I N NOVATI N G WH I LE DR I LLI N G
Combination of extended-reach
drilling, maximum reservoir
contact wells and artificial
islands helps ADNOC access
offshore reserves with land rig
Wellbore tortuosity and instability, hole cleaning
and collision risk among many challenges
ADNOC overcame to drill 32,101-ft MD well
BY STEPHEN WHITFIELD, ASSOCIATE EDITOR
To increase production from shallow-
water reservoirs in the Arabian Sea, the
Abu Dhabi National Oil Company (ADNOC)
has been utilizing a combination of artifi-
cial islands and land rigs to drill extended-
reach drilling/maximum reservoir contact
(ERD/MRC) wells.
Built out of sand dredged from the sea-
bed, these islands can provide a cost-effec-
tive alternative to deploying offshore rigs.
Then, by drilling multiple ERD sidetrack
wells from a single pilot well from that
island, ADNOC can explore the far reaches
of the reservoir in the ocean without need-
ing to install new subsea infrastructure,
said Muhammad Ased Hashmi, Senior
Drilling Engineer at ADNOC Onshore. The
MRC aspect of the wells, which typically
means the well has an aggregate reservoir
contact in excess of 5 km, is intended to
help the operator achieve higher levels of
productivity with each well.
CONDUCTOR INTERMEDIATE CASING
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0 The 32,101-ft MD well had a TD of just 9,127 ft, making it 2 an 000 exceptionally long and
torturous well with a 3.52:1 extended-reach ratio. The well
was drilled this way in
0 order to maximize its aggregate reservoir contact and increase productivity.
20 While this approach to accessing off-
shore reserves has clear benefits, there
are also myriad challenges. For one, drill-
ing ERD wells can be extremely diffi-
cult, as it requires wellbore stability to be
maintained and higher levels of torque
to be managed over longer distances.
Additionally, because ADNOC uses a clus-
ter drilling approach in order to maximize
the well capacity of each island, devising
optimal well locations and trajectories can
be complex due to space limitations. “With
an artificial island, we have a difficult well
scheme from a trajectory point of view,” Mr
Hashmi said. “In one cluster, we can have
several wells being drilled in one area, all
going in different directions and into differ-
ent formations. It’s a planning challenge.”
In this cluster drilling approach, ADNOC
first drills a pilot well, which can serve as
a reference well for acquiring open-hole
data. That data can then be processed to
assess and define nearby opportunities, as
well as determine the number and location
of additional wells to be drilled from the
same pad.
Speaking at the 2023 IADC Drilling
Caspian Conference in Baku, Azerbaijan,
on 8 February, Mr Hashmi discussed his
experience while drilling one such well
offshore Abu Dhabi. As the target reservoir
was shallow, the total vertical depth of
the well was only 9,127 ft even though its
MD reached 32,101 ft. This resulted in a
fairly high extended-reach ratio of 3.52:1,
which is well above the 2:1 ratio that typi-
cally defines an extended-reach well. This
meant that the well would be exceptional-
ly long and torturous, which has implica-
tions on the well completion phase. Other
difficulties anticipated included high
torque, difficulty in hole cleaning, collision
risk and subsurface deviation errors.
The well was drilled in six sections:
■ a 157-ft, 36-in. hole section using surface
casing with an OD (outer diameter) of 30 in.;
a 2,054, 22-in. section with 18 5/8-in.
casing;
a 7,458-ft, 16-in. section with 13 3/8-in.
casing;
a 5,326-ft, 12 1/4-in. section with 9 5/8-in.
casing;
a 3,772-ft, 8 ½-in. section with 7-in. cas-
ing; and
the 6-in. lower completion section,
which was 13,334 ft in length and was
M A R C H/A P R I L 2023 • D R I L L I N G C O N T R AC T O R