Overcome bit-balling to run-dual-zone completion and improve efficiency
An operator needed to intersect two reservoir sand
targets and run a dual-zone completion to maximize
the production. Reaching the top of the first reservoir
sand from the 13 5/8-in casing shoe requires directional
drilling a long intermediate hole section within a tight
mud-weight window and containing it behind one casing
string. Borehole enlargement reduces ECD; hence,
underreaming-while-drilling technologies were needed.
One underreamer would leave approximately 60 m of rathole
if placed above the LWD or MWD tools and expose them
to greater shocks and vibrations if placed near the bit.
A long rathole would require a separate cleanout run,
while underreaming with LWD and MWD tools in a larger
hole size increases the risk of downhole tool failure due
to higher bending stresses and shock and vibration.
Additionally challenging in the formation are bit-balling
tendencies and high stick/slip vibrations in an upper
shale. The corresponding formation intervals in offset
wells were either shorter (less than 1,500 m), shallower,
or used multiple drill bits to reach the casing depth
(section TD). This fueled doubts during well planning on
whether the long 12.25-in × 13.5-in hole section could be
drilled in one run.
Unintentional indexing slowed ROP
Drop-ball-activated reamers can’t be used below MWD tools,
and previous experience with flow-activated reamers had
mixed success. Separate applications of reamers experienced
by this operator had incidents of unintentional indexing to
the “open” position at various phases of the drilling operation.
There were also failed attempts of indexing the tool to
the desired open or close position. The challenge of keeping
the lower reamer in the “closed” position throughout the run
and through numerous pump cycles is crucial, especially
for a long hole section where a BHA trip is costly.
Use multiactivated dual-reamer for unlimited number of activations cycles
Schlumberger recommended deploying a dual-reamer configuration in the BHA, using
as a lower reamer the Rhino XM on-demand multiactivated reamer because it provides
complete control of reamer activation, eliminating pumpdown device activation. This enables
placing the Rhino XM reamer below ID-restricted BHA components, such as MWD and
LWD tools. Additionally, the reamer’s flow actuation changes the reaming mode in minutes,
reducing reamer activation time and enabling an unlimited number of reliable activation
cycles during a run.
The recommended upper reamer is the Rhino XS2 full-cycle expandable reamer
to open the 12.25-in pilot hole to 13.5 in, while the lower reamer, the Rhino XM
reamer, is kept closed as the 12.25-in drill bit bores ahead. This configuration enables
enlarging the long interval to 13.5 in while sensitive LWD or MWD tools are confined
within the smaller 12.25-in hole diameter, thereby minimizing shock and vibration.
At section TD, the Rhino XS2 reamer is closed with a deactivation ball and the lockout
mechanism is sheared off with high flow rate. Positioned above the 12.25-in hole,
the Rhino XM reamer is indexed to the open position with a set sequence of flow
rates. It enlarges the remaining 12.25-in hole to 13.5-in hole diameter.
Drilled and reamed in single run while eliminating rathole, revved up ROP
The combined hole enlargement while drilling (HEWD) and rathole elimination (RHE) operation was achieved in a single BHA trip, from the 13 5/8-in casing shoe to the target sand reservoir.