|West Texas 1992
||Problem: A workover
resulted in an unintentional sidetrack through the existing casing of this production
well. Junk in the hole made it impossible to re-enter the well below the sidetrack
utilizing conventional methods. Perforations in the lower section of the production casing
were open to an over pressured reservoir in this waterflood area of the field. A cross
flow situation and charging of shallower zones resulted and caused concern for field
production, environmental implications and subsequent drilling operations. Several
unsuccessful and very costly attempts to plug the well utilizing conventional methods and
techniques were tried.
|Remedial Strategy: The
flowing well would have to be plugged by unconventional techniques. The remedial
operation, utilizing the existing wellhead, was planned to intersect the existing
production casing in several intervals. After setting of casing on the remedial wellpath
hole, a perforating operation would establish hydraulic communication for a final plug and
abandonment of the well. The remedial path would begin at a sidetrack plug set atop the
corroded casing stub. Very close proximity to the target wellpath was critical to allowing
selective perforating to seal off water zones.
|Special Services: John
Wright Company (JWCO) was contracted to supervise the special services. This would include
pre-planning and on-site supervision of: directional drilling, surveying, casing detection
and perforating. Vector Magnetics provided electromagnetic ranging services and worked
together with JWCO to create a single team.
|Challenges: The project
was complicated by the following:
- There were no borehole surveys of any kind on the flowing
- Casing had to be milled out of the conductor to provide
adequate hole size.
- Shallow charging required an intermediate string to be set
to seal that zone.
- Condition of the casing string was suspect and flow was
expected when close.
- Drilling parallel and alongside existing casing without
surveys would require precise directional control and accurate casing detection
- Team concept for special services was successfully and
- Existing wellhead was successfully utilized for the remedial
- Surface excitation and electromagnetic ranging techniques
- A rate gyro was successfully used to orient drill with less
than 1û inclination.
- Remedial well placement to within 6" proximity over
long intervals achieved.
- Communication was achieved over two intervals with oriented
- Cement was squeezed into two perforated zones with a cement
plug on top.
- The Texas Railroad Commission approved the P & A project