Bluff
Bench Prospect
Bluff Bench Project
Area
Southern Paradox Basin
San Juan County, Utah
Executive
Summary
Dwight A. Ingram et al
has identified two (2) Lower Ismay/Desert Creek drillsites
covering approximately 1500 net acres in the Bluff Bench
Area of San Juan County, Utah, on the southwest shelf
of the Paradox Basin.
Production occurs in
algal mounds and shoals of the Pennsylvanian Lower Ismay and
Desert Creek Formations, which formed in a shallow marine
shelf environment.
The prospect area is a
classic example where earlier abandoned tests were later
recognized as productive yet believed to be
non-commercial.
Potential recoverable
reserves average 250-350 MBO per well and can reach more
than 700 MBO per well.
The target field size
is 4-5 wells with combined total reserves of 1.5-2.0
MMBO.
Enhanced oil recovery
applications are currently being investigated by a
multidisciplinary team led by the Utah Geological Survey.
The project hopes to demonstrate both the technical and
economic feasability of enhanced oil recovery techniques
which could be applied to the more than 50 small fields in
the southern Paradox Basin.
Recent prolific short
radius, multi-lateral, completions within the Aneth Field
complex have resulted in efficient use of new drilling and
completion technologies in a mature waterflood.
3-D seismic
applications will optimize future development drilling
operations. Conventional CDP seismic has been successful in
imaging algal mounds, indicating 3-D can be used to further
define more complex mound geometries and smaller
features.
The dual pay potential
combined with shallow drilling depths makes the area an
attractive, low risk exploratory drilling
opportunity.
Introduction
The Bluff Bench
Prospect is located in the Paradox Basin of southeast Utah
in San Juan County. The first oil discovery in the Paradox
Basin was in 1908, near Mexican Hat, Utah. The discovery was
drilled near an active oil seep, and production was
established in shallow sands of the upper Pennsylvanian.
Algal mounds have been the successful target of exploratory
activities since the early 1950's. Aneth Field was
discovered in 1956, and when the magnitude of the field was
recognized, exploration activity intensified, resulting in
the discovery of numerous smaller fields. These fields
typically are developed with one to four wells with primary
production ranging from 500-2000 MBO. Geologically, the
Prospect Area is on the southwest shelf of the Paradox
Basin. Oil and gas production occurs in a series of shelf
carbonate cycles of the Ismay and Desert Creek
Formations.
The Paradox Basin is a
depositional basin which developed primarily during
Pennsylvanian time. The basin is elongate with a northwest
trending axis. Evaporites accumulated in the interior of the
basin during part of the Pennsylvanian time. While salt was
being deposited in the basin center, carbonates accumulated
on the southwest shelf.
Structure
Productive algal mound
trends in the Aneth Area of the southwest shelf of the
Paradox Basin area related to broad, basement related,
low-relief anticlinal features. These structures influenced
the development of algal mounds but play a subordinate role
to stratigraphic controls on hydrocarbon production. The
controls on the development of the mounds on the southwest
shelf were water depth, prevailing currents, wave energy,
and paleostructural position. Present regional dip is to the
east-northeast at about 100' per mile.
Stratigraphy
The primary objective
of the play is the "stacked" algal buildups of the Lower
Ismay and Desert Creek Formations. The offsetting well
control suggests that these buildups are flat bottomed, low
relief, bar-like carbonate banks with elongate geometry's
which reach 60-70' maximum thickness. The buildups are
enclosed by impermeable carbonates, shales, and evaporites.
A Lower Ismay and Desert Creek algal bank complex has been
identified throughout the Bluff Bench Area. Heterogeneity
and multiple mound facies have been identified in studies
conducted by the Utah Geological Survey. Model of Complex
Mound Geometry
The Desert Creek
Formation is a complex heterogeneous carbonates deposited in
a repeating series of mudstones and evaporites between algal
mounds and ooilitic shoals. Cycles in deposition were
primarily controlled by rapid marine transgressions and
slow, interrupted regressions resuting from periods of ice
cap building. These cycles were additionally influenced by
regional tectonic activity, basin subsidence, proximity to
basin margin or evaporites,episodic blockage of open marine
waterways, and local fluctuations of water energy. Thickness
of the entire interval range from about 100' to more than
150' in the prospect area, grading from a basal, normal
marine, into mostly limestones, occasionally dolomitized
limestones, overlain by anhydrite. Black shales both under
and overlie the zone. Inter-mound troughs occur as tidal
channels and add the the overall heterogeneity of the
complex. Porous intervals within the Desert Creek are
described as light-gray to tan, fossil fragment limestone.
Intercrystalline porosity ranges from poor to good. Vuggy
porosity and natural fractures may also be
present.
Shelf
Facies Depositional Model
The best reservoirs
are associated with mud poor phylliod algal buildups. These
are widely distributed, small in areal extent, and can be
recognized seismically. Ivanovia is the typical algal plate
material. Stylolitization often occurs and influences
vertical permeability. Flanking carbonates, tidal channel
carbonate sands, and associated depositional features have
lacked sufficient porosity and permeability to be important
reservoirs. See Model
Petrophysics
Initial porosity and
permeability seen in the buildup type reservoirs are
inferred to have been high in the grain supported, mud
deficient algal carbonates. Some porosity may be due to
solution, with the distribution of leaching being affected
by the original properties. Inter-particle porosity occurs
in the more permeable reservoir rocks. Moldic porosity is
also common. Porosity can be reduced by calcite or anhydrite
infill of early diagenetic origin. Drillstem tests and
conventional downhole logs will accurately characterize the
reservoirs.
Type
Log
Permeabilties from
cored wells on the southwest shelf in the Bluff Bench Areas
range from less than 0.1 md to more than 100 md. Generally,
algal plate type reservoirs with high permeabilty may be
associated with low log calculated porosity. Productive
zones are characterized by a low gamma ray log
response.
Reserves
and Economics
Total drilling depths
throughout the prospect area are about 5800'. Drilling costs
for the initial test will be approximately $175,000.00.
Drillstem tests and open hole logs can successfully be used
to evaluate productivity potential. Completion expenses,
including 5 1/2" production casing, perforating, zone
treatment, and surface equipment will total $225,000.00. The
total successful well cost is $400,000.00. Initial flow
rates are in the 250 BOPD range and potential reserves are
350MBO per well. Payout occurs within six months resulting
in a ROI of 7.15. An economic summary is
attached.
Land
Dwight A. Ingram, et
al holds a total of 6,073 net and gross acres in the project
area, all of which are State of Utah, School and
Institutional Trust Lands. A Net Revenue Interest of 81.5%
will be delivered on the leases. An area of of Mutual
Interest will be determined for the individual prospect
areas. Negotiations for additional prospect acreage either
by drilling option or farmout are in progress.
Lease
Schedule
Legal descriptions,
expiration dates, acreage and lease numbers can be found
here.
Acoma
Prospect
The proposed location
on the Acoma Prospect, SWSW-5-T40S-R22E, will test a
northeast trending, elongate closure as defined by
subsurface well data. This feature covers an area about 1
mile long by I/2 miles wide Total structural relief across
the feature is 75-100'.
Coincident with the
mapped structural feature is a thick algal mound developed
in the Lower Ismay. The mound is identified on logs in the
British-American Oil No. B-1 Government-Norwood. The mound
can be identified directly by the clean gamma-ray log curve
response and associated sonic log porosity. Drape of the
Hovenweep Shale occurs over the mound and is identified in
cross-section. The proposed location is an updip offset to
this well drilled to a total depth of 5850' in October 1963.
A drillstem test of the Lower Ismay from 5630-5674' flowed
gas to surface in 15 minutes, gauged at 25 MCFGPD. Pipe
recovery was 30' HGCM, and 360' free OIL. Flow pressures
during the test ranged from 62-166#, with shut-in pressures
recorded at 2134-2063#. No water was recovered during the
test.
Sonic log calculated
porosities in the Lower Ismay in the No. B-1
Government-Norwood range from 2-10%, typical of productive
algal mounds in the Bluff Bench Area. Archie calculated
water saturations are as low as 30% over the drillstem test
interval.
Laguna
Prospect
The proposed location,
SWNE-13-T40S-R21E is an updip offset to the Humble Oil and
Refining No. 12 Bluff Bench, located SESE-12-T40S-R21E.
Mapped closure and Lower Ismay algal builup covers about 600
acres. Net pay potential at this proposed location could
reach more than 50' in three zones. The well pumped 47 BO +
40 BWPD from Ismay and Desert Creek perforations at
5381-5410' and 5660-5676'. This is one of the few wells in
the area to have tested oil from both the Upper and Lower
Ismay and from the Desert Creek. Perforations at 5381-5389'
and 5398-5410' in the Upper Ismay recovered 58 BO + 38 BW in
a 10 hour pump test. The Lower Ismay swabbed 30 BO + 130 BW
from 5507-5514'. Porosity development in the Lower Ismay
reaches 26'. The Desert Creek swabbed 46.5 BO + 3.5 BW in 24
hours from perforations at 5660-5666' and
5670-5676'.
Tecolote
Prospect
The proposed
location,SWNE-22-T40S-R22E, will test a thick Lower Ismay
section identified on the sonic log in the Colorado Oil,
Bluff Bench No. 1, SESW-22-T40S-R22E, from log depths
between 5430-5490'. The interval was not tested. A core from
5352-5389' recovered 37' light gray tight limestone and 9'
of brown argillaceous limestone with abundant black chert
from the Upper Ismay. This core interval missed the Lower
Ismay target zone by more than 50'. The well was plugged and
abandoned untested in December 1964. The thick Lower Ismay
zone correlates to the Ladd Petroleum, No. 23-32 Federal,
SWNE-23-T40S-R22E, which pumped 78 BO + 94 BW + 20 MCFGPD
from perforations at 5438-46' in May 1981. The interval from
5420-68 drillstem tested 2542' GIDP, 124' oil, 124
G&MCO, 555' G&OCM, 62' GCW&M, and 2043'GCW.
Initial and Final flow pressures ranged from 413-1092# and
1118-1786# respectively. Shut-in pressures reached 2041 and
2028#. Cumulative production reached 6282 BO and the well
was converted to a salt water disposal facility. This well
appears to be near the oil-water contact for the Lower
Ismay. The proposed location is mapped 100' high to the No.
23-32 Federal. Areally, the algal mound is almost 2 miles
long by 3/4th's miles wide and is draped over a northeast
trending closure containg 50-75' relief.
Summary
Algal mounds in the
southern Paradox Basin have historically been important oil
and gas exploratory targets. The above geologic analysis
indicates that the oil and gas potential of the prospect
area has been ineffectively exploited by previous operators.
Numerous shows, multi-pay objectives, firm oil prices, and
advances in drilling and completion technologies make the
area an attractive exploratory play.
Full
Report
An extensive report
including graphs, Geologic Models and maps are available to
interested parties.
Prospects
Click
Baxter to see - Baxter
Ranch - San Joaquin Basin, Kings County, California
Click
Bluff Bench to see - Southern
Paradox Basin - Bluff Bench - Aneth Area, San Juan County,
Utah
Click
Madden to see - Philp
- Knapp Lease Madden Unit, Fremont County,
Wyoming
Click Owl
Creek to see - Owl
Creek Thrust Trend - Wind River Basin, Fremont County,
Wyoming
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