Eliminate intermediate 18-in liner in deepwater well with shock and
After drilling its first vertical exploration well in the presalt area
of the Jacare field offshore Angola, Statoil aimed to eliminate the planned
intermediate 18-in liner in the subsequent well. To accomplish this objective,
Statoil would need to drill the 18 1/8-in section to the planned TD for the
next section. This would require drilling through the salt in minimum time
while opening the borehole to 21 in, and, ideally, in one run to avoid salt
creep. If extended, this 18 1/8-in hole would be drilled from 2,555 m [8,382
ft] to 5,647 m [18,527 ft], passing through a layer of hard stringers at
approximately 4,350 m [14,272 ft]the original TD for the 181/8-in
Based on the first well drilled, Statoil anticipated shock and vibration
in medium to hard salt formations that would negatively affect BHA performance.
In the first well, this resulted in the need for a second bit run. Interbedded
formations would likely make managing weight on reamer challenging and lead to
premature cutting structure damage.
Use OptiDrill service to enhance BHA performance
Based on the length of the run and prejob modeling, Schlumberger
recommended a multisegment solution with a primary focus on the use of the
OptiDrill real-time drilling intelligence service. The OptiDrill service
provides downhole drilling mechanics and dynamics measurement on a rigsite
display for improved decision making. This information is also made available
offsite for remote interpretation by the drilling team.
With increased knowledge of downhole conditions, Statoil could optimize
drilling parameters to improve ROP, mitigate risk, and enhance cutting
structure life. To improve management of vibration and to optimize bit and
reamer weight distribution, Schlumberger recommended remote interpretation by a
drilling analyst from Geoservices, a Schlumberger company. The BHA included the
PowerDrive X6 RSS and Rhino system to maintain verticality and open the 18
1/8-in hole to 21 in.
Drilled 3,100 m of salt interval in one run, saving Statoil 10
Using the OptiDrill service and complementary technologies and services,
Statoil accurately applied optimal drilling parameters. This led to enhanced
BHA performance that enabled Statoil to drill through the Angolan salt at a
record-breaking 30-m/h ROP and set a record for the longest salt run ever
drilled in Angola. Furthermore, verticality was maintained throughout the
interval, and the hole was underreamed without premature wear to cutting
We successfully drilled 3,100 m of a salt section in one run and
avoided setting a potential intermediate liner in the salt, thereby saving
around 10 days, Statoil Drilling Engineer Marcel Emile Ngueguim said.
We recommend the use of the OptiDrill service where accurate information
is needed to improve drilling performance and bit life, especially in deep
water with hard or abrasive formations. It is also recommended in underreaming
applications to accurately evaluate the weight distribution between the reamer
and the bit.