American Oil and Gas Reporter - PBIOS 2014 Official Program Guide - 142

Permian Basin Reports
FIGURE 2
CBP Tight Oil Formations and Areas of One Operator

FIGURE 3
Structure, Ellenberger Top

Shelf, most of the wells have been drilled
in the Delaware Basin. The Bone Spring
formation in the Delaware Basin contributed 1,772 wells.
There have been 845 wells completed
in the San Andres formation, mainly in
the CBP. Other CBP formations with
completed horizontals include the Wichita-Albany/Fullerton and Grayburg,
with a combined 175 wells.

Hybrid Formations
A number of formations in the Permian
Basin contain hydrocarbons, but do not
fit the strict definition of either a conventional or unconventional reservoir. Instead,
they truly are hybrid formations, combining shales and stringers of tight conventional sand or carbonate rock. These
hybrid formations always have been considered subcommercial, yielding a poor

142 THE AMERICAN OIL & GAS REPORTER

or even negative return on investment.
It is interesting to note that these formations are known for high quality conventional reservoirs elsewhere in the Permian Basin. In some areas, however, they
have only small pockets of good reservoir
rock.
Several operators have decided to use
horizontal drilling in an attempt to contact
enough reservoir, and to intersect enough
of the small amounts of good conventional
rock through fracturing, to get good results.
The Penn Detrital along the southeastern edge of the CBP is a good example
of a subcommercial play (see Figure 2).
The conventional reservoir rock itself is
excellent, but typically is found in small,
poorly connected deposits. Formation
rock is distributed by debris flows coming
off the CBP, and is isolated by permeability
barriers into pods that can be too small
individually to be economic when drilled
and produced.
Wellbores placed horizontally can connect these discreet pods. Results are starting to come in on the Penn Detrital from
horizontal drilling programs kicked off
earlier this year. Operators are evaluating
their initial results and enhancing their
positions.
The best documented hybrid developments are in the Wichita-Albany/Fullerton
(W-A) in the center of the CBP. The WA is a hydrocarbon-bearing carbonate
with some sand and silt stringers in the
same geologic age as the Bone Spring
formation. It is found over a wide area,
but has poor average reservoir quality.
The formation's reservoir-quality rock is
insufficient to make economic vertical
wells over most of the CBP.
However, core analysis shows that
within the larger interval, there are thin
beds of conventional reservoir. For a
few wells, oil recovery has reached commercial levels, but most production has
been from recompletions following abandonment of deeper formations.
Wichita-Albany/Fullerton
Apache Corporation was the first, and
remains the front-runner, in horizontally
developing the Wichita-Albany/Fullerton
formation in the north-central portion of
the CBP. The company had drilled vertical
wells with shows in the W-A. Its wells

American Oil and Gas Reporter - PBIOS 2014 Official Program Guide

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