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 well
  • Salt saturated drilling fluids required special casing detection techniques
  • 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 special techniques.
Results:
  • Team concept for special services was successfully and efficiently utilized.
  • S-shaped well was modified continuously by electromagnetic ranging results
  • Surface excitation and electromagnetic ranging techniques were successful.
  • A rate gyro was successfully used to orient drill with less than 1û inclination.
  • The intermediate target was achieved within the required tolerance.
  • A 6' slot was cut into casing and tubing at the intersection. See Figures 1 & 2.
  • Light weight thixotropic cement was circulated back to casing break.
  • The Texas Railroad Commission approved the P & A operation as implemented.