ATP Oil & Gas Corporation

Deloitte Dutch North SeaOil & Gas Conference

22 June 2005

G. Ross Frazer, P.E.Vice President-Engineering &

Director, U.K. Projects

Ing. Rob HappéGeneral Manager, ATP NL

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This presentation contains projections and other forward lookingstatements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. These projections and statements reflect the Company’s current view with respect to future events and financial performance. No assurances can be given, however, that these events will occur or that these projections will be achieved, and actual results could differ materially from those projected as a result of certain factors. A discussion of these factors is included in the Company documents filed with the Securities and Exchange Commission.

This presentation does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy or an attempt to influence any voting of securities, by any person.

Forward Looking Statement

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ATP’s Goals

2004 Offshore Energy Achievement

Innovation/Technology Award

Acquiring

Developing

Operating

Producing

Since 1991 ATP has focused its strategy on:

Low risk strategy with focused development operations

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Diversified Areas of Operation

Gulf of Mexico

Gulf of Mexico• 1991 – Shelf

• 2000 – Off the Shelf to 1,500’

• 2003 – Deeper water to 3,000’

North Sea 2000 – United Kingdom Sector

• 2003 – Dutch Sector

North Sea

The same strategy has been proven in all areas

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Exclusively Offshore

Gulf of MexicoGulf of Mexico202 Bcfe 202 Bcfe

North SeaNorth Sea101 Bcfe101 Bcfe

Gulf of MexicoGulf of Mexico202 Bcfe 202 Bcfe

North SeaNorth Sea101 Bcfe101 Bcfe

Proved Reserves By RegionDecember 31, 2003

Gulf of Mexico

181 Bcfe (P1)

256 Bcfe (P1+P2)

302 Bcfe (P1+P2+P3)

North Sea(1)

95 Bcfe (P1)

166 Bcfe (P1+P2)

307 Bcfe (P1+P2+P3)

(1) Cheviot not yet includedNote: Reserves prepared by Ryder Scott (U.S. and Netherlands) and Troy-Ikoda (U.K.)

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Superb Execution

37 of 38 non-producing properties with proved but as yet undeveloped reserves (PUD’s) converted to commercial production

495 Bcfe of P1+P2+P3 scheduled for development• Gulf of Mexico 238 Bcfe• North Sea 257 Bcfe

97% Success Rate

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ATP’s Strategy

Advanced 3-D seismic interpretationIntegrated reservoir analysisExtended reach drillingSubseaSpecifically designed platforms

ATP is an innovator and implementer of

technology, including:

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Repeatable Strategy

Gulf of Mexico37 of 38 Developments to Production 97%

North Sea1 for 1 Development to Production 100%

Focus is the same, which is to acquire properties for development with previous drilling into known reservoirs.

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Representative Gulf of Mexico Projects

WorkingProspect InterestRegion

Ladybug (GB 409) – Subsea tieback; on

production since 2001

Gomez (MC 711) – Well test 134 MMcfe/d,

Initial production fourth quarter 2005

Matia/Cabrito (GB 142/186) – Award

winning plinth design (leg extensions)

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Garden Banks 409 – “Ladybug”

1340’ (410m) Water depth

ATP innovation

• Longest oil subsea tieback (17.4 miles)

• Exceeding original reserve estimates

• First Production 2001

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Mississippi Canyon 711 – “Gomez”

ATP operates with a 100% WIWell test 134 MMcfe/dApproximately 3,000’ (~1,000m) water depthFive wells encountered hydrocarbons; four wells re-enterableGross proved reserves @ 12/31/03 > 100 Bcfe

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ATP’s Commitment to the North Sea

Opened U.K. office in 2000 and

Netherlands office in 2003

$50+ million invested to date

With 307 Bcfe, ATP is a

significant owner of reserves in

the North Sea

North Sea

$500 million to $1.0 billion in planned future investment

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Growth Through Acquisitions

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1112

2000 2001 2002 2003 2004

Open U.K.Office

Cumulative North Sea Blocks Acquired

Open NL Office

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Helvellyn

Acquired in 2001

Began production February 2004

One-well, subsea development

ATP operates with a 50% working

interest

Rotliegend/Carboniferous

Water depth less than 120 ft

(37 m)

First North Sea development

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Venture

ATP Operator 50% W.I.

One-well, sub-sea tieback

Two prior wells drilled and tested at 47 mmscfd

First gas 2006

Rotliegend/Carboniferous

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The Tors

ATP operates with a 100% working

interest

The Tors Reservoirs

• Garrow tested – two wells at 18

and 19 mmscfd

• Kilmar tested – one well in each

structure at 12 and 33 mmscfd

• Two platforms projected

Located in 170 (52m) feet of water

First production currently scheduled

in 2006

Possible development acceleration

Acquired 2001 and 2002

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Cheviot

Originally drilled and developed on 2D seismic

ATP operates with a 100%

working interest

Acquired in 21st Licensing Round

Original in place hydrocarbonsOil 232 MMbblsGas 59 Bcf

Produced 1992-1996 and

recovered less than 8% of

original oil in place

3-D Seismic Area

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•

Cheviot

Complete new 3-D seismic interpretation

Complete detailed G&G reservoir studies

Formulate redevelopment plan Keys to booking proved reserves at year end 2005• Innovative

development• Exploration

opportunities

2005 Program

Cheviot, potentially the Company’s largest field,

not yet included in ATP’s reserve report

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L-06d

ATP operator 50% W.I.

Well tested at 40 MMcf/d with a 17psi drawdown

Single well subsea development

Jurassic Sand

First gas late 2005

Top of reservoir

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Area Map of Location

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L-06d Project Overview

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Overview Tree Safety Valves

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Well Head Control System L6-S1

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Capital Deployment

Since 2001 the CAGR of investment in the North Sea is 245%, more than double that in the U.S.

1991-2001 2002 2003 2004 Gulf of Mexico 209,548$ 315,675$ 412,455$ 490,155$

North Sea -$ 3,831$ 47,240$ 56,040$

Total Capital Deployed ('000)

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Investment into the North Sea

Planned North Sea Capital Investment

($ Millions)Helvellyn, Venture, The Tors, L-06d $225 - $325

Cheviot $275 - $675Total $500 - $1000

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Gulf of Mexico to the North Sea

Similarities in the growth and development of ATP U.S. and the North Sea

Repeatable strategy

Execution of project plan

Capital deployed

Public ownership

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ATP Oil & Gas Corporation4600 Post Oak Place,

Suite 200Houston, TX 77027-9726

713-622-3311

ATP Oil & Gas (UK) LimitedVictoria House, London Square, Cross Lanes

Guildford, Surrey GU1 1UJ United Kingdom

44 (0) 1483 307200

ATP Oil & Gas (Netherlands) B.V.Water-Staete Gebouw

Dokweg 31 (B)1976 CA IJmuidenThe Netherlands

31 (0) 255 523377

www.atpog.com

ATP Oil & Gas Corporation -NASDAQ: ATPG