonnenberg 2013. Characterization for
Source Rock Potential of the Bakken Shales in the Williston
Basin, North Dakota and Montana. SPE Conference Paper, v.
1581243, p. 1-10. (XURBB_532277).
Magoon, L.B. and W.G. Dow 1994. The Petroleum System-
From Source to Trap. AAPG Memoir no. 60, American
Association of Petroleum Geologists (AAPG), 1-655 p.
(XURBB_460484).
Roller, E. and A. Pepper 2018. Estimating the Ultimate
Expellable Potential of Source Rocks: Defining “World Class”
for Aquatic Organofacies with Examples from the Arabian,
West Siberian, Bohai, and Williston Basins. AAPG Search and
Discovery, v. 11055, p. 1-7. (XURBB_638403)
Schmoker, J.W. 1994. Volumetric calculation of hydrocarbons
generated. In L.B. Magoon and W.G. Dow (Eds.), The
Petroleum System-From Source to Trap. AAPG Memoir no.
60, p. 323-326. (XURBB_614365).
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AUTHORS
Rachel Round — Senior Geochemist, Halliburton
Landmark
Rachel works on the Neftex Insights
Petroleum Systems Analysis team as an
organic geochemist and basin modeler. She
has 10 years of industry experience, and prior
to joining Neftex in 2014 she worked as an
organic geochemist at APT (UK), and carried out internships
at Fugro Robertsons and Getech. Rachel holds an MSc in
Organic Geochemist from Newcastle University, and BSc in
Geological Sciences from the University of Leeds.
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