15070.0 13800.0
35000 40000 1.700

1.800

1.900

2.000

2.100

2.200

2.300

2.400

2.500

2.600

2.700

2.800

2.900

3.000

3.100

3.200

3.300

3.400 Line: Trace: WATER FLOW AND GAS POTENTIAL Shallow Water Flow and Gas Potential HIGH
0 1 2 3 0 = NEGLIGIBLE 1 = LOW 2 = MODERATE 3 = HIGH NEGLIGIBLE

Horizon Lithology/Stratigraphy



## Illustration MC555-A-2. Tophole Prognosis Chart, Proposed Wellsite MC555-A, Mississippi Canyon, Block 555 Potential Drilling Constraints Filename: 122117b_ill_MC555-A-2.cdr Project No. 0712-2117b

Water Flow Gas 3-D Seismic Section Through Proposed Wellsite MC555-A X = 1,109,157 FT; Y = 10,320,035 FT Inline 15070 at Crossline 13840 

# NW SE

Horizon TWT (sec, bsl) Depth (ft, bml) Depth (ft, bsl)



### INLINE 15070TWO-WAY TIME TRAVEL (SEC) SEAFLOOR

HORIZON 10

HORIZON 30

HORIZON 40 0.084

1.609 0.467

0.925 200

4,812 1,234

2,620 -4,651

-4,851

-9,463 -5,885

-7,270 

### Proposed Wellsite MC555-A

INTERFACE 2 FAULT 0.821 2,297 -6,948 Distance (ft): Horizontal

Negligible potential for encountering overpressured sands and shallow gas.

Silt- to sand-prone turbidites. Mud-dominated rotated slide blocks possible.

Muddy- to sandy turbidites. Mass-transport deposits and thick continuous sands possible. Moderate potential for encountering overpressured sands and low potential for minor shallow gas. Horizon TWT (sec, bml)

1.891

1.975

3.500 2.358

2.816 2.712 Sand-prone slope fan system. Mud-dominated rotated slide blocks possible. Mass-transport deposits underlain by muddy- to sandy turbidites. Sand-prone erosional remnants possible within the MTD.

LIMIT OF INVESTIGATION HORIZON 20 2.149 0.258 -5,300 649 Mass-transport deposits (MTD) interlayered by siltyto silty-clay turbidites.

Moderate potential for encountering overpressured sands and low potential for minor shallow gas.

Low potential for encountering overpressured sands and minor shallow gas. The Seafloor slopes less than 2° to the SE. There is no potential for benthic communities within 2,000 ft of the wellsite. The closest well lies 1.3 miles southeast of the proposed location. No shallow water flow conditions were reported at this location.

INTERFACE 1 0.628 1,709 -6,360 2.519 Mud-dominated turbidites. Sand pockets possible. Low potential for encountering overpressured sands and minor shallow gas. MC 554 MC 555

UNIT 1

UNIT 2

UNIT 3

UNIT 4

UNIT 5 Hemipelagic clay- to silt-rich sediments.**Project No. 0712-2117b Green circle represents 2,000 ft** **radius and** **outer dashed** **purple**(A)ExpulsionfeaturesFaultsGridNorthBuried raftedblocksMC 554 MC 555BACKSCATTERBuried slumpBuriedslumpExpulsionfeaturesBuried raftedblocks(C)FaultsSEAFLOOR RENDERINGGridNorthMC 554 MC 5551,000 ftMC555-A**Filename: 122117b_ill_MC555-A-3.ppt Potential for Benthic Communities** **radius and** **outer dashed** **purple circle represents 11,500 ft maximum** **anchor radius. 1,000 ft buffer beyond maximum** **anchor radius**1,000 ft(A)FaultsMC555-A**Illustration MC555-A-3 .** (B)ExpulsionfeaturesFaults1,000 ftBuried raftedblocksGridNorthSIDE-SCAN SONAR MOSAICMC 554 MC 555Buried slumpMC555-A**High reflectivity on backscatter data (A), hard returns and irregular rocky topography on sonar data (B), are indicators** **of carbonate hard grounds at expulsion sites. The rendered multibeam bathymetry (C), show some of the expulsion** **features (mounds and depressions) within the mooring radius. The presence of hard grounds are conducive for the** **growth and support of potential benthic communities. The mound-like features associated with buried rafted blocks** **lack hard returns. This validates that the features are not hydrocarbon related.** **10615 Shadow Wood Drive, Suite 200 Houston, Texas 77043**  **713.468.1410[o] 713.468.1438 [f]**

**www.gemsinc.com**



### February 20, 2013 **Project No. 0712-2117b Apache Deepwater LLC**  **2000 W. Sam Houston Parkway South Suite 1600**  **Houston, TX 77042**

**Attention: Mr. John Worthen**



## Site Clearance Letter Proposed Wellsite MC554-A Block 554 (OCS-G-34444) Mississippi Canyon Area Gulf of Mexico

**Apache Deepwater LLC (Apache) contracted Geoscience Earth & Marine Services, Inc. ®**  

### , (GEMS) to **prepare a Site Clearance Letter for the proposed well location in Block 554 (OCS G-34444), Mississippi Canyon (MC) Area. This letter addresses specific seafloor and subsurface geologic conditions around**  **the proposed location (2,000 ft radius) to the limit of investigation, 4,819 ft below the mudline (bml). Apache will drill the proposed MC554-A with a semi-submersible or dynamically positioned (DP)**  **semi-submersible. The seabed conditions within an 11,500 ft mooring radius plus an additional 1,000 ft buffer zone are discussed to satisfy seabed disturbance guidelines.**  **Surface conditions are clear at the proposed wellsite; however, moorings or other seabed disturbance activities need to avoid a potential shipwreck, possible unexploded ordnance sites, and potential sites for**  **benthic communities. Sandy units with potential for shallow water flow occur at 714 ft bml (546 ft thick) and 1,456 ft bml (492 ft thick).**  **This letter provides the following details specific to the well location: available data, attachments (accompanying the letter), Notice to Lessees (NTL) requirements, man-made features and archaeological**  **assessment, wellsite conditions, anchoring considerations, and the conclusions and recommendations.**


## Proposed Well Location and Available Data **The proposed MC554-A surface location lies in the eastern portion of MC 554 (Figure MC554-A-1). Apache provided the following coordinates:** 
Proposed Wellsite MC554-A Spheroid & Datum: Clarke 1866, NAD27 Projection: UTM Zone 16 North Line Reference Block Calls MC 554 **X: 1,108,169 ft Latitude: 28o 25’ 35.9228” N Inline 15055 631 ft FEL Y: 10,319,561 ft Longitude: 88o 39’ 22.9797” W Crossline 13849 7,721 ft FSL** 
**The details provided in this letter are based on the findings from a geohazard assessment performed by GEMS (GEMS, 2012). The report which was submitted to Apache in December, 2012 described the**  **geologic and archaeological conditions within the Guadalupe Prospect (in Blocks 554 and 555) and vicinity. Apache provided two sets of geophysical data for this assessment: a conventional,**  **3-D exploration seismic volume and a high-resolution Autonomous Underwater Vehicle (AUV) data. The detailed data specifications are provided in the main report (GEMS, 2012). Well logs and drilling**  **reports from the closest existing well (ExxonMobil #1 in MC 555) to the proposed location were also**

### Proposed Wellsite MC554-A Clearance Letter

**Apache Deepwater LLC //**  **February 20, 2013**

**Geoscience Earth & Marine Services, Inc. ®** // 2 FORUM ENERGY TECHNOLOGIES, INC. 

### provided by Apache. Integrating these data allowed a thorough analysis of potential drilling hazards **within the suprasalt stratigraphy at the proposed wellsite.**



## Attachments **The page-size maps and accompanying illustrations were extracted from the available data provided by Apache. A maximum anchor radius of 11,500 ft and an additional 1,000 ft buffer zone are included on the**  **maps should Apache use a moored rig to drill. The figures embedded within the body text are also provided below.**  **Map No. MC554-A-1: Bathymetry Map Map No. MC554-A-2: Seafloor Features Map**  **Map No. MC554-A-3: Side-Scan Sonar Mosaic Map No. MC554-A-4: Geologic Features Map**  **Illustration MC554-A-1: Portions of Inline 15055 and Crossline 13849 Showing Conditions Beneath Proposed Wellsite MC554-A**  **Illustration MC554-A-2: Tophole Prognosis Chart, Proposed Wellsite MC554-A, Mississippi Canyon, Block 554**  **Illustration MC554-A-3: Potential for Benthic Communities Figure MC554-A-1: Regional Rendering of Mississippi Canyon Area, Gulf of Mexico**  **Figure MC554-A-2: Power Spectrum Analysis Curve, Proposed Wellsite MC554-A Figure MC554-A-3: Seafloor Conditions at the Proposed Wellsite**  **Figure MC554-A-4: Suprasalt Stratigraphy between the Proposed Wellsite and ExxonMobil #1**

Figure MC554-A-1 **. Regional Rendering of Mississippi Canyon Area, Gulf of Mexico** MC554-A

MC555-A

MC555-B Grid North

MISSISSIPPI CANYON AREA

3 miles **Survey Area AUV Survey Area** 
**High-potential Archaeological Area**  **Chemosynthetic Area**

**Shallow Water flow Area Ordnance Disposal Area**  **Existing Platform**
**Existing Well**
**Proposed Well Location Existing Pipeline/**  **Umbilical** MENSA Mass-wasting Pathway Erosional Remnants

### Proposed Wellsite MC554-A Clearance Letter

**Apache Deepwater LLC //**  **February 20, 2013**

**Geoscience Earth & Marine Services, Inc. ®** // 3 FORUM ENERGY TECHNOLOGIES, INC. 

## NTL Requirements **The following letter complies with the Bureau of Ocean Energy Management (BOEM) Notice to Lessees (NTL’s) 2008-G04, 2008-G05, and 2009-G40, (MMS, 2008a, b and 2010). The requirements set forth in**  **NTL 2005-G07 are applicable because the Federal lease block MC 554 is considered to be a high probability archaeological block (MMS, 2005 and BOEM, 2011). In compliance with NTL 2005-G07, the**  **required archaeological assessment was performed by GEMS and included as an appendix in the main report (GEMS, 2012).**  **According to NTL 2008-G05 (MMS, 2008b), 3-D seismic reflection data may be used for shallow hazard assessments with approval from the BOEM, Gulf of Mexico Region. A power spectrum analysis was**  **conducted from the 3-D seismic data cube provided by Apache to illustrate the data parameters (Figure MC554-A-2). The power spectrum curve was generated within a 500 ft radius of the intersection**  **of the inline and crossline at the proposed wellsite. We converted the amplitude vs. frequency spectrum, generated by the SMT software, to power vs. frequency by squaring the amplitude values as described by**  **J. A. Coffeen, 1978.**

Figure MC554-A-2 **. Power Spectrum Analysis Curve, Proposed Wellsite MC554-A**


## Man-Made Features and Archaeological Assessment **The surface location is clear of any wells, pipelines, or platforms within a 2,000 ft radius from the proposed wellsite. The closest existing well (ExxonMobil #1) is located approximately 1.4 miles southeast**  **of the proposed wellsite location in MC 555 (Map MC554-A-1). The well was an exploratory well and is currently temporarily abandoned.**  **GEMS delineated 27 unidentified side-scan sonar contacts in the digital data within 12,500 ft (11,500 ft maximum anchor radius plus 1,000 ft buffer) of the proposed MC554-A (Maps MC554-A-2 and 554-A-3).**  **Side-Scan Sonar Contact Number 54 appears to represent a potential shipwreck. The contact is located approximately 2.3 miles southeast of the proposed wellsite and a 1,000 ft archaeological avoidance is**  **recommended around the contact. No known shipwrecks or objects exist within the area of potential effect for the proposed well location.** 

**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**Power (Amp2)

Frequency (Hz) POWER SPECTRUM

### Proposed Wellsite MC554-A Clearance Letter

**Apache Deepwater LLC //**  **February 20, 2013**

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### None of the other 26 contacts appear to represent cultural resources. Several of the unidentified sonar **contacts form part of a northeast-southwest trending debris trail in MC Blocks 554 and 598. The debris likely represents unexploded ordnance because the designated historic ordnance disposal area lies west**  **of the Guadalupe prospect (Figure MC554-A-1). The side-scan sonar contacts within 12,500 ft of the proposed wellsite forming part of the debris trail are Side-Scan Sonar Contact Numbers 43, 45-46, 48,**  **and 73-78. None of these unidentified side-scan sonar contacts are recommended for archeological avoidance or investigation, but Apache should use caution when working near the debris trail because of**  **the risk for contact with unexploded ordnance. Other similar contacts along the path of the debris trail were identified in the side-scan sonar data, but were not retained in the final contact list. Since these**  **contacts were not visible in two or more overlapping swaths of data, it was not possible to verify if the contacts represented actual debris or noise in the sonar record. A 100 ft shallow hazard avoidance is**  **recommended for the remaining 26 side-scan sonar contacts.**

Table 1. Sonar Contacts Located Within 12,500 ft of MC554-A.

No. Area Block Length (ft) Width

(ft) Height

(ft) Shape X NAD27 (ft) Y

NAD27 (ft) Avoidance

Radius (ft)

**19 MC 511 5.44 1.86 0.00 Linear 1112591.97 10329220.90 100 20 MC 511 14.68 7.23 1.75 Irregular 1112902.20 10329423.85 100**  **21 MC 511 35.69 13.33 1.24 Irregular 1112951.32 10329320.37 100 42 MC 554 12.42 6.58 0.00 Linear 1100325.29 10313357.68 100**  **43 MC 554 10.12 2.37 0.00 Linear 1101971.94 10312550.76 100 44 MC 554 16.49 7.46 0.00 Irregular 1102351.14 10324394.30 100**  **45 MC 554 26.64 9.48 0.00 Irregular 1102457.87 10313328.31 100 46 MC 554 16.93 3.61 0.00 Linear 1102620.96 10313548.00 100**  **47 MC 554 13.22 2.94 0.00 Linear 1102642.15 10327125.63 100 48 MC 554 12.65 4.52 0.00 Linear 1103307.63 10315340.61 100**  **49 MC 554 11.29 3.64 0.00 Linear 1104028.27 10311991.31 100 50 MC 555 11.52 4.74 0.00 Irregular 1112644.89 10312564.17 100**  **51 MC 555 10.50 8.70 0.00 Linear 1113273.53 10315889.23 100 52 MC 555 11.52 2.48 0.00 Linear 1116727.29 10314034.61 100**  **53 MC 555 20.24 5.06 0.00 Linear 1118118.76 10326028.12 100 54**  **MC 555**  **42.49 24.57**  **0.00 Irregular**  **1119186.80 10314174.41**  **1,000 73 MC 598 15.67 5.79 0.00 Linear 1100286.61 10310357.55 100**  **74 MC 598 9.26 3.17 0.00 Linear 1100695.83 10310457.55 100 75 MC 598 7.48 2.30 0.00 Linear 1100794.98 10310635.80 100**  **76 MC 598 15.20 3.37 0.00 Linear 1101123.39 10311196.89 100 77 MC 598 10.12 2.17 0.00 Linear 1101235.39 10311328.45 100**  **78 MC 598 9.00 2.18 0.00 Linear 1101247.04 10311266.08 100 82 MC 598 10.86 2.08 0.00 Linear 1105782.24 10308511.16 100**  **83 MC 598 10.86 2.65 0.00 Linear 1106972.13 10311235.93 100 86 MC 599 17.16 18.29 0.00 Irregular 1110651.55 10309177.14 100**  **87 MC 599 14.68 5.20 0.00 Linear 1111038.82 10307413.92 100 89 MC 599 15.74 5.94 0.00 Linear 1113261.85 10308889.05 100**  ***Blue indicates a recommended archaeological avoidance.**



## Wellsite Conditions **The proposed surface location is clear of any constraining seafloor geologic conditions as defined by the available geophysical data. MC554-A is not expected to intersect faults (seabed or buried) and the**  **potential for encountering significant amounts of shallow gas is low. However, there is a moderate potential for encountering shallow water flow within possible overpressured sands.** 

### Proposed Wellsite MC554-A Clearance Letter

**Apache Deepwater LLC //**  **February 20, 2013**

**Geoscience Earth & Marine Services, Inc. ®** // 5 FORUM ENERGY TECHNOLOGIES, INC. 

### Water Depth and Seafloor Conditions **The water depth at the proposed surface location is approximately -4,647 ft and the seafloor slopes southeast at less than 1° (Map MC554-A-1). Side-scan sonar data show that the seabed in the vicinity of**  **the proposed wellsite is primarily characterized by uniform low reflectivity (Map MC554-A-3). The low reflectivity is likely associated with very soft clays.**  **The proposed wellsite MC554-A is located along a relatively shallow mass-wasting pathway trending northwest-southeast across the Survey Area (Figure MC554-A-1 and Map MC554-A-2). The hummocky**  **topography within the vicinity of the proposed location represents the seafloor expression of buried slumps. The slumps are buried by more than 100 ft of strata (Figure MC554-A-3, GEMS, 2012). Mound-like**  **features in the same area are associated with rafted blocks within the mass-transport deposits (MTD) matrix and are not hydrocarbon related (GEMS, 2012). A drainage feature (gully) located approximately 950 ft to**  **the northwest suggests low-level sediment transport activities in the recent geologic past (> 10,000 yrs), Figure MC554-A-1.** 

Figure MC554-A-3 **. Seafloor Conditions at the Proposed Wellsite** 

### Deepwater Benthic Communities **BOEM and BSEE did not designate Federal lease Block MC 554 as having high-density deepwater benthic communities (MMS, 2010). There are no apparent geophysical indicators at the seafloor or at**  **depth that would suggest conditions capable of supporting significant deepwater benthic communities within 2,000 ft of the proposed wellsite (Maps MC554-A-2 and 554-A-3).**  

### Stratigraphy **Stratigraphic conditions are shown on Illustrations MC554-A-1 and 554-A-2. The lithology at the proposed wellsite was inferred by integrating the seismic facies with the well log response at the existing**  **well, ExxonMobil #1. Generally, the suprasalt seismic facies were correlated across both locations; however, only remnants of the sand-prone channel system observed within Unit 4 at ExxonMobil #1 is**  **present at the proposed location (Figure MC554-A-4). The sediments below the seafloor to the limit of** Portion of AUV Line 130

**Seafloor expression of rafted blocks** 

**500 ft**

**Assumed velocity: 5,000 ft/sec** W E**Two-way travel time (secs) Horizontal**  **Distance (ft)** Proposed Wellsite MC554-A **138 ft north of AUV Line 130**

**Weakly stratified** INDEX MAP

AUV Line 130

**Seafloor expression of rafted blocks**  Grid North

MC 554

**1,000 ft** MC554-A

**Circle represents 2,000 ft radius around**  **proposed wellsite Gully** 

**10 ft** Seafloor Rendering **Buried slump**

**Mound-like features at the seabed represent the seafloor expression of**  **rafted blocks within buried slumps. The slumps are buried by more than**  **100 ft of strata. The lack of direct hydrocarbon**  **indicators (DHI) at these sites confirm that the features are not hydrocarbon**  **related. See the main report for more details (GEMS, 2012).**  **Shallow strata comprises of hemipelagic clay- to silt-rich**  **sediments. Well-layered**  **unit**

### Proposed Wellsite MC554-A Clearance Letter

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### investigation (4,819 ft bml or -9,466 ft bsl) **consist primarily of hemipelagic clays, muddy- to sa nd-prone**  **turbidites, slope fan deposits, and mass-transport deposits. The shallow stratigraphy (Seafloor to Horizon 10, Unit 1) is interpreted to be hemipelagic clay- to silt-rich**  **sediments down to approximately 205 ft bml. The sediment units between Horizon 10 and Horizon 30 (Units 2 and 3) are dominated by mass-transport deposits (MTD) with intermittent silty- to sandy turbidites**  **to approximately 1,260 ft bml. Sand-prone erosional remnants from older strata are possible within the MTD matrix. Unit 3 is associated with a regional basin-floor fan system known as the “Blue Unit” (GEMS,**  **2012). The low gamma ray log response (inferring sand) at ExxonMobil #1 suggests that there is a high potential for sandy turbidites within the Blue Unit between 714 ft bml and 1,260 ft bml**  **(Figure MC554-A-4). Remnants of a sand-prone channel system occur in the upper portion of Unit 4 (Horizon 30 to**  **Horizon 40). A vertical borehole at the proposed location will intersect the channel system from approximately 1,456 ft bml to 1,948 ft bml. The lower portion of the strata to approximately 2,732 ft bml**  **comprises of mud-dominated rotated slide blocks and silt- to sand-prone turbidites. The underlying strata, Unit 5 (Horizon 40 to the limit of investigation) comprises of muddy- to sandy turbidites and**  **possibly MTDs. Thick, continuous sand layers are possible within this sediment unit (between 2,732 ft bml and 4,819 ft bml), Figure MC554-A-4.** 

Figure MC554-A-4 **. Suprasalt Stratigraphy between the Proposed Wellsite and ExxonMobil #1**


### Faults **A vertical wellbore at the proposed location will not penetrate seafloor or buried faults between the seafloor and the limit of investigation (Illustrations MC554-A-1 and 554-A-2). The top of the nearest**  **buried fault occurs at approximately 1,400 ft northwest of the proposed wellsite MC554-A. The fault is downthrown southeast towards the wellbore and is buried by up to 2,700 ft of sediments.**  INDEX MAP

Seafloor Rendering Grid North

MC 554

**2,000 ft** MC554-A

**Circle represents 2,000 ft radius around proposed**  **wellsite** ExxonMobil #1

MC 555

MC 599**Two-way travel time (secs) Horizontal**  **Distance (ft)** Proposed Wellsite MC554-A ExxonMobil #1

**MC 599**

**MC 555 MC 554** 

Arbitrary Line A-A` **5,000 ft** NW SE **Seafloor**

**H orizon 10** 

**Horizon 20**

**Horizon 30**

**Horizon 40**

**Limit of Investigation**  GR R GR - Gamma Ray R - Resistivity

**UNIT 1**

**UNIT 2**

**UNIT 3**

**UNIT 4**

**UNIT 5 Channel** 

**Generally, the suprasalt stratigraphy at the existing well location (ExxonMobil #1) and**  **the proposed wellsite MC554-A is similar. The main difference observed is within Unit 4**  **where only remnants of the channel system exist at the proposed location.**  **The 22” casing got stuck and was later jarred free at ExxonMobil #1. The casing was stuck**  **in possibly clay-prone sediments within the channel system in Unit 4.**  Relative Amplitude **High Low**  Blue Unit

22” casing stuck

### Proposed Wellsite MC554-A Clearance Letter

**Apache Deepwater LLC //**  **February 20, 2013**

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### Shallow Gas and Shallow Water Flow **The scout tickets from ExxonMobil # 1 did not report any shallow geohazard conditions related to shallow water flow and/or shallow gas. As a result, significant shallow gas is not expected at the proposed**  **wellsite; however, a moderate potential for shallow water flow is possible within the identified sand prone sequences (Illustration MC554-A-2).** 
Shallow Gas. **There are no apparent subsurface high-amplitude anomalies directly below the proposed location (Map MC554-A-4). The potential for encountering shallow gas is considered negligible in the**  **clay-prone unit between the Seafloor and 714 ft bml. There is a low potential for encountering significant accumulations of shallow gas in underlying sand-prone layers above the limit of investigation**  **(4,819 ft bml).**
Shallow Water Flow. **There is a moderate potential for encountering overpressured sands within the Blue Unit, Unit 3 (714 ft bml to 1,260 ft bml) and the underlying sand-prone channel remnants (1,456 ft**  **bml to 1,948 ft bml), Illustration MC554-A-2. Although, numerous wells in the Mississippi Canyon Area have experienced water flow within the Blue Unit, no such occurrence was reported at ExxonMobil #1.**  **Potential overpressures may have been mitigated while drilling the well, and hence not reported. A low potential for shallow water flow is interpreted between 1,260 ft bml to 1,456 ft bml and beneath**  **1,948 ft bml. The shallow, clay-rich sediments (Seafloor to 714 ft bml) are considered to have a negligible potential for shallow water flow.**  

## Anchoring Considerations **The 11,500 ft radius outlined on the accompanying maps represents the area of potential effect for anchoring. An additional 1,000 ft buffer zone is also included. The following discussions address the**  **seafloor conditions related to anchoring considerations within the total 12,500 ft radius.** 

### Water Depth and Seafloor Conditions **Water depths within the potential mooring area range from about -4,440 ft to -4,830 ft (Map MC554-A-1). The seafloor slopes southeast with shallow water depths in the western portion of the mooring radius.**  **Seafloor gradients within the mooring radius range from nearly flat to approximately 42° (GEMS, 2012). Most of the seafloor has low gradients (less than 3°).**  **Irregular seafloor morphology within the potential mooring area is associated with erosion-related features (e.g. gullies and erosional scarps) and seep-related features (e.g. mounds and pockmarks),**  **Map MC554-A-2. The hummocky seafloor across most of the remaining area represents shallow buried slumps and the mound-like features within the slumps represent buried rafted blocks (Figure MC554-A-3).**  **Seafloor slopes associated with the erosion-related and seep-related features range from 5° to 13° (GEMS, 2012).**  **Seafloor faulting is located in the northeastern portion of the radius in central MC 555. The faults trend northeast-southwest, are downthrown mainly to the northeast, and bound the expulsion features.**  **Seafloor offsets associated with the faults are up 50 ft with associated slopes reaching 42°.** 

### Deepwater Benthic Communities **The expulsion features that exhibit high backscatter reflectivity and “rocky” topography on sonar data are likely associated with carbonate hard grounds (conditions conducive for benthic communities),**  **Map MC554-A-3 and Illustration MC554-A-3. These expulsion features have a high potential for supporting densely populated benthic communities and are shown as orange polygons on**  **Map MC554-A-2. The features lacking irregular topography but still exhibit high backscatter and sonar reflectivity represent limited hard ground areas. These sites have a lower potential for supporting seep**  **communities and are shown as green polygons on Map MC554-A-2. BOEM requires at least a 250 ft buffer around potential benthic community sites for all proposed seafloor**  **disturbances (including those caused by anchors and anchor chains), MMS, 2010. However, if seafloor disturbances occur within 500 ft of these sites, Apache is required to submit an as-placed anchor plat to** 

### Proposed Wellsite MC554-A Clearance Letter

**Apache Deepwater LLC //**  **February 20, 2013**

**Geoscience Earth & Marine Services, Inc. ®** // 8 FORUM ENERGY TECHNOLOGIES, INC. 

### BOEM. We recommend conducting an ROV investigation to confirm or deny the existence of deepwater **benthic communities at the potential hard grounds if these areas occur near the proposed anchors or anchor chains.** 



## Conclusions and Recommendations **We appreciate the opportunity to be of service to Apache and look forward to working with Apache on future projects. The conclusions and recommendations from this assessment are as follows:** 


### Wellsite Conditions **No major seafloor hazards or constraints are defined by the available data within 2,000 ft radius of the proposed location. Caution and possible mitigation is recommended when encountering potential**  **overpressured sands between 714 ft bml to 1,260 ft bml, and 1,456 ft bml to 1,948 ft bml.**


### Anchor Maximum Radius Conditions **The potential seafloor constraints within the mooring radius include possible hard grounds that could support benthic communities, a potential shipwreck, and possible unexploded ordnance sites.**  **A minimum of a 250 ft radius is recommended around the potential benthic communities’ sites. Other recommendations include, a 1,000 ft archaeological avoidance around Side-Scan Sonar Contact Number**  **54, and a 100 ft shallow hazard avoidance for the remaining 26 side-scan sonar contacts. Care should be taken near the debris trail of potential unexploded ordnance in MC 554 and 598. All operations must**  **cease and BOEM notified within 48 hours should any potentially historic materials such as textiles, wood, ceramics, or other items be uncovered during operations in the area.** 

**Sincerely,**
GEOSCIENCE EARTH & MARINE SERVICES, INC. ®



### Oluwayomi Oyedele **Daniel Lanier Geoscientist**  **Vice President-Geosciences**

**Erin Williams Janes Project Manager/Senior Geoscientist** 
**Attachments (4 Maps and 3 Illustrations)**
**Distribution: Mr. John Worthen, Apache Deepwater LLC (3 copies)** 

REFERENCES **Bureau of Ocean Energy Management, 2013, ASCII Data Files, published on the BOEM Gulf of Mexico Region Homepage, <http://www.gomr.boem.gov/homepg/pubinfo/freeasci/freedesc.html>, accessed January, 2013.**  **Bureau of Ocean Energy Management, 2012, Seismic Water Bottom Anomalies Map Gallery, published on the BOEM Homepage, <http://www.boem.gov/Oil-and-Gas-Energy-Program/Mapping-and-Data/Map-Gallery/Seismic**  **Water-Bottom-Anomalies-Map-Gallery.aspx>, accessed November, 2012.**

### Proposed Wellsite MC554-A Clearance Letter

**Apache Deepwater LLC //**  **February 20, 2013**

**Geoscience Earth & Marine Services, Inc. ®** // 9 FORUM ENERGY TECHNOLOGIES, INC. **Bureau of Ocean Energy Management, 2011, Notice to lessees and operators (NTL) of federal oil and gas leases and pipeline right-of-way (ROW) holders on the outer continental shelf (OCS), Revisions to the list of OCS lease**  **blocks requiring archaeological resource surveys and reports: U. S. Department of the Interior, Bureau of Ocean Energy Management, Bureau of Safety and Environmental Enforcement Gulf of Mexico Region (GOMR), NTL 2011-**  **JOINT-G01. Effective Date December 29, 2011. Coffeen, J. A., 1978, Seismic Exploration Fundamentals: Tulsa, the Petroleum Publishing Co., p. 125.**  **Geoscience Earth & Marine Services, Inc. ®**  **(GEMS), 2012, Geohazard assessment, Guadalupe Prospect, blocks 554 and 555, Mississippi Canyon Area, Gulf of Mexico, Project No. 0712-2117b.**  **Minerals Management Service, 2005, Notice to lessees and operators of federal oil, gas, and sulphur leases and pipeline right-of-way holders in the outer continental shelf, Gulf of Mexico OCS region, Archaeological resource**  **surveys and reports: U. S. Department of the Interior, Minerals Management Service, Gulf of Mexico, NTL 2005-G07. Minerals Management Service, 2008a, Notice to lessees and operators of federal oil, gas, and sulphur leases and**  **pipeline right-of-way holders in the outer continental shelf, Gulf of Mexico OCS region, information requirements for exploration plans and development operations coordination documents: U. S. Department of the Interior, Minerals**  **Management Service, Gulf of Mexico, NTL 2008-G04. Minerals Management Service, 2008b, Notice to lessees and operators of federal oil, gas, and sulphur leases and**  **pipeline right-of-way holders in the outer continental shelf, Gulf of Mexico OCS region, shallow hazards requirements: U. S. Department of the Interior, Minerals Management Service, Gulf of Mexico, NTL 2008-G05.**  **Minerals Management Service, 2010, Notice to lessees and operators of federal oil and gas leases in the outer continental shelf, Gulf of Mexico OCS region, deepwater benthic communities: U. S. Department of the Interior,**  **Minerals Management Service, Gulf of Mexico, NTL 2009-G40. Effective Date January 27, 2010.**