||Problem: In 1938 the
control of a well was lost resulting in a blowout with only the surface casing set. A 100
ft diameter crater formed and swallowed the rig. A relief well was drilled the following
year, but was only partially successful. The crater had remained with a fence around it
since that time. The well continued to bubble gas at various rates. The new field operator
desired to permanently plug and abandon the well and backfill the crater.
|Remedial Strategy: The
flowing well would require unconventional plugging techniques in order to fulfill proper
plug and abandon mandates. The original relief well had been spudded 165 ft from the
center of the crater and would be utilized for the operation. Drilling would continue from
the existing relief well casing into the area under the center of the crater. The
electromagnetic ranging tools would be instrumental in locating the original drillstring
that was left in the hole in 1938. After locating the old drillstring and establishing
communication, a light weight cement slurry would be circulated to stop the gas migration
and ultimately the crater would be backfilled with gravel.
|Special Services: John
Wright Company (JWCO) was contracted to supervise the special services required for this
project. Special services included pre-planning engineering and on-site supervision of:
directional drilling, surveying, and casing detection. The field operator and drilling
contractor supervised the normal drilling activities. Vector Magnetics was contracted and
was responsible for electromagnetic ranging services and worked together with the JWCO on
this project as one team.
|Challenges: The project
was complicated by the following:
- There were no borehole surveys of any kind on the flowing
- It was not known if the existing relief well would pass
- It was not known if the drillpipe was still intact after 50
years in saltwater flow.
- Formation strength was low requiring light weight cement.
- The fresh water zone was not sealed requiring precautions
- The competency of the formations surrounding the blowout
after 54 years was questionable and hole stability was a major concern.
- Team concept for special services was successfully and
- Existing relief well was successfully utiliized for the
- The existing drillpipe was not located immediately by
electromagnetic ranging techniques. This indicated either severe corrosion or missing
- The drillpipe was located deeper with a strong signal at
distance of 7 ft.
- Cement was squeezed into the reservoir and the crater was