I have direct
experience with this formation, having mapped it in the subsurface over a large
area early in the play and having geosteered approximately 15% of the
horizontal wells drilled in the formation.
The Burket or Geneseo is the basal black organic shale member of the Upper Devonian Genessee Formation. The main ‘hot gamma ray’ organic rich shale member is the productive interval. The main productive interval is generally thin. Where we drilled it near the Western margin of the play it was generally 10-15 ft thick. Some general stratigraphy is shown below.
In 2015 Gregory Wrightstone did some good analysis of the state of the play at the time. That analysis should probably be updated since there are now many more wells drilled in the formation and production histories are being developed. I know from a few companies’ investor presentations that the high reserves predicted in the play seem to still be valid. It is also thought that since there is a very clear ‘frac barrier’ directly below the formation, the Tully Limestone, and fracs tend to propagate upward rather than downward when they go out of formation, that gas from formations above the Burket/Geneseo is likely also producing gas in those wells. This includes some other hot shale members of the Genesee Formation, the Middlesex Shale hot zone, and possibly even the Rhinestreet Formation, where it is within a few hundred feet. Wrightstone noted at the time six-month cumulative production from the wells in the northeast (524 MMCF) vs. those in the southwest (685 MMCF) and those in the southwest core of the core (746 MMCF). Much of the southwest part of the Geneseo/Burket accumulation occurs in the wet gas window where NGLs such as ethane, propane, butanes, pentanes, and some condensate are also produced. Several slides from Wrightstone's work are shown below.
A 2022 study in
Marine and Petroleum Geology characterized the sequence stratigraphy of the
Geneseo Formation in New York, dividing it into two sequences and three
lithostratigraphic units:
“The Geneseo Formation herein has been subdivided into
two depositional sequences comprising three lithostratigraphic units (i.e.,
Lower Geneseo, Fir Tree, and Upper Geneseo members respectively). The Lower and
Upper Geneseo members show systematic aggradational to progradational
parasequence stacking patterns, as well as downlap‒onlap stratal terminations with
underlying strata; these members represent highstand systems tracts. The Fir
Tree Member occurs between the Lower and Upper Geneseo members, truncates the
underlying Lower Geneseo, shows progradational‒aggradational‒retrogradational
parasequence stacking patterns, and spans two systems tracts: lowstand and
transgressive.”
It is the basal,
or Lower Geneseo member that is the horizontal drilling target. The study also
noted the key characteristics of a hydrocarbon reservoir, which the Geneseo obviously
has:
“Key controls on unconventional reservoir quality and
distribution in fine-grained, mudstone-dominated successions include total
organic carbon (TOC), organic matter type (e.g., Type I-II liquid prone, Mixed
Type II/III, or type III gas prone), mineralogy (i.e., clay content/ductility,
brittleness, “fracability”), presence and distribution of high-strength rocks
(i.e., fracture barriers/baffles), thermal maturity (0.8–1.3 for liquids-rich
play), porosity/permeability, presence and distribution of natural fractures,
and thickness of pay interval (Bohacs et al., 2005, 2012; Gale et al., 2014;
Passey et al., 2010; Wilson and Schieber, 2016; Wilson et al., 2020; Katz et
al., 2021; Venieri et al., 2021).”
The potential of
this black shale for hydrocarbon production was recognized as early as 1892 as
noted in the Pennsylvania Geological Survey’s 2017 source-rock evaluation study
of Upper Devonian rocks:
“The black Geneseo Shale Member of the Genesee Formation
extends from western Pennsylvania to the north-central area of the state.
Lesley (1892, p. 1,323) observed, “In New York and in other states it is a
black laminated mud formation, with wall-like outcrops; but where its surfaces
are exposed it weathers into loose leaves; often iron-stained on account of the
abundance of iron pyrites; but usually deep black.” Carbonate concretions were
also recognized as discriminating features then as they are today, with pyrite
found in the cavities of the concretions. Lesley (1892, p. 1,334) was obviously
a visionary when he foretold “and in future times when the petroleum production
has been exhausted and our cities must again be lighted by artificial coal
shale gas by Young’s process this ‘black shale’ formation will yield an
infinite supply.”
The depositional
history of the Genessee Formation is in an epicontinental sea to the west of what
would later become the Catskill Delta. The region of black shale deposition of
the Geneseo/Burket member is shown below.
Gary Lash at SUNY
Fredonia noted that the Geneseo onlaps onto the underlying erosional surface of
the Tully limestone. He also noted that by Geneseo time the basin forebulge had
migrated to the west.
Spencer Leonard
Williams Jr. in his 2022 Master’s Thesis described the depositional history of
the Geneseo based on a core analysis from Westmoreland County, Pennsylvania as
follows:
“Genesee sediments have been interpreted as deposited in
the deeper part of an epicontinental sea west of the Late Devonian Catskill
Delta. The interpretation is that a euxinic environment occurred in the deeper
part of the sea and the upper waters of the sea were relatively clear with high
oxygen levels. During this time,
depositional energy was low and only fine-grained sediments accumulated in the
calm waters.”
The contact between
the basal Geneseo member and the Tully Limestone is considered to be an
unconformity in some places but is generally considered to be a hiatus that
extends through much of its depositional basin. Williams also concluded that
the mineralogy of the Burket/Geneseo is similar to that of the Marcellus Shale.
“Both units are composed mainly of quartz and clay
mixture with scattered intervals of higher carbonate content. Average total organic carbon (TOC) approaches
4 weight percent in both shale units.
However, the Marcellus Shale has a significantly higher TOC, approaching
12 weight percent at its base, than the Geneseo-Burket.”
He also noted that the depositional sequences of the
Marcellus and Burket-Geneseo are similar as are the mechanical properties and the
presence of carbonate units above the main basal hot zone.
A core analysis
of both the Geneseo/Burket and the Marcellus in Doddridge County, West Virginia
published in 2017 by Randy Blood, Gary Lash, and Ashley Douds, utilized pyrite
morphology as pyrite framboid size analysis and chemostratigraphy to predict
oxygenation conditions during deposition.
“These observations suggest that while the Geneseo Shale
accumulated under occasionally anoxic conditions, the unit also experienced
more frequent and likely more robust oxygenation events as compared to the
underlying Marcellus, a model consistent with the less robust enrichments of
both U and Mo (Fig. 15). This
interpretation is slightly at odds with the framboid size analysis of the
Geneseo Shale of New York State of Formolo and Lyons (2007). Although MFDs were
not presented in this study, a mean diameter of 4.9 µm would indicate more
dominantly euxinic conditions in this part of the basin (Formolo and Lyons,
2007). This, perhaps unsurprisingly, provides evidence for variations in redox
conditions across the basin of roughly time-equivalent strata.”
They also noted
that importance of understanding these redox conditions for assessing the
hydrocarbon productive aspects of the rocks.
“An understanding of the litho- and stratigraphic
framework provides geologic context in which to interpret changes in sediment
flux and redox conditions through time and across a basin. While at first these
aspects do not seem related to hydrocarbon production, they ultimately control
the quality and distribution of organic matter and therefore the location of
hydrocarbon producing strata and unconventional reservoirs.”
Below is a sequence stratigraphy chart of the Burket/Geneseo through Marcellus interval and an explanation of pyrite framboid sie analysis used to define redox conditions.
Where the
Burket/Geneseo is close to the underlying Marcellus as in the Southwest
producing area, it is advisable to hydraulically fracture both formations simultaneously
so that the pre-existing induced fractures in the Marcellus that propagate upward
don’t bleed off frac pressure when the Geneseo is hydraulically fractured, resulting
in an ineffective frac. This may have affected some of the early Burket/Geneseo
production. A 2018 AAPG study published by Kimberly Ayers. Henry Jacot, and Alivia
Ayers utilized bottomhole pressure gauges to study “frac hits” from three child
Marcellus wells and two Burket wells to a Marcellus parent well that had been
producing for nine months. They found that 75% of the Marcellus frac stages
were registered as hits in the parent well. Unfortunately, there was no
information in the abstract about frac hits from the Burket child wells.
The EIA added the
Burket-Geneseo to its shale gas production database in 2019, showing that it
was nearing 1 BCF/day of production, as shown below.
Nine years have
gone by since Wrightstone’s work. Since then, the play has not grown very fast.
This is likely due to the Marcellus still being slightly better in most areas and
the play being produced in its 'core of the core' area along with Marcellus in
staggered laterals. According to the Appalachian Basin Horizontal Well Database, there are just 281 horizontal wells drilled in the Burket/Geneseo. Many of
these are early test wells that were short laterals. Longer laterals beqan to
be drilled in 2019 but have been shortened since 2021. This is likely due mainly to
acreage constraints. Cumulative production is at about 1.2TCF as of September
2024. That is less than 1% of predicted reserves. That is an average of 4.3 BCF
per well so far produced. Most of the wells were drilled between 2013 and 2019.
Since 2019 the well count has been down. The reasons for the lower well count likely
have to do mostly with low natural gas prices. The 1.2 TCF produced is about 4%
of Wrightstone’s 30TCF threshold for a “supergiant” field. There is little
doubt that the Burket/Geneseo can reach that amount of production if it were to
be developed. Of the 281 producing wells, 248 of them are in Pennsylvania, and the
rest in West Virginia. The slides below are from that database.
When I mapped the
Middle and Upper Devonian intervals in the Appalachian Basin, I noticed that along
the western margin of the basin of the time the Hamilton Shale thinned and pinched
out to zero along the Ohio border, and the Tully Limestone even disappeared which
resulted in a few cases where the Burket sat right on top of the Marcellus,
looking as if they were a single hot shale formation. At least that is how I
interpreted a well we drilled in Belmont County, Ohio around 2006.
Wrightstone noted
in a 2015 article in Hart Energy:
“As with the Marcellus, structural complexity is a key
negative to production performance and complicates geosteering. Additionally,
since the Burket/Geneseo is significantly thinner than the Marcellus,
additional geosteering challenges are presented to the operator to stay in the
sweet zone of high TOC, and rotary steerable drilling may be the optimal
solution.”
Where I geosteered
wells in the play along its western margin the geology was fairly flat without
any significant folding. These wells were generally easy to steer and drilled
fast, a few exceeding 7000 ft of horizontal drilling in 24 hours. Even with the
thin reservoir they were easy to steer due to the lack of structure and the
clear upper and especially lower boundary (Tully Limestone) of the formation. We
did utilize rotary steerable drilling successfully, but previous to that we still
did not have any trouble staying in zone in our non-structural area.
The USGS upped
its reserves for Appalachian shale reservoirs in 2019 but that is still likely a
severe undercount. They assessed the Burket/Geneseo as a minor part of
Marcellus reserves. They assessed the total Marcellus reserves as follows: “96.5
trillion cubic feet of undiscovered, technically recoverable continuous (or
unconventional) resources of natural gas.” The AAPG estimates are similar, but
the EIA estimates are higher. I am inclined to go with the highest estimates. A
January 2024 paper in the APPG addresses the wide variation in Marcellus
reserve predictions:
“A study by the Bureau of Economic Geology (BEG) at The
University of Texas at Austin (Ikonnikova et al., 2018), predicted the
technically recoverable resources (TRRs) of the Marcellus to be 560 TSCF. The
US Department of Energy’s Energy Information Administration (EIA) recently
published a prediction of 310.6 TSCF of technically recoverable gas (Energy
Information Administration, 2020a). Lastly, the US Geological Survey (USGS)
estimated only 96.5 TSCF of total undiscovered resources in the Marcellus. This
divergence of total producible resource predictions in the Marcellus shows just
how difficult and uncertain the resource assessment in unconventional
reservoirs is.”
As indicated
below in Gas-In-Place maps from Range Resources, the inaccessible natural gas reserves under the city of Pittsburgh and its metropolitan
area in Allegheny County, which include Utica, Marcellus, and Burket/Geneseo,
are immense, easily exceeding the reserves of whole countries or regions.
References:
Appalachian
Basin Horizontal Well Database. Monthly Overview. September 2024. Ayers
Petroleum Consultants. (subscription). November 4, 2024. Home - App Basin Database
Upper
Devonian Drilling. Nuttall Legal, LLC. West Virginia Oil and Gas Lawyer. Blog. May
2015- July 2016. Burket Formation | Nuttall Legal, LLC
Burket/Geneseo
Shale: Appalachia’s little brother to the Marcellus & Utica. Gregory
Wrightstone. Presented at: Pittsburgh Association of Petroleum Geologists. Pittsburgh,
Pennsylvania. October 8, 2015. PAPGWrightstone20151008.pdf
Source
rock evaluation of the Upper Devonian Genesee, Harrell, and West Falls
Formations in Pennsylvania. Schmid, K. W., and Markowski, A. K. 2017. Pennsylvania
Geological Survey. Mineral Resources Report 102. M102_text.pdf
Regional
Correlation and Depositional History using Well Log and Core Data of the
Geneseo-Burket from the Poseidon 8M Well, Westmoreland County PA, USA. Spencer
Leonard Williams Jr. Masters Thesis. West Virginia University. Regional Correlation and Depositional
History using Well Log and Core Data of the Geneseo-Burket from the Poseidon 8M
Well, Westmoreland County PA, USA
Marcellus
Assessment: USGS Ups Appalachian Gas Estimate. American Oil & Gas Reporter.
November 2019. USGS Ups Appalachian Gas Estimate
Influence
of Basin Dynamics on Upper Devonian Black Shale Deposition, Western New York
State and Northwest Pennsylvania. Gary G. Lash. AAPG Search and Discovery
Article #30050. April 22, 2007. Influence of Basin Dynamics on Upper
Devonian Black Shale Deposition, Western New York State and Northwest
Pennsylvania, By Gary G. Lash , #00000 (2007).
Sequence
stratigraphic reconstruction of the late Middle Devonian Geneseo Formation of
NY, USA: Developing a genetic model for “Upper Devonian” unconventional targets
in the Northern Appalachian Basin. Ryan D. Wilson, Juergen Schieber, and Kevin
M. Bohacs. Marine and Petroleum Geology. Volume 138, April 2022, 105547. Sequence stratigraphic reconstruction
of the late Middle Devonian Geneseo Formation of NY, USA: Developing a genetic
model for “Upper Devonian” unconventional targets in the Northern Appalachian
Basin - ScienceDirect
Sedimentary
Facies and Depositional Environment of the Middle Devonian Geneseo Formation of
New York, U.S.A. November 2015. Journal of Sedimentary Research
85(11):1393-1415. Ryan D. Wilson and Juergen Schieber. (PDF) Sedimentary Facies and
Depositional Environment of the Middle Devonian Geneseo Formation of New York,
U.S.A.
Physical
Stratigraphy of the Genesee Formation (Devonian) in Western and Central New York.
WALLACE de WITT, JR., and G. VV. COLTON. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1032-A.
1978. report.pdf
Refined
Lithostratigraphy of Upper and Middle Devonian Shales in West Virginia. Ray
Boswell and Susan Pool. AAPG Search and Discovery Article #30607. June 10, 2019.
ndx_boswell.pdf
THE
MIDDLE DEVONIAN MARCELLUS AND GENESEO SHALES REPRESENTED BY THE EQT J. LEESON
#1 CORE, DODDRIDGE COUNTY, WEST VIRGINIA, USA: INSIGHTS INTO DEPOSITIONAL
ENVIRONMENT AND RESERVOIR ARCHITECTURE. David R. Blood. Ashley S.B. Douds, and
Gary G. Lash. Conference Paper. 2017. THEMIDDLEDEVONIANMARCELLUSANDGENESEOSHALESREPRESENTEDBYTHEEQTJLESSONCORE
(1).pdf
Statistical
Analysis of Generational Effect on Marcellus Well Completions Using Bottomhole
Gauge Data. Kimberly Ayers; Henry Jacot; Alivia Ayers. Paper presented at the
SPE/AAPG Eastern Regional Meeting, Pittsburgh, Pennsylvania, USA, October 2018.
Paper Number: SPE-191785-18ERM-MS. Statistical
Analysis of Generational Effect on Marcellus Well Completions Using Bottomhole
Gauge Data | SPE Eastern Regional Meeting | OnePetro
America’s
Natural Gas Juggernaut. Gregory Wrightstone. Real Clear Energy. April 11, 2022.
America’s
Natural Gas Juggernaut | RealClearEnergy
Forecast
of economic gas production in the Marcellus Shale. Wardana Saputra; Wissem
Kirati; David Hughes; Tadeusz W. Patzek. AAPG Bulletin (2024) 108 (1). Forecast
of economic gas production in the Marcellus Shale | AAPG Bulletin |
GeoScienceWorld
Little
Brother To The Utica And Marcellus:The Upper Devonian Burket/Geneseo Shale
holds yet more Appalachian riches. Gregory Wrightstone. Hart Energy. July 1,
2015. Little
Brother To The Utica And Marcellus | Hart Energy
Allegheny
County: A Challenged Gas Super-Giant. Gregory Wrightstone and Justin Skaggs.
Oil & Gas Investor. December 2016. Allegheny_County__A_Challenged_Natural_Gas_Super-Giant_Final.pdf
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