Deepwater Subsalt-Suprasalt Middle to Lower Slope Sands and Reservoirs of the U.S. Gulf of Mexico: The Evolution of an Exciting Giant Field Concept*

Transcription

1 Deepwater Subsalt-Suprasalt Middle to Lower Slope Sands and Reservoirs of the U.S. Gulf of Mexico: The Evolution of an Exciting Giant Field Concept* Dwight Clint Moore 1 and Bill Lefler 1 Rich Heaney 1, Mike Neese 1, and Tom Uphoff 1 Search and Discovery Article #42048 (2017)** Posted March 30, 2017 *Unsolicited manuscript submitted by senior author March 21, 2017, accepted March 27, 2017, and adapted from oral presentation at GCAGS 65 th Annual Convention, Houston, Texas, September 20-22, Abstract copyrighted 2015 by GCAGS, Houston, Texas. Please refer to closely related article by these authors, Search and Discovery Article #42047 (2017). **Datapages 2017 Serial rights given by author. For all other rights contact author directly. 1 GulfSlope Energy, Houston, Texas (clint@clintmoore.com) Abstract For almost 70 years, the U.S. Gulf of Mexico (GOM) has been an incubator of new depositional system models, and more recently, the focus for complex and dynamic subsalt-sediment trapping styles. Early passive margin models applied to the GOM suggested short slopes between delta fronts and basin floors and concluded that most slopes were sand bypass areas. However, subsequent study of the GOM s present-day salt-supported slope, which extends nearly 125 miles from its present-day shelf edge to the basin floor, suggested possible new sand depositional models applicable to the Cenozoic sediments below, if the slope was similarly salt-supported at time of deposition. Today, well control has dispelled this sand bypass thinking by demonstrating the presence of thick sand sequences and, when combined with seismic stratigraphy and depth imaging that shows the ancestral salt sheets, yields a robust potential for both lowstand and highstand sands in many subsalt Cenozoic cycles. Most importantly, the Miocene confined mini-basin sand bodies of amalgamated fans, amalgamated channels, and amalgamated channel levees of the ancestral mid-lower slopes, have proven sandstone reservoirs that have produced significant oil and gas fields. Undoubtedly, there are more of these to be discovered and developed.

2 This is not the first time that geologists in the GOM have pioneered new depositional concepts. When the authors started their GOM geoscience careers in the 1970s, industry was starting to apply Miocene delta depositional models seaward. In the 1950s and 1960s, these models had been pioneered in the nearshore. By 1970, Plio-Pleistocene deltas were hypothesized seaward of the Miocene deltaic fields, and billions of dollars of lease bonus monies were invested in the 1970s lease sales. Those massive Plio-Pleistocene deltaic sandstone reservoirs deposited in the last million years were discovered to contain billions of boe, all generated from oil and gas shale source rocks deposited in the Early Cretaceous Aptian ( mya) and Late Jurassic Tithonian ( mya). One of these most notable giants on the present-day outer shelf, Eugene Island (EI) 330 field (the 3 rd largest single field in GOM per BOEM [EUR 770 mmboe]), was discovered and produced suprasalt, in about 300 ft of water just 20 miles north of the edge of the Outer Continental Shelf. During the first 40 years of offshore GOM industry exploration, all petroleum reservoir objectives were suprasalt, that is above all sheets or beds of salt, like EI 330. The original bedded deep salt (autochthonous) was first deposited soon after the opening of the GOM, during Mid-Jurassic Callovian Louann time ( mya), and all horizontal salt sheets (allochthonous) originated from that Jurassic salt. The old concepts of vertical-only salt dome structuring have evolved toward dual-structuring models of both the traditional vertical doming AND the concept of horizontal translation of salt sheets across broad areas of the ancestral shelf and slope, similar to today s salt-supported slope. Exploratory drilling, both on the shelf and in deepwater, has demonstrated that most salt bodies in the Gulf of Mexico are part of these extensive allochthonous salt sheets that have translated more horizontally than vertically throughout the ancestral shelves and slopes. Much of what the mobilized salt has covered are thick untested sedimentary sections containing reservoir quality sand bodies and effective sealing shales. Preservation of petroleum liquids is also greatly assisted by the heat transfer properties of these extensive, subsurface lateral salt sheets. Economically significant fields of oil, condensate, and natural gas have been discovered and produced from these high porosity-permeability sandstone reservoirs, despite 15,000-20,000 feet of overburden, which contained these thick salt sheets. Today, the present-day outermost shelf and uppermost slope of the Louisiana GOM is well understood as a renewed exploration area of high potential, building on the fields discovered ( ) in the early days of poor seismically-imaged GOM subsalt traps. Over 300 mmboe has been produced to date (400+ mmboe EUR) from Conger, Hickory, Mahogany, Tanzanite, and Tarantula fields, all in ft water depth, near the present-day shelf-slope break.

3 Explorers have always known the Gulf of Mexico to be a world class exploration basin with tremendous potential. The thousands of explorers that have worked its complex geology over the last 70 years know that it has always been a great incubator for all forms of innovation that have then been adapted worldwide. The Gulf of Mexico has never been a dead sea. In its latest report on future GOM petroleum potential, BOEM reported that the GOM has tremendous recoverable petroleum resources, with over 50 billion boe yet to be discovered. Much of it will be subsalt and found in slope-basin floor sand reservoirs. The Offshore U.S. Gulf of Mexico is still a Mother Lode of petroleum, where new giant fields like these will continue to be discovered and produced. Selected References Diegel, F. A., J. F. Karlo, D. C. Schuster, R. C. Shoup, and P. R. Tauvers, 1995, Cenozoic structural evolution and tectonostratigraphic framework of the northern Gulf coast continental margin, in M.P.A. Jackson, D.G. Roberts, and S. Snelson, editors, tectonics: A Global Perspective: AAPG Memoir 65, p ; Search and Discovery Article (2001). Website accessed March 28, 2017, Gulf Slope Energy, 2014, Exploring the Gulf of Mexico: Independent Petroleum Association of America, Presentation September 22, Website accessed March 27, 2017, Presentation-OGIS pdf. Gulf Slope Energy, 2015, Creating value in the Gulf of Mexico: OTCQB:GSPE: Investor Presentation, January, Website accessed March 27, 2017, Gulf Slope Energy, 2015, Creating value in the Gulf of Mexico: Investor Presentation, August, Website accessed March 27, 2017, Prather, B.E. J.R. Booth, G.S. Steffens, and P.A. Craig, 1998, Classification, lithologic calibration, and stratigraphic succession of seismic facies of intraslope basins, deep-water Gulf of Mexico: AAPG Bulletin, v. 82/5A, p

4 Prather, B.E, J.R. Booth, G.S. Steffens, and P.A. Craig, 1998, Classification, lithologic calibration, and stratigraphic succession of seismic facies of intraslope basins, deep-water Gulf of Mexico: Errata, AAPG Bulletin, v. 82/12, p. 707R.

5 Deepwater Subsalt-Suprasalt Middle to Lower Slope Sands & Reservoirs of the US Gulf of Mexico: The Evolution Of An Exciting Giant Field Concept Dwight Clint Moore & Bill Lefler with Rich Heaney, Mike Neese, & Tom Uphoff GCAGS 2015 Houston, Texas September 21, 2015

6 Objectives Highlight depositional systems of reservoir sands in the ancestral middle and lower Miocene slope section of the Central LA GOM Describe these Conger-Mahogany-Hickory Miocene slope sands as proven highly productive reservoirs, with further potential in surrounding mini-basins Demonstrate that the Miocene ancestral middle and lower slope is NOT a bypass zone, but is a broad, widespread area of sand-filled confined mini-basins with amalgamated fans and channels as reservoir sands

7 Subsalt Miocene Slope Sand Production EUR 400+ MMboe were discovered in the 1990s Conger >250 MMBoe Discovered 1 St Prod Hickory >55+ MMBoe Discovered 1 St Prod Mahogany >50+ MMBoe Discovered 1 St Prod Tanzanite >20 MMBoe Discovered 1 St Prod Enchilada >30 MMBoe Discovered 1 St Prod Tarantula >15 MMBoe Discovered 1 St Prod Monazite Enchilada Conger Tanzanite Mahogany Agate Teak Tarantula Hickory GSPE Lease Blocks Previous Sub- Discoveries Oil and Gas-Producing Field

8 Conger-Mahogany-Hickory Play Area ST GI VR SMI EI SS EW GB GC

9 Middle & Lower Slope Miocene Sand Area ST GI VR SMI EI SS EW GB GC

10 Conger-Mahogany-Hickory Play Area North 5,000 10, ' 10,000' 15,000' Ultra-Deep Gas North Lafitte Target Zone Shelf Plio-Pleistocene Supra Shelf Plio-Pleistocene Supra- Shelf Miocene North North North Mahogany Hickory Lafitte Tahiti Lafitte Lafitte Jack ' 10,000' 15,000' Deepwater ' 10,000' 10,000' Plio-Pleistocene Plio-Pleistocene Plio-Pleistocene 5000' Supra Supra Supra Target Target Target Zone Zone Zone 15,000' 15,000' 0 Shelf Shelf Shelf South North North South South South Mahogany Mahogany Mahogany Mahogany Mahogany Hickory Hickory Hickory Lafitte Tahiti Tahiti Jack Lafitte Tahiti Jack Jack Hickory Hickory Tahiti J Deepwater Deepwater Deepwater Shelf ' 10,000' 15,000' Deepwater Miocene & Lower Tertiary Mahogany Hickory Conger Tahiti Jack Deepwater Target Zone 0 Plio-Pleistocene 5000' Supra 10,000' 15,000' Target Zone Shelf Plio-Pleistocene Supra South Deepwater Deep Sal 15,000 20,000 20,000' 25,000' 30,000' 25,000 30,000 Upper Miocene Lower Miocene Lower Miocene Upper Miocene Lower Tertiary 20,000' 25,000' 30,000' 20,000' 20,000' Proven & Potential Section 20,000' UpperMiocene Upper Miocene Miocene Miocene Upper Miocene Upper Miocene Upper Miocene 25,000' 25,000' 25,000' Lower Miocene Lower Miocene Lower Miocene Lower Lower Miocene Lower Lower Miocene Miocene Miocene 30,000' 30,000' Lower Tertiary 30,000' Lower Tertiary Lower Tertiary Lower Tertiary 25,000' Lower Miocene Lower Miocene Lower Miocene Lower Miocene Lower Lower Miocene Miocene Lower Tertiary 30,000' Upper Lower Tertiary Lower Tertiary Lower Tertiary Lower Tertiary 20,000' Upper Upper Miocene Upper Miocene Upper Miocene Upper Miocene Upper Miocene Miocene Miocene Lower Miocene Lower Lower Miocene Lower Tertiary Lower Tertiary Upper Miocene Uppe Sa 35,000 Moore & Lefler 2014

11 Highly Productive Slope and Basin Floor Sands Slope Sand Miocene Producing Fields UM UM Miocene Subsalt Pay Sands Slope Fans + Basin Floor Fans UM MM UM UM MM MM LM LM UM MM LM Upper Miocene Middle Miocene Lower Miocene Basin Floor Sand Miocene Producing Fields LM Moore 2014

12 Porosity vs Depth (BML) for Miocene Slope Sands Trend Line POROSITY % 15.0 Above 22,000 you can expect >25% Porosities DEPTH BML ft Lefler 2014

13 Dynamic & Sediment Model ModeL - Upper Miocene Tjme... ~ Si3lt Model - Thick Si3lt Ci35E'... ~,,, =, =,,,,,,,,,, ~ul FE~~;:F-~ UUIF"e:~~~r-e ModEL - Late Pliocene to Early Pleistocene Time... ~ Model. - Pleistocene T ime... 1IIj Heaney 2014

14 Bathymetry of Modern Sea Floor * An Analog for sediment fed Intraslope Basins *Modified from Diegel et al., 1995, Prather et al., 1998

15 Delta, Slope, & Basin Floor Prograde Seaward No rth GOM Extended -Supported Slop e Sand Depocenter Model S ou th nrl."v"c:. Seaflo or P liocene Deltas GS P le istocene Deltas C o nfined M in i-basin Unconfined Basin ~s~:::::~~s~&=.~c::h~a:::n::::n~e~l s::::::s:~",<:>--~ Floo Fans P lio-ple istocen e -Supported S lope Basin F loor 5 MYA U p per M iocene Deltas 3 and Upper M iocen e S upported S lope Confined IVI l ni-~ als Fans & C Unconfined Basin F loor Fan s / U pper M iocene Basin F loor 1 5MYA Lower M iocene Deltas Moore 2014 Confined M in i-basin Fan s & C h an ne ls Lower M iocen e Supported S lope I I I I I B a U n co nfin ~d F loor F'an s Lower M iocene Basin F loor

16 15+ Sequences - Lowstand Sand Potential mya Sequences Primary Zones ~ I ~ Ml --.~ -~ I~ I- -~-~ '-< ~ MiA < M2 I ~ -...;; 1---< ~... V -. u-~.. :a.._ --< I- n M3 M4 MS M6 Sub Epoch UPPER MIOCENE MIDDLE I-----< " M7 MIOCENE ~-3. < " ---- ~ M8 I ~ -< f- 1---_ < " M9 --. ~~~ " LOWER " MiD MIOCENE - -.~ n L ~ Mil

17 15+ Successive Lowstand Cycles in Miocene North Today's Seafl oor GOM Extended -Supported Slope Sand Depocenter Model GSPE Play Confined Mini:-Basin South Unconfined Basin 'C=:;~:;iF",a:;n~S~&~C~h;.;a~n;;.n~e:?l s;:-'b--,,>- FI Fans S oh Basin Floor 5MYA Confined Mini-Basin Fans & Channels Un co nfined -;.---,sin F I ~oor Fans U M iocene Moore ,0 00' ±

18 Lowstand Deltas Fed the -Supported Extended Slope, Creating Confined Mini-Basins with Amalgamated Fans & Channels Moore 2014

19 15+ Sequences - Lowstand Sand Potential mya Sequences Primary Zones Sub Epoch The 6+ LSTs of the Tortonian Stage MYA

20 Bathymetry of Upper Miocene Tortonian Stage OUTER SHELF TORTONIAN PALEOENVIRONMENTS* Locations for Cross Sections A-A and B-B SHELF MARGIN DELTAS SHELF MARGIN DELTAS UPPER BATHYAL SHELF EDGE MIDDLE BATHYAL A HICKORY B LOWER BATHYAL EI385 TANZANITE MAHOGANY TARANTULA GARDEN BANKS AREA B AREA OF DETAIL CONGER FIELD GREEN CANYON AREA ABYSSAL PLAIN TIGER TAHITI CRESTED BUTTE ASPEN KNOTTY HD DBL MTN Lefler 2015 A TONGA * Interpretation based upon BOEM Public Data

21 Bathymetry of Upper Miocene Tortonian Showing Lower Slope Mini-Basins as Primary Basins * FILL AND SPILL LOWER SLOPE MINI-BASINS LOWER BATHYAL SALT-SUPPORTED RIDGES/SHEETS AREA OF DETAIL Lefler 2015 GARDEN BANKS AREA GREEN CANYON AREA ABYSSAL PLAIN Primary Basin *Interpretation based upon 3D Seismic Isopach mapping

22 A A MIDDLE BATHYAL NORTH-SOUTH STRUCTURAL SECTION LOWER BATHYAL TOE OF SLOPE ABYSSAL PLAIN MESSINIAN PLIOCENE TORTONIAN PLIOCENE SALT OLIG EOCENE Lefler 2015

23 WEST-EAST STRATIGRAPHIC SECTION B Showing 3 Major Tortonian Lowstand Episodes B CONGER FIELD EI 385 MAHOGANY FIELD TARANTULA FIELD HICKORY FIELD STRATIGRAPHIC DATUM TOP TORTONIAN 7.1 MY LST 100+ GAS PAY 200+ OIL PAY CATINASTER MEXICANUS 7.83MY HST 100+ OIL PAY#A14 8.4MY LST DISCOASTER BOLLII 9.21MY LST MINI-BASIN TOP SERRAVALLIAM 11.6MY SALT DOME GLOBOROTALIA MAYERI 10.5MY LST DISCOASTER KUGLERI 11.58MY SALT RIDGE Lefler 2015

24 Dynamic & Sediment Model ModeL - Upper Miocene Tjme... ~ Si3lt Model - Thick Si3lt Ci35E'... ~,,, =, =,,,,,,,,,, ~ul FE~~;:F-~ UUIF"e:~~~r-e ModEL - Late Pliocene to Early Pleistocene Time... ~ Model. - Pleistocene T ime... 1IIj Heaney 2014

25 Trap Styles result from & Sand Dynamics Heaney 2014

26 Conclusions Lower slope sands are extensively deposited across the Miocene ancestral slope and are most commonly found as amalgamated fans and channels in confined mini-basins. Lower Slope Miocene sands have produced well in Conger- Mahogany-Tanzanite-Hickory reservoirs to date (350+ MMBOE produced 400+ MMBOE EUR). GOM Miocene ancestral lower slope is NOT a bypass zone, but consists of widespread sand-filled confined mini-basins with sizeable untested field potential.

27 Geological & Geophysical Advantages Confined Mini-basin Fan Sands Continuous Reservoirs Excellent Porosities 25% to 30+% Key Fields Conger, Mahogany Deep, Hickory, Tarantula, Aspen Proven Petroleum System Reservoirs, Traps, Seals, Sources Advanced Seismic Processing (RTM+) Clarifes Sub- Images Economic Advantages Water Depths: Modern Drilling Technology below Mostly Jack-up Rig Access - $70K/day - $20-40MM per Wildcat Mostly Conventional Platforms - $40-50 MM per Platform Extensive Existing Platform-Pipeline Infrastructure across Area

28 Acknowledgements The Authors would like to thank all their fellow members of the GulfSlope Energy Geoscience team, especially Sheila Wilkins Bruce. We also gratefully acknowledge Petroleum Geo-Services ASA (PGS) for their permission to display their geophysical data in this presentation.