Tom Lantz and David Greene, Enerplus Resources, and Mike Eberhard, Scott Norrid,
and Richard Pershall, Halliburton
The Bakken reservoir development in Richland County, eastern Montana, has been a
center of activity and has received significant attention in the industry since
the first horizontal well was completed there in 2000. For one operator the initial
completion program utilized cemented liners in the laterals in wells oriented to
promote longitudinal hydraulic fractures. As discussed by Wiley, et al.,1
radioactive tracer logs indicated that there were often significant intervals, especially
in the heel section of laterals that were not stimulated using this technique.
In late 2003, one operating company decided to attempt a refracture treatment in
a well that showed long lengths of unpropped interval based on its tracer log. The
approach was to emulate the completion technique then in use on new wells with uncemented
liners. The result from this first refracture treatment was encouraging with a peak
post-refracture treatment production rate in excess of the peak production rate
after the original completion stimulation. As a result of this success, a refracture
treatment program was initiated.
To date, all but one of the initial cemented liner wellbores have had refracture
treatments pumped into them. The overall result has been an increase of over 1,300,000
stock tank barrels (STB) in the estimated ultimate recovery (EUR) for the wells
in this program. Results showing the improved coverage from tracer logs will be
presented along with examples of pre- and post-treatment production curves.
Over the course of this refracture treatment program, the fracture treatments have
evolved. Treatment size has remained the same; however, the method of pumping the
treatments has changed. This paper discusses how the refracture treatments were
pumped and the results of the program.