macondo gh swf bd 09092011

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Macondo GH-SWF-BD 11092011.doc 11th September 2011 Page 1 of 17

Macondo Gas Hydrates Shallow Water Flows and Burst Disks

Introduction

Macondo MC 252 is in an area of well known severe geological hazards (known asgeohazards, including gas hydrates, slump deposits, weak surface soils, seabed moundsand permeable shallow (< 5,000 ft BML) artesian water pressurised sand layers which cancause casing distortion and even buckling collapse, high inflow of drilling fluids, washout andpartial collapse of those layers due to rapid or poorly controlled drilling operations. Ignore thegeology at your peril.

The plot below shows the Macondo well together with the Texaco Rigel well [OCS-G-18207#1], drilled in 1999 in 5200 water depth and a number of seabed dome features, Biloxi,Gloria and Marshall. Purple markers are the locations of seabed seeps reported andsurveyed in 2010 by NOAA (Ref. 9).

Well site selection appears to have been based upon maximising the distance from thesefeatures. However it is of note that the following reports mentioned in the BP original MMSapproved Application Permit to Drill (Ref. 14, Attachment 9, p. 11, Shallow Water Flow ZoneManagement) and the Initial and Supplemental Exploration Plans (Refs. 4 and 5, Section3.1, Geological and Geophysical Information) do not appear to have been referred to orlisted in any of the post-spill investigative Macondo reports to date and appear to be

unavailable in the Public Domain.


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a) A regional shallow hazards survey and study carried out in 1998 by KC Offshore, an

independent business development company;b) High resolution 2D seismic data along with 3D exploration seismic data collected by Fugro

Geoservices in 2003, and mapping of the block by BP America in 2008 and 2009.

c) A site specific Shallow Hazards and Archaelogical Assessment produced by C & Ctechnologies in 2009 base upon AUV data acquired in January 2009.

What remains to be explained is the reason why this blow-out did not get contained likemany others in the past in similar conditions and water depths, but was so utterly disastrous.

This report contends that the source of this gas was shallow melted gas hydrates, whichentered the 16 casing annulus probably via channelling in the casing cement and safetyvalves known as burst disks placed at levels of mapped sand layers present at depths of1,500 to 4,600 ft. below mudline.

Shallow Water Flow Sands

The well known GoM geohazard known as shallow water flow [SWF] and the associatedrisks have been extensively reported in the technical literature and have been ranked andmapped by the MMS across much of the GoM (Ref. 13). They were and are very well knownby individuals within all major GoM operators, including BP (see Refs. 1, 2 and 7).

Shallow water flows are flows from overpressured sands encountered at shallow depthbelow the mud line in deepwater regions of the world. Frequently sand flows with the waterand flow rates as high as 25,000 bbls/day have been reported (~730 gal/min).

SWF typically occur in water depths in excess of 1,500 ft, at depths ranging from 300 to3,500 ft below mudline and represent a recently encountered phenomenon in the Gulf of

Mexico, West of the Shetlands, the Norwegian Sea, the South Caspian, and the North Sea.It has been suggested that 30 to 40% of all deepwater wells in the Gulf of Mexico encounter


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this problem. Once the flow begins it is very difficult to stop, making it difficult, and

sometimes impossible, to obtain a competent cement job around the casing.

Shallowwater flow [SWF] is a serious drilling hazard encountered across severalareas ofthe Gulf of Mexico. Numerous incidents have occurred in which intense SWF have disrupteddrilling, added millions to the cost of a well, or caused a well to be abandoned. In anextensive survey of 74 offshore wells, Mark Alberty, an SWF specialist at BP Houston andcolleagues (Refs. 1 and 2) found that only 34% of the wells did not encounter problemsrelated to SWF. A 1998 Joint Industry Forum reported that 97 of 123 wells in deepwaterGoM in 1997 experienced SWF problems, with 30 not reaching target depth.

In a paper published in 1999, Eaton of Shell (Ref. 7) commenting on problems caused bySWF at the nearby URSA site in the GoM stated that:

Shallow flow sands can cause problems ranging from preventing full well evaluation to loss of alldevelopment wells at a site. Drilling massive shallow sands underbalanced can cause largewashouts leading to casing buckling. Minimizing lost returns during drilling and running andcementing casing is essential to preserve site integrity.


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There is a strong possibility that either the outer casing(s), the production casing (or both) atMacondo may have been buckled, bent and/or damaged as a result of an SWF drilling fluidfracture, washout and collapse over some or several SWF depth intervals. A similar eventoccurred at the URSA project to the west (Refs 16 and 17). Severe drilling problemsincluding gas kicks and drilling mud losses were recorded at the depths shown in the Table

below, which are all below the level of the probable base of gas hydrate stability (the GHSZ,often represented geophysically as a Bottom Simulating reflector, BSR).


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Table 1: Shallow Water Flow Layers

Layer Description Depth [ft. BML] Depth [ft. BSL]

SWF 1Overbank channel levee clays andpossible silts and sands.

1,489 1,620 6,556 6,687

SWF 2Continuous sands and silts with shallowgas to northwest.

1,832 1,944 6,899 7,011

SWF 3Interbedded clay turbidites and thin clay-prone debris flows with possible sands.

1,944 2,533 7,011 7,600

SWF 4 Continuous sands 3,202 3,367 8,269 8,434

SWF 5 Continuous sands 3,761 3,958 8,828 9.025

SWF 6 Continuous sands 4,372 4,618 9,439 9,685

Page 13 of the original BP Application Permit to Drill document [the APD, Ref. 14] clearlyidentifies these six layers, as shown below. The upper 3 layers are described as being at lowrisk and the lower three of moderate risk from SWF problems. However it is of note that thehigher risk due to the lower 3 SWF layers is essentially discounted since they are below thedepth of the planned first pressure containment 22-inch casing string. It is possible that this

statement was made without knowledge of the placement of the burst disks, or in theknowledge that Macondo was planned to be an eventual production well.


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Gas Hydrates

In addition to SWF, the presence of frozen gas hydrates [GH] in the Mississippi Canyon areacontinental shelf edge is well known and documented (Refs 1, 2 and 7) and detailed

warnings were reported to the MMS in 2009 and apparently ignored (Refs. 18 and 19). Theprimary cause of blowouts, spills and uncontrolled releases of gases from offshoreoperations is drilling into methane hydrates, or through them into free gas trapped below

The Macondo well was drilled very close to a seabed mound 100s of feet in height to theSW which is almost certainly a gas hydrate bearing mud volcano known as The BiloxiDome, the edge of which is approx. 5 miles from the well site. Locating the well this close tothis deep gas chimney feature, with strata dipping upwards towards the well site wasprobably viewed as necessary necessary in order to maximise the potential for a positiveresult at Target Depth, and the risk was accepted, with such a high pay-off anticipated.Similar seabed mounds are observed to the east and northeast of the well site, at similardistances.

A US Congressional Research Service report dated May 2010 by P. Folger (Ref. 12)recognises that gas hydrate dissociation may have had a role to play at Macondo (p. 5):

Indeed, gas hydrates may have had some role in the original blowout. If a sufficient amount ofmethane were present in the seafloor sediments, gas hydrates could have formed at thetemperatures and pressures in the sediments 1,000 or perhaps 1,500 feet below the seafloorat the Deepwater Horizon drill site (depending on the geothermal gradienthow rapidly theearth changes temperature with depth in that part of the Gulf of Mexico). As discussed in thetext of this report, drilling and well completion activities may have disturbed hydrate-bearingsediments, resulting in depressurization or heating that could have caused the hydrate todissociate into a gas. If the gas were able to enter the wellbore through some defect in thecasing or cement, it may have contributed to the anomalous gas pressure inside the wellborethat led to the April 20 blowout. Pending an analysis of the causes for the blowout, however, itis currently unknown whether gas hydrates were involved.

Reproduced below is Figure 4.2.4 from the Presidential Commission Chief Counsels Report(Ref. 15), which clearly shows a classic seabed mound with drawn down geophysical andgas blanked reflectors. The Biloxi Dome, is the probable source of seabed leaks reportedduring the NOOA cruises of 2010 (Ref. 9) and again more recently during August 2011.

Consideration of the temperature and pressure regime in the shallow tophole section belowseabed suggests that naturally occurring in-situ hydrates are likely to have been present at

Macondo below mudline. Reports from the Atwater Valley and Walker Ridge sites to theWest, investigated in 2005 and 2009 as part of the Chevron-led Gulf of Mexico Gas HydrateJoint Industry Project (JIP) and work by Archer (Ref. 3) and Milkov (Ref. 8) suggest thisdepth (the base of potential GH formation, commonly termed the GHSZ) may be of the orderof 950 to 1150 m BML (3,100 to 3,800 ft. BML [8,167 to 8.867 ft. bsl]. This level issomewhere between the 4th and 5th of the SWF sand layers. Free gas may have beenpresent within the 5th and 6th SWF layers and below that.

There is little to no mention of gas hydrates in the subsequent formal reports on theDeepwater Horizon incident (see Appendix A).


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Drilling, Casing and Burst Disks

Despite the risks inherent in all of the above, BP took the decision to continue to attempt todrill the one of the worlds deepest wells to date in a slapdash, corner-cutting, driving downcost, maximise added value fashion. These cut corners and lack of management controlhave been well documented to date and will not be recounted here.

With proper drilling design, control and cementing, wells have been completed under theseconditions in the past. However the risks should always be thoroughly assessed, withappropriate prevention and mitigation techniques and controls in place. Such measures arealso well documented based upon the past experiences of GoM operators, including BP.The original well plan with casing depths is shown below, taken from the original ApplicationPermit to Drill [APD] document approved by the MMS (Ref. 14).


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In addition to adopting a high risk "long string" well, the Macondo Exploration Well was

designed to be fitted with safety valves (known as "Burst or Rupture disks) at shallowdepths, coincident with the levels of two of the SWF sands, and in a GH prone area. Thiswas part of the plan to convert the exploration well to production at a later stage, in order tofurther reduce costs.

Table 3: Burst Disk Depths in 16 Casing

BD No. Depth [ft. BML] Depth [ft. BSL]

1 980 6,047

2 3,237 8,304

3 4,493 9,560

The burst disks are believed to have been Hunting APRS (Annular Pressure ReleaseSystem) type as shown in Table 3 above, which are used in order to provide insuranceagainst trapped annular pressure build-up and subsequent catastrophic structural well failureas a result of thermal pressure increases.

Page 56 of the National Commission Chief Counsels Report (Ref. 15, Chapter 4.2 WellDesign) discusses the rupture disks. The plot below shows that two were placed more or


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less coincidental with the two lowest SWF sand units identified and reported in the original

BP Application for Permit to Drill document for Macondo (Ref. 14), presumably as potentialpermeable pathways for any outward pressures blowing through the 7500 psi rated disks.However the inward pressure of 1600 psi was probably not thought of as a risk from a buildup of either free gas below a GHSZ level or from melted hydrate gas at pressure.

Further, it appears that due to the severe drilling problems, lost returns and gas kicks, asshown in Table 2 below, the 18 and 16 casing strings were set to depths much shallowerthan intended based upon the original Application to Drill permit (see Fig. 47 from Ref. 10shown below).

Table 2: Lost Returns and Kicks

Date Depth [ft. BML] Depth [ft. BSL]

Kicks

March 8th

8,232 13,305

March 25th*1

10,046 15,113

Lost Returns

February 17th 21st 7,283 12,350

March 2nd

6,520 11,587

March 3rd

5th 6,508 11,575

March 21st

8.083 13,150

March 31st

12,096 17,163

April 3rd

12,694 17,761

April 4

th

7

th

13,193 18,260

April 9th

13,126 18,193

Notes:

1. BML = Below Mudline; BSL = Below Sea level

2. Mudline @ 5.067 ft.

3. Ballooning. 11 7/8 casing set @ 15.103 BSL

It is of note that the lost returns and gas kicks started occurring at depths of 6,520 ft. BML,

which is well below the likely depth of the possible gas hydrate stability zone [GHSZ].


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Table 3: Planned Vs Actual Casing String Depths

Casing StringPlanned[ft. BSL]

Actual[ft BSL]

Difference (-ve)[ft.]

36 5,361 5,321 40

28 6,275 6,217 58

22 8,000 7,937 63

18 9,900 8,969 931

16 12,500 11,585 915

13-5/8 15,300 13,145 2,155

11-7/8 n/p 15,103 n/a

The above summary diagram and Table 3 show that the planned and actual depths of the18 and 16 casings were substantially different, with the 18 casing terminating at roughlythe level of the 5th SWF layer and the 16 casing terminating at a level such that there was aconsiderable depth interval between the cement jobs for the 18 and 16 casing strings where

there was no cement seal. This interval also contains the lowest 6th SWF sand, is in a depthzone of potential free gas below the GHSZ and contains an unprotected burst disk. The


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following diagram illustrates this, showing the as-built casing depths together with the

depths of the three burst disks and the depths and thicknesses of the 6 SWF sand layers.

Potential Casing Failure and Leak Mechanisms

The detailed DNV forensic report on the BOP failure (Ref. 6) as well as an internal highlydetailed Transocean Report (see Appendix A) leads to the conclusion that a BOP wouldhave failed even if it had been in perfect condition, due to the condition of the well, its out ofvertical alignment and the sudden immense force of the gas and fluid flow. The question thatshould be asked is: where did that huge quantity of gas come from?

Calculations may show that the valve system at the bottom of the well is unlikely to havesomehow failed as a result of the sudden pressure changes far up the drillstring during theend of the negative leak-off test, causing a sudden influx of a vast quantity of gas from the

hydrocarbon reservoir some two and half miles below seabed to burst upwards through fairlydense drilling mud at such a high velocity.

The final negative leak off test is well documented, including the fact that the displacement ofdrilling mud with seawater to a depth of 3,000 ft. below mudline was excessive andmiscalculated. This would have led to a sudden large pressure difference between theproduction string and annulus pressures and the possibly gas charged zones in the sandlayers adjacent to the burst disks.

Due to increased temperatures during cement curing, expanding pressurised melted hydrategas may have blown through damaged/leaking casing and weak pathways in the badcement job following the final negative leak off test. Drilling mud was displaced by seawater

within the drillstring over too great a depth, leading to reduced internal hydrostatic pressureand a sudden imbalance between the internal (fluid) and external (expanding gas in sand)pressures. The hydrate almost certainly would have been steadily melting around the casingdue to heat given off by the curing cement, a problem well understood by Halliburton (Ref.11), explaining their concerns over the use of a nitrogen based lightweight foam cement.

The heat generated as a result of cement curing is likely to have led to melting of somesections of this natural hydrate bearing zone some distance radially from the cement and asubsequent increase in pressure as the gas rapidly expanded and flowed into and within oneor more of the known SWF sand layers.

The presence of channels at certain levels within the cement is likely to have permitted apathway(s) to form along part(s) of the 16 casing. Due to possible earlier drilling disturbance

of the known layers of SWF sands prior to the melting of the hydrates, the 16 casing mayhave been out-of-straight or even slightly buckled as a result of partial liquefaction andsoftening of the SWF sands (similar to that observed at the BP/Shell URSA in 1999 in theGoM). This loss of lateral support may have caused a crack or breach in the casing, or aloosening at the casing joint(s). This casing is suspected to have been of too low a yieldstrength for the well design. At the point during the negative leak-off test when the pressuredifferential became sufficiently high, it is well documented and accepted that the three burstdisks placed at certain points on the casing joints down the casing string blew out at theirinwards blowing rated burst pressure of 1600 psi.

At this point the large pressure drop occurring within the mud fluids in the annulus betweenthe production casing and the 16 casing might have been sufficiently dramatic to allow a

rapid influx of trapped pressurised gas lying within the SWF sand(s) and in the pathwaysworked within the cement. This build up may have caused a very high pressure jet to blow


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out some or all of the rupture disks in the 16 casing, if the pressure differential between the

seawater filled production casing and the annulus on the other side were sufficiently high.This gas would have travelled very quickly up the production casing,


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The subsequent upwards rush of gas probably caused a siphoning of seawater, mud and

subsequently oil with it as the production casing shoe was blown due to the very high suctionforce exerted. Once the initial shallow blast of GH sourced gas blew the BOP, reservoirpressures would have been sufficient to allow the flow of oil to be maintained.

Conclusion

Much has been written in detail in formal reports, books and publications to date about themechanics of what happened at Macondo. However virtually nothing has been stated aboutthe probable root "geohazard" causes - shallow water flows and gas hydrates, a horrible butall too feared combination, which when combined with a series of serious organisationalfailures, cost cutting, schedule pressures, design errors led to the blowout.

However, the main root cause was the decision to locate the well so close to a major mud

volcano and gas chimney.

The identification of the probable true source of the high velocity gas stream matters hugely,since gas hydrates are present in many offshore deepwater areas, including environmentallyhighly sensitive areas such as Alaska.

It is clear that current drilling technology is unable to guarantee absolute safety in suchcases. The potential consequences of further blowouts are too enormous for such risks to beallowed to continue to be taken in pursuit of ever more remote oil and gas reserves

References

1. Alberty, M. W., M. E. Hafle, J. C. Minge and T. M. Byrd, "Mechanisms of Shallow

Water Flows and Drilling Practices for Intervention," Proc. Offshore Tech.Conference, Houston, Texas, Paper No. OTC 8301, 1997.

2. Alberty, M., "Shallow Water Flows: A Problem Solved or a Problem Emerging," OTCPaper No. 11971, 2000 Offshore Technology Conference, Houston, Texas.

3. Archer, D. (2007), Methane Hydrate Stability and Anthropogenic Climate Change,Biogeosciences, Vol. 4, pp. 521544 [www.biogeosciences.net/4/521/2007].

4. BP Exploration & Production Inc. (2009), Initial Exploration Plan, Mississippi CanyonBlock 252, OCS-G-32306, p.53. [Public Information Copy; Information Withheld].

5. BP Exploration & Production Inc. (2010), Supplemental Exploration Plan, MississippiCanyon Block 252, OCS-G-32306, p.60. [Public Information Copy; Information

Withheld].

6. Det Norske Veritas (2011), Final Report for United States Department of the InteriorBureau OF Ocean Energy Management, Regulation and Enforcement; WashingtonDC 20240. Forensic Examination of Deepwater Horizon Blowout Preventer,Contract Award No. M10PX00335, Volumes I and II (Appendices). Report No.EP030842, 20th March 2011.

7. Eaton, L.F. (1999), Drilling Through Deepwater Shallow Water-Flow Zones at Ursa,by L.F. Eaton, Shell Deepwater Development Inc., SPE 52780, 1999 SPE/IADCDrilling Conference, Amsterdam, 9th 11th March 1999.

8. Milkov, A.V., Sassen, R., Novikova, I. And Mikhailov, E., (2000), Gas Hydrates at

Minimum Stability Water Depths in the Gulf of Mexico: Significance to Geohazard


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Assessment, Gulf Coast Association of Geological Societies Transactions, Vol. 1,

2000,, p.217 224.

9. NOAA (2010), NOAA Ship Thomas Jefferson Deepwater Horizon Response MissionReport, Interim Project report Leg 2, June 3-11, 2010, 11th June 2010, p.42.

10. Parsons, P. (2010), The Macondo Well; Part 3 in a Series about the Macondo Well(Deepwater Horizon) Blowout, Energy Training Resources Llc, July 15th 2010, p. 40.

11. Tahmourpour, F. (2009) Halliburton Presentation: Deepwater CementingConsideration to Prevent Hydrates Destabilization, AADE Chapter Meeting, 18th

November 2009, p. 25.

12. United States Congressional Research Service (2010), Gas Hydrates: Resource andHazard, Peter Folger, Specialist in Energy and Natural Resources Policy, Ref.

RS22990, May 25th 2010,

13. United States Dept. of the Interior. Minerals Management Service, Gulf of Mexico,OCS Region, (2009), Updated SWF Risk Map on 4/15/2009 15th April 2009.

14. United States Dept. of the Interior. Minerals Management Service, (2009),Application for Permit to Drill a New Well; Form MMS 123A/123S, Lease G2306,Area/Block MC 252, ref. BP-HZN-CEC018022, p. 29.

15. United States National Commission on the BP Deepwater Horizon Oil Spill andOffshore Drilling (2011), Macondo; The Gulf Oil Spill Disaster; Chief CounselsReport 2011, p.371.

16. Winker, C.D. and Stancliffe, R.J. (2007), Geology of Shallow Water Flow at Ursa: 1.

Setting and Causes Proc. Offshore Technology Conference, Houston Texas, 30th

April 3rd May 2007, OTC Paper No. 18822.

17. Winker, C.D. and Stancliffe, R.J. (2007), Geology of Shallow Water Flow at Ursa: 2.Drilling Principles and Practice, Proc. Offshore Technology Conference, HoustonTexas, 30th April 3rd May 2007, OTC Paper No. 18823.

18. Zimmerman, D. (2009), 2010-2015 Oil and Gas Leasing in the Outer ContinentalShelf , Northcoast Ocean and River Protection Association (NORPA), PO Box 1000,Trinidad, CA 95575 ; Letter To: Ms. Renee Orr, Chief, Leasing Division, MineralsManagement Service, MS 4010, 381 Elden Street, Herndon, VA 20170-4817, 26thAugust 2009, p.59.

19. Zimmerman, D. (2010), An Open Letter to the Offshore Oil and Gas Industry,Especially BP, June 2010, p.2.

The Gallowglaich 11th September 2011

[email protected]


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Appendix A- Formal Macondo Disaster Reports

Ref. Title

A US National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling

Deep Water; The Gulf Oil Disaster and the Future of Offshore Drilling, Report to the President, January2011, p.398

www.oilspillcommission.gov/sites/default/files/documents/

Macondo; The Gulf Oil Spill Disaster; Chief Counsels Report 2011, p.371.

http://bookstore.gpo.gov/actions/GetPublication.do?stocknumber=040-000-00787-3

B US National Academy of Engineering and National Research Council

Interim Report on Causes of the Deepwater Horizon Oil Rig Blowout and Ways to Prevent Such Events.

Committee for the Analysis of Causes of the Deepwater Horizon Explosion, Fire, and Oil Spill to IdentifyMeasures to Prevent Similar Accidents in the Future; National Academy of Engineering; National ResearchCouncil, November 16

th2010, p.29.

www.nap.edu/catalog/13047.html [Final Report Due in June 2011]

C Center for Catastrophic Risk Management, University of California, Berkeley.

Progress Report 2, Deepwater Horizon Study, July 15th

2010, p. 42.

http://ccrm.berkeley.edu/deepwaterhorizonstudygroup/dhsg_articles.shtml

D The Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE)/U.S.Coast Guard (USCG) Joint Investigation Team

The Official Site of the Joint Investigation Team

www.deepwaterinvestigation.com/go/site/3043/ [Final report Due 27th

July 2011]

E US Congressional Research Service

Deepwater Horizon Oil Spill: Selected Issues for Congress, Curry L. Hagerty, Coordinator Specialist inEnergy and Natural Resources Policy and Jonathan L. Ramseur, Coordinator Specialist in EnvironmentalPolicy, July 30, 2010, p. 29.

Deepwater Horizon Oil Spill: Highlighted Actions and Issues, Curry L. Hagerty, Coordinator Specialist inEnergy and Natural Resources Policy and Jonathan L. Ramseur, Coordinator Specialist in EnvironmentalPolicy, January 28, 2011, p. 10.

Gas Hydrates: Resource and Hazard, Peter Folger, Specialist in Energy and Natural Resources Policy,May 25

th2010, p.9.

www.fas.org/sgp/crs/


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M d GH SWF BD 11092011 d 11th S t b 2011 P 17 f 17

F BOEMRE Presentation

Perspectives on Deepwater Drilling Safety and Blowout/Spill Containment

Bureau of Ocean Energy Management Hosted Forum, September 13, 2010 - Lafayette, LA, p.17.

www.boemre.gov/forums/documents/Panel_II_Presentation_4_lafayette.pdf

G BP Accident Investigation Report

Deepwater Horizon; Accident Investigation Report, September 8th

2010, p. 191 plus Appendices.

www.bp.com/liveassets/bp_internet/globalbp/globalbp_uk_english/incident_response/STAGING/local_assets/downloads_pdfs/Deepwater_Horizon_Accident_Investigation_Report.pdf

www.bp.com/liveassets/bp_internet/globalbp/globalbp_uk_english/incident_response/STAGING/local_assets/downloads_pdfs/Deepwater_Horizon_Accident_Investigation_Report_Executive_summary.pdf

H DNV Report on Blowout Preventer

Final Report for United States Department of the Interior Bureau OF Ocean Energy Management,Regulation and Enforcement; Washington DC 20240. Forensic Examination of Deepwater Horizon BlowoutPreventer, Contract Award No. M10PX00335, Volumes I and II (Appendices). Final Report. Report No.EP030842, 20th March 2011.

www.deepwaterinvestigation.com/external/content/document/3043/1047291/1/DNV%20Report%20EP030842%20for%20BOEMRE%20Volume%20I.pdf

www.deepwaterinvestigation.com/external/content/document/3043/1047295/1/DNV%20BOP%2

0report%20-%20Vol%202%20(2).pdf

J US Department of the Interior

National Incident Command, Interagency Solutions Group, Flow rate Technical Group: Assessment of FlowRate Estimates for the Deepwater Horizon/Macondo Well Oil Spill, March 10

th2011, p.30.

www.doi.gov/deepwaterhorizon/loader.cfm?csModule=security/getfile&PageID=237763

K Transocean

Macondo Well Incident; Transocean Investigation Report, Volume I and I plus Appendices A to Q.

http://www.deepwater.com/fw/main/Public-Report-1076.html

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