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XI-16
(Fig. 25). Updip limits to economic production on the northwest coincide with lateral
thinning the channel, and for this report have been mapped conservatively a: .:le
40-ft thickness,contour (Fig. 24). Downdip limits to production on the southeast side
of the pool are also mapped at the 40 ft thickness contour. Although production has
been es,",blished where the channel is as thin as 33 ft, it appears that an insufficient
volume of reservoir-qual;' sandstone is present in most of these thinner areas. In the
area around the WIPP :: withdrawal area, structure does not control trap boundaries,
although the prese:· ..e of an unsuccessful test well in SEtA NE'i4 sec. 6 T22S
R32E suggests that an oil-water contact or oil-water tranSition zone .may be present
where the top of the lower Brushy Canyon is at -4600 ft. The area within the 4O-ft
contour of channel thickness was used to project the oil accumulation in the livingston
Ridge main pay into undrilled areas (Fig. 26). Eighteen undrilled 40-acre units
are indicated within the WIPP_land withdrawal area and 107 undrilled 4O-acre units
are indicated within the additional study area.
In most wells in the Livingston Ridge - Lost Tank pool. three casing strings
are used during drilling:ld completion operations (Fig. 27). Typically, surface casing
of 13o/e-inch diameter is,et and cemented at approximately 900 it and an intermediate
string of 8 5 /e-inch diame'~r casing is set and cemented at a depth of approximately
4000 ft. After the well has been drilled to total depth. 5 'h-inch production casing is
set and cemented to total depth of approximately 8400 ft. It has been the practice of
most operators in the Livingston Ridge - Lost Tank pool to perforate casing and
produce only from the main pay channel. Before economic production can be
obtained, the pay zone must be acidized and artificially fractured. Volume of the acid
load is typically 2000 to 7000 gallons. After acidization. the reservoir is hydraulically
fractured. The size of fracture treatments varies widely. but a typical treatment uses
25.000 to 75.000 gallons of water and 50.000 to 100,000 lbs of sand; sand loads in
excess of 250,000 lb nave been used.
Yates Petroleum Corp. has drilled several wells in the west half of the
Livingston Ridge pool. but completed them differently from the other operators. All
the wells perforated the Livingston Ridge main pay and in most cases also perforated
from one to four other sandstones, and established commingled production from these
sandstones. These other sandstones are present in the Brushy Canyon and lower part
of the Cherry Canyon. Apparently. selection of perforation intervals was based on
analyses of shows reported on the rnudlogs and analyses of electric and porosity logs,
From comparison of production data from these wells with data from wells in which
only the main pay was perforated. it is thought that thcseadditioD8l pay zones will
increase production incrementally; most produc.tion will still be obtained from the
main pay zone. In most cases, Yates has reported only the gross interval of casing
perforations. It is not possible to determine which sandstones have been completed in
anyone well except those present at the top and the base of the gross interval. Other
operators may eventually re-enter their wells and perforate additionaCiones when the
main pay ceases to yield economic volumes of oil.