Eliminate need for pilot holes in development campaign
As part of its drilling campaign in the North Sea Balder
field—underway since 2013—ExxonMobil sought solutions that would
eliminate the need for costly pilot holes in development wells. Due to the
nature of the injectite sand reservoir, the operator found that pilot holes
often failed to provide sufficient information to help land the producer wells.
Moreover, pilot holes are associated with their own drilling challenges and
The operator also experienced challenges related to accurately landing
wells in the injectite reservoir's massive sands instead of in thin injectite
sills or dikes. Because of the heavy mud weight used for drilling shale in the
landing section, ExxonMobil limited drilling into the massive sands to less
than 10-m MD to avoid losses. Drilling was complicated further by the fact that
the thin injectite sills or dikes found above the massive sands look just like
these sands on conventional LWD logs. ExxonMobil wanted to avoid setting the
casing point in the thin injectite sands because that can lead to drilling and
wellbore stability issues in the shale between the casing shoe and the massive
Map complex lithology to distinguish sands
To address these challenges, ExxonMobil selected the GeoSphere service
to land the producer wells without pilot holes. With a depth of investigation
of more than 30-m [100-ft] TVD from the wellbore, the service enabled the
operator to detect the top of the main reservoir from more than 20-m TVD away.
In addition, the GeoSphere service also successfully mapped the OWC before the
top of reservoir was penetrated. All of this information was acquired in real
time while drilling the 12 1/4-in section of the producer wells.
The ultradeep measurements provided via the GeoSphere service enabled
ExxonMobil to identify whether the sands entered by the well were thin
injectite sands or massive sands based on their unique signatures on the
service's inversion canvas. By landing and setting the 9 5/8-in casing in the
massive sands, the operator reduced drilling and completions risks by casing
off unstable shale above the main reservoir.
Maximize production with optimized well placement
For ExxonMobil, optimal placement of the wellbore was critical to ensure
maximum production. To geosteer effectively, the operator needed to overcome
constraints such as standoff from the OWC, gas/oil contact, or both, as well as
the uneven and changing nature of the top of the massive sands. The GeoSphere
service was used to track the OWC and determine the lowest-acceptable TVD
during reservoir geosteering. The accurate mapping of the roof of the massive
sands enabled ExxonMobil to make informed decisions regarding changes to the
well path, staying close to, but still avoiding, the roof.
The reservoir geometry mapped by the GeoSphere service, in combination
with seismic interpretation, enabled ExxonMobil geoscientists to plan the
geosteering strategy ahead of the bit. Production from the wells drilled with
the GeoSphere service in this drilling campaign significantly boosted
production from the field. Oil production in 2015 increased 37% compared with
2012, the year before the campaign began.