Kansas 1992

 Problem: An old well in a prospective gas storage field was improperly plugged and abandoned. The 8-5/8" casing was cut and pulled at 825' MD, followed by a cement plug. The prospective storage reservoir, a sandstone formation at 3000' MD, was exposed to the open hole up to the 8-5/8' casing shoe at 992' MD. In order to utilize the sandstone formation as a storage reservoir the openhole must be properly plugged and abandoned. After several unsuccessful attempts, re-entry into the well at the top of the casing stub utilizing conventional methods became futile. See Figure 1.
Remedial Strategy: The leaking well would have to be plugged by unconventional techniques. A remedial operation was planned to parallel the existing casing and to mill a slot just above the casing shoe. The intersection would be achieved using electromagnetic ranging techniques, steerable motors and an integrated rate gyro steering system. Re-entry into the well would be attempted, and if allowed, a string of 4-1/2" casing would be run to cover the openhole section to the reservoir. If re-entry could not be obtained, a cementing operation to plug the well would commence 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, and re-entry into the well. Directional drilling and wellbore surveying services were contracted from Scientific Drilling Controls. Vector Magnetics provided electromagnetic ranging services and worked together with JWCO and SDC to create a single team.
Challenges: The project was complicated by the following:
  • There were no borehole surveys of the 8-5/8" casing target.
  • Short casing stub complicated the ranging operations.
  • The formations were very soft where the slot was to be milled.
  • The angle of incidence had to be less than 4° to run the 4 1/2" liner in the slot.
  • Window had to be started below a collar to prevent separation during milling.
  • Drilling parallel and alongside existing casing with poor surveys would require precise directional control and accurate casing detection techniques.
Results:
  • Team concept for special services was successfully and efficiently utilized.
  • Existing wellhead was successfully utilized for the remedial well.
  • Electromagnetic ranging techniques were critical for success of the operation.
  • Remedial well intersection was made at 800 ft with 3° incidence angle.
  • Casing was milled from 800 ft to 835 ft with a custom designed mill.
  • 4-1/2" casing was run to 3000' MD and cemented in the openhole interval.
  • The well became suitable for use as an injector/withdrawal well, saving the cost of new well.