Summary
Multistage fracturing in the Bakken formation, Elm Coulee field, Williston
basin, Montana, has been performed using hydraulic packers for zonal isolation
with ball-actuated fracture sleeves to improve performance of horizontal wells.
Optimizing development drilling and fracture-treatment designs for horizontal
wells requires an estimation of the fracture geometry (azimuth, height, and
half-length, with respect to lateral orientation). A fracture treatment
designed under the assumption that a longitudinal fracture (along the length of
the borehole) will be entirely inadequate if the actual fracture propagates in
a transverse orientation (perpendicular to the length of the borehole) and vice
versa. Recovery factor and reserves estimation, interference, drainage, and
well spacing require an understanding of the created fracture geometry from
multistage completions.
This paper describes how real-time downhole microseismic monitoring,
fracture-treatment pressure interpretation, and subsequent production
evaluation were used to better understand the created-fracture geometry,
completion staging efficiency, and fracture-stimulation effectiveness in a
project with two parallel 4,000-ft middle-Bakken treatment horizontal wells
2,000 ft apart with a horizontal well in between. The following topics will be
discussed as part of this paper:
- Success and failure in achieving proper stage isolation, diversion, and
fracture-stimulation coverage using hydraulic packers for zonal isolation with
ball-actuated fracture sleeves in two 4,000-ft laterals.
- Fracture azimuth and half-length as related to entry-point spacing and
intersections with nearby wells.
- Fracture-height growth up into the Lodgepole limestone and down into the
Three Forks formation as related to microseismic location uncertainties and use
of this information in fracture-model calibration.
- Discussion and comparison of the production response for past completion
strategies to the current approach, as well as discussion about production
interference between horizontal wells.
The integration of fracturing-mechanics studies that began with the initial
vertical wells and concluded with current-day horizontal applications in
concert with detailed reservoir-engineering evaluations has resulted in
significant production improvement in the Bakken formation, Elm Coulee field,
Williston basin, Montana. Detailed reservoir engineering led to optimized
multistage fracturing that was applied using hydraulic packers for zonal
isolation with ball-actuated fracture sleeves to improve performance of
horizontal wells. Using a calibrated/customized fracture model that had been
developed from evaluation of hundreds of wells in the basin, the
fracture-treatment pump schedules were designed to minimize fracture complexity
and optimize lateral proppant placement to attempt to create an ideal
transverse-fracture geometry within a horizontal well. Microseismic imaging was
used to confirm the historical information in the basin, fracture mechanics
studies, and customized models relative to the azimuth, height, and half-length
with respect to lateral orientation.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
14 December 2010
- Meeting paper published:
24 January 2011
- Revised manuscript received:
6 June 2011
- Manuscript approved:
23 August 2011
- Published online:
16 February 2012
- Version of record:
28 February 2012
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