||Problem: Deep gas well
drilled to top of reservoir at 4700m, became stuck on trip 1000m off bottom. Abandoned BHA
and sidetracked 350m BHA fish. Took kick at first permeable zone below fish with intensity
of gas zone 1000m deeper. Set 9-5/8 casing and continued to drill to objective for
testing. After testing completed, concern about gas crossflow and possibility of broach to
shallow zones and the surface dictated management find a solution. See figure 1.
|Remedial Strategy: Four
options were evaluated for control. The option chosen would be to cut a window in the
existing sidetrack through 9-5/8 casing. Then directional drill along side the fish
BHA using electromagnetic ranging for proximity control. Set a 7 liner +/- 100m
above the bit on the fish then intersect the open hole at an approach angle that would
allow the original 12-1/4 wellbore to be re-entered after the well was killed. If
re-entry was achieved the 12-1/4 hole would be cleaned out back to 4700m and plugged
|Special Services: John
Wright Company (JWCO) was contracted to supervise the special services for the relief
well. This would include pre-planning and on-site supervision of directional drilling,
surveying, casing detection, re-entry into the open hole and kill hydraulics. Vector
Magnetics provided electromagnetic ranging services and Well Flow Dynamics provided
hydraulic simulations support. Both companies worked together with JWCO to create a single
|Challenges: The project
was complicated by the following:
- Casing from original sidetrack created error signal for
- Section of claystone formations would cause hole stability and
- Drilling parallel and alongside existing BHA and aligning for
re-entry would require precise directional control and accurate casing detection
- The re-entry intersection would be implemented with
4-3/4" directional tools.
- Unknown gas flow situation in 12-1/4 hole created the
necessity to be prepared for several different scenarios upon intersection (e.g. total
losses, kick, H2S).
- Team concept for special services was successfully and
- Existing wellhead was successfully utilized for the remedial
- Electromagnetic ranging techniques were critical for project
- Directional drilling control required high dog-legs for final
- Open hole was intersected below bit at 1 deg inclination and
alignment was such that the relief well bit and BHA slipped into the 12-1/4 hole
with only slight increase in torque.
- No gas was encountered. The BHA was washed to total depth and
the 12-1/4 wellbore plugged and abandoned.