Gathering and Analyzing Vertical Permeability Data to Evaluate Horizontal Wells in North San Juan CBM
Karpov, Alexander1, Charles Morris2, Celine Segondy2, Reza
Naimi-Tajdar1, John Hebert3, and Edward Boratko4
1BP America,
Houston, TX
2Schlumberger, Houston, TX
3Schlumberger,
Lafayette, LA
4Schlumberger, Houston, TX
Coalbed methane resources have become an important part of
the natural gas supply. A large fraction of the gas is adsorbed on
internal coal surfaces and pressure must be reduced to produce the
gas through the cleats and fractures. Horizontal wells can offer certain
advantages in CBM development compared to vertical wells: high
initial gas rate, pressure reduction over a larger drainage area and
reduced surface impact. However, coal vertical permeability and layer
connectivity need to be high enough to ensure the entire coal interval
is effectively drained by the horizontal lateral. Gathering data on
vertical communication within and/or between coal layers is critical
to justify horizontal wells, select an optimal number of horizontal
laterals, and choose a completion strategy.
In addition to obtaining formation openhole logs, several wells
were tested using wireline formation testers for pressure,
permeability, permeability anisotropy, fluid identification, and lateral
continuity of barriers to vertical flow. These tools are able to collect a
large amount of data at multiple depths thus helping to quantify
changes in rock and fluid properties along the wellbore, to define
hydraulic flow units, and to understand the reservoir architecture. The
use of formation imaging data helps place the tool probes and/or
packers at optimum formation and depth locations, thereby reducing
risk and operating time, easing interpretation, and maximizing data
and sample recovery. This methodology represents a new approach to
the evaluation of coalbed methane reservoirs.
Application of the wireline formation tester techniques in the
Fruitland coal of the North San Juan Basin in Colorado is illustrated
with data acquired in several wells. Formation tester measurements
were then incorporated into a numerical simulation model. This
model was used to analyze the performance of horizontal versus
vertical wells and select optimal drilling and completion strategy
depending on CBM reservoir parameters.
AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah