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Prominent Activity and Technology Trends
Oklahoma’s Woodford Gas Shale
Play
Drilling in Oklahoma’s Woodford Shale first became
popular in 2005. The Woodford in Oklahoma ranges in
depth from just a few thousand feet to more than 16,000
feet. Most of the current development is in southeast
Oklahoma where the shale layer is about 7,000 to 9,000
feet deep. There are some early, early wells, but it is
really the last 2-3 years that the play has become
active. Newfield Exploration Company, the most active
player, drilled their first Woodford well in 2003.
Results were positive enough for them to acquire a large
land position in an area 15-20 miles wide and 60 miles
long in southeast Oklahoma. Horizontal drilling has been
the biggest spark to Newfield and Woodford activity in
general. Newfield alone spudded 47 horizontal wells in
2006 and expects to spud another 150 in 2007. A Newfield
presentation in May 2007 indicates that there were 227
horizontal wells at that time, with Newfield operating
88 and having working interest in 58% of the wells. In
2007 Newfield expects to keep 12-15 rigs busy drilling
horizontals. Newfield has drilled enough wells that, in
their words “after experimenting with different drilling
and completion techniques, the company has tended to
find an optimum well design.” (May 25, 207 Newsok
article) Devon Energy Corp and Antero are the next most
active companies in the play. The Oklahoma Geologic
Survey maintains a gas shales completion database,
available at no charge on its
website. Woodford
activity may be spreading. In July 2007 Devon Energy
Corp announced they would be drilling a Woodford well in
western Oklahoma’s Canadian County, more than 150 miles
from the heart of activity.
Arkansas’s Fayetteville Gas Shale
Play
Located
on the Arkansas side of the Arkoma Basin, the
Mississippian-age Fayetteville Shale ranges in thickness
from 50 to 550 ft at depths ranging from 1,500 to 6,500
feet. It encompasses a 15-county area that stretches
from Arkansas’s western border to the Mississippi River.
Southwestern Energy Company pioneered the play and is by
far and away the biggest player. Information from
Southwestern’s website, as of April 30, 2007,
notes that they had completed 263 wells in the
Fayetteville, of which 208 were horizontal. Of those
horizontals, 87% were fracture stimulated using
slickwater or crosslinked gel fluids. The wells are
located in 33 separate pilot areas in eight Arkansas
counties. Production was up to 155 MMcfd, basically an
eight-fold increase just in the last year. Southwestern
anticipates participating in 400 horizontals in 2007,
being the operator in 75% of them.
The Arkansas Geological Survey
maintains Fayetteville Shale Gas Play maps containing
planned, permitted and completed well locations plotted
on either a standard base map or color-enhanced digital
elevation base map. With either the Survey provides an
Excel database of well information. Products are
routinely updated.
Testing Disproportionate
Permeability Reduction Concepts in Gelled Polymer
Treatments in Kansas’ Arbuckle Wells
In a
project co-funded by the Stripper Well Consortium, the
Tertiary Oil Recovery Project at the University of
Kansas evaluated disproportionate permeability reduction
(DPR) concepts in gelled polymer treatments in three
Arbuckle wells in the Bemis Shutts Field. In the DPR
process, following a conventional gelled polymer
treatment, there is a post placement process in which
some of the gel that is formed in situ is dehydrated by
injection of oil to create flow channels that exhibit
preferential permeability to oil and significantly lower
permeability to water. After a gelled polymer treatment,
the treated well is shutin for a period of time (for the
three wells tested: 10, 27 and 14 days) to allow the gel
to set. Then lease crude is injected at low rates for
several days (for the three wells tested: 10 bopd over
seven days, 9.6 bopd over 11 days, 11.3 bopd over 14
days). The well is then placed online and production
monitored. The three tested wells had been previously
treated conventionally, so there was a basis for
comparison to see if there was a DPR effect. The results
– sustained reduction in water production was achieved
in two of the three wells. Incremental oil was produced
in two of the wells. One well did not respond to the gel
treatment. In wells producing incremental oil,
production declined to at or below pretreatment rates
within a few months after treatment. Looking at the
total picture, the overall conclusion was that the
results were inconclusive – positive benefit could not
definitively be shown.
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