A new modeling system enabled PDC bit designers to increase
cutter efficiency and reduce susceptibility to impact damage by optimizing back
rake in the nose and shoulder areas. Engineers used the data to update the bit’s
torque and efficiency response, resulting in record-high ROP.
JAFRI, KYLE VRNAK
and SAAD JAMAL, Halliburton
often involves drilling long lateral sections across reservoirs of varied
density, typically with a rotary steerable system. Drilling across these
reservoirs can present unique challenges that put limits on the optimal potential
performance of the section. Traditionally, an analysis of surface parameter
data in conjunction with a standard drill bit dull analysis can identify and
address such operating limits.
This approach can
be effective but has limitations as well. It can be a challenge to properly identify
and document the downhole severity of the operating limiting issue, along with
the correlation and effects of this limitation to that of the drill bit design.
This can lead to uncertainties in quantifying the overall effectiveness of a chosen
design modification to address the operating limit.
team used the latest digital intelligence technologies within the existing
Design at the Customer Interface (DatCI) process to successfully identify the
type of downhole dysfunction limiting performance and its severity. The
approach enabled precise decision-making on the drill bit design modifications and
captured downhole feedback on the design changes to limit downhole dysfunction,
which further increased overall section performance. This improved process is
at the core of the Hedron line of drill bits, which integrates downhole Cerebro
data intelligence, in conjunction with an automated dull grading system (Oculus),
to achieve record-breaking field performance.
The traditional process
to optimize performance relies on an analysis of the basic surface parameters
applied, responding torque and rate of penetration (ROP) signature, along with the
condition of the retrieved bit dull. With this information, a team makes alterations,
either through step changes in applied parameters or a modification to the
drill bit design to further improve maximum achievable ROP performance of the
section. This approach is limited by a lack of understanding of downhole
dysfunctions that hinders continuous section improvement. Because surface
parameters are not always an accurate depiction of what’s occurring closer to
the formation being drilled, Halliburton introduced Cerebro downhole
in-bit sensor equipment to better understand and accurately document
motions of the drill bit from well to well, with modifications to surface
parameters, formations, and drill bit design.
The first step of
the process identified any limitations potentially correlated to the drill bit design.
Halliburton worked with the directional company to optimize parameters, to
reach the maximum potential of the existing design. During the development process,
the team combined information from multiple sources to make an accurate present-day
performance case. This includes surface drilling parameters, downhole vibrations
data (from the RSS), at-bit vibrations data and post-run intelligent drill bit
dull grading. Halliburton used this information to determine the maximum
performance that the current design and bottomhole assembly (BHA) could achieve
without inducing an undesirable downhole dysfunction.
Once the team
established the base case for the current bit and BHA combination and
dysfunction signatures, they modified the existing design to reduce occurrence
of bit-induced dysfunctions to push the performance beyond the recognized
maximum. In the past, design
modifications only produced incremental performance improvements, partially due
to uncertainties of the true section drilling mechanisms, which limited
performance. However, the holistic nature of the available downhole at-bit data
made a more substantial design change possible. The team then conducted a wide-ranging
study of the various vibration mechanisms, including at-bit stick slip,
torsional, lateral and axial. Each bit dull passed through an automated dull
grading system to digitally document and identify dull trends in comparison to
the dysfunctions seen downhole. The team used a combination of these results as
a guide to design a modified bit specifically for the subject application.
The at-bit sensor
helped identify problematic areas and the type of vibrations being experienced while
drilling the section. In addition to this, the team quantified the magnitude of
the vibrations. With the vibrations now clearly mapped, they accurately
integrated vibration mitigation mechanisms into the design philosophy. Artificial
intelligence-based, automated bit dull grading helped to quickly classify the
exact type of cutter damage observed at different profile areas of the existing
design. By linking this dull grading profile with the bit design, the team
identified potential design improvements to increase efficiency without exacting
extra damage to the cutting structure, which improved the location and orientation
of the cutters. Finally, they identified where to place the latest Geometrix-shaped
cutters, along with premium, high-impact cutters to minimize damage risk and
maximize drilling efficiency.
This improved bit
design delivered lower vibrations, due to enhanced drilling efficiency. Because
of the increase in bit stability, additional benefits from the RSS in the form
of reduced dysfunctions showed further improvement in the overall rate of
penetration. The new design improved the drilling efficiency and proved the
prowess of the applied holistic model. This simple-but-powerful approach can be
modified and applied to improve bit design, to fit any type of application
requirement. The subsequent sections will delve deeper into how each technology
was used to aid the digitally enhanced design process, Table 1.
At-bit vibration analysis. Effective
drill bit performance analysis requires crucial information. Accurate high-frequency
measurements over the course of the entire run provide a very powerful starting
point to a clear picture of what occurs downhole. The Cerebro electronic data
capture system gives a high-frequency look at data from the bit. The technology
gives reliable, high-data-rate measurements of inclination, vibration,
rotation, and the earth’s magnetic field movement around the bit.
motion, the team can map the source and type of drilling dysfunction. Once they
identify the drilling dysfunction, they can map against operating conditions
and parameters or formation. This map provides a guide to optimizing drilling parameters
in each application. Drilling dysfunction identification may also be used in
certain cases to optimize bit design, to mitigate dysfunction and improve
overall drilling performance.
For the current
bit design approach, the team used the Cerebro system to get a sense of actual,
downhole at-bit vibrations. The classification of vibrations required them to pinpoint
the exact type of vibrations to apply design modifications, which assists in
reducing that specific type of vibrations. The team used multiple, repeatable runs
with Cerebro to plot vibrations, to visualize the highest and most problematic dysfunction
Due to the nature
of the section, lateral vibrations were the biggest point of concern. The team
collected the actual magnitude of lateral vibrations from several runs and compared
them, using different parameters. The team verified the hypothesis of lateral
vibrations, illustrating lateral vibration severity with different parameter
combinations, Fig. 1.
In addition to
looking at runs separately, the team plotted multiple runs to understand
vibrations at different depths with changing parameters, Fig. 2. The
team looked simultaneously at multiple runs, which helped them understand the
nuances in different areas of the field and to better understand how variations
in depths and locations correlated to changes in drilling mechanics and
vibrations. Following is an example of such plotted data, which show vibrations
for three different runs that use the same bit and BHA.
The ability to gather and study
minute details like this helped to gain insight into the application that was
not previously possible. Similarly, incorporating these insights provides a
paradigm shift that changes drill bit design. Now, companies can understand the
dysfunction downhole and assess the effects of this on the durability and
performance of the drill bit’s cutting structure.
Automated dull grading. Conventionally, bits are dull-graded, based on visual
inspection: examiners identify different cutter damage patterns, based on
theory and personal experience. In addition, the only way to combine dull
analysis of a large number of bits is to identify damage patterns by entering
the cutter data across all blades. The possibility to merge big sets of data
becomes tedious because of this labor-intensive examination technique. The new
Halliburton Hedron platform of fixed cutter PDC drill bits uses Oculus advanced
dull analytics. The Oculus system is a state-of-the-art automated dull grading
system that utilizes machine-learning algorithms to capture precise dull
information for each individual cutter of drill bits.
Accurate dull bit forensics have
always been a key tenant to delivering superior drill bit performance. The Oculus
system transforms this critical process from one that is largely subjective
into something that is data-driven. It increases the potential number of data
points analyzed from single digits to potentially thousands of relevant
offsets. The Oculus system efficiently captures the dull data for every cutter,
and it also provides modern analysis and visualization tools. The drill bit
system can use big data analytics techniques and cloud infrastructure to seamlessly
correlate all relevant data streams and integrate them into the bit design
process. To implement the Oculus system in the current application, a dedicated
field analysis of reference bit design showed a consistent dull pattern across
the design profile of the bit, Fig. 3.
Excluding the occasional
aggressive dull condition, most of the cutter dull pattern signified smooth bit
condition with minimal damage. A majority of the bit runs in this application
operated at maximum drilling parameters, in terms of WOB and rotary RPM.
Interval lithology is comprised of homogenous layers with some slight interbedding.
This formation’s characteristics were supported by the bit dull condition, as
there was no abnormal over-engagement of cutters across the primary cutting
structure. This lowered the risk of cutter overload that can lead to premature
chippage or breakage.
Initially, to improve
performance, the team tested a PDC bit with axially point- loaded shaped
cutters in the shoulder area of the bit in this application. Subsequently, they
established it as a main drill bit for this section; however, they took BHA and
other performance improvement steps for efficiency improvements. Results from these
changes were capped at a certain level, which led to the need for a more
aggressive design. When the team decreased the diamond volume, it negatively
affected the bit’s performance in terms of stability and also exacerbated the minor
breakage seen in the shoulder during formation transitions. Therefore, the team
required a different solution with the existing design profile of the bit.
Bit design change. The team used the subject bit on a rotary steerable
drive BHA, so the aggressiveness, stability and directional response of the bit
had to be considered before making design changes. Based on the Oculus analysis,
the team decided to increase cutter efficiency while keeping the same profile
and cutter positions. The reference bit was limited by weight on bit (WOB)
controlling parameters inside the reservoir, due to excessive vibrations in the
The team introduced optimum back
rake scheme as a first iteration step to increase efficiency with low
susceptibility to impact damage. Three basic areas in the design profile—the
cone, nose, and shoulder—were examined for changes in back rake regime, Fig.
4. No changes were made in the cone area of the bit, as cone cutters
normally see high engagement forces. Over-engagement of cone cutters could
adversely affect bit stability, which leads to aggravated vibration levels.
However, in the nose and shoulder areas of the bit, the team arranged a calculated
change in back rakes for efficiency improvement.
The team conducted theoretical
comparison of reference and updated the new design’s torque and efficiency
model while keeping the remaining parameters constant for both bits. Proprietary
modeling software calculated a theoretical increase of bit efficiency by approximately
26%, compared to reference design at various WOB inputs, Fig. 5.
The team tested the new Hedron design in the 2022 drilling campaign and
set a field record after the first run. In the first lateral well, the bit
demonstrated its potential by exceeding all other 2022 offset well ROPs, Fig.
6. It delivered 17% more overall ROP while drilling with same parameters constraint
of limited WOB. It recorded lower vibrations throughout the interval, which the
following Cerebro vibration data analysis verifies in Fig. 7. Bit dull
was graded 1-1-WT-X-I-NO-TD.
After the success of the 6 1/8-in.
bit in the lateral section, the team executed a swift study to implement the
new design in the curve section, drilling through interbedded layers of
carbonates. Oculus analysis confirmed the smooth dull pattern with no abnormal
chippage or breakage on the parent 05 blade round cutter design. The challenge
of drilling a curved section with a bent motor requires smooth directional
control to achieve required build rates. Based on the historical field
experience, existing 05 blade design profile gives smooth directional control
results. As a first step of optimization, the new shaped cutters were
introduced on the same parent design to maximize ROP efficiency, Fig. 8.
These latest cutters work on the chip
breaker concept to reduce friction on face by sharp edge at higher engagement
and improved chip flow to help deflect cutting efficiency. The team selected a
targeted profile location to deploy the new cutters, to maximize cutter
productivity and minimize risk of any damage that can hamper durability. The team
tested the new Hedron design in the same, ongoing, 2022 drilling campaign. The
five-bladed bit incorporated with Gladius cutters outperformed the field ROPs and
achieved a 114% efficiency improvement, Fig. 9. The bit shows excellent
stability, along with durability and dull came as 1-1-WT-X-I-NO-TD, Fig. 10.
The Hedron bit improves drilling
efficiency and keeps the parameters within operating limits. This success
covered the full solution development: the team identified the challenge;
verified it with an advanced automated analytical approach; and developed a
technical solution. Based on the success of the first lateral run, the operator
elected to use the technology for most common lateral drilling sections,
targeting efficiency improvement across the entire project. The Hedron bit emerged
with promising dull grading, as there was no uncharacteristic damage seen on
the bit profile. WO
Opening photo: Electronic data capture at the bit mitigates stick-slip, while improving ROP and bit dull condition.
MOHAMMED OSAMA JAFRI is a senior application evaluation specialist, based in
Dhahran, Saudi Arabia. He has been with Halliburton for seven years.
KYLE VRNAK has been with
Halliburton for 14 years. He is based in Dubai, UAE.
SAAD JAMAL is deployed as a
technology lead, based in Saudi Arabia. He has been with Halliburton for 11