UNITED STATES GOVERNMENT MEMORANDUM

To: Public Information (MS 5030)

Plans Section, Office of Field 

Operations (MS 5231)

Public Information copy of Exploration Plan

Control # - S-07587

Type - Supplemental Exploration Plan

Lease(s) - OCS-G31938 Block - 51 Walker Ridge Area

Operator - Anadarko Petroleum Corporation

Wells CC and DD

Not Found

Attached is a copy of the subject plan for public comments on issues that 

should be addressed in an Environmental Assessment.

It has been deemed submitted as of this date and is under review for approval.

Michelle Griffitt

Plan Coordinator

Description -

Rig Type -

Subject:

From:

November 20, 2012
SUPPLEMENTAL EXPLORATION PLAN (S-7587) 

ANADARKO PETROLEUM CORPORATION 

WALKER RIDGE BLOCK 51 

OCS-G 31938 

PUBLIC COPY 

RECORD OF CHANGE LOG 

Submission 

Type 

Date Sent to 

BOEM 

Summary of Submission Page 

Numbers 

Initial 09/18/2012 Supplemental EP submission. All 

Amendment 10/05/2012 Provided wellbore schematic for proposed Location CC. 

(Proprietary data not included within Public Copy.) 

N/A 

Final Copy of 

Plan 

11/06/2012 Complete EP submittal. All 

Add Record of 

Change Log 

11/06/2012 Add record of change log. 1 
 

PUBLIC 

SUPPLEMENTAL EXPLORATION PLAN 

WALKER RIDGE BLOCK 51 

OCS-G 31938 

OFFSHORE, LOUISIANA

 

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive 

The Woodlands, Texas 77380 

Contact: Bridget O’Farrell 

Bridget.OFarrell-Villarreal@anadarko.com 

(832) 636-1694 

1 – Hard Copy Confidential 

1 – CD Confidential 

1 – Hard Copy Public Information 

1 – CDs Public Information

September 2012 
 

SUPPLEMENTAL EXPLORATION PLAN 

LEASE OCS-G 31938 

Walker Ridge Block 51 

 A. Plan Contents 

 B. General Information 

 C. Geological, Geophysical 

D. Hydrogen Sulfide Information 

 E. Biological, Physical and Socioeconomic Information 

F. Wastes and Discharge Information 

 G. Air Emissions Information 

 H. Oil Spill Information 

I. Environmental Monitoring Information 

 J. Lease Stipulations 

 K. Support Vessels and Aircraft Information 

 L. Onshore Support Facilities Information 

M. Coastal Zone Management Act Information 

N. Environmental Impact Analysis 

O. Administrative Information 
 

A 

PLAN CONTENTS

(a) Plan Information Form 

Under this Supplemental Exploration Plan (EP), Anadarko Petroleum Corporation (Anadarko) 

proposes to drill and complete two wells in Walker Ridge Block 51, Locations “CC” and “DD”. 

Both wells will have their surface and bottom-hole locations in Walker Ridge Block 51. The 

wells will be drilled using a drillship, dynamically positioned (DP) semi-submersible drilling rig, 

or a semi-submersible drilling rig. It is anticipated that anchors will not be utilized at this time, 

however, an anchor radius has been provided for reference if the decision is made to utilize a 

semi-submersible drilling unit in the future. Drilling and completion operations for all well 

locations will utilize a Subsea BOP stack. OCS Plan Information Form BOEM-137 is enclosed 

as Attachment A-1.

(b) Location 

Enclosed as Attachment A-2 is a well location plat at a scale of 1 inch = 2000 feet that depicts 

the surface location and water depth of the proposed well. 

(c) Safety and Pollution Prevention Features 

Safety features on the drilling unit will include well control, pollution prevention, safe welding 

procedures, and blowout prevention equipment as described in Title 30 CFR Part 250, Subparts 

C, D, E, G and O; and as further clarified by BOEM/BSEE Notices to Lessees, and applicable 

regulations of the Environmental Protection Agency and the U.S. Coast Guard. The appropriate 

life rafts, life jackets, ring buoys, etc., as prescribed by the U.S. Coast Guard, will be maintained 

on the facility at all times. 
 

(d) Storage Tanks and Production Vessels 

The Walker Ridge Block 51 well locations will be drilled with a drillship, DP semi-submersible 

drilling rig, or a semi-submersible drilling rig. 

Type of Facility Type of 

Storage Tank 

Tank 

Capacity 

Number 

of 

Tanks 

Total 

Capacity 

Fluid 

Gravity 

(API) 

Total 

Capacity of 

all Tanks for 

Rig Type 

Drillship Fuel Oil Storage 

Tank 

16,564 bbls 1 16,564 bbls No. 2 Diesel 6 tanks total= 

36,595.9 bbls 

Fuel Oil Storage 

Tank 

16,685.5 bbls 1 16,685.5 bbls No. 2 Diesel 

Fuel Oil Settling 

Tanks 

836.6 bbls 2 1,673.2 bbls No. 2 Diesel 

Fuel Oil Day 

Tanks 

836.6 bbls 2 1,673.2 bbls No. 2 Diesel 

DP Semi-submersible Fuel Oil Hull 

Tanks 

4,541 bbls 2 9,082 bbls No. 2 Diesel 7 tanks total= 

16,689 bbls 

Fuel Oil Hull 

Tanks 

3,392 bbls 2 6,784 bbls No. 2 Diesel 

Fuel Oil Deck 

Day Tank 

629 bbls 1 629 bbls No. 2 Diesel 

Fuel Oil Deck 

Settling Tank 

164 bbls 1 164 bbls No. 2 Diesel 

 Fuel Oil 

Emergency 

Generator 

30 bbls 1 30 bbls No. 2 Diesel 

Semi-submersible Fuel Oil Storage 

Tanks 

3,331.5 bbls 2 6,663 bbls No. 2 Diesel 4 tanks total= 

6,900.7 bbls 

Fuel Oil Day 

Tank 

214.8 bbls 1 214.8 bbls No. 2 Diesel 

 Fuel Oil 

Overflow Tank 

22.9 bbls 1 22.9 bbls No. 2 Diesel 
 

(e) Pollution Prevention Measures 

The drilling rig utilized for these operations will comply with all applicable regulations regarding 

pollution prevention and control. The rig has a Shipboard Oil Pollution Emergency Plan 

(SOPEP), which is reviewed and approved annually by the American Bureau of Shipping (ABS). 

The SOPEP is provided to assist employees in dealing with an unexpected discharge of oil. Its 

primary purpose is to set in motion the necessary actions to stop or minimize the discharge of oil 

and to mitigate its effects. Effective planning ensures that the necessary actions are taken in a 

structured, logical, and timely manner. 

Pollution prevention measures include installation of curbs, gutters, drip pans, and drains on deck 

areas to collect all contaminants and debris. Most deck drains and some of the joints at the edge 

of the rig floor go overboard or into the moonpool, respectively. To prevent ocean discharge 

from the drains there is a dedicated drip pan under the rotary table. The pipe racks, mud pump 

room, sack store, and drill floor drains go to a holding tank, which is served by a dedicated oily 

water separator. The well test area, engine room, and other major machinery spaces drains all go 

to slops tanks, which are served by a large general-service, oily water separator. The containment 

devices are temporary. They are not meant for permanent storage of waste. On the rare occasion 

that they contain wastes, they are pumped, mopped, or cleaned within a short period of time. The 

chances of damage to a containment structure during such time as it contains wastes are 

exceedingly small. 

(f) Additional Pollution Prevention Measures 

No additional measures are proposed under this plan. The activities proposed in this plan are not 

located offshore Florida. 
 

(g) Description of Previously Approved Lease Activities 

Anadarko was granted approval to drill and complete the following locations in Walker Ridge 

Block 51. The Initial EP was filed and approved under Anadarko E&P Company LP for 

Locations “A” and “B” under Plan Control No: N-9291. Anadarko Petroleum Corporation filed a 

Supplemental Exploration Plan for additional well locations in Walker Ridge Block 51 for Well 

Locations “C” and “D” which were approved in Plan Control No: S-7513. 

The proposed locations “CC” & “DD” are replacement locations for the approved EP locations 

“C” & “D” from Plan Control No: S-7513. In early September 2012, the Walker Ridge Block 51 

#001 wellbore , OCS-G31938, which was drilled at the approved “C” location, was junked and 

abandoned before reaching objective section, due to a mechanical failure. A replacement well 

was spud at the approved “D” location (back-up location), which is approximately 1,000' due 

west of “C”. Both the “CC” and “DD” locations are positioned 100' due west of the “C” and “D” 

locations, respectively, with the primary goal of having additional back-up locations in the event 

of further mechanical failure. 

Control # Plan 

Type/Approval 

WR 51 

Well Location Status of Well Location 

N-9291 Initial EP 

Approved 3/30/2009 

A 

B 

Open location for future 

drill site N/A 

S-7513 Supplemental EP 

Approved 3/7/2012 

C 

D 

Drilled as Well #001 

Drilling as Well #002 

P&A’d, 9/2012 

Currently drilling 
MMS FORM MMS-137 (December 2008 - Supersedes all previous editions of form MMS-137 which may not be used.) Page 1 of 3 

U.S. Department of the Interior 

Minerals Management Service OCS PLAN INFORMATION FORM 

OMB Control Number: 1010-0051 

OMB Approval Expires: 12/31/2011 

General Information 

Type of OCS Plan: x Exploration Plan (EP) Development Operations Coordination Document (DOCD) 

Company Name: Anadarko Petroleum Corporation MMS Operator Number: 00981 

Address: 1201 Lake Robbins Drive Contact Person: Bridget O’Farrell 

The Woodlands, TX 77380 Phone Number: (832) 636-1694 

 E-Mail Address: Bridget.OFarrell-Villarreal@anadarko.com 

Lease(s): OCS-G 31938 Area: WR Block(s): 51 Project Name (If Applicable): Shenandoah 

Objective(s): x Oil x Gas Sulphur Salt Onshore Base: Fourchon, LA Distance to Closest Land (Miles): 153 

Description of Proposed Activities (Mark all that apply) 

x Exploration drilling Development drilling 

x Well completion Installation of production platform 

Well test flaring (for more than 48 hours) Installation of production facilities 

Installation of caisson or platform as well protection structure Installation of satellite structure 

x Installation of subsea wellheads and/or manifolds Commence production 

Installation of lease term pipelines Other (Specify and describe) 

Have you submitted or do you plan to submit a Conservation Information Document to accompany this plan? Yes x No 

Do you propose to use new or unusual technology to conduct your activities Yes x No 

Do you propose any facility that will serve as a host facility for deepwater subsea development? Yes x No 

Do you propose any activities that may disturb an MMS-designated high-probability archaeological area? Yes x No 

Have all of the surface locations of your proposed activities been previously reviewed and approved by MMS? Yes x No 

Tentative Schedule of Proposed Activities 

Proposed Activity Start Date End Date No. of Days 

Drill and complete Location CC 2/12/2013 7/12/2013 150 

Drill and complete Location DD 1/1/2014 5/31/2014 150 

 

 

 

 

Description of Drilling Rig Description of Production Platform 

Jackup x Drillship Caisson Tension leg platform 

Gorilla Jackup Platform rig Well protector Compliant tower 

x Semisubmersible Submersible Fixed platform Guyed tower 

x DP Semisubmersible Other (Attach Description) Subsea manifold Floating production system 

Drilling Rig Name (If Known): Spar Other (Attach Description) 

Description of Lease Term Pipelines 

From (Facility/Area/Block) To (Facility/Area/Block) Diameter (Inches) Length (Feet) 

 

 

 
MMS FORM MMS-137 (December 2008 - Supersedes all previous editions of form MMS-137 which may not be used.) Page 2 of 3 

OCS PLAN INFORMATION FORM (CONTINUED) 

Include one copy of this page for each proposed well/structure

Proposed Well/Structure Location 

Well or Structure Name/Number (If renaming well or structure, reference previous name): 

CC 

Subsea Completion 

Anchor Radius (if applicable) in feet: 

12,000' (with 1,000' buffer)* Only if a semi-submersible rig is utilized x Yes No 

Surface Location Bottom-Hole Location (For Wells) 

Lease No. 

OCS-G 31938 

Area Name 

Walker Ridge 

Block No. 

51 

Blockline 

Departures 

(in feet) 

N/S Departure: 6,174' FNL N/S Departure: F L 

E/W Departure: 2,616' FEL E/W Departure: F L 

Lambert X-Y 

coordinates X: 2,104,104 X: 

Y: 9,767,106' Y: 

Latitude/ 

Longitude Latitude: 26.9093243 Latitude: 

Longitude: 91.5767518 Longitude: 

TVD (Feet): MD (Feet): Water Depth (Feet): 5,838' 

Anchor Locations for Drilling Rig or Construction Barge (If anchor radius supplied above, not necessary)

Anchor Name 

or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

Paperwork Reduction Act of 1995 Statement: The Paperwork Reduction Act of 1995 (44 U.S.C. Chapter 35) requires us 

to inform you that MMS collects this information as part of an applicant’s Exploration Plan or Development Operations 

Coordination Document submitted for MMS approval. We use the information to facilitate our review and data entry for 

OCS plans. We will protect proprietary data according to the Freedom of Information Act and 30 CFR 250.197. An 

agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays 

a currently valid Office of Management and Budget Control Number. The use of this form is voluntary. The public 

reporting burden for this form is included in the burden for preparing Exploration Plans and Development Operations 

Coordination Documents. We estimate that burden to average 600 hours per response, or 640 with an accompanying EP 

(1,000 hours in AKOCSR), or 690 (1,700 in AKOCSR) with an accompanying DPP or DOCD, including the time for 

reviewing instructions, gathering and maintaining data, and completing and reviewing the forms associated with subpart B. 

Direct comments regarding the burden estimate or any other aspect of this form to the Information Collection Clearance 

Officer, Mail Stop 5438, Minerals Management Service, 1849 C Street, NW., Washington, DC 20240.
MMS FORM MMS-137 (December 2008 - Supersedes all previous editions of form MMS-137 which may not be used.) Page 3 of 3 

OCS PLAN INFORMATION FORM (CONTINUED) 

Include one copy of this page for each proposed well/structure

Proposed Well/Structure Location 

Well or Structure Name/Number (If renaming well or structure, reference previous name): 

DD 

Subsea Completion 

Anchor Radius (if applicable) in feet: 

12,000' (with 1,000' buffer)* Only if a semi-submersible rig is utilized x Yes No 

Surface Location Bottom-Hole Location (For Wells) 

Lease No. 

OCS-G 31938 

Area Name 

Walker Ridge 

Block No. 

51 

Blockline 

Departures 

(in feet) 

N/S Departure: 6,239' FNL N/S Departure: F L 

E/W Departure: 3,641' FEL E/W Departure: F L 

Lambert X-Y 

coordinates X: 2,103,279' X: 

Y: 9,767,041' Y: 

Latitude/ 

Longitude Latitude: 26.9091710 Latitude: 

Longitude: 91.5792857 Longitude: 

TVD (Feet): MD (Feet): Water Depth (Feet): 5,837' 

Anchor Locations for Drilling Rig or Construction Barge (If anchor radius supplied above, not necessary)

Anchor Name 

or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

Paperwork Reduction Act of 1995 Statement: The Paperwork Reduction Act of 1995 (44 U.S.C. Chapter 35) requires us 

to inform you that MMS collects this information as part of an applicant’s Exploration Plan or Development Operations 

Coordination Document submitted for MMS approval. We use the information to facilitate our review and data entry for 

OCS plans. We will protect proprietary data according to the Freedom of Information Act and 30 CFR 250.197. An 

agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays 

a currently valid Office of Management and Budget Control Number. The use of this form is voluntary. The public 

reporting burden for this form is included in the burden for preparing Exploration Plans and Development Operations 

Coordination Documents. We estimate that burden to average 600 hours per response, or 640 with an accompanying EP 

(1,000 hours in AKOCSR), or 690 (1,700 in AKOCSR) with an accompanying DPP or DOCD, including the time for 

reviewing instructions, gathering and maintaining data, and completing and reviewing the forms associated with subpart B. 

Direct comments regarding the burden estimate or any other aspect of this form to the Information Collection Clearance 

Officer, Mail Stop 5438, Minerals Management Service, 1849 C Street, NW., Washington, DC 20240.
Walker Ridge

Block 51

Anadarko SL WR 51 “CC”

2,616’ FEL

6,174’ FNL

X = 2,104,104’

Y = 9,767,106’

LAT = 26.9093243 N

LONG = 91.5767518 W

Anadarko SL WR 51 “DD”

3,641’ FEL

6,239’ FNL

X = 2,103,279’

Y = 9,767,041’

LAT = 26.9091710 N

LONG = 91.5792857 W

Walker Ridge

Block 7

Walker Ridge

Block 95

0 2,000

FEET

Walker Ridge Block 51

OCS‐G‐31938

Well Locations
 

B 

GENERAL INFORMATION 

(a) Applications and Permits 

Prior to beginning exploration operations the following application(s) will be submitted for 

approval: 

Application/Permit Issuing Agency Status 

Permit to Drill BSEE To be submitted 

(b) Drilling Fluids 

Type of Drilling Fluid Estimated Volume Per Well 

Water-based (16.0 ppg SSRiser Vis) for 

Pump and Dump 

25,000 bbls per well 

Synthetic-based (internal olefin, ester) 15,000 bbls per well 

Oil-based N/A 

(c) Oils Characteristics 

Oil will not be produced under this Supplemental Exploration Plan. Therefore the oil(s) 

characteristics information is not required per NTL 2008-G04 2(d). 

(d) New or Unusual Technology 

Anadarko does not propose to use any new or unusual technology to drill the wells proposed in 

this plan. 

(e) Bonding Statement 

The bond requirements for the activities and facilities proposed in this EP are satisfied by an 

area-wide bond furnished and maintained according to 30 CFR part 256, subpart I; NTL No. 

2000-G16, “Guidelines for General Lease Surety Bonds,” and National NTL No. 2008-N07, 

“Supplemental Bond Procedures”. 

(f) Oil Spill Financial Responsibility (OSFR) 

Anadarko Petroleum Corporation (Company Number 00981) has demonstrated oil spill financial 

responsibility for the facilities proposed in this EP according to 30 CFR Part 253, and NTL No. 

2008-N05, “Guidelines for Oil Spill Financial Responsibility for Covered Facilities”. 
 

(g) Deepwater Well Control Statement 

Anadarko Petroleum Corporation (Company Number 00981) has the financial capability to drill 

a relief well and conduct other emergency well control operations if required. 

(h) Blowout Scenario

Anadarko prepared this blowout scenario pursuant to guidance provided in NTL No. 2010-N06. 

The previously approved Walker Ridge Block 51 #1 (Location “C”) well is addressed in this 

blowout scenario since it is the location with the highest potential worst case discharge (WCD) 

rate for Walker Ridge Block 51. A similar approach would be taken in the event of a blowout 

for the wells covered under this plan. Based on NTL No. 2010-N06 guidance, the maximum 

hydrocarbon discharge for Walker Ridge Block 51 is calculated to be 80,000 bopd (approved 

under Plan Control No: S-7513). 

Purpose 

This information provides a generic blowout scenario, additional information regarding any 

potential oil spill, the measures Anadarko Petroleum will take to prevent a blowout, and if 

necessary, promptly respond to manage a blowout scenario if one occurs. The following 

information is pursuant with 30 CFR 250.213(g), 250.219, 250.250 and NTL No. 2010-N06. 

Background 

This overview has been developed to document the additional information requirements for EPs 

as requested by NTL No. 2010-N06. 

Information Requirements: 

Blowout Scenario 

The Walker Ridge Block 51 #1 (Location “C”) exploration well was to be drilled utilizing a 

MODU rig with a marine riser and sub-sea BOP. A typical casing program will be used 

including a wellhead system, conductor casing, surface casing, intermediate casing, as well as 

two drilling liners to reach the planned total depth. 

The blowout scenario assumes that a hydrocarbon influx occurs followed by a well control event 

from the objective sands. The sub-sea BOP and marine riser subsequently fail followed by a 

blow out to the seabed. The worst case discharge (WCD) scenario assumes 

8-1/2" open hole with a 9-3/8" drilling liner, an 11-7/8" drilling liner, and 14" x 13-5/8" 

intermediate casing string set as shown in the wellbore schematic. 
 

Estimated flow rate of the potential blow out: 

Category Supplemental EP 

Type of Activity Exploration Drilling 

Facility Location (area/block) WR 51 

Facility Designation Location “C” 

Distance to Nearest Shoreline (miles) 153 

Uncontrolled blowout (volume per day) 80,000 bopd 

Type of Fluid(s) Crude oil 

API Gravity 26°

a) Potential for the well to bridge over:

Discussions regarding geologic information are considered proprietary and have been 

omitted from this public copy of the EP. 

b) Measures to enhance ability to conduct effective and early intervention in the event 

of a blowout: 

The likelihood of surface intervention to prevent, or stop, a blowout is high and is based 

on the following equipment specific to a capable MODU that will be contracted to do this 

drilling program: 

 ROV Secondary BOP Control System: The BOP will be confirmed to have 

an ROV Intervention Panel and circuits that have the following attributes: 

 Hot stab capable of closing one set of: 

 Blind-Shear Rams 

 Pipe Rams 

 Unlatch the Lower Marine Riser Package 

 Hot stab has been function tested in conjunction with the Stump Test 

and was tested at the same rate and pressure as the pump installed on 

the ROV used by the rig. 

The panel can also be operated by an ROV from an independent supply 

boat in the event of a loss of rig scenario. 

 Deadman / Autoshear function: The rig will be equipped with an 

automated sequence that closes the blind shear rams in the event of 

any of the following scenarios: 

 Inadvertent disconnect of the LMRP 

 Loss of both hydraulic pressure and electrical supply from the 

surface BOP control system 

No human interface is to be required once these systems are armed. 
 

c) Availability of a rig to drill a relief well: 

As per the preliminary Mutual Aid agreements that are being worked between E&P 

Operators in the Gulf of Mexico, Anadarko will select from the best rig option available 

in the Gulf of Mexico fleet if and when it is required for relief well work. 

As of September 18, 2012 there were 19 additional rigs in the Gulf of Mexico which 

would be capable of operating under the conditions associated with drilling a relief well 

for this prospect. A rig which could be used to drill a relief well is the Discoverer 

Inspiration which is a dynamically positioned drillship capable of operating in the water 

depths, and drilling to the total well depths, associated with a relief well for this prospect. 

The rig is currently under contract to Chevron and is on location in Walker Ridge Block 

677. 

There are no nearby platforms from which to drill a relief well. 

It is not feasible to drill a relief well from land. 

d) Rig constraints: 

A rig with a 15,000 psi BOP Stack and capable of drilling in 5,838' of water is required 

for any relief well operations. 

e) Time taken to mobilize a rig and drill a relief well: 

An estimated 7-21 days is required to suspend operations on a deepwater GOM well, 

mobilize to a relief well location, and begin relief well drilling operations. This estimate 

includes 0-14 days to suspend current operations on an existing well and acquire a 

contracted rig, and 7 days to mobilize to location and be ready to spud a relief well. The 

estimated time to drill the relief well and perform kill operations is 150 days for an 

estimated total of 157-171 days from time of blowout to finishing the relief well. 

The time estimate provided for the plan well is inclusive of 'both' drilling 'and' 

completion operations. As a completion is not typically part of relief well operations no 

time has been included for completion operations in the relief well estimate. In addition, 

information and learning from the drilling of the original well may provide opportunities 

to optimize drilling performance for relief well operations and thus reduce the required 

drilling time. 
 

f) Assumptions and calculations used in approved or proposed Oil Spill Response 

Plan: 

Garden Banks Block 346, Regional Oil Spill Response Plan 

 Petroleum Expert’s Prosper software was used for the nodal analysis. The WCD for 

the Garden Banks Block 346 #002 (Location A) is 321,108. 

 The maximum total volume during a blowout could potentially be 37,890,744 bbls 

assuming 118 days for the maximum duration of a blowout. 

 The volume denoted in the Regional OSRP is higher than the NTL No. 2010-N06 

(256,700 bopd) and BOEM (321,108 bopd) calculations approved under the Initial EP 

(Plan Control No.: N-9579). Anadarko elected to denote a higher volume (350,000 

bbls) in the Regional OSRP for planning purposes to demonstrate equipment response 

capabilities per previous discussions with Rusty Wright. 

Walker Ridge Block 51–Supplemental EP, Plan Control No: S-7513 

 Nodal analysis was performed to calculate worst case discharge volumes. Input data 

and assumptions utilized for the analysis of the Walker Ridge 51 #1 (Location “C”) 

well, along with the respective outputs, were included in Plan Control No: S-7513. 

The result being that at the seafloor, the estimated worst case discharge for the well 

is 80,000 bopd. 

 The maximum total volume during a blowout could potentially be 13,680,000 bopd 

assuming 171 days for the maximum duration of a blowout, multiplied by the worst 

case daily uncontrolled blowout volume of 80,000 bopd. 

g) Measures taken to enhance the ability to prevent or reduce the likelihood of a 

blow-out 

 Well design: Anadarko utilizes a systematic well design process for the planning and 

construction of a well operation. This process utilizes the depth of experience 

Anadarko possesses in the deepwater arena and involves a multi-disciplinary team 

peer review of the well design, shallow hazards, and formation pressure hazards 

expected during the drilling phase of the well. This process minimizes the potential 

for an unplanned well control event that could lead to a blowout. This process will 

also include Professional Engineer review and certification of the final casing design 

and cementing program. 

A detailed pre-drill assessment of formation pressure provided by Anadarko’s 

Geologic/Geophysical team, along with third party consultants, allows for 

development of a mud program that provides an overbalanced mud weight for the 

safe drilling of the well. For an exploration well this may also include taking 

formation pressures to confirm the actual formation pressure during the well 

construction process and minimize the risk of an unplanned well control event. 
 

The well construction process also requires a systematic review and management 

acceptance of the start-up preparation work for the rig and crews along with the third 

party technical audit work on the rig and the rig’s well control equipment. This 

review and audit process measures the rig’s ability to handle an unplanned well 

control event and provides assurance that the rig can successfully mitigate a loss of 

well control event and prevent it from becoming a blowout scenario. 

 Barrier Philosophy: For all well designs, Anadarko requires and uses a redundant 

barrier philosophy, that being two independent barriers for both internal and external 

flow paths in the final wellbore. It is also standard practice to conduct pressure 

testing, in accordance with the applicable regulations, to evaluate integrity on all 

relevant barriers. In addition, all intermediate and production casings returned to the 

wellhead will be locked down before subsequent wellbore construction proceeds. 

 BOP and well control equipment: The rig will have an 18-3/4" 15,000 psi BOP 

with primary and secondary BOP control systems. The BOP will have been 

completely recertified compliant to OEM specifications and all applicable federal 

regulations by a qualified third party. Prior to commencement of operations at the 

Walker Ridge Block 51 #1 (Location “C”) well an independent third party 

verification was obtained to verify that the subsea BOP was designed for the specific 

equipment on the rig and this specific well design. 

 BOP and well control equipment testing: To ensure effectiveness of the BOP and 

well control equipment, a testing program was conducted prior to running the BOP 

and then during the well operations at the Walker Ridge Block 51 #1 (Location “C”) 

well. This testing program will be in compliance with applicable federal regulations 

for pressure and function testing and will also provide periodic assessment on the 

performance of both primary and secondary BOP control systems including actual 

interface operations with the ROV and the ROV panel. 

 Well control training and drills: Anadarko requires that key nominated onshore and 

offshore positions including rig contractor personnel to hold a WellCAP, or 

equivalent, well control training certificate, renewable every two years for the type of 

floating drilling operation being conducted. Anadarko also monitors compliance of 

its personnel with the applicable federal regulations, including those found in 30 CFR 

Part 250 Sub-Part O. 

A comprehensive program of well control drills will be conducted offshore to ensure 

readiness to identify and then manage a well control situation and thereby minimize 

the potential for a well control event to lead to a blowout scenario. 
 

h) Arrangements for drilling a relief well 

 Anadarko maintains a master agreement with Wild Well Control for advice, 

management, engineering, well kick pre and post modeling, and resource support for 

an unplanned loss of well control event. In the event of any well control event, Wild 

Well Control would be contacted and mobilized if required to support Anadarko’s 

operational team both in the onshore and offshore locations. This agreement and 

expertise, along with additional equipment access, enhances the ability to conduct 

effective and early intervention in the event of a blowout. 

 The conceptual relief well design will be similar to the design of the Walker Ridge 

Block 51 #1 (Location “C”) in that casing weights, grades and setting points are 

anticipated to be identical or very similar. A finalized relief well design can be 

prepared within two days of initialization. 

 A block wide shallow hazard assessment was previously submitted for Walker Ridge 

Block 51 under Plan Control No: N-9174. The potential for high density chemosynthetic communities in the study area were negligible. Depending on the nature of 

the blowout scenario, well geometry, and total depth required to intersect the 

blowout, the most suitable surface location will be chosen and submitted for approval 

as the location for the relief well. 

 Anadarko’s philosophy is to carry an adequate inventory of well construction 

equipment to drill a complete well from surface to total depth. Back-up long lead 

equipment equivalent to the original well design will be carried in stock to allow a 

rapid response. This includes a spare deepwater sub-sea wellhead system and the 

large OD casing (36", 22", 18", 16", and 13-5/8") and connectors required for the first 

part of the well. Smaller OD casing is considered readily available on the ground in 

the GoM and would be resourced out of existing inventory or from suppliers as 

required. 

 Existing service agreements will be in place for support services including drilling 

fluids, casing running, cementing, ROV’s, solids control, mud logging, directional 

drilling, LWD/MWD, logging, boats and helicopters. 

 Specialist services for range finding to drill the relief well in close proximity to the 

original wellbore at the reservoir depth may potentially be provided through Vector 

Magnetics LLC. During drilling operations Anadarko maintains in-house directional 

drilling services personnel, (e.g. Schlumberger and/or Halliburton), to support and 

supplement Vector Magnetics under our existing directional drilling agreements. 
 

C 

GEOLOGICAL AND GEOPHYSICAL INFORMATION 

(a) Geological Description 

Discussions regarding geologic information are considered proprietary and have been omitted 

from this public copy of the EP, along with some of the associated geologic attachments. 

(b) Structure Contour Maps 

Current structure maps drawn to the top of each productive hydrocarbon sand showing the entire 

lease block, the surface locations of each well and locations of geological cross-sections, are 

enclosed as Attachment C-1.

(c) Interpreted 2-D and/or 3-D Seismic Lines 

Interpreted seismic lines are enclosed as Attachment C-2.

(d) Geological Structure Cross-Sections 

Interpreted geological structure cross-sections showing the location and depth of each proposed 

well are enclosed as Attachment C-3.

(e) Shallow Hazards Report 

A Shallow Hazards Report prepared by AOA Geophysics, Inc. was previously submitted with 

the Initial Exploration Plan (Plan Control No: N-9174) that covered Walker Ridge Blocks 8, 51 

and 52. 

(f) Shallow Hazards Assessment 

The proposed well locations in Walker Ridge Block 51 will utilize the Site Clearance Letters 

from the previously approved Walker Ridge Block 51 #1 and #2 (Location “C” and “D”). A 

copy of the Walker Ridge Block 51 “C” and “D” site clearance letters are enclosed as 

Attachment C-4 since the proposed “CC” and “DD” locations are within 100' of the approved 

locations. 

(g) High-resolution Seismic Lines 

High resolution seismic lines are enclosed as Attachment C-5.

(h) Stratigraphic Column 

A generalized stratigraphic column depicting the wells from the seafloor to total depth is 

included as Attachment C-6. 
 

(i) Time Vs. Depth Tables 

The proposed activities under this EP are not considered to be in areas where there is no well 

control. Therefore, a seismic travel time versus depth table is not required per NTL No. 2008-

G04. 
WR51 Proposed Location C 1 

AOA Geophysics Inc.

Marine Geoscience Division

2500 Tanglewilde, Suite 120

Houston, TX 77063

713-532-2624

Letter Report No. 4064-ANA-GOM-WR51C

08 March 2011

Anadarko Petroleum Corporation

1201 Lake Robbins 

The Woodlands, Texas 77380

Attention: Mr. Rick Kincaid

Site Clearance Letter

Location C 

Block 51, Walker Ridge Protraction Area

 

UTM Zone 15, NAD 1927

X = 2,104,204 ft Y = 9,767,106 ft

Longitude: 91.576445° W Latitude: 26.909323° N

Nearest Inline 31700 Nearest Crossline 3174

2,516 ft FEL 6,174 ft FNL

Introduction. AOA Geophysics Inc. (AOA) was contracted by Anadarko Petroleum Corporation 

to prepare a site clearance letter for Location C in Block 51, Walker Ridge Protraction Area. This letter 

report describes well site specific conditions but often refers to conditions and findings described in the 

main block-wide shallow hazards reports for Walker Ridge blocks Southern WR7, Southern WR8, Northcentral WR51, and North-central WR52 in the Walker Ridge Protraction Area, Gulf of Mexico, report 

number 4026-ANA-GOM dated 28 March 2008, prepared for Anadarko Petroleum Corporation by AOA 

Geophysics Inc. The principal scope of this site clearance letter is to assess seafloor disturbance from 

drilling with respect to possible deepwater benthic communities and to identify and assess potential 

drilling hazards in the tophole section to a limit of about 1.5 seconds below mudline (BML) or top of salt, 

whichever is shallower. If the well is drilled from a moored drilling rig, the anchor zone must be assessed 

in addition to the well site. We have specifically assessed conditions between 5,000 ft and 13,000 ft of the 

wellbore, as the grounded anchor chains should fall between those distances, with an assessment within 

an additional buffer zone of 1,000 ft beyond the maximum potential anchor spread. 

This site clearance letter is based on the interpretation of reprocessed 3-D exploration seismic

data integrated with offset well data. Annotated data examples of the nearest inline and crossline from the 

3-D survey are attached. A 1:12,000 water depth and seafloor features map shows the proposed location 

relative to seafloor features (Anchor Chart C). The proposed location with a 2,000 ft radius circle and a 

1,000-foot buffer area beyond the approximate maximum anchor radius are shown as per Bureau of 

Ocean Energy Management, Regulation and Enforcement (BOEMRE) Notice to Lessee's (NTL) No. 

2009-G40. The attached chart conforms to the digital structure requirements for drawings as per NTL No. 

2008-G05. The proposed wellsite is not in an area that requires an archeological assessment (NTLs 

2008-G20, 2006-G07, and 2005-G07). 

Data Set and Offset Well Information. The 3-D data were reprocessed by AOA Geophysics Inc

to enhance resolution in the tophole section. The data show significant energy above 50 Hz with good 

signal to noise ratio and are consistent with the guidelines for the use of 3-D seismic data for shallow 

hazards analysis. The 3-D data are centered on WR51 and WR52 and cover twelve blocks. Frequency 
WR51 Proposed Location C 2 

and power spectra show significant content at 50 Hz and higher in the tophole section at the well site. At 

50 Hz and assuming the average velocity of the tophole sediments to be approximately 5,500 ft/sec, the 

limit of separability (λ/4) is about 27.5 ft. Data were provided at a 4 ms vertical sampling rate, were loaded 

to 4 seconds two-way traveltime (TWT), and interpreted to approximately 3 seconds TWT (0.5 seconds 

BML because of shallow salt). Inlines are spaced 41.0104 ft (12.5 m) and crosslines are spaced 65.6166 

ft (20 m) apart. Inline increment is 5 and crossline increment is 1. These data meet or exceed the current 

NTL requirements including the requirements for the frequency and power content (Figure Amplitude and 

Power Spectrum). Tophole logs and drilling reports from WR08#1 (5,819 to 7,736 ft) were reviewed in the 

assessment of geological conditions and constraints for this proposed location.

Depth Conversion. The water depth at the well site was calculated using the velocity function 

published by Advocate and Hood (1993). This function is based on velocimeter profiles from the northern 

Gulf of Mexico and is expected to be accurate to about ±16.8 ft (~0.3% of water depth) at this location. 

The water depth was further calibrated by additional wide azimuth seismic data that ties the location 

WR08#1 well (water depth 5819 ft BSS, which was within 4 ft of the uncalibrated water depth calculation). 

Subsurface depths at the well site are based on depths derived from well WR08#1 (API: 608124003400). 

The following function was used for subsurface depth conversions in this report.

D = 3780.2 (T)

where D is depth (ft BML) and T is two-way-travel time (seconds BML). 

Water Depth and Seafloor Slope. The water depth at proposed Location C is predicted to be 

5,838 ft below sea surface (BSS). The local slope (gradient) of seafloor at the proposed well site is less 

than 1o dipping to the southwest. 

Seafloor Features. In general, WR51 is located within an area of irregular seafloor controlled by 

the interaction and migration of shallow salt. Although there are possible localized low-angle surficial 

mass movement deposits to the east and northeast, especially in WR52, and there is a steep scarp to the 

west in WR50, in general the block WR51 has no obvious evidence of seafloor instability. Furthermore 

the immediate region around the proposed well location C has no evidence for seafloor instability within 

2,000 ft of the well site. The nearest seafloor fault is northeast-southwest trending, dipping southeast, and 

is about 300 ft east of the proposed wellsite. 

There is no evidence for high-density benthic communities in the vicinity of the well location C. 

Within 2,000 ft of the proposed location, there are no interpreted seeps that would support a high-density 

chemosynthetic community, and there are no interpreted seafloor hardgrounds or stable bathymetric 

highs that might support a slow-growing filter-feeding coldwater coral community. The nearest reported 

deepwater benthic community is located in WR269 (26°41.07', 91°40.28') about 16.5 miles SW from 

proposed well WR51C.

Man-Made Obstructions. The nearest existing well location is WR8#1, more than 5,642 ft NE 

from the proposed well site. No other man-made features or other potentially hazardous seafloor 

conditions are identified in the vicinity of the proposed well site. However, there may be uncharted 

obstructions present that are not detectable within the resolution of the reprocessed 3-D data set, so it is

recommended that an ROV be used to inspect the seafloor at the proposed well site immediately before 

spud-in to confirm that there are no seafloor obstructions.

Assessment of Touchdown Area for Notional Anchor Pattern. The BOEMRE NTL 2009-G40 

mandates that proposed seafloor disturbances (including those caused by anchors, anchor chains, wire 

ropes, seafloor template installation, and pipeline construction) be more than 500 ft from areas that could 

support high-density deepwater benthic communities. If design requires seafloor disturbances between 

250 ft and 500 ft of potential deepwater benthic communities a state-of-the-art positioning system (e.g., 

differential global positioning system) on anchor-handling vessel(s) must be used, and the BOEMRE must 

receive plats that depict the “as-placed” location of all anchors, anchor chains, and wire ropes within 60 
WR51 Proposed Location C 3 

days after completion of operations to demonstrate that the features or areas were not physically 

impacted by the anchoring activities.

The notional anchor touchdown area is between 5,000 and 13,000 ft from the proposed well site. 

An additional 1,000-foot buffer area beyond the approximate maximum anchor radius is between 13,000 

ft and 14,000 ft from the proposed well site. The areas contain ridges and scarps associated with salt 

tectonics. 

There are numerous faults within the anchor touchdown area, predominantly to the northeast and 

south (see Anchor Chart C). The immediate vicinity of the fault scarps should be avoided if possible but 

otherwise the faults should not significantly constrain the anchor placement. In the vicinity of the faults, 

there may be locally variable soil properties and steep slopes. The steep slopes associated with minibasin formation and salt tectonics are located west and southwest of the well location at slightly greater 

than 14,000 ft. Some small channels and gullies are present in the touchdown area.

There are five sites, two in the notional touchdown area and three in the additional 1,000-foot 

buffer area, that are interpreted to have potential seepage of hydrocarbons and/or brines (Anchor Chart 

C). These sites may host high-density chemosynthetic communities. None of the bathymetric highs or 

steep margins, where nutrient-rich bottom water is necessary to support a high-density epi-benthic 

community of filter feeders, was interpreted to be stable over the length of time necessary to establish a 

slow-growing coldwater coral community (typically around 1 meter of growth per 100 years). The three 

regions likely to have the required exposure to nutrient-rich bottom waters that were examined most 

closely in the data were: the scalloped head scarp in the northeast of WR8, the steep scarp running 

north-south through WR6, WR50, WR94; and the irregular seafloor resulting from mass movement 

predominantly in WR52, WR96, and WR53. There were no obvious seafloor hardgrounds interpreted 

from the seafloor amplitude data that may form a suitable substrate for a high-density coldwater coral

community in the provided data and especially in these regions. Because the exposure to nutrient-rich 

bottom water, a hard substrate on which to anchor, and greater than centuries-scale stability in the 

geomorphology are all required for high-density epi-benthic coldwater coral communities, the only sites 

interpreted to have potential for high-density biomass are the five seep locations with potential for 

chemosynthetic activity (Anchor Chart C). These five sites, which are possible high-density deepwater 

benthic communities, should be avoided by more than 500 ft during anchor placement as per NTL

requirements.

Tophole Stratigraphy. The seafloor and two subsurface horizons, H1 and Top of Salt, were 

mapped. Depths below sea surface and below mudline to each of these intervals are included on the 

attached Tophole Prognosis Chart.

Unit 1 is about 284 ft thick and is composed of flat-lying and laterally continuous reflectors 

possibly representing recent mud-rich sediments. 

Unit 2 is about 468 ft thick. The reflectors show chaotic features in the unit due to the vertical and 

lateral movement of the salt. The unit is subdivided into an upper and lower section. The upper section is 

interpreted to be composed of mostly clay-prone sediment interbedded with thin mass transport

complexes (120 ft thick). The lower section is interpreted to be composed of mostly clay-prone sediment 

with possible sands (348 ft thick). Salt stringers may be present near base of the unit. The base of this 

unit is the Top of Salt. 

Unit 3 composed of salt. The top of salt is at 752 ft BML. The slope at the top of salt is 5.3o to the 

south. Possible inclusions and rafted sediments in the uppermost salt.

Fault Penetrations. Although the area is faulted to the east and northeast of the wellsite, no

obvious fault planes are interpreted to crosscut the wellbore path at proposed well location C. The closest 

prominent seafloor fault is located 300 ft to the east of the well location. 
WR51 Proposed Location C 4 

Gas Hazards. No amplitude anomalies suggestive of gassy sediments are penetrated at the 

proposed well site. There is a negligible risk for gas hazards at the proposed well location C. The nearest 

interpreted gassy sediments are about 563 ft NE in Unit 2. 

Shallow-Water-Flow (SWF). A negligible risk for severe SWF is assessed. There is a possible 

contribution of salt movement to overpressure pore fluids. However, it is not a strong driver of 

overpressure in thin shallow sediments that overlie the salt. 

Suitability for Temporary Occupation for Drilling. Proposed WR51 Location C is suitable for 

temporary occupation for drilling provided that the conditions and constraints that have been identified are 

considered and planned for in the final well design.
WR51 Proposed Location C 5 

We appreciate the opportunity to work with you on this project and look forward to continuing as 

your geohazards and marine geoscience consultants. Please call us at 713-532-2624 if you have any 

questions or if we can offer further assistance.

Sincerely,

AOA GEOPHYSICS INC.

Brenda I. Monsalve

Geophysicist- Marine Geohazards Specialist

Dan McConnell, P.G.

Manager- Marine Geohazards

Attachments:

• Description of 3-D Seismic Data including Amplitude and Power Spectrum Figure and Wavelet 

Figure

• Figure Appendix C-51C-1: Tophole Prognosis Chart Location C, Block 51, Walker Ridge Area

• Figure Appendix C- 51C-2: 3-D Seismic Record, Line 31700, Location C, Block 51, Walker Ridge 

Area

• Figure Appendix C- 51C-3: 3-D Seismic Record, Crossline 3174, Location C, Block 51, Walker 

Ridge Area

• Water Depth & Seafloor Features Showing Potential Anchor Touchdown for Proposed Well C, 

Walker Ridge (WR) 51, and Vicinity, Gulf of Mexico, Anchor Chart C (1:12,000)
WR51 Proposed Location C Description of 3-D Seismic Data

Description of 3-D Seismic Data Sets:

The 3-D seismic surveys that have been provided to AOA Geophysics Inc., by Anadarko, are of good 

quality to interpret the shallow section. The 3-D seismic data volume called VTS Walker Ridge I

(wrph1_3d) are interpreted around the proposed well sites and are used for most of the surface and all 

of the subsurface interpretation. These data are thirty-two-bit format. The 3-D seismic data parameters 

for VTS Walker Ridge I are described in the table below:

3-D Seismic Data VTS Walker Ridge I (wrph1_3d)

Spacing, Increment, and 

Orientation 

Spacing Increment Orientation

Inlines 41.0143 ft (12.5 m) 5 EW

Traces 65.6161 ft (20 m) 1 NS

Frequency Content in Tophole 

Section

Spectral analysis shows significant (0.45 to 0.65 on a normalized scale of 0 to 1) 

50 Hz frequency content in the data at each of the proposed well locations. 

Reprocessed for Shallow 

Section?

Yes, spectral whitening

Processed sample interval Acquired at 2 ms- Processed at 4 ms

Acquisition Parameters • Acquisition Contractor CGG Veritas

• Vessel Polar Princess/Polar Search

• Date Available 1998

• Source Airgun 

• Streamer length 7,200 meters

• Shotpoint Interval 37.5 meters 

• CMP Xline 40 m

• Record Length 12.5 seconds

• Nominal Fold 48

Processing Parameters • Reformat 

• Anti-alias filter (Minimum Phase, Out – 90 Hz) 

• Resample to 4 ms 

• Adjustment for differences in recording systems 

• Trace edits 

• Merge navigation with seismic 

• Spherical divergence correction (V2T) 

• Mute - First break suppression 

• Gap deconvolution based on waterbottom

- Operator Length: 240 ms

- Predictive Gap: 24 ms

- 15 trace average 

• Mutiple attenuation, Radon transform algorithm 

• DMO velocity analysis (2 km grid) 

• Bin offset regularization (Utilizing 2 km grid) 

• 3D dip moveout correction on common offsets, (V(Z)) 

• Bin fold normalization 

• Interpolation to 12.5 x 20 m bins on each common offset 

• One pass phase shift migration of each offset (V(Z)) 

• Migration velocity analysis (Moves Velocity Analysis) 0.5 km grid 

• 3D normal moveout correction (Moves Velocity Field) 

• Offset weighting - based on waterbottom 

• Mute - based on waterbottom 

• Common mid-point stack 12.5 x 20 m bins 

• Inverse migration of MOVES stack, (V(Z)) 

• One pass migration with velocity model generated from inversion of moves 

velocities (GLINVEL) 

• Datum correction to sea level +10 ms

Quality of Primary 3-D Data with 

respect to NTL Guidelines and 

Comments

• The 32 bit data were loaded as 16 bit format for interpretation and these 

data show good quality.
WR51 Proposed Location C Description of 3-D Seismic Data

• The data show significant energy in the 50 Hz range.

• Assuming a shallow section velocity of ~5500 ft/sec at 50 Hz the limit of 

separability between reflectors is approximately 27.5 ft. 

• There are no indications of over migration artifacts in the shallow section.

• The seabed reflector is continuous at faults and is characterized by a 

wavelet of stable form.

• The data are good at imaging gas.

• Faults are well imaged in the data.
0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

A

m

p

l

i

t

u

d

e

Frequency (Hz)

Reprocessed Amplitude Spectrum Well WR51_C

WR51_C

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

P

o

w

e

r

Frequency (Hz)

Reprocessed Power Spectrum Well WR51_C

WR51_C

Report No. 4064-ANA-GOM WR52C Amp and Power Spectra
Wavelet Report No. 4064-ANA-GOM

-0.6 -0.4 -0.20

0.2

0.4

0.6

0.81

-0.05-0.04-0.03-0.02-0.010 0.01 0.02 0.03 0.04 0.05

Original: 33 ft

Reprocessed:27.5ft

0.024 sec

0.021 sec

Wavelet

NormalizedAmplitude

Time (sec)
Trace: 3100.0 3200.0

WR51_D WR51_C

1027 ft

2.400

2.500

2.600

2.700

2.800

WR51_A WR51_A Inferred Lithology

and Comments

W E

Event and

Unit

Designations

Depths

BML

(ft)

BSS

(ft)

TOPHOLE PROGNOSIS CHART

LOCATION C

BLOCK 51, WALKER RIDGE AREA

Thickness

(ft)

TWT 

BSS

(s)

thole51C.cdr

Hazardous

Shallow Gas

Risk

Shallow

Water Flow

Risk

TWT: Two-Way Travel Time

BML: Below Mudline

BSS: Below Sea Surface

3-D Seismic Record at

Proposed Location C

Walker Ridge Block 51

X = 2,104,204 FT, Y = 9,767,106 FT

LINE 31700 ~1000 ft

0 5838 2.402

284 6122 2.477

404 6242 2.509

752 6590 2.601

2261 8099 3.000

SEAFLOOR

1

284 NEGLIGIBLE NEGLIGIBLE

HOR. 1

2

120 NEGLIGIBLE NEGLIGIBLE

Topsalt

3

348 NEGLIGIBLE NEGLIGIBLE

salt

1509 NEGLIGIBLE NEGLIGIBLE

468

Seafloor slopes less that 1 degree to 

southwest

Marine clays with mass transport 

deposits

Mostly clay-prone sediments with 

possible mass transport deposits

Most clay-prone deposits with possible 

sand

WR 08#1 is located 5,642 ft NE from 

proposed well WR51C.

Reflectors show a chaotic feature in the 

unit due to the vertical and lateral salt 

movement. Faults may cross the wellbore 

in the unit, but do not have clear seismic 

expression. 

Report No. 4064-ANA-GOM-WR51C Figure Appendix C-51C-1

Slope at top of salt is 5.3o to the south

All depths and thicknesses are 

approximate and are based on 

drilling report of WR08#1 provided 

by Anadarko

A possible salt stringer was found 140 ft 

above top of salt in WR08#1 well.

Possible inclusions and rafted sediments
Pos

31700.0

2800.0

31700.0

2900.0

31700.0

3000.0

31700.0

3100.0

31700.0

3200.0

31700.0

3300.0

31700.0

3400.0

31700.0

3500.0

31700.0

3600.0

Line:

Trace:

Offset: 15000 20000 25000 30000 35000 40000 45000

WR51_D WR51_C

2.400

2.500

2.600

2.700

2.800

2.900

3.000

Report No. 4064-ANA-GOM-WR51C Figure Appendix C-51C-2

3-D Seismic Record, Line 31700, Location C, Block 51, Walker Ridge Area

Two-Way Travel Time (s)

Unit 1

Unit 2

H1

Topsalt

5000 ft

WR51 WR52

R

e

l

a

t

i

v

e

A

m

p

l

i

t

u

d

e

Neg

W E

Salt Salt

Possible 

gassy 

sediments

Possible 

gassy 

sediments
30800.0

3174.0

31300.0

3174.0

31800.0

3174.0

32300.0

3174.0

32800.0

3174.0

33300.0

3174.0

Line:

Trace:

Offset: 15000 20000 25000 30000 35000 40000 45000

WR51_C

2.300

2.400

2.500

2.600

2.700

2.800

2.900

Report No. 4064-ANA-GOM-WR51C Figure Appendix C-51C-3

3-D Seismic Record, Crossline 3174, Location C, Block 51, Walker Ridge Area

Unit 1

Unit 2

Seafloor

H1

Topsalt

WR51 WR07

S N

Two-Way Travel Time (s)

5000 ft

Salt Salt

Pos

R

e

l

a

t

i

v

e

A

m

p

l

i

t

u

d

e

Neg