NTL FAQs for Info Requirements

NTL No. 2015-N01
Information Requirements for Exploration Plans, Development and Production Plans, and
Development Operations Coordination Documents on the OCS for Worst Case Discharge
and Blowout Scenarios

Frequently Asked Questions (FAQ’s)

Exploration Plan (EP), Development and Production Plan (DPP) and a Development Operations
Coordination Document (DOCD) will be collectively referred to herein as “Plan or Plans” in this
FAQ document.
Worst Case Discharge will be referred to as WCD.
1. Q. What OCS areas are affected by this NTL?
A. This is a National NTL; it applies to Plans in the Gulf of Mexico, Pacific, Atlantic and
Alaska OCS areas.
2. Q. What water depths does this NTL affect?
A. This NTL affects Plans that propose activities in both shallow water and deepwater (for
purposes of this NTL, water depths less than 500’ and water depths 500’ and deeper,
respectively).
3. Q. What Plans are subject to these information requirements?
A. You must submit the information identified in the NTL with a new Plan, or a pending Plan,
or if submitting a revision or supplement to a previously-approved Plan. You must submit this
information for the following:
• Those pending or approved Plans or documents that propose to conduct an activity that
requires approval of an APD (application for permit to drill) or AST (approved
sidetrack), and the APD or AST is submitted after June 18, 2010 or was filed but had not
been approved by that date, and
• Those Plans that propose to conduct an activity that requires approval of an APD, and the
initial, supplemental, or revised Plan that covers the activity is submitted after June 18,
2010.
4. Q. For what Plans do I not need to submit information required by this NTL?
A. You do not need to submit the additional information for the pending or approved Plans in
order to conduct the following activities:
• Activities for which an APD was approved prior to June 18, 2010;
• Drilling intervention or relief wells for emergency purposes;
• Drilling waterflood, gas injection, or disposal wells, unless you determine the waterflood
well is your well with the highest volume of liquid hydrocarbons;
• Drilling operations or other activities that are necessary to safely shut in, temporarily
abandon, or decommission a well, or to accomplish well completion operations under 30
CFR 250.500; and
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Activities that do not require the submittal and approval of an APD.

5. Q. What if I am currently conducting a rig-related workover or am waiting on an
application for permit to modify (APM) approval to conduct a rig-related workover?
A. You may conduct the rig-related workover without submitting the additional information
required by this NTL for your Plan.
6. Q. If this NTL does not require me to submit additional information for my Plan, when
may I conduct operations?
A. If you want to conduct an activity that does not require you to submit the additional
information required by this NTL, you may conduct the activity when or if you have received all
necessary approvals.
7. Q. When should I submit this information?
A. If you want to conduct an activity that requires approval of an APD, you should submit the
information listed in the NTL to BOEM in your Plan. If a Plan for the well(s) was previously
approved, then submit information as a Revised Plan.
8. Q. Where do I submit this additional information?
A. For the Gulf of Mexico OCS Region and Atlantic Planning Areas, submit the additional
information required by this NTL by mailing or delivering it to: Regional Supervisor, Office of
Leasing and Plans, Plans Section (GM 274E), Bureau of Ocean Energy Management, Gulf of
Mexico OCS Region, 1201 Elmwood Park Boulevard, New Orleans, Louisiana 70123-2394. For
the Alaska and Pacific OCS Regions, submit the additional information described in this NTL to
the address and contact for the respective OCS Region that is used to submit Plans. For
additional information submitted for approved Plans or documents, provide the Plan Control
Number of the referenced Plan or document and include the name of the well for which you
provided blowout and WCD scenario information.
9. Q. When is the information in this NTL required for a sidetrack?
A. You must submit a Revised Plan to cover sidetracks:
• For wells that cross into an adjacent lease, and the information required in this NTL was
not submitted for that lease;
• For wells drilling into a formation not previously penetrated; however, for the Gulf of
Mexico (GOM) submit this information only if you require a subsea BOP or surface
BOP on a floating facility; and
• For wells that you did not submit with the original Plan and you have determined will be
your well with the highest volume of liquid hydrocarbons.
10. Q. How should I calculate the daily discharge rate for the WCD scenario?
A. You should determine the daily discharge rate as the cumulative discharge over the course of
the day (i.e., 24 hour consecutive period) in which the maximum flow rate is observed, and the
flow model should include the contributions from all producible reservoirs in contact with the
open wellbore. For example, if the maximum observed discharge rate occurs in the first 24 hours
of the uncontrolled flow, then the “worst case” discharge rate would be the cumulative oil
discharge over the first day of the uncontrolled flow. Though the maximum daily rate typically
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occurs on the first day, it is possible for the highest (worst case) daily rate to occur later. The
package of reservoirs exposed to an open borehole with the greatest discharge potential will be
considered the WCD scenario. Shallower producible reservoirs isolated by casing and cement
will not be considered in the uncontrolled flow.
11. Q. What factors should I consider in determining the daily discharge rate?
A. In determining the daily discharge rate, you must consider any known reservoir
characteristics. If reservoir characteristics are unknown, you must consider the characteristics of
any analog reservoirs from the area and give an explanation for the selection of the reservoir(s)
used. You may consider analog drilling or production data, rock and fluid compressibility,
formation age, variance in pore pressures, and other relevant geologic and engineering factors to
support your determination.
12. Q. What reservoirs do you consider producible?
A. In the Gulf of Mexico, 30 CFR 550.116(b)(4) considers “A resistivity or induction electric
log of the well showing a minimum of 15 feet (true vertical thickness except for horizontal wells)
of producible sand in one section” as one method to qualify your lease as capable of production.
However, there are several reservoirs that currently produce from sands less than 15 feet (true
vertical thickness except for horizontal wells). Thus, you must consider any analog reservoir that
is capable of flowing liquid hydrocarbons and is exposed to the open hole. For other regions see
30 CFR 550.115.
13. Q. What specific data should I submit regarding the assumptions and calculations used
to determine the volume (daily discharge rate) used in my WCD scenario?
A. You must supply the assumptions and calculations used to determine the volume (daily
discharge rate) of the proposed well in your Plan or document that you expect will have the
highest volume of liquid hydrocarbons. This information is used as part of your WCD scenario
for Plans. Provide in a narrative the assumptions that you made (with analog data cited)
concerning well design, reservoir and fluid characteristics, and pressure volume temperature
(PVT) characteristics. Provide an explanation of the reasoning for the analogs used and all
calculations employed to derive the WCD volume.
Form BOEM-0137 (http://www.boem.gov See Quick Links: BOEM OCS Operations Forms)
provides tables for the operator to submit geologic and engineering parameters used in the WCD
calculation. However, Form BOEM-137 is not sufficient by itself to support the WCD scenario
but allows BOEM to easily identify critical factors used in the calculation. For all Plans (i.e.
structure maps or cross-sections), data must be provided at a level of detail necessary to verify a
WCD. The following is a general guide for additional data that should be submitted:
Wellbore:
• Wellbore schematic showing casing program for the proposed well to include casing/liner
sizes (outside and inside diameters) and setting depths (MD/TVD), and hole size and
depths (MD/TVD) as the well is being drilled; and
• Proposed directional survey with coordinates noted in x/y or lat/long.
Geologic Information:
• Structure Maps for each potentially producible sand to be encountered;
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Cross-section depicting all anticipated hydrocarbons bearing zones; and
Annotated seismic section through well site location using the most recent seismic data
available.
Reservoir Simulation and/or Nodal Analysis:
• For input data, screen-shot images of data input panels as viewed in the model. For
output data, provide screen-shots of the summary reports/graphs of the nodal programs.
For example, screen shots could include fluid, reservoir and wellbore data; PVT
correlations; inflow/outflow tables; solution point data; and, if available, inflow
performance relationship (IPR) versus outflow or vertical lift performance (VLP) plot;
and
• BOEM may request input and output files of proprietary nodal software. If requested,
send simulation input/output files in ASCII or txt format readable by common software
accessories. An alternative form of input/output report would be to print the simulation
input/output file to an Adobe Acrobat “printer” in order to create a pdf-format file.
14. Q. In my calculations and model runs can I assume the presence of restrictions in the
wellbore that would reduce flow?
A. You must assume that the wellbore is free of drill pipe, logging tools, or other similar
equipment. Bridging is not considered in the daily rate for the WCD scenario.
15. Q. Should I assume that the blowout preventer is attached to the wellhead and
calculate flow through the BOP?
A. No. Assume that the BOP is not connected to the wellhead. If circumstances indicate a
WCD discharge point at the top of the BOP, assume for modeling purposes that the innermost
casing string at the wellhead extends to the top of the BOP.
16. Q. How long will it take BOEM to verify the WCD volume calculations and
assumptions?
A. Each WCD calculation will be completed within the regulatory approval time frame.
17. Q. I recently drilled a development well but the well data is not due to be sent to BSEE
until later. Should I include the recent well data with the information required in this
NTL?
A. If new well data contains important analog data, submitting that well data will facilitate
BOEM’s review of the Plan.
18. Q. Will BOEM use the analog data that I submit with the supplemental information to
verify the WCD scenario?
A. BOEM will consider the submitted analog data as the basis for the assumptions and
calculations that support your WCD volume determination. BOEM has proprietary data that
might not be available to you. If appropriate, BOEM will use that data as an analog.
19. Q. What information should I provide concerning my arrangements for drilling relief
wells and the availability of a rig to drill a relief well?
A. If you submit a Plan or supplemental information to a previously approved Plan, you must
identify (by name and current location) at least one drilling rig capable of drilling a relief well in
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the event you have a blowout. This rig must be capable of drilling in the water depth where your
well is located and to the total depth of your well. You must discuss rig package constraints and
specify as accurately as possible the time it would take to contract the rig, move it onsite, and
drill a relief well. Also, discuss the feasibility of drilling a relief well from a neighboring
platform or an onshore location.
20. Q. What does BOEM mean by “package of reservoirs exposed to an open borehole
with the greatest discharge potential” will be considered the WCD scenario?
A. The WCD daily volume is calculated for the entire strata being drilled, not necessarily the
target objective. The target objective may, in fact, produce the maximum discharge; however,
BOEM identifies all potentially producible hydrocarbon sands (PPHS) simultaneously exposed
to any open segment of the wellbore during drilling to determine the package of reservoirs that
will discharge the maximum daily volume.
The graphic Example Well Casing Program and the companion graphic Example Potential
Producible Hydrocarbon Sands Encountered in Attachment A illustrates how BOEM determines
maximum discharge. The maximum discharge may not be from the combination of PPHS “D”
and “E”. The maximum daily liquid hydrocarbon discharge may be from the thicker, high
permeability PPHS ‘’A”, “B”, and “C” reservoirs during drilling when those sands are exposed
to the open wellbore. A loss of well control that initiates the oil discharge event should be
assumed to occur at the depth of full penetration of the “A”, “B”, and “C” sands. Once the
intermediate casing has been set to isolate the “ABC” sands, then BOEM assumes that the casing
does not fail and the next open hole interval is evaluated.
21. Q. What are the common problems that hinder the timely verification of the
calculations and assumptions used in the determination of the WCD volume?
A. There are four main problems that BOEM encounters in data submitted in support of the
WCD volume determination:
• Data supplied by the operator is insufficient to verify the critical parameters needed to
perform a reservoir simulation/nodal analysis;
• Data supplied by the operator is inconsistent. For example, the depth of the top of sand
in the wellbore schematic does not agree with the depth of the top of sand in the
directional survey;
• Analogs used in the assumptions and calculations are not identified; and
• Borehole data (PVT, permeability, reservoir pressure, etc.) derived from the analogs were
not submitted to BSEE. Analytical and interpretive data obtained from the drilling of
wells must be submitted to BSEE.
22. Q. At what conditions do you want the reservoir fluid data?
A. Oil data in an unproduced reservoir must be provided at initial reservoir conditions and at
bubble point conditions, including the formation volume factor, oil viscosity, bubble point, Rsi
(initial solution gas-oil ratio), API oil gravity, gas specific gravity, oil compressibility and
reservoir rock compressibility. Gas reservoir data should include initial reservoir pressure, dew
point, API gravity of condensate, specific gas gravity, condensate yield (BBLS/MMCF), and
reservoir rock compressibility. The reservoir data in a produced or producing reservoir should
be at current reservoir conditions.
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23. Q. Does BOEM recognize skin in the WCD analysis?
A. Operators have used the term skin to represent various conditions in the wellbore; BOEM
guidance is to assume skin is equal to zero. BOEM does recognize the calculation of a geometric
skin to account for the direction of the drill bit’s interface with the productive interval, and a gas
turbulence factor (D factor) in high rate gas wells.
24. Q. What exactly is considered the WCD in terms of the reservoir characteristics that
are used in the calculations? Does BOEM want the P10 (larger) numbers for all reservoir
and rock properties for the reservoir simulation?
A. You must consider any known reservoir characteristics. If reservoir characteristics are
unknown you must consider the characteristics of any analog reservoir from the area and explain
the selection of the reservoir(s) used. In simple terms, it can be considered the best drilling
results the operator can expect to encounter at the well site. The WCD model is not expected to
be formed as a combination of extreme values for key variables (for example, maximum
conceivable thickness combined with maximum conceivable permeability to obtain an extremely
improbable “kh”) but rather a “success” exploration case typified by analog reservoirs, analog
commercial fields, and recent discoveries.
25. Q. The operator may not have access to all data in the vicinity of the well site,
especially in exploratory drilling. What data does BOEM use to complete a WCD analysis?
A. BOEM uses the data from valid analogs to derive the WCD volume. Our corporate database
contains proprietary and nonproprietary information that can be used in the reservoir simulation.
BOEM will not release proprietary data to the public.
26. Q. How does BOEM convey the reason(s) for disparity between the operator’s
calculation of WCD and BOEM’s WCD?
A. BOEM will notify the operator when the operator’s WCD volume is less than BOEM’s
volume. Included will be a list of the major parameters (sand thickness, permeability, yield, etc.)
that we determined were the reason(s) for disparity.
27. Q. I was notified that my WCD volume was less than BOEM’s WCD volume. Can I
receive more clarification on the actual critical parameters and analogs that BOEM used in
their analysis?
A. BOEM does not release the analogs and their corresponding data due to potential proprietary
issues. However, BOEM will discuss the methodology and nonproprietary analogs,
assumptions, and calculations used in the WCD analysis with the operator. For the Gulf of
Mexico OCS Region and Atlantic Planning Areas, contact the Reserves Section Chief at 504736-0557, BOEM Point of Contact on WCD technical issues. For WCD technical issues in the
Alaska OCS Region contact the Regional Supervisor for Resource Evaluation at 907-334-5320.
For the Pacific OCS Region contact the Regional Supervisor for Office of Strategic Resources at
805-389-7855.
28. Q. I was notified that BOEM’s verification of the WCD volume resulted in differences
which need to be reconciled. What must I do to resolve the WCD differences?

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A. 1. You must respond to BOEM to reconcile the differences between the BOEM verification
and your WCD volume. You may submit additional information, request a meeting or
teleconference, or determine to concur with BOEMs verification of your WCD volume.
2. Once you have reconciled the WCD volume with BOEM, you need to determine if your
OSRP will need to be revised.
a. If you determine that your OSRP should be revised, then submit to BOEM the amended
pages for the blowout scenario section and oil spill section with the reconciled WCD volume,
ensuring to include the statement that a revision to the OSRP will be or has been submitted to
BSEE.
b. If you determine that your OSRP does not need to be revised, then submit to BOEM the
amended pages for the blowout scenario section and oil spill section with the reconciled WCD
volume.
29. Q. My WCD calculated volume was deemed adequate by BOEM. Does that mean that
the analogs and methodology were accurate?
A. Even when the operator’s WCD calculated volume is determined to be adequate there still
may be large discrepancies between analogs, assumptions and/or calculations used by the
operator and BOEM. The differences may counter each other with the net result that the
operator’s submitted WCD flow is higher than that modeled by BOEM.
30. Q. There are water sands in the WCD open hole interval. Does BOEM model water
sands in the WCD analysis?
A. BOEM will model water sands that are in contact with the open hole stratigraphically above,
or between, potentially productive hydrocarbon sands (PPHS) only if the water sand(s) has been
modeled by the operator. Only water sands that would contribute to the flow should be modeled.
The water sand(s) modeled by the operator may be considered hydrocarbon bearing sands by
BOEM unless evidence is submitted by the operator that conclusively indicates the sand(s) to be
water bearing. No water sands below the PPHS are modeled as contributing to the well
discharge.
31. Q. What flow correlations are used by BOEM in reservoir simulation?
A. Reservoir simulators have a selection of various flow correlations within the applications.
BOEM uses the following depending on various reservoir parameters and casing designs:
Flow Correlations
Hagedorn and Brown

Reservoir
Oil

Orkiszewski
Duns and Ros
Beggs and Brill
Cullender and Smith
Gray and Ross

Oil
Oil
Oil
Dry Gas
Wet Gas

General Conditions
Vertical well with 2- or 3-phase (GLR* < 5000 scf/stb) flow with or
without water cut.
Vertical well with 2- or 3-phase flow with or without water cut.
Vertical well with 2-phase. Not applicable with water cut.
Deviated and vertical wells with water cut (<10 %).
Vertical dry gas wells.
Condensate of < 50 stb per mmscf and water < 5 bbl per mmscf.

* GLR=gas-liquids ratio; scf= standard (surface) cubic feet; stb=stock tank (surface) barrels; mmscf=millions of
standard cubic feet

Other flow correlations may be used if the operator submits data in support of the correlation.

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32. Q. I used proprietary reprocessed seismic data in the WCD analysis. Do I need to
submit the reprocessed seismic data with the assumptions, analogs and calculation in
support of the WCD volume to the Plan Coordinator?
A. No. BOEM compares the quality of the seismic data submitted with the Plan to the seismic
data that BOEM possesses. BOEM will request the operator’s reprocessed seismic data if
needed for the WCD analysis.
33. Q. What should be shown on the proposed wellbore diagram schematic?
A. Submit the wellbore diagram that represents the wellbore casing and open hole components
that will exist during the drilling of the potential WCD open hole intervals. Do not show any
completion or production tieback liners that would be involved in the completion process and
that would not form part of the WCD flow path. Do not include any contingency liners that
might be run if problems arise. List the open hole size as-proposed and specify any assumed
washout size that may exist at the time of the WCD event. Include casing inside diameter for the
planned casing strings. If a hole opener or reamer will be used to drill the open hole section be
sure to include that information.
34. Q. Is BOEM considering the receipt of reservoir property maps in a digital format to
speed up the WCD review process?
A. Yes. The reservoir simulation software BOEM uses can import mapped data of various
reservoir properties. As an example, the operator exports a data file of the reservoir property, in
a three column table containing X, Y, and Z coordinates, into Excel as an ascii data file, and
saves as a *.csv file. The reservoir simulation software BOEM uses can only receive map data in
a comma separated table (*.csv). Submission of an image file of the map(s) will verify the data
was loaded successfully into the software and will help identify any significant differences in
software gridding and contouring.
35. Q. Where does BOEM consider the discharge point?
A. The discharge point is considered to be at the location of the BOP in the GOM and Pacific
Regions. In Arctic drilling environments, special conditions or atypical riser-BOP
configurations may mandate an alternative discharge point (operators are recommended to
contact the BOEM Alaska OCS Region). For example, if the operator places the BOP in a mud
cellar to avoid drifting icebergs, BOEM models the WCD point of discharge at the top of the
BOP and assumes that the innermost casing string at the wellhead extends to the top of the BOP
(i.e., approximately the mudline). Another example is if a well is proposed in the Arctic to have
a two-part BOP system with one BOP at the base of the riser sitting on a wellhead a few feet
above the mudline and a second BOP on deck or under the rig floor, then BOEM considers the
BOP-riser-BOP arrangement to constitute a BOP system and places the WCD model point of
discharge at the wellhead near the mudline. For Artic drilling on an artificial island, the point of
discharge should be assumed to be the top of the BOP for purposes of the WCD scenario.
36. Q. BOEM has requested a proposed directional survey for the well that I expect to
have the highest volume of liquid hydrocarbons, but a directional survey is not required for
a Plan. Why is that information requested?

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A. BOEM geologist uses the directional survey to project the length (drilled thickness) of the
potential producible hydrocarbon sands in contact with the open wellbore for the purpose of flow
modeling.
37. Q. How do I estimate the maximum duration and volume for the potential blowout
discussed in the blowout scenario of 30 CFR 550.213 (g)/30 CFR 550.243 (h)?
A. In the public part of the Plan, report the blowout scenario discharge volume during the days
estimated to arrest the oil discharge at the incident well by drilling a relief well. The blowout
scenario discharge volume is the cumulative daily volume of oil discharged during the period
necessary to mobilize, drill and kill the flow from the incident well. If no discharge schedule
(reflecting rates that progressively decline with reservoir de-pressurization) is reported, the
discharge volume is calculated as the daily discharge rate in bbls/day multiplied by the duration
of the blowout scenario.
38. Q. Will there be occasions where after the Plan has been approved the operator is
expected to submit a revised or new WCD scenario?
A. BOEM or BSEE may determine that a new WCD scenario is required to be submitted.

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ATTACHMENT A

Figure 1. Well Casing Program

Figure 2. Identifying PPHS.

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Figure 3. Structure Map.
Please note the entire reservoir is shown on the image and is not cut
off at the lease lines.

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