American Oil and Gas Reporter - April 2020 - 58

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SpecialReport: Drilling Innovations
determined the influence of torque and
drag on the drill string, and analyzed the
design and configuration of the BHA and
hydraulics systems.
The well's lithology was the main
cause of the operator's poor drilling performance and the driving factor behind
the search for a better directional drilling
solution. The operator's wellbore objective
required drilling the curve section in ge-

ology that transitioned between multiple
interbedded formation layers that consist
of a wide variety of multistratigraphic
rock types, including marls, bentonite
shale, shale loam, mudstone and wackestone with microfractures presenting
pyrite.
The landing zone and lateral targeted
a Middle Cretaceous formation made up
of mudstone, wackestone, pyrite, black

shale and fragmented flint. The well path
called for a catenary curve building from
3.5 degrees per 100 feet and landing at
an inclination of 90 degrees before extending into a 1,640-foot lateral. The operator set the expectation that this project
would entail approximately 45 days of
drilling time, given the formation issues
and equipment-related limitations.
The engineering analysis revealed that
an optimized BHA configuration for this
project would consist of a 4¾-inch RSS,
MWD tools, and a multifrequency resistivity tool with gamma ray capabilities
and extended-life batteries. Running such
a configuration with RSS was the only
feasible option for drilling this well, since
slide drilling was impossible using a conventional mud motor with a bent housing.
The operator chose an RSS to address
several other issues as well, including
wellbore quality, hole cleaning, and directional drilling efficiencies.
The nature of a directional wellbore
drilled with RSS lends itself to a smoother
well profile, with the RSS using autonomous near-bit sensors to update wellbore trajectory in real time. A combination
of 100% rotary drilling and full rotation
stabilizers allowed cuttings agitation, while
a through-bore internal diameter of the
system accommodated optimal flow rates.
With projected slide drilling rates as low
as 3.28 feet/hour and rotary drilling rates
better than 32.8 feet/hour, the team recognized that eliminating the need for slide
drilling would increase actual daily footage
drastically compared with projections.
The MWD tool was incorporated into
the BHA design to provide real-time gamma and resistivity measurements. The
data was transmitted to surface through
mud-pulse telemetry and cyphered by a
surface transducer integrated onto the
rig's pressure system along with an MWD
data visualization platform. The MWD
system helped the operator to better understand wellbore geology and downhole
location. Additionally, the system also
provided a higher tolerance for lost circulation materials, as the operator expressed
concerns for losing drilling fluid volume
for the duration of this operation.
Drilling Road Map
After selecting the suite of technologies
and designing the BHA that best met the

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American Oil and Gas Reporter - April 2020

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