| Table
2. Details of CWD option |
| Target application |
Advantages vs. normal
operations |
Disadvantages vs. normal
operations |
Potential refinements |
| NCR
1 |
| Size csg.: 20 in. |
| Well type: Subsea, vertical |
| Reason for application: |
|
Address potential shallow water flows seen in deep
water by drilling, casing and cementing in one trip |
|
|
|
| On bottom circulation can be maintained at
all times which permits shallow water flows to be controlled effectively |
| Once a flow has started, serious hole
enlargement can compromise stability of conductor in well and any adjacent wells |
| In normal operations flows can start during
tripping when control is impossible |
|
|
|
| Assembly more difficult to trip if problems
occur |
| Risk of casing becoming stuck before
reaching planned setting depth |
| No cementing float collar, so must balance
cement with displacement fluid and wait on cement before pulling BHA |
|
|
|
| Use of a steerable motor assembly to allow
directional drilling |
|
|
|
| NCR
2 |
| Size csg.: 13 3/8-in. surface casing
|
| Well type: Surface BOP, vertical |
| Reason for application: |
|
Saving tripping time |
|
Push casing point deeper into unstable drilling
environment |
|
|
|
| No drill pipe tripping required |
| Adequate annular velocities for hole
cleaning can be achieved at lower mud flow rates compared with drilling with drill pipe
in the hole |
|
|
|
| Potentially higher ECDs |
| BHA more difficult to trip if tool problems
occur |
| Risk of casing becoming stuck before
reaching planned setting depth |
| Fishing BHA if stuck below end of casing
|
| To permit conventional cementing, float
collar has to be run on wireline after pulling BHA |
|
|
|
| Use of a steerable motor assembly to allow
directional drilling |
|
|
|
| CR
1 |
| Size csg.: 11 3/4 in. |
| Well type: Deviated |
| Reason for application: |
|
To drill liner a short distance into depleted
reservoirs prone to lost circulation |
|
Drill far enough into reservoir to case off interface
effectively |
|
|
|
| Avoid stuck drilling assemblies |
| Get required liner size into top of target
depleted reservoir |
|
|
|
| Assembly more difficult to trip if tool
problems occur |
| No directional control possible |
| Drilling distance limited by fatigue life
of liner connections (Less than 100 ft of drilling planned) |
| Cementing limited to squeezing shoe after
pulling drilling tools and isolating liner top with packer |
|
|
|
| Use of high torque liner hanger running
tool with flow path for return mud flow inside the liner (Spear used had by-pass area
for return flow inside the liner) |
| Use of casing connections with higher
resistance to drilling related fatigue |
|
|
|
| CR
2 |
| Size csg.: 7 in. & 9 5/8 in. |
| Well type: Deviated, sidetracked |
| Reason for application: |
|
Drill short distance into depleted reservoirs with lost
circulation |
|
Drill far enough into reservoir to case off interface
effectively |
|
|
|
| Avoid stuck drilling assemblies |
| Get required liner size into top of target
depleted reservoir |
|
|
|
| Potentially higher ECDs |
| Assembly more difficult to trip if tool
problems occur |
| No directional control possible |
| Drilling distance limited by fatigue life
of liner connections (Less than 100 ft of drilling planned) |
| Cementing limited to squeezing shoe after
pulling drilling tools and isolating liner top with packer |
|
|
|
| Use of casing connections with higher
resistance to drilling related fatigue |
|
|
|
| CR
3 |
| Size csg.: Up to 7 in. |
| Well type: Vertical, deviated or
sidetracked |
| Reason for application: |
|
Drill and under-ream to install production liner
|
|
Drill short distance into depleted reservoirs with lost
circulation |
|
Drill far enough into reservoir to case off interface
effectively |
|
|
|
| Install production liners and gravel pack
in one trip |
| Avoid stuck drilling assemblies in pressure
transitions associated with depleted reservoirs |
| Get required liner size into top of target
depleted reservoir |
|
|
|
| Potentially higher ECDs |
| Assembly more difficult to trip if tool
problems occur |
| No directional control possible |
| Drilling distance limited by fatigue life
of liner connections (Less than 100 ft of drilling planned) |
| Cementing limited to squeezing shoe after
pulling drilling tools and isolating liner top with packer |
|
|
|
| Use of casing connections with higher
resistance to drilling related fatigue |
|
|
|
| CR
4 |
| Size csg.: Up to 16 in. |
| Well type: Vertical |
| Reason for application: |
|
Drill long distance into depleted reservoirs with lost
circulation |
|
Push casing point deeper into unstable drilling
environment |
|
Save drilling related tripping time |
|
|
|
| No drill pipe tripping required for
drilling |
|
|
|
| Potentially higher ECDs |
| BHA more difficult to trip if tool problems
occur |
| Risk of casing becoming stuck before
reaching planned setting depth |
| Hydraulics may require by-pass above liner
to provide enough flow for hole cleaning |
| For conventional cementing, a float collar
has to be run on wireline after pulling bit |
|
|
|
| Use of casing connections with higher
resistance to drilling related fatigue |
| Use of drillable bit to permit normal
cementing without pulling bit. (Amoco built such bits for 7-in. drill-in liners. Nodeco
continued development. Also, British Bits Ltd. has drillable bit concept that looks
promising) |
|
|
|
| CR
5 |
| Size csg.: Up to 16 in. |
| Well type: Vertical |
| Reason for application: |
|
Drill long distance into depleted reservoirs with lost
circulation |
|
Push casing point deeper into unstable drilling
environment |
|
Save drilling related tripping time |
|
|
|
| No drill pipe tripping required for
drilling |
|
|
|
| Potentially higher ECDs |
| BHA more difficult to trip if tool problems
occur |
| Risk of casing becoming stuck before
reaching planned setting depth |
| Hydraulics may require by-pass above liner
to provide enough flow for hole cleaning |
| For conventional cementing, a float collar
has to be run on wireline after pulling bit |
|
|
|
| Use of casing connections with higher
resistance to drilling related fatigue |
| Use of steerable motor assembly to allow
directional drilling, preferably rotary steerable |
| Add LWD for logging while drilling |
|
|
|
| CR
6 |
| Size csg.: 4 1/2 in., 5 1/2 in., 7 5/8 in.,
9 5/8 in. |
| Well type: Vertical |
| Reason for application: |
|
Save drill pipe tripping time |
|
Push casing point deeper into unstable drilling
environment |
|
|
|
| No drill pipe tripping required |
| Adequate annular velocities for hole
cleaning can be achieved at lower mud flow rates compared with drill pipe in hole
|
|
|
|
| Potentially higher ECDs |
| Bit hydraulics limited by ECD
considerations |
| BHA more difficult to trip if tool problems
occur |
| Risk of casing becoming stuck before
reaching planned setting depth |
| For conventional cementing, a float collar
has to be pumped down after pulling bit. May be integrated into one of the cementing
plugs |
|
|
|
| Use of casing connections with higher
resistance to drilling related fatigue |
| Use of drillable bit to permit normal
cementing without pulling bit. (Amoco built such bits for 7-in. drill-in liners. Nodeco
continued development. Also, British Bits Ltd. has a drillable bit concept that looks
promising) |
| Add LWD for logging while drilling |
|
|
|
| CR
7 |
| Size csg.: 5 1/2 in., 7 in. |
| Well type: Directional or sidetracked from
vertical wellbore |
| Reason for application: |
|
Save drill pipe tripping time |
|
|
|
| No drill pipe tripping required |
| Adequate annular velocities for hole
cleaning can be achieved at lower mud flow rates compared with drilling with drill pipe
in the hole |
|
|
|
| Potentially higher ECDs |
| Bit and motor hydraulics limited by ECD
considerations |
| BHA more difficult to trip if tool problems
occur |
| Risk of casing becoming stuck before
reaching setting depth |
| For conventional cementing, a float collar
has to be pumped down after pulling bit. May be integrated into one of the cementing
plugs |
|
|
|
| Use of casing connections with higher
resistance to drilling related fatigue |
| Employ rotary steerable system to permit
continuous rotation to enhance ROP and minimize sticking potential during sliding
|
| Pump down running and retrieving system for
hole angles above 60º inclination |
| Add LWD to BHA for logging while drilling
|
|
|
|
