American Oil and Gas Reporter - August 2018 - 54

SpecialReport: Horizontal Wellbore Construction
coupled with the simplified risk management assessment, help
create an aggressive, yet encompassing anti-collision methodology
dubbed the "Stoplight Method."
Stoplight Method
The Stoplight Method incorporates the directional and
geologic planning considerations, the operational requirements,
zonal determination, communication protocols, and risk management practices. It combines all of these anti-collision considerations and reduces them into clear instructions and visuals.
The method creates a visual representation by categorizing
target zones in tiers associated with the colors green ("go"),
yellow and orange ("proceed with caution"), and red ("stop").
The zone colors are defined by the risk matrix, and each zone
contains specific operational requirements, geologic requirements
and communication protocols.
These considerations and protocols include TVD and measured
depth requirements, survey requirements, drilling parameter
adjustments, target shifts, and communication workflow with
alert requirements.
The zones are defined in overlapping, stair-stepping geologic
target windows for specific predefined intervals, essentially
sectioning the wellbore into the "stoplight" (Figure 3). The
geologic targets are shifted in a design away from the stratigraphic
placement of the existing wellbore and narrowed in the "red"
zone. So, even though the two wellbores are proximally closer,
stratigraphically the wellbores are in different horizons.
The zones are defined using the risk matrix and the potential
collision indicators. The image at the right in Figure 3 illustrates
a cross-section of the stoplight method's geologic overlapping
target windows for each zone, while the left figure is an aerial
representation of the zones implemented across the planned
wellbore.
FIGURE 3
'Stoplight Method' Visual Representations
Of Zones against Aerial Wellbore Sections (Left)
And Stratigraphic Target Zones (Right)

The method applies these tiered zones to the risk management
plan, with each zone having specific survey requirements,
drilling parameter adjustments, targets shifts and communication
workflows.
Green denotes minimal or no risk, where standard operating
practices can be employed. This zone is used to understand wellbore
parameters and geologic signatures, and no additional communication
workflows are required outside of standard practices.
Yellow denotes low risk. The drilling team begins adjusting
standard operations practices within this section toward the
medium-risk (orange) parameters, allowing for operations to
adapt to the changing parameters (including directional
steering toward the high-risk (red) geologic window). No additional communication workflows are required outside of
standard practices.
Orange denotes medium-risk parameters, which include
small limitations in ROP, increased survey frequency for better
geologic placement accuracy, and directional steering toward
the high-risk geologic window. Additional communication workflows outside of standard practices are required, and the communication workflow should outline communication requirements
for any anti-collision indications and risk assessment events.
Red denotes high-risk parameters. These include limiting ROP
to slower than 50 feet/hour to allow for wellbore adjustments and
risk monitoring protocols, increased survey frequency for better
geologic placement accuracy, and a tightened geologic window.
Heightened communication protocols are required. The communication workflow should outline communication requirements
for any anti-collision indications and risk assessment events. If
any indicators are encountered, operations stop and only resume
after review and approval by both geology and drilling.
These zones become the risk management plan, with each
zone having distinctive mitigation requirements based on the
adjusted risk matrix. To help further diminish wellbore placement
concerns related to the potential for minimal survey error or
offset wellbore magnetic inference concerns not previously
mitigated, real-time survey monitoring with magnetic interference
correction is used in all zones to diminish the negative effects
of any near-wellbore interferences.
Case Study Wells
The stoplight method was designed and implemented in
three horizontal wells drilled between 2015 and 2017, designated
DSU A, DSU B and DSU C. Each case study well provided
unique challenges, including geologic properties, operational
conditions, offset wellbore considerations, geographic locality,
etc. Figure 4 shows the aerial view of all three new wells in
addition to existing wellbores. From left to right, the panels
show DSU A, DSU B and DSU C, with the colors of the
wellbores indicating like formations (green for the Middle
Bakken and orange for the Three Forks).

54 THE AMERICAN OIL & GAS REPORTER

American Oil and Gas Reporter - August 2018

Table of Contents for the Digital Edition of American Oil and Gas Reporter - August 2018