Arco Totek Hills #1 1984 TD 3,590’ Totek Hills Rock Eval...
Transcript of Arco Totek Hills #1 1984 TD 3,590’ Totek Hills Rock Eval...
Mudlog Arco Totek Hills #1 1984 TD 3,590’
Drilling costs (1984) = $2.146 MM less $0.678 MM State drilling credits
10 ¾”
7 5/8”
5”
4”
Note in “VIII Well Summary”: “Temperature log problems” – (quoted as part of the reason for time delays with final logs, no explanation and unsure what this refers to)
BHT at TD 3560’ (3545’ Tvd) = 160-165◦F Corrected BHT = 167-172°F (accounts for circ. cooling) T gradient = 2.7-3.0°F/100’ using assumed surface T of 65°F (Arco estimate) (Note: with surface permafrost, surface T must be close to 32°F or less, which yields minimum 3.9°F/100’ gradient) Nenana #1 well had 87°F @ 3052’ in meta. basement
Alaska GMC has core from the intervals 1443-2670’ and 2984-3577’
3163’ Top basement schist
Sanctuary Fm
Healy Creek Fm
Suntrana Fm
Grubstake Fm and/or
Lignite Creek
Nenana Gravel
Oligocene-Eocene pebble conglomerate and sandstone
Usi
bel
li G
rou
p
Surficial fill
Formation picks estimated by GVK (2012) based on lithologic similarity with Nunivak #1 and outcrop data.
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S2 (
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TOC
TOC vs S2 -- Totek Hills #1 and Nunivak #1
Nunivak #1
Totek Hills #1
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HI vs TOC, Totek Hills #1 and Nunivak #1
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Totek Hills #1
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Oxygen Index (mg CO2/g org C)
Circles from USGS (Stanley et al, 1989). Open circles are mudstones, filled circles are coal samples from the Usibelli Group at Suntrana, Alaska. Triangles are Arco Alaska field samples, Healy Creek Fm, Lemmerman and Podsen, 1983.
Outcrop samples of Miocene Usibelli Group coal and mudstone
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Oxygen Index (mg CO2/g org C)
Coal and mudstone samples from the Totek Hills #1 well, Nenana basin, Alaska. From Lemmerman and Podsen
Nunivak #1 well, Usibelli Group
N = 28, TOC = 11-61%
Mixed oil and gas
Oil prone
Gas prone
Totek Hills Rock Eval datavr visual
depth Tmax S1 S2 S3 TOC HI OI VR sample kerogen
220 0.26 coal
520 0.27 coal
1060 0.29 coal
1300 0.31 coal
1360 0.31 coal
1518 411 0.18 2.87 0.78 1.59 180 49 0.27 core Am-W,H
1556 421 0.84 37.37 2.52 9.72 384 25
1616 0 0.07 0.13 0.17 41 76
1676 0.01 0.08 0.15 0.26 30 57 0.32 core H,W
1736 425 0.01 0.49 1.74 0.93 52 187
1796 416 0 0.55 2.37 0.87 53 272
1856 413 0.02 0.89 3.71 1.12 79 331 0.36 core W,H,Am
1916 420 0.24 12.37 0.78 3.74 330 20
1976 422 0.98 21.28 0.91 4.51 471 20
2036 414 0.03 0.19 0.22 0.3 63 73 0.35 core W, ,H
2096 421 0.03 1.41 1.85 1.42 99 130
2156 413 0.1 3.36 0.6 1.68 200 35
2216 416 0.02 0.87 1.27 1.21 71 104 0.37 core Am-W,H
2276 416 0.02 0.89 1.71 1.14 78 150
2337.2 420 0.29 22.7 2.95 12.33 184 23
2397 417 0.13 8.34 0.82 3.95 211 20 0.35 core W, Am-H
2463.5 418 0.08 5.4 0.53 2.43 222 21
2520 419 0.7 47.77 3.88 17.76 268 21
2580 422 0.49 24.7 2.42 10.36 238 23 0.38 core W, Am-H
2670-2710 428 0.02 0.37 0.31 0.68 54 45
2730-2790 425 0.07 1.47 0.39 0.95 154 41
2790-2850 428 0.01 0.08 0.13 0.31 25 41 0.41 core H, ,W
3172.2 0.01 0 0.15 0.22 0 68 0.39 core B,H,-
3204.3 0.01 0 0.11 0.21 0 52
3236.5 0.02 0 0.09 0.18 0 50 no vitrinite B,H,W
3283-3302 384 0.21 0.4 0.66 0.36 111 183
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Oxygen Index (mg CO2/g org C)
Coal and mudstone samples from the Totek Hills #1 well, Nenana basin, Alaska. From Lemmerman and Podsen
Totek Hills #1, Usibelli Group
Source Rocks: Nenana Basin
Totek Hills #1 Stratigraphy and Source Rocks
The Totek Hills #1 was drilled by Arco Alaska in 1984 and penetrated about 3000’ of clastic sedimentary rocks of the Usibelli Group. The
well was drilled on a basement high along the southern margin of the Nenana basin and metamorphic basement was encountered at 3163’
(drillers log). The Tertiary section was thinner than expected and basement was about 3000’ shallower than expected. No significant oil and
gas shows were encountered in the well.
The well logs are more useful in reconstructing the well lithology than the mud log. The mud log is highly generalized from surface to 1425’
at which depth continuous coring commenced with the slim-hole drilling rig. Continuous small-diameter core was taken from 1443’ to 2674’
and cutting returns during drilling were very poor due to pulverization of cuttings by the coring bit. The hardcopy mud log was scanned and
converted to digital format for this display, but the well logs are preferred to pick lithology and interpret the stratigraphy in the well.
Stratigraphy
Coals are common throughout the Tertiary section and these rocks in general correlate to the Miocene Usibelli Group which is well exposed
in outcrop and mined extensively for coal at Healy, Alaska. A paly pick at 1200’ assigns an Early-Middle Miocene age with this horizon
being Upper Healy Creek. If this paly pick is accurate, the Healy Creek Fm in Totek Hills #1 is about 1300’ thick compared to 240’ in
Nunivak #1. This discrepancy in thickness is considered unlikely and this paly pick is ignored when assigning formation tops. The
formation tops shown on this display are lithologic picks made using the mud log and wireline logs.
The Suntrana Formation is dominated by sand in the Nunivak #1 well and in Totek Hills is chosen to include most sands in the upper part of
the Tertiary section. The Sanctuary Formation in Nunivak #1 is fine-grained and dominated by shale and siltstone. The Sanctuary Formation
in Totek Hills is picked to include the dominantly fine-grained section from about 1650’ to 2600’. The contact between the Sanctuary and
Healy Creek Formations is uncertain as both of these formations are dominated by fine-grained clastic rocks. In Totek Hills the contact is
somewhat arbitrarily chosen at about 2600’.
The lower about 500’ of Tertiary sediment (~2690 to 3126’ wireline) is primarily sand, lacks coal, and a paly pick assigns an Early Oligocene
age at 2507’ and an Eocene age at 2970’. Sediments of this age are missing in the Nunivak #1 well where Miocene sediments overlie Late
Paleocene rocks with an intervening erosional unconformity. The Oligocene and Eocene rocks in Totek Hills are thick sands which
underlying the potential seal facies of the Usibelli Group. This potential reservoir/seal couplet could have significant resource potential in
the Nenana basin.
Source Rock Potential Good to excellent source rocks for mixed oil and gas are found in Totek Hills #1, Nunivak #1 and outcrops of the Tertiary Usibelli Group.
Plots of RockEval data from Totek Hills #1 show HI (hydrogen index) values up to 471. Although samples in Totek Hills were taken at
systematic intervals rather than high-grading attractive zones, 8 of 26 samples have HI values of 200 or above. Three samples have HI above
300. These samples are similar to many other analyses from Nunivak #1 and outcrop samples and confirm that Tertiary mudstones and coals
contain good to excellent source potential in Nenana basin.
The three samples in Totek Hills with HI above 300 are all described as “shale dark green gray”. No mention is made of coal, although coal
is described as present in other samples. The lack of coal raises the possibility that the dark green gray shales are lacustrine and these
samples are lacustrine source rocks. If so, documentation of true lacustrine source rocks capable of oil and gas generation in Nenana basin
would be a significant finding. Further sampling of the intervals near 1525’, 1950’ and 2500’in Totek Hills is recommended.
By Gerry Van Kooten
Gas show C1 500-600’ Max 74 units
Gas show C1 845’ 44 units
Gas show C1 1080’ 100 units
Gas show C1 2060-75’ 30 units
Gas show C1, C2, C3 2138’ 43 units
Gas show C1, C2, C3 2365-86’ 53 units max
No Tests attempted No sidewall cores Heaviest gas detected: C3 No oil shows
Paly: 1200’ - Top E-M Miocene – U. Healy Creek Fm
Possible unconformity Sanctuary Fm and lower part of
Suntrana Fm may be missing
Paly: 2507 - E. Oligocene
Paly: 2970 - Eocene
105’ Top Nenana Gravel
145’ Top Coal-bearing Group
1,719’ of slim-hole core was cut; 1,228’ (71.4%) was recovered. Core diameter is 1.875” and 1.434”
Porosity and Permeability 15 samples from 1500’ to 3050’. Avg porosity 17.4% (range 7.1-27.5%) 9 samples for permeability Avg permeability 11.65 md (range 0.44 to 43 md)
Sand composes 55% of Tertiary section from 150-3160’
1719’ por=27.5% pm=10md ss vf-fg
1884’ por=22.4% pm=0.44md ss vf-fg
1902’ por=26% pm=53 md ss f-mg
1985’ por=23.9% pm=8.66 md ss vf-cgr
2141’ por=19.9% pm=7.01 md ss vf-mgr
2206’ por=23.1% pm=16 md ss f-mgr
2253’ por=18.9% pm=3.65 md ss vf-fgr
2269’ por=21.5% pm=5.12 md ss vf-fgr
2490’ por=18.7% pm=0.94 md ss vf-fgr
2535’ por=20.4% ss vf-fgr, frac
2550’ por=15.7% ss f-cgr, frac
2613.5’ por=15.9% cgl, frac
3050.3’ por=7.1% cgl, frac
Depths shown in this column are drilling depths, which are 23 to 38’
deeper than wireline log depths
Source rock interval 1 52’/43’ net (Arco) Excludes coal and sands
Source rock interval 2 88’/68’ net (Arco) Excludes coal and sands
Source rock interval 3 71’/58’ net (Arco) Excludes coal and sands
Source rock interval 4 272’/164’ net (Arco) Excludes coal and sands
Nenana Basin Lithostratigraphy Nunivak #1 well
DT
DT
DT density
dotted - NPHI
dashed - SPHI
dotted - NPHI
dashed - SPHI
dotted - NPHI
dashed - SPHI
dotted - NPHI
dashed - SPHI
DT
Coal
Coal
Coal
Coal
Coal
Coal Coal
Coal
Coal
Coal
Bottom 7 5/8” casing
Coals 0-1400’ picked by GR
Coals 1400’-TD picked by NPHI
Top Basement 3163’ drill log 3126’ wireline log
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TOC = 1.59 mudstone gray grn HI=180
TOC = 9.72 shale dk grn gray HI=384
TOC = 0.17 mudstone grn gray HI=41
TOC = 0.26 siltstone olive gray HI=30
TOC = 0.93 shale brn gray HI=52
TOC = 0.87 shale olive gray HI=53
TOC = 1.12 shale dk grn gray HI=79
TOC = 3.74 shale dk grn gray HI=330
TOC = 4.51 shale dk grn gray HI=471
TOC = 0.3 mudstone olive gray HI=63
TOC = 1.68 siltstone olive gray HI=200
TOC = 1.21 mudstone dk grn gray HI=71
TOC = 1.14 siltstone olive gray HI=78
TOC = 12.33 shale with coal HI = 184
TOC = 3.95 mudstone dk grn gray HI=211
TOC = 2.43 shale with sltst olive gray HI=222
TOC = 17.76 shale olive black HI=268
TOC = 10.36 shale with coal, olive gray
HI=238
TOC = 0.68 sandstone, trace shale HI=54
TOC = 0.95 sandstone, trace shale HI=154
TOC = 0.31 sandstone, trace shale HI=25
TOC = 0.22 shale med. Dark gray HI=0
TOC = 0.21 shale med. Gray HI=0
TOC = 0.18 shale med. dark gray HI=0
TOC = 0.36 shale med. dark gray
HI=111
TOC = 1.42 mudstone dk grn gray HI=99
Coals picked by low GR and low neutron
Density run only below 2935’
Arco Totek Hills #1 1984 TD 3,590’
Sanctuary Fm
Healy Creek Fm
Suntrana Fm
Grubstake Fm and/or
Lignite Creek
Nenana Gravel
Usi
bel
li G
rou
p
Surficial fill Nenana Gravel
Metamorphic basement schist and
phyllite
3163’ Top basement
schist (drill log) 3126’ wireline
log
Oligo-Eocene pebble
conglomerate and sandstone
Formation tops were picked from mudlog using
lithology and adjusted slightly to wireline logs
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Hydrogen Index
Co
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