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 Boratko^4
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