In early 1998, Miller Energy of Kalamazoo, Mich., scored
one of the best Ismay algal mound discoveries of decade in the southern
Paradox Basin.
The prospect was drilled on a 10-square-mile 3-D program.
Miller used a dynamite source in 80-foot shot the holes. Bin size
was 110 feet x 110 feet.
Good Upper Ismay algal mound production was established
in the early 1980s in the same province. Miller based its project
on 2-D anomalies mapped by Thomasson Partner Associates.
Nevertheless, finding Upper Ismay mounds with 2-D data
alone is a little like trying to pick up a wet cake of soap on the
shower floor in the dark. The crest of the mound has a way of slipping
sideways away from the drill bit.
Miller's subsequent 3-D program, on the other hand,
nailed the crest of the best mound "dead-on" with the first
well. The proper migration of steep dips on mound flanks provides
a more accurate areal shape for the mound.
This greatly increases the chances for a successful
first well -- a critical factor in keeping joint venture partners
on-board.
Miller and partners drilled and completed the 1-10
Horse Canyon Federal, which is the discovery well for Horse Canyon
Field. The field is located in the western portion of the Blanding
sub-basin of the southern Paradox Basin (figure 1
In early 1998, Miller Energy of Kalamazoo, Mich., scored
one of the best Ismay algal mound discoveries of decade in the southern
Paradox Basin.
The prospect was drilled on a 10-square-mile 3-D program.
Miller used a dynamite source in 80-foot shot the holes. Bin size
was 110 feet x 110 feet.
Good Upper Ismay algal mound production was established
in the early 1980s in the same province. Miller based its project
on 2-D anomalies mapped by Thomasson Partner Associates.
Nevertheless, finding Upper Ismay mounds with 2-D data
alone is a little like trying to pick up a wet cake of soap on the
shower floor in the dark. The crest of the mound has a way of slipping
sideways away from the drill bit.
Miller's subsequent 3-D program, on the other hand,
nailed the crest of the best mound "dead-on" with the first
well. The proper migration of steep dips on mound flanks provides
a more accurate areal shape for the mound.
This greatly increases the chances for a successful
first well -- a critical factor in keeping joint venture partners
on-board.
Miller and partners drilled and completed the 1-10
Horse Canyon Federal, which is the discovery well for Horse Canyon
Field. The field is located in the western portion of the Blanding
sub-basin of the southern Paradox Basin (figure 1).
The discovery well had an initial potential, flowing,
of 960 BOPD and 940 MCFGPD (no water). The well has been producing
since July 1998, flowing at the highly restricted rate of 230 BOPD
and 200 MDFGPD. It has produced 48,837 BO and 37 MMCFG through March
1.
The reservoir is a porous and highly permeable limestone
in the algal mound facies of the Upper Ismay (figure
2). The drive mechanism appears to be solution gas. The reservoir
does not appear to have any associated water. The GOR has remained
relatively constant at approximately 800 to 1000 scf/bbl.
Directly beneath the producing horizon is another potentially
productive zone in the Upper Ismay. This uncompleted zone is a dolomite
with higher porosity than the perforated zone.
Potential pay zones also have been identified in the
lower Desert Creek and lower Ismay intervals of the Paradox Formation
in the project area.
The Ismay and Desert Creek members are in the upper
five cycles of the Pennsylvanian Paradox Formation, of which there
are more than 40 upward shoaling cycles identified.
To date there has been little exploration for carbonate
reservoirs in the lower 35 cycles, making the Paradox one of the least
drilled proved petroleum basins in the United States.
Choice of Drillsite
The drillsite was chosen mainly on the basis of a reduced
amplitude "dim" of the Upper Ismay event.
Figure 3 is a northeast oriented
profile passing through the discovery well and dry hole (the Wintershall,
10-43 Ute Canyon Federal, a well drilled in 1984, 780 feet west of
the new Miller well). The geologic cross-section in figure
2 passes through the same wells.
The Upper Ismay anhydrite (the light blue event in
figure 3) provides a strong reflector at the top
of the Upper Ismay. Where the Anhydrite pinches out on the side of
the porous mound, the event becomes dim.
Passing southwestward, the event strengthens at the
dry hole, becomes slightly dim to the west of the dry hole (another
possible mound), then increases in amplitude toward the southwest
end of the profile.
Genesis of Upper Ismay Mound
The model for mound development consists of a thickened
Hovenweep shale providing a shoal or island in the Upper Ismay sea.
Note on the cross-section (figure 2)
that there is a thickened Hovenweep Shale, which is 47 feet thick
in the dry hole but only 20 feet thick at the Miller discovery.
The shale can be seen as a high amplitude event under
the mound on figure 3 (the yellow line).
Figure 4 is an amplitude map of
the Hovenweep event, showing the shape of the island inside the black
line. The black outline of the island is carried forward to the other
figures. A thick Hovenweep Shale is associated with all Upper Ismay
mound production in the Blanding sub-basin.
The algal mound develops on either side of the Hovenweep
thick, perhaps wrapping around the shale thick to form an atoll.
This atoll is illustrated on two maps.
- Figure 5 displays the amplitude of the Upper
Ismay event. The dim areas in red and yellow are shown to be on
either side of the Hovenweep island but not in the middle, where
the dry hole is located.
If mound growth had been more robust, possibly mound debris would
have washed into the central lagoon providing an Upper Ismay reservoir
at the location of the dry hole.
- A somewhat more dramatic presentation of the atoll shape is shown
on the map of figure 6. This is an isochron
from the Hovenweep Shale event to the Upper Ismay event. The interval
includes the productive mound.
Again, it is clear that an Upper Ismay Algal mound (red, yellow
and green) is built around the fringe of the Hovenweep island.
The central lagoon and shoal waters surrounding the mounds
are shown in shades of blue.
Secondary objectives seem to be easier to find and analyze
on high quality 3-D data.
A Desert Creek mound is indicated northeast of the Miller
well on the profile of figure 3 and the cross-section
of figure 2.
On figure 7 a possible mound trend
shows as a red and yellow amplitude dim passing northwesterly across
the entire shoot.
This has not been drilled -- but nearby wells do have
porosity and possible calculated pay.
Conclusions
Miller and Thomasson have shown that 3-D seismic can
locate carbonate reservoirs in areas already saturated with old 2-D
data. Three-D interpretation can be done in sufficient detail as to
document the genesis of a mound.
Miller found sufficient encouragement from its Horse
Canyon success to extend the program to the north as shown by the Mustang
Flat 3-D program, currently in progress (figure 8).
There has been little exploration for pre-Ismay mounds
in the western Blanding Basin, but new 3-D programs based on 2-D interpretations
will open this province.
).
The discovery well had an initial potential, flowing,
of 960 BOPD and 940 MCFGPD (no water). The well has been producing
since July 1998, flowing at the highly restricted rate of 230 BOPD
and 200 MDFGPD. It has produced 48,837 BO and 37 MMCFG through March
1.
The reservoir is a porous and highly permeable limestone
in the algal mound facies of the Upper Ismay (figure
2). The drive mechanism appears to be solution gas. The reservoir
does not appear to have any associated water. The GOR has remained
relatively constant at approximately 800 to 1000 scf/bbl.
Directly beneath the producing horizon is another potentially
productive zone in the Upper Ismay. This uncompleted zone is a dolomite
with higher porosity than the perforated zone.
Potential pay zones also have been identified in the
lower Desert Creek and lower Ismay intervals of the Paradox Formation
in the project area.
The Ismay and Desert Creek members are in the upper
five cycles of the Pennsylvanian Paradox Formation, of which there
are more than 40 upward shoaling cycles identified.
To date there has been little exploration for carbonate
reservoirs in the lower 35 cycles, making the Paradox one of the least
drilled proved petroleum basins in the United States.
Choice of Drillsite
The drillsite was chosen mainly on the basis of a reduced
amplitude "dim" of the Upper Ismay event.
Figure 3 is a northeast oriented
profile passing through the discovery well and dry hole (the Wintershall,
10-43 Ute Canyon Federal, a well drilled in 1984, 780 feet west of
the new Miller well). The geologic cross-section in figure
2 passes through the same wells.
The Upper Ismay anhydrite (the light blue event in
figure 3) provides a strong reflector at the top
of the Upper Ismay. Where the Anhydrite pinches out on the side of
the porous mound, the event becomes dim.
Passing southwestward, the event strengthens at the
dry hole, becomes slightly dim to the west of the dry hole (another
possible mound), then increases in amplitude toward the southwest
end of the profile.
Genesis of Upper Ismay Mound
The model for mound development consists of a thickened
Hovenweep shale providing a shoal or island in the Upper Ismay sea.
Note on the cross-section (figure 2)
that there is a thickened Hovenweep Shale, which is 47 feet thick
in the dry hole but only 20 feet thick at the Miller discovery.
The shale can be seen as a high amplitude event under
the mound on figure 3 (the yellow line).
Figure 4 is an amplitude map of
the Hovenweep event, showing the shape of the island inside the black
line. The black outline of the island is carried forward to the other
figures. A thick Hovenweep Shale is associated with all Upper Ismay
mound production in the Blanding sub-basin.
The algal mound develops on either side of the Hovenweep
thick, perhaps wrapping around the shale thick to form an atoll.
This atoll is illustrated on two maps.
- Figure 5 displays the amplitude of the Upper
Ismay event. The dim areas in red and yellow are shown to be on
either side of the Hovenweep island but not in the middle, where
the dry hole is located.
If mound growth had been more robust, possibly mound debris would
have washed into the central lagoon providing an Upper Ismay reservoir
at the location of the dry hole.
- A somewhat more dramatic presentation of the atoll shape is shown
on the map of figure 6. This is an isochron
from the Hovenweep Shale event to the Upper Ismay event. The interval
includes the productive mound.
Again, it is clear that an Upper Ismay Algal mound (red, yellow
and green) is built around the fringe of the Hovenweep island.
The central lagoon and shoal waters surrounding the mounds
are shown in shades of blue.
Secondary objectives seem to be easier to find and analyze
on high quality 3-D data.
A Desert Creek mound is indicated northeast of the Miller
well on the profile of figure 3 and the cross-section
of figure 2.
On figure 7 a possible mound trend
shows as a red and yellow amplitude dim passing northwesterly across
the entire shoot.
This has not been drilled -- but nearby wells do have
porosity and possible calculated pay.
Conclusions
Miller and Thomasson have shown that 3-D seismic can
locate carbonate reservoirs in areas already saturated with old 2-D
data. Three-D interpretation can be done in sufficient detail as to
document the genesis of a mound.
Miller found sufficient encouragement from its Horse
Canyon success to extend the program to the north as shown by the Mustang
Flat 3-D program, currently in progress (figure 8).
There has been little exploration for pre-Ismay mounds
in the western Blanding Basin, but new 3-D programs based on 2-D interpretations
will open this province.