|West Texas 1991
||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. See Figure 1.
|Remedial Strategy: The
flowing well would have to be plugged by unconventional techniques. The remedial
operation, utilizing a relief well, was planned to intersect the existing production
casing just above the reservoir. A slot would be milled at that point and thixotropic
light weight cement circulated up the well to the casing break. The slot milled must cut
into the 2-3/8" tubing string to establish hydraulic communication for a proper plug
and abandonment of the well. The relief well would be spudded at approximately 200' from
the problem well, leaving sufficient area for a workover rig on the existing wellhead if
desired. See Figure 1.
|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, milling, pumping, cementing and polymers. Vector Magnetics provided
electromagnetic ranging services and Ely & Associates provided pumping, cementing and
P & A procedures and engineering . All special services groups 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
- Salt saturated drilling fluids required special casing
- An intermediate target which placed the relief well within
5-10' proximity of the target well was required at the casing point prior to intersection.
- Both the 5" casing and 2 3/8" tubing would require
severing at the intersection
- Low formation strength and fluid loss problems required
- Team concept for special services was successfully and
- S-shaped well was modified continuously by electromagnetic
- Surface excitation and electromagnetic ranging techniques
- A rate gyro was successfully used to orient drill with less
than 1û inclination.
- The intermediate target was achieved within the required
- A 6' slot was cut into casing and tubing at the
intersection. See Figures 1 & 2.
- Light weight thixotropic cement was circulated back to
- The Texas Railroad Commission approved the P & A
operation as implemented.