10615 SHADOW WOOD DRIVE 

SUITE 200 

HOUSTON, TEXAS 77043 

Phone: (713) 468-1410 

Fax: (713) 468-1438 

E-mail: gems@gemsinc.com

November 4, 2011 Project No. 0210-1741 

Noble Energy, Inc. 

100 Glenborough, Suite 100 

Houston, TX 77067 

Attention: Mr. Glenn Adams 

Site Clearance Letter 

Proposed Wellsite “C” 

Block 949 (OCS G-32363) 

Mississippi Canyon Area 

Gulf of Mexico 

Geoscience Earth & Marine Services, Inc.®, (GEMS) was contracted by Noble Energy, Inc., (Noble) to 

prepare a Site Clearance Letter for the Proposed Wellsite “C” in Block 949 (OCS G-32363), Mississippi 

Canyon (MC) Area. This letter addresses specific seafloor and subsurface conditions near the proposed 

location to the top of salt at a depth of about 3,544 ft below the mudline (bml). 

This wellsite assessment is based on findings provided within the main body of the geohazard report 

“Geologic and Stratigraphic Assessment, Blocks 904-905, 948-949, 991-993, and Portions of the 

Surrounding Blocks, Mississippi Canyon Area, Gulf of Mexico” (GEMS Report No. 0210-1741). The text, 

maps, and figures included in the above report provide detail on the regional geology of the Study Area. 

This letter supplements that report with details pertaining directly to the proposed wellsite. 

The surface location for the proposed “C” wellsite lies in the northwestern quadrant of MC 949. Noble 

provided the following coordinates for the proposed location: 

Proposed Wellsite “C” 

Spheroid & Datum: Clarke 1866, NAD27 

Projection: UTM Zone 16 North Line Reference Block Calls MC 949 

X: 1,080,790 ft Latitude: 28.039029125o N Inline 13245 3,670 ft FWL 

Y: 10,179,010 ft Longitude: -88.735290552o W Crossline 11897 6,110 ft FNL 

Attachments 

Wellsite maps are centered on the proposed “C” location and are displayed at a scale of 1:12,000. The 

maps included in this letter are as follows: 

Map 949-C-1: Bathymetry Map 

Map 949-C-2: Seafloor Rendering 

Map 949-C-3: Seafloor Amplitude Rendering 

Map 949-C-4: Side-Scan Sonar Mosaic 

Map 949-C-5: Geologic Features Map 
Project No. 0210-1741 

 - 2 - Wellsite MC 949 “C” 

The figures accompanying this letter were extracted from the 3-D data volume. The figures listed below 

are centered on the proposed well location. 

Figure 949-C-1: Power Spectrum Curve, Proposed Wellsite MC 949 “C” 

Figure 949-C-2: Portions of Inline 13245 and Crossline 11897 Showing Conditions Beneath Proposed 

Wellsite MC 949 “C” 

Figure 949-C-3: Tophole Prognosis Chart, Proposed Wellsite MC 949 “C”, Mississippi Canyon Block 

949 

NTL Requirements 

This wellsite assessment complies with the Bureau of Ocean Energy Management (BOEM, formerly 

Minerals Management Service, MMS) Notice to Lessees (NTL’s) 2008-G04, 2008-G05, and 2009-G40 

(MMS, 2008a, b, and 2009). NTL 2008-G06 is also pertinent with respect to pre- and post-spud ROV 

visual inspection surveys (MMS, 2008d). 

The above-stated Federal lease block is located within a historically significant area (MMS, 2008c); 

therefore, requirements set forth in NTL 2005-G07 (MMS, 2005) are applicable. Fugro Geoservices, Inc., 

(2007) conducted an archaeological survey and compiled an assessment for Noble covering most of 

MC 949. Their results in regards to the proposed location are mentioned herein. If anchors are planned 

beyond the extent of the current archaeological survey, an additional archaeological survey and assessment 

will be required at and around the planned anchor locations. 

In accordance with NTL 2008-G04 and NTL 2008-G05 (MMS, 2008a,b), we have extracted the power 

spectrum diagram (Figure 949-C-1) from the 3-D seismic data cube. The extraction was generated within 

a 500-ft radius of the intersection of the inline and crossline at the proposed wellsite. The amplitude 

versus frequency spectrum, generated by the SMT software, was converted to power versus frequency by 

squaring the amplitude values as described by J. A. Coffeen, 1978. 

Figure 949-C-1. Power Spectrum Curve, Proposed Wellsite MC 949 “C” 

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Power

Frequency

POWER SPECTRUM
Project No. 0210-1741 

 - 3 - Wellsite MC 949 “C” 

Man-Made Features 

There are no existing wellsites in MC 949. Two existing exploration wellsites are located in MC 948 

(Maps 949-C-1 through 949-C-5). The MC 948 #1 well was spudded on May 19, 2008, but abandoned 

within a week because of shallow water flow problems. The wellsite was moved approximately 160 ft to 

the southwest and MC 948 #2 was spudded on May 25, 2008. MC 948 #1 is located approximately 

9,700 ft southwest of the proposed “C” location. MC 948 #2 is approximately 9,800 ft southwest of the 

proposed location.

Mariner’s 8-inch gas pipeline and 3-inch umbilical trend north-south through MC 949, east of the proposed 

location (Map 949-C-1). The closest point to the proposed location is approximately 1,500 ft. A 2-inch, 

BP fiber-optic cable trends southwest-northeast across MC 948, 904, and 905 (Map 949-C-1). Its closest 

point to the proposed “C” location is approximately 11,600 ft to the northwest. 

An evaluation of high-resolution geophysical data collected within MC 949 and the surrounding blocks 

indicates the area is clear of any unusual seafloor targets that could represent shipwreck remains or debris 

of archaeological significance (Fugro Geoservices, Inc., 2007), see Map 949-C-4. 

Wellsite Conditions 

The surface location is clear of any geologic constraints within 2,000-ft of proposed wellsite. 

Water Depth, Slope, and Seafloor Sediments. The water depth at the proposed location is 

approximately -5,956 ft (Map 949-C-1). The seafloor at the proposed site dips to the southwest at 

approximately 1.0° (1.7%). The proposed location occurs in a relatively flat area where the seafloor is 

smooth and featureless (Maps 949-C-1 and 949-C-2). The near-surface sediments are expected to be 

normally consolidated, soft clays forming a drape over the area. 

Deepwater Benthic Communities. The Seafloor Amplitude Rendering (Map 949-C-3) shows normal or 

ambient amplitudes along the seabed near the proposed wellsite. There is no evidence of hydrocarbon 

seepage within 2,000 ft of the proposed location, and the potential for high-density deepwater benthic 

communities is negligible (Map 949-C-4). 

Stratigraphy. The stratigraphy at the proposed well location is illustrated on Figures 949-C-2 and 

949-C-3. The Tophole Prognosis Chart (Figure 949-C-3) shows the inline annotated with calculated 

depths to the various horizons and predicted lithology of the sequences, along with their potential for 

shallow water flow and shallow gas. In general, the sediments between the seafloor and the top of salt 

(3,544 ft bml) consist of hemipelagic clays and stratified turbidites, interbedded with mass-transport 

deposits. 

The potential for encountering sands is highest within slope-fan and channel complexes from 821 ft to 

1,386 ft bml and 2,206 ft to 2,797 ft bml (Figure 949-C-3). These stratigraphic units consist of turbidite 

and slope-fan deposits that have been modified by submarine slides and mass-wasting events. The 

potential sands between 821 ft to 1,136 ft bml are likely to be discontinuous; however, the section between 

1,136 ft and 1,386 ft bml appears to be fill at the base of a channel or failure zone. Coarse sands may be 

ponded within this erosional low. 

Flat-lying turbidites are interbedded with channelized intervals and mass-transport deposits between 

2,206 ft and 2,797 ft bml. Immediately above the sediment/salt interface is a rubble-like zone consisting of 

chaotic, discontinuous to amorphous reflectors. The deformation of this zone is the result of salt 

movement. The sediments within the zone are probably turbidites and mass-transport deposits consisting 

of clays and silts, interspersed with thin, discontinuous sands. 
Project No. 0210-1741 

 - 4 - Wellsite MC 949 “C” 

Faults. The proposed wellsite will not penetrate any seafloor or buried faults in the shallow section to the 

top of salt at 3,544 ft bml (Figures 949-C-2 and 949-C-3). The nearest fault occurs approximately 270 ft 

north of the planned borehole between 1,386 ft and 2,206 ft bml. The fault does not extend to the seafloor 

making it geologically inactive. 

Shallow Water Flow. The potential for shallow water flow is considered moderate within the slope-fan 

sequence between 821 ft and 1,386 ft bml (Figure 949-C-3). This interval correlates to the “Green Unit”, a 

regional slope-fan and channel complex. These turbidite and slope-fan deposits appear to be modified by 

mass-wasting events at the proposed location. Potential sands in the upper portion of this section (821 ft to 

1,136 ft bml) appear discontinuous and are unlikely to produce sustained flow; however, the MC 948 #1 

well flowed within this unit (MMS, 2010b). The base of the section between 1,136 ft and 1,386 ft bml 

appears to be the fill material in an erosional cut and shows slightly elevated amplitudes. Sand layers and 

pockets may have ponded at this location. 

A moderate potential for encountering overpressured sands also occurs between 2,206 ft and 2,797 ft bml 

(Figure 949-C-3). Potentially thick and continuous sand deposits may exist within these stratified 

slope-fan deposits. 

The intervals from 398 ft to 821 ft bml and 2,797 ft to 3,544 ft bml have a low potential for shallow water 

flow. Thin sands may be encountered within these intervals, but the sands are discontinuous and unlikely 

to produce sustained flow. 

Shallow Gas. The potential for encountering shallow gas at the proposed wellsite is negligible to low. 

There are no high-amplitude anomalies in the shallow stratigraphy near the proposed wellsite (Map 949-C5). A low potential is assigned to the slope-fan intervals from 1,136 ft to 1,386 ft bml and 2,206 ft to 

2,797 ft bml (Figure 949-C-3). Continuous sands may be encountered in the 2,206 ft to 2,797 ft bml 

interval, while discontinuous sands are likely in the sequence between 1,136 ft to 1,386 ft bml. The 

elevated amplitudes in these intervals suggest a potential increase in minor amounts of solution gas within 

sand-rich layers. 

Anchoring Considerations 

An anchored drilling vessel is likely to be used for the proposed wellsite. The exact anchor pattern for the 

proposed location is undetermined. An anchoring radius representing a typical maximum length of chain 

and anchor on bottom is displayed at 10,000 ft from the proposed wellsite (Maps 949-C-1 through 949-C5). An additional 1,000-ft buffer beyond the maximum anchor radius was also assessed per MMS NTL 

2009-G40 (MMS, 2009). 

Seafloor Conditions. The seafloor throughout the northwestern portion of the anchor radius and buffer is 

irregular and hummocky, while the southeastern half is generally smooth and featureless (Maps 949-C-1 

and 949-C-2). A southwest to northeast trending ridge extends across the northwestern portion of the 

proposed anchor radius (Maps 949-C-1 and 949-C-2). The ridge is irregular in the far western portion of 

the anchor radius along the eastern flank of a large, diamond-shaped bathymetric high (Map 949-C-2). 

Gradients in this area approach 20o. The ridge is more subtle to the northeast of the high with gradients 

approaching 10o. The hummocky seafloor in the northwestern portion of the anchor radius has slopes 

generally less than 5o. 

Several seafloor faults occur along the northeastern edge of the anchor radius (Map 949-C-2). These faults 

trend northwest to southeast and are downthrown to the northeast, forming the southwestern flank of a 

graben. 

Deepwater Benthic Communities. There are no elevated seafloor amplitudes within the proposed anchor 

radius (Map 949-C-3). Seafloor staining visible in the sonar mosaic, however, suggests gas/fluid has 

vented to the seafloor along some of the faults in the northeastern portion of the anchor radius 

(Map 949-C-4 and 949-C-5). Anchors should avoid the seafloor faults and associated gas venting. 
Project No. 0210-1741 

 - 5 - Wellsite MC 949 “C” 

Archaeological Blocks. No targets of potentially cultural importance were identified in this area (Fugro 

Geoservices, 2007), see Map 949-C-4. Based on the available data, a sonar contact was identified in the 

northeastern portion of MC 992. The sonar contact appears to be either wire rope or a wooden shipwreck. 

Per the MMS database, the sonar contact was listed as a possible natural feature, such as a seafloor 

outcropping (personal communication with Ms. K. Faulk, access to MMS database 2008, April 15, 2010). 

We cannot confirm or deny this based on the available data. 

The sonar contact is located approximately 3,100 ft southwest of the proposed anchor radius buffer 

(Map 949-C-5). No avoidance zones were designated within the potential anchor radius and buffer. 

Existing Infrastructure. Mariner’s 8-inch gas pipeline and 3-inch umbilical trend generally north to 

south across the eastern portion of the anchor radius (Map 949-C-5). A 500-ft avoidance zone surrounds 

the existing pipeline and umbilical. 

The MC 948 #1 and #2 wells occur within the southwestern portion of the anchor radius (Map 949-C-5). 

A 500-ft avoidance zone surrounds the existing wells. 

Closing 

The Proposed Wellsite MC 949 “C” in Mississippi Canyon Area, Block 949, appears suitable for 

exploration drilling operations. 

Overpressured sands are possible within the slope-fan sequences from 821 ft to 1,386 ft bml and 2,206 ft to 

2,797 ft bml. Potential sands encountered in the upper interval are likely discontinuous, while the lower 

unit probably contains more continuous sands. The potential for shallow water flow and shallow gas is 

elevated in these intervals. 

Anchoring conditions are generally favorable throughout the proposed anchor radius. Conditions are 

relatively smooth and featureless in the southeastern half of the anchor radius; however, anchor locations 

should avoid an existing pipeline and cable trending north-south across this area. The seafloor in the 

northwestern half of the anchor radius ranges from irregular and hummocky. Irregular seafloor associated 

with the eastern flank of a large, diamond-shaped bathymetric high exists in the far western portion of the 

anchor radius. Steep seafloor gradients (>15o) occur in this area. Gradients approaching 10o occur along a 

ridge extending to the northeast from the high. Several seafloor faults occur along the northeastern edge of 

the proposed anchor radius. There is evidence of gas venting along some of the faults. The faults and 

associated venting should be avoided by anchors. 

The proposed well will be required to follow NTL 2008-G06 (MMS, 2008c) with respect to pre- and 

post-spud ROV visual inspection surveys. 
Project No. 0210-1741 

 - 6 - Wellsite MC 949 “C” 

We appreciate the opportunity to be of service to Noble, and look forward to working closely with you on 

other projects. 

Sincerely, 

GEOSCIENCE EARTH & MARINE 

SERVICES, INC.®

Christopher J. Madere Daniel L. Lanier 

Senior Geoscientist Vice President - Geoscience 

Attachments (5 Maps and 3 Figures) 

Distribution: 

Mr. Glenn Adams, Noble Energy, Inc., Houston, TX (4 copies) 

REFERENCES 

Bureau of Ocean Energy Management, 2011a, ASCII Data Files, published on the BOEM Gulf of Mexico Region Homepage, 

<http://www.gomr.boemre.gov/homepg/pubinfo/freeasci/freedesc.html>, Accessed October, 2011. 

Bureau of Ocean Energy Management, 2011b, Safety performance review - shallow waterflows can pose significant hazards to 

deepwater drilling, http://www.gomr/boemre.gov/homepg/offshore/saftey/waterflow/wtrflow.html website accessed October, 

2011. 

Coffeen, J. A., 1978, Seismic exploration fundamentals: PPC books, a division of Petroleum Publishing Co., Tulsa, Ok. 277 p. 

Fugro Geoservices, Inc., 2007, Archaeological assessment, block 948, Mississippi Canyon Area, Gulf of Mexico: Fugro Report 

No. 2407-5001. 

GEMS, 2010, Geologic and stratigraphic assessment, blocks 904-905, 948-949, 991-993, and portions of the surrounding blocks, 

Mississippi Canyon Area, Gulf of Mexico: GEMS Report No. 0210-1741. 

Minerals Management Service, 2005, Notice to lessees and operators of federal oil, gas, and sulphur leases and pipeline right-ofway 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. Effective Date July 1, 2005. 

Minerals Management Service, 2008a, Notice to lessees and operators of federal oil, gas, and sulphur leases 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. 

Effective Date May 1, 2008. 

Minerals Management Service, 2008b, Notice to lessees and operators of federal oil, gas, and sulphur leases and pipeline right-ofway holders in the outer continental shelf, Gulf of Mexico OCS region, shallow hazards program: U. S. Department of the Interior, 

Minerals Management Service, Gulf of Mexico, NTL 2008-G05. Effective Date May 1, 2008. 

Minerals Management Service, 2008c, Notice to lessees and operators of federal oil and gas leases and pipeline right-of-way 

holders on the outer continental shelf, Gulf of Mexico OCS region, Revisions to the list of OCS lease blocks requiring 

archaeological resource surveys and reports: U. S. Department of the Interior, Minerals Management Service, Gulf of Mexico, 

NTL 2008-G20. Effective Date October 20, 2008. 

Minerals Management Service, 2008d, Notice to lessees and operators of federal oil, gas, and sulphur leases and pipeline right-ofway holders in the outer continental shelf, Gulf of Mexico OCS region, Remotely Operated Vehicle Surveys in Deepwater: U. S. 

Department of the Interior, Minerals Management Service, Gulf of Mexico, NTL 2008-G05. Effective Date May 26, 2008. 

Minerals Management Service, 2009, Notice to lessees and operators of federal oil, gas, and sulphur leases and pipeline right-ofway holders 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.