Summary
This paper covers the optimization of hydraulic fracture treatments in a new
coalbed methane (CBM) reservoir in Wyoming. A multiwell pilot project
was conducted in the Copper Ridge (CR) field to assess future development
potential. Hydraulic fracture mapping was successfully performed with
treatment-well tiltmeters on six wells including the first-ever used on propped
treatments. The mapped fracture height was then used to calibrate the
fracture model, perform on-site fracture-design changes, and optimize future
fracture treatments. This paper shows how early use of fracture diagnostics can
assist in the development of a new reservoir.
Introduction
CBM development continues to increase in the U.S.A. Many CBM reservoirs
require hydraulic fracture stimulation to produce meaningful gas rates.
Fracture diagnostics have drastically improved their capabilities over the last
decade (Wright et al. 1998, 1999, 2001; Stutz et al. 2002; Cipolla and Wright
2000; Lehman et al. 2002; Mayerhofer et al. 2000; Weijers et al. 2000;
Warpinski et al. 1998). They now enable real-time measurements of of how
fractures actually grow. The newest technology is treatment-well tiltmeter
mapping (TWTM) (Wright et al. 2001; Stutz et al. 2002), in which an array of
downhole tiltmeters is lowered into the treatment well to measure fracture
height and, in some cases, fracture width. Previously, these measurements were
only performed during the minifrac without proppant (Wright et al. 2001; Stutz
et al. 2002). In this project, TWTM was successfully peformed during the
propped treatment, thus providing a significant improvement over previous
“minifrac-only” measurements. Experience has shown that fracture modeling
without proper calibration from actual growth measurements and net-pressure
behavior can lead to completely erroneous fracture-geometry estimates (Lehman
et al. 2002; Mayerhofer et al. 2000).
The CR field, operated by Anadarko Petroleum Corp., is in southwest Wyoming,
near the town of Rock Springs. Anadarko is evaluating development of the
Almond coals in this field with a 16-well pilot program. The coals in the
CR field are usually present as multiple 2- to 20-ft stringers, which cover 100
to 300 ft of gross section at depths of approximately 2,600 to 3,000
ft. The most prolific coal(s) are usually perforated in 20-ft intervals
and fracture treated with one to two stages by use of crosslinked gel with a
combination of 16/30- and 20/40-mesh sand. Underlying this section is the
Ericsson sand, which is used for water disposal. Hydraulic fracturing must
avoid the Ercisson sand under all circumstances. Overlying the coal sections
are higher-permeability shoreface water sands, which also need to be avoided
during hydraulic fracturing. Fig. 1 shows a typical log section from the
field.
In this project, fracture-mapping results from several wells were integrated
to build a calibrated fracture model. Fracture mapping was performed on
six wells, and fracture engineering and modeling was performed on all 16 wells
in the pilot program. In addition to a general assessment of how these
coals treat, the objective of the study was to optimize treatment designs to
(1) stay out of prolific water sands, (2) provide pay-zone coverage, and (3)
create long fractures with adequate conductivity. Fracture growth was
monitored in real time, and fracture volume and injection rates were adjusted
on site to avoid fracturing into any water sands.
© 2006. Society of Petroleum Engineers
View full textPDF
(
1,617 KB
)
History
- Original manuscript received:
18 February 2004
- Revised manuscript received:
6 July 2005
- Manuscript approved:
9 July 2005
- Version of record:
20 May 2006
View Cart
