petroleum system in cuba

8/12/2019 Petroleum System in Cuba

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Chapter 2

Jurassic-Cretaceous Composite TotalPetroleum System And Geologic ModelsFor Oil And Gas Assessment Of TheNorth Cuba Basin, Cuba

By Christopher J. Schenk

U.S. Geological Survey Digital Data Series DDS69M

U.S. Department of the InteriorU.S. Geological Survey

Chapter 2 ofJurassic-Cretaceous Composite Total Petroleum System and Geologic Assessment ofOil and Gas Resources of the North Cuba Basin, CubaBy U.S. Geological Survey North Cuba Basin Assessment Team
http://69_m_chapters.pdf/


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U.S. Department of the InteriorDIRK KEMPTHORNE, Secretary

U.S. Geological SurveyMark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

For product and ordering information:World Wide Web: http://www.usgs.gov/pubprodTelephone: 1888ASKUSGS

For more information on the USGSthe Federal source for science about the Earth, its natural and living resources,natural hazards, and the environment:World Wide Web: http://www.usgs.govTelephone:1888ASKUSGS

Publishing support provided by:Denver Publishing Service CenterManuscript approved for publication October 17, 2008

For more information concerning this publication, contact:Team Chief Scientist, USGS Central Energy ResourcesBox 25046, Mail Stop 939Denver, CO 80225(303)236-1647

Or visit the Central Energy Resources Team site at:http://energy.cr.usgs.gov/

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Governmen

Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce anycopyrighted materials contained within this report.

Suggested citation: Schenk, C.J., 2008, Jurassic-Cretaceous Composite Total Petroleum Systemand geologicmodels for oil and gas assessment ofthe North Cuba Basin, Cuba,in U.S. Geological Survey North Cuba Basin Assessment Team, Jurassic-CretaceousCompositeTotalPetroleumSystem andgeologicassessment of oil andgas resources of the North Cuba Basin, Cuba: U.S. Geological SurveyDigital DataSeries DDS69M, chap. 2, 94 p.

ISBN 1-4113-2253-0


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Contents

Abstract 1

Introduction 1Geologic Evolution of the northern Caribbean area 1 Late Triassic to Middle Jurassic Rifting 4 Opening of the Gulf of Mexico in the Late Jurassic 7 Opening of the Proto-Caribbean Ocean Basin 7 Movement of the Caribbean Plate 8 Collision of Cuba Arc-Forearc with the Bahama Platform 9 Tectonic Summary 9Jurassic-Cretaceous Composite Total Petroleum System 16

Source Rocks 16 Lower to Middle Jurassic Rift-related Mudstones 16

Upper Jurassic-Lower Cretaceous Deep-Marine Carbonates 18 Upper Cretaceous Deep-Marine Carbonates and Mudstones 18 Paleogene Mudstones 19 Summary of Cuban Oil Geochemistry 19 Petroleum Generation 20 Petroleum Migration 21 Significance of the DSDP Site 535 well, southeastern Gulf of Mexico 21 Significance of the Doubloon-Saxon #1 well, Bahama Platform 23 SummaryJurassic-Cretaceous Composite Total Petroleum System 24Geologic Definition of Assessment Units 25 North Cuba Fold and Thrust Belt AU 25 North Cuba Foreland Basin AU 32 North Cuba Platform Margin Carbonate AU 32Assessment of Undiscovered Oil and Gas Resources 34 Geologic Models for Assessment 34 North Cuba Fold and Thrust Belt AU 35 North Cuba Foreland Basin AU 35 North Cuba Platform Margin Carbonate AU 35 Assessment Methodology 35 Assessment Input Data 36 North Cuba Fold and Thrust Belt AU 36 North Cuba Foreland Basin AU 37 North Cuba Platform Margin Carbonate AU 39 Assessment Results 39Conclusions 40References Cited 41Appendix 1. Assessment input data for North Cuba Fold and Thrust Belt AU 46Appendix 2. Assessment input data for North Cuba Foreland Basin AU 48Appendix 3. Assessment input data for North Cuba Platform Margin Carbonate AU 51Appendix 4. Detailed assessment results for North Cuba Fold and Thrust Belt AU 54Appendix 5. Detailed assessment results for North Cuba Foreland Basin AU 65Appendix 6. Detailed assessment results for North Cuba Platform Margin Carbonate AU 84

III


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Figures

1. Locations of Cuba, Yucatan Platform, Yucatan Basin, Florida Peninsula, BahamaPlatform, and the general bathymetry of parts of the Gulf of Mexico, YucatanBasin, Cayman Trough, Caribbean Sea, and Atlantic Ocean 2

2. Physiographic features of northwestern Cuba and southeastern Gulf of Mexico 2 3. Locations of onshore oil fields of northwestern Cuba 3 4. Interpretation of the tectonostratigraphic units of northern Cuba 4 5. Map and schematic cross section showing general positions of tectonostratigraphic

units of central Cuba 5 6. Stratigraphic column showing repetition of thrust sheets in the Cuban fold and thrust

belt in northern Cuba 5 7. Lithostratigraphic column for northwestern Cuba and offshore showing reconstructed

stratigraphy of the proto-Caribbean basin 6 8. Reconstruction of paleogeographic elements in the western Caribbean region during

Middle Oxfordian time 7 9. Reconstruction of paleogeographic elements in the Caribbean region during

Tithonian time 810. Reconstruction of paleogeographic elements in the Caribbean region during

Hauterivian-Barremian time 811. Reconstruction of paleogeographic elements of the Caribbean region during Late

Maastrichtian time 912. Reconstruction of the Guaniguanico terrane along the Yucatan margin and the

development of the active margin west of the El Pinar fault zone of northwestern Cuba 10

13. Correlation of stratigraphic units of the Guaniguanico terrane as itdeveloped along the eastern margin of the Yucatan Platform 10

14. Reconstruction of the position of the Caribbean plate relative to the proto-Caribbeanplate in the Early Paleocene 11

15. Structure of the Yucatan Basin during Paleogene time 1116. Map showing a reconstruction of structural features in the western Caribbean region

during Middle Eocene time. 1217. Tectonic model for the development of the Cuban fold and thrust belt and foreland 1318. Sequential development of the northwest Cuban fold and thrust belt and the

foreland associated with the fold belt 1419. Chart showing chronology of major tectonic events affecting the northwest Cuba area and

the main elements of the Jurassic-Cretaceous Composite Total Petroleum System 1520. Present-day distribution of synrift Jurassic source rocks 1621. Present-day distribution of Upper Jurassic deep-water carbonate source rock 1722. Present-day distribution of Lower Cretaceous deep-water carbonate source rocks 1823. Postulated present-day distribution of Cenomanian-Turonian source rocks 1824. Geochemical classification of Cuban oil families 1925. Map of western Cuba showing distribution and classification of three main oil families 1926. Plot of percent sulfur and API gravity for some Cuban oils (from

Magnier and others, 2004) 19


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27. Plot of Rock-Eval data in Cuban onshore source rock samples and samples from DeepSea Drilling Project well 535 20

28. Plot of geochemical depositional-source indicators (gammacerane and hopane) showing the general separation of Jurassic and Cretaceous deep-water carbonates withTertiary siliciclastic source rocks 20

29. Boundaries of the Jurassic-Cretaceous Composite Total Petroleum System and the threeassessment units defined in this study 20

30. Seismic profiles and offshore DSDP well locations northwest of Cuba 2131. Stratigraphic column showing interpretation of carbonate sequences

cored at DSDP Site 535 2232. Modified van Krevellen diagram for potential hydrocarbon-bearing source rocks at

DSDP Site 535 2233. Stratigraphic column showing positions of oil-stained intervals in DSDP Site 535 core 23

34. Map showing locations of oil and gas exploration wells in the southwestern part of theBahama Platform 24

35. Cross section of wells drilled and tested in the Bahama Platform 2536. Map showing boundaries of the three assessment units defined in the

Jurassic-Cretaceous Composite Total Petroleum System 2637. Schematic structural cross section of the North Cuba Basin showing general boundaries

of the three assessment units defined in the Jurassic-Cretaceous Composite TotalPetroleum System 26

38. Boundary of the North Cuba Fold and Thrust Belt Assessment Unit 2739. Schematic geologic cross section across onshore northwestern Cuba 2740. Schematic geologic cross section illustrating the complex structure of the Cuban fold and

thrust belt and the underlying rift zone, and the definition of exploration play types 2841. Two selected seismic sections showing general expression of the Cuba fold and thrust

belt, foreland, and margin of the carbonate platform 2842. Structural cross section of the Boca de Jaruco oil field in northern Cuba 2943. Map and structural cross section of the Punta Allegre oil field, northern Cuba 3044. Geologic model for assessing undiscovered resources in the North Cuba Basin 3145. Composite petroleum-system events chart for North Cuba Fold and Thrust Belt

Assessment Unit 3146. Boundary of the North Cuba Foreland Basin Assessment Unit 3247. Composite petroleum system events chart for the North Cuba Foreland Basin

Assessment Unit 33

48. Boundary of the North Cuba Platform Margin Carbonate Assessment Unit 3349. Paleoenvironmental map showing the distribution of platform margin reefs and deep

water calcareous sediments during Albian time 3450. Petroleum system events chart for the North Cuba Platform Margin Carbonate

Assessment Unit 3451. Plot showing oil-field size versus discovery year for the North Cuba Fold and Thrust

Belt Assessment Unit 3652. Prospective areas for petroleum exploration in the area northwest of Cuba 37

V


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Tables

1. Oil fields of the onshore North Cuba Fold and Thrust Belt Assessment Unit 32. Geological attributes of four main groups of potential petroleum source rocks,

North Cuba Basin 193. Geochemical parameters of some onshore oils, North Cuba Basin 214. North Cuba Basin Assessment Results 40


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Jurassic-Cretaceous Composite Total PetroleumSystem and geologic models for oil and gasassessment of the North Cuba Basin, CubaBy Christopher J. Schenk

AbstractPetroleum generation in the North Cuba Basin is

primarily the result of thrust loading of Jurassic andCretaceous source rocks during formation of the North Cubafold and thrust belt in the Late Cretaceous to Paleogene. Thefold and thrust belt formed as Cuban arc-forearc rocks alongthe leading edge of the Caribbean plate translated northwardduring the opening of the Yucatan Basin and collidedwith the passive margin of southern North America in thePaleogene. Petroleum uids generated during thrust loadingmigrated vertically into complex structures in the fold andthrust belt, into structures in the foreland basin, and possiblyinto carbonate reservoirs along the margins of the Yucatanand Bahama carbonate platforms. The U.S. GeologicalSurvey dened a Jurassic-Cretaceous Composite TotalPetroleum System (TPS) and three assessment units (AU)North Cuba Fold and Thrust Belt AU, North Cuba ForelandBasin AU, and the North Cuba Platform Margin CarbonateAU-within this TPS based mainly on structure and reservoirtype. There is considerable geologic uncertainty as to theextent of petroleum migration that might have occurredwithin this TPS to form potential petroleum accumulations.Taking this geologic uncertainty into account, especially inthe offshore area, the mean volume of undiscovered oil in thecomposite TPS of the North Cuba Basin is estimated to be4.6 billion barrels of oil (BBO), and the mean ranges froman F95 probability of 1 BBO to an F5 probability of 9 BBO.The mean volume of undiscovered gas is about 9.8 trillioncubic feet of gas (TCFG), and of this total, 8.6 TCFG isassociated with oil elds, and about 1.2 TCFG is estimatedto be gas in nonassociated gas elds in the North Cuba

Foreland Basin AU.

Introduction

The purpose of this paper is to present an assessmentof the undiscovered oil and gas resources in the North CubaBasin (g. 1) and to discuss the geologic uncertainties inherentin the assessment. This assessment was completed as part ofthe U.S. Geological Survey World Energy Project in whichundiscovered oil and gas resources were assessed in 128

basins worldwide (U.S. Geological Survey World EnergyAssessment Team, 2000).

The North Cuba Basin is a geologically complex areaand includes several disparate geologic entities, including theYucatan carbonate platform, the Florida carbonate platform,the southeastern Gulf of Mexico, and the fold and thrust beltof Cuba (g. 2). The tectonic evolution of this area includescounterclockwise movement of the Yucatan Platform,the opening of the Gulf of Mexico oceanic basin, and theformation of the Cuban archipelago. The tectonic history hada direct bearing on the petroleum systems in the North CubaBasin.

The onshore part of the North Cuba Basin has a longhistory of petroleum exploration and production. The rsteld, Motembo, was discovered onshore in northwestern Cubain 1881, and Motembo remains the only condensate eld inCuba. More than 20 oil elds have been discovered in Cubasince then, mostly in the North Cuba Basin (Oil and GasJournal, 1993) (g. 3; table 1). Although most of the onshoreoil elds are small, shallow, and contain heavy oil (Petzet,2000), the fact that oil exists there is strong evidence that oneor more petroleum systems either are or were active in thesubsurface of the northwestern part of Cuba. Based on oilproduction of onshore Cuba and the knowledge gained fromseveral recent geologic and geochemical studies, the offshoreis interpreted to have potential for undiscovered oil and gasresources, and was the focus of the present study.

Detailed geological and geochemical investigationsby Navarrete-Reyes and others (1994), Lopez-Quintero andothers (1994), Moretti and others (2003a, b), and Magnier

and others (2004) provided much basic oil and gas data andbackground information that signicantly aided this oil andgas assessment.

Geological Evolution Of The NorthernCaribbean Area

The geology of the Caribbean area in general and Cubain particular is complex, and many decades of geologic


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900'0"W900'0"W 850'0"W 800'0"W 750'0"W

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Y u c a t a nB a s in

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0 100 Kilometers

0 100 Miles

2 Geologic Assessment of Oil and Gas in the North Cuba Basin, Cuba

Figure 1. Locations of Cuba, Yucatan Platform, Yucatan Basin, Florida, Florida Escarpment, West Florida Shelf, Bahama Platform, and the general bathymetry of parts of the Gulf of Mexico, Yucatan Basin, Cayman Trough, Caribbean Sea, and Atlantic Ocean. Jurassic-Cretaceous Composite TPS shown by yellow line. North Cuba Basin boundary is same as composite TPS boundary in this study. Faultsare shown as dark green lines; ball and bar on downthrown side of fault (after French and Schenk, 2004).

Figure 2. Physiographic features of the northwestern Cuba and the south-eastern Gulf of Mexico area. SeveralDeep Sea Drilling Project (DSDP) wellsare shown in red symbols(from Cubapetroleo, 2002).


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?

N

COAST LINE

THRUST FAULTS AS BOUNDARIES OF THE CENTRALEASTERN TECTO UNITSLIMIT BETWEEN G EOLOGICAL PROVINCESUPPER CRETACEOUS-PALEOCENE BASINS

REMEDIOSCAMAJUANI

PLACETAS?

?

CAYO COCO

Punta Alegra

Turiguan

Loma CunaguaCAYO COCO

REMEDIOSCAMAJUANI

PLACETAS

SCALE 1: 5,000,000

0 200 Miles

200 Kilometers


investigations have pieced together the main elements ofthe geologic evolution of Cuba, the Gulf of Mexico Basin,and the proto-Caribbean oceanic basin (Pardo, 1975; Lewisand Draper, 1990; Pindell and Barrett, 1990; Hemptonand Barros, 1993; Pindell, 1993, 1994; Piotrowska, 1993;Draper and Barros, 1994; Iturralde-Vinent, 1994; Schlager

and others, 1984; Gordon and others, 1997; Meschede andFrisch, 1998; Kerr and others, 1999; Pszczolkowski, 1999;Cobiella-Reguera, 2000; Pindell and Kennan, 2001, 2003;Pszczolkowski and Myczynski, 2003; Pindell and others,2005; Iturralde-Vinent, 2006; Fillon, 2007). From the earlieststudies the geology of Cuba was recognized as a series ofnorth-verging thrust-fault-bounded tectonostratigraphic units(TSU), and the geologic denition of many TSUs was thefocus of many previous investigations (gs. 4, 5). Eventually,tectonic studies in Cuba and in the northern Caribbeanplaced these TSUs in a framework of modern tectonic theory(Pindell and Kennan, 2001, 2003; Pindell and others, 2005).Detailed work demonstrated that the TSUs were the productof the collision between shelf, slope, and basinal sedimentsof the Mesozoic passive margin of the Yucatan and Bahamaplatforms and the arc-forearc rocks of the leading edge of thePacic-derived Caribbean Plate as the Yucatan Basin openedin the Paleogene (Pindell and others, 2005). The stratigraphyof Cuba is complex, and many stratigraphic studies reect thestacked thrust sheets produced during plate collision (g. 6).However, the general stratigraphy of many TSUs has beeninterpreted and restored, documenting general stratigraphicrelations (g. 7).

Major events in the geologic history of northwesternCuba include: (1) rifting between North America, SouthAmerica, and Africa in Late Triassic-Early Jurassic time;(2) the tectonic evolution and passive-margin sedimentaryhistory of the southeast Gulf of Mexico; (3) the developmentof the proto-Caribbean ocean basin and its passive margin; (4)movement of the Caribbean plate since the Early Cretaceous;and (5) Paleogene development of the Yucatan Basin and

resultant collision and suturing of allochthonous Cuba terraneswith the passive margin of the Bahama Platform. These eventswill be described briey as each relates to the developmentof petroleum systems in the northwestern part of Cuba. Thetectonic evolution of the Caribbean, especially the origin ofthe Caribbean plate, is somewhat controversial and is not the

primary subject of this report.

Late Triassic to Middle Jurassic Rifting

The continents of North America, South America, andAfrica composed the supercontinent of Pangea in the latePaleozoic and Triassic time (Salvador, 1991). In the LateTriassic, rifting began between North America and Africa andthen between North and South America. Rifting continuedthrough the Early and Middle Jurassic (Callovian), formingstretched or attenuated continental crust between the divergingcontinents (Marton and Bufer, 1993; 1994). During rifting,the extensional regime resulted in the formation of graben andhalf-graben structures in many areas of stretched continentalcrust, and these structures were lled with typical synriftsedimentary facies. The rift-related structures formed in thearea underlain by continental crust in the northwestern part ofoffshore Cuba, and rift structures underlie part of the BahamaPlatform (Sheridan and others, 1983; Ladd and Sheridan,1987).

Facies of the rift-related grabens and half grabens includecoarse red clastics, marine clastics, marine mudstones, andevaporites. These strata have been described from exposureson Cuba as the San Cayetano Formation (Haczewski, 1976)and as the Eagle Mills Formation from the subsurface ofthe northern Gulf Coast (Salvador, 1991). The synrift SanCayetano Formation might contain petroleum source rocks.

As rifting waned in the Middle Jurassic, evaporiticconditions within the extensional province resulted in thedeposition of widespread evaporites (halite and anhydrite)

Figure 4. An interpretation of tectonostratigraphic units (TSU) of northern Cuba. TSUs are north-verging thrust-fault-bounded rockunits that formed mainly as a result of the collision between Cuba and the passive margin of the Bahama Platform during the Paleogene(from Echevarria-Rodriguez and others, 1991)


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OLDMARGIN

BASEMENT

YABUWINDOW

EOCENEBACKTHRUST

CRUZWINDOW

FIDENCIA WINDOW

EOCENETHRUST

JARAHUECA WINDOW

SALTDIAPIRS

JATIBONICOWINDOW

FRONTALTHRUST

EXPOSEDIN OUTCROP

SURFACEFOLDS

&THRUSTS(inLASVILLASBELTmarginsediment s

INDEX MAP Explanation

MELANGE(in shearedPLACETAS & CIFUENTESBELTS = margin sedimentsplus serpentinite)

OBDUCTED ARC(& ???? foundation

SOUTHERNMETAMORPHICS

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Eocene thrustMELANGE = deformed slope/rise + basinal sediments

SUBSURFACEFAULTS & FOLDS(in CAYO COCO BELTplatform carbonates

decreasingstraingradient

Folds

ThrustFaults

N

0 50 Miles

50 Kilometers

TSU AGE

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Explanation

5Oil And Gas AssessmentNorth Cuba Basin, Cuba

Figure 5. Map and diagrammatic crosssection showing general positions of tectonostratigraphic units (TSU) of central

Cuba. The TSUs have been studied andnamed across Cuba (from Hempton andBarros, 1993).

Figure 6. Stratigraphic column showing thrust repetitions in the Jurassic throughTertiary section in the Cuban fold and thrust belt in northern Cuba (modified fromCubapetroleo, 2002).


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F O R M A T I O N S MAIN DEPOSITIONAL ENVIRONMENT

PLACETAS

PALEOGEOGRA

STRATIGRAROSARIOROSARIOPLACETAS/

OFFSHORE N CUBA

CACARAJICARA AMARO

UNCONFORMITYMID CRETACEOUS

PINALILLA ANGELITA

M A R T I N M E S A

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MegabrecciasCalcarenites (slope)

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Mixed Carbonate/ Siliclastic slope

toCarbonate basin

Inner platform

Outer platformCarbonate basin

Outer platformCarbonate basin

Inner platformMixed outer PF

Sandy

Turbidite

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EROSIONAL (CURRAND OMISSION

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DEEPENING TRE(Cifuentes units V

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E O C E N E

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U P P E R

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E

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T R I A S

50

100

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131

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5.2

TORTONIAN

PLEISTOCENE

PLEISTOCENE

SERRAVALIAN

BURDIGALIAN

AQUITANIAN

CHATTIAN

RUPELIAN

PRIABONIAN

LUTETIAN

YPRESIAN

THANETIAN

BARTONIAN

DANIAN

MAASTRICHTIAN

CAMPANIAN

SANTONIAN

TURONIANCENOMANIAN

ALBIAN

APTIAN

BARREMIAN

HAUTERIVIAN

VALANGINIAN

BERRIASIAN

PORTLANDIAN

KIMMERIDGIAN

OXFORDIAN

CALLOVIAN

BATHONIAN

BAJOCIAN

AALENIAN

TOARCIAN

PLIENSBACHIAN

SINEMURIAN

HETTANGIAN

RHETIAN

NORIAN

CARNIAN

LADINIAN

ANISIAN

SCYTHIAN

54

96

152

179

236

Figure 7. Lithostratigraphic column for northwestern Cuba and offshore (fold and thrust beltraphy of the proto-Caribbean oceanic basin. Placetas and Rosario tectonostratigraphic units) foSanchez-Arango and others, 2003).


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Middle Oxfordian

NORTH AMERICA

SOUTH AMERICA

Y U C A

T A N

F L O R I D A - B A H A M A S

B L O C K

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S O

Oceaniccrust

Carbonateplatform

San CayetanoFormation

300Kilometers

0 300 Miles


known as the Louann Salt in the northern part of the Gulfof Mexico and the Campeche Salt in the southern part.Evaporites also were deposited in the Bahama area (Walles,1993), but these evaporites are not stratigraphically connectedto the evaporites in the Gulf (Iturralde-Vinent, 2003). Asrifting continued, the continental crust was stretched to the

point where individual crustal blocks were mobilized, andsea-oor spreading commenced in the central part of theGulf of Mexico as the Yucatan crustal block began to rotatecounterclockwise. The rift-related structures formed duringthis time might have their own source rocks, reservoirs, andtraps (Magnier and others, 2004).

Opening of the Gulf of Mexico In the LateJurassic

In Callovian and possibly into Oxfordian time, the Yucatancrustal block began to rotate counterclockwise from its pre-riftposition to its present conguration (g. 8). The Yucatan blockrotated about a hypothetical pole in Florida (Pindell, 1993), androtated along a western transform margin in Mexico known asthe Tamaulipas fault system. In the process, sea-oor spreadingformed oceanic crust that oors the central part of the Gulf ofMexico. The spreading also resulted in the separation of theCallovian salt into two accumulationsthe northern LouannSalt and the southern Campeche Salt. Thinner salt accumulationsmight exist to the east in the northwestern Cuba area. In aboutValanginian time, the Yucatan block docked in its presentposition following its counterclockwise rotation, and sea-oorspreading ceased in the central part of the Gulf of Mexico.

The margin of the Gulf of Mexico from the Oxfordian tothe Valanginian was passive (g. 9). Several depositional unitsof this time interval are interpreted to be signicant petroleumsource rocks in the Gulf of Mexico, and they might haveextended into the northwestern Cuba area. The basinal facies ofthe Oxfordian Smackover Formation is known to be a prolicsource rock in the northern Gulf of Mexico (Sassen and others,1987). The basinal facies of the Tithonian (Pimienta Formation)is well known as the source for giant oil accumulations in thesouthern part of the Gulf of Mexico (Magoon and others, 2001),and the coeval Bossier Formation is a potential source rock forgas in the northern Gulf of Mexico Basin (Wagner and others,

2003). The Tithonian organic-rich source rock facies, like theOxfordian shales, might have extended into the northwesternCuba area, which would have been a deep-water environmentduring the Late Jurassic.

Opening of the Proto-Caribbean Ocean Basin

As South America continued to drift away from NorthAmerica, sea-oor spreading was initiated south of theYucatan block and the Bahama Platform in about Oxfordiantime, forming what has been called the proto-Caribbean ocean

Figure 8. Reconstruction of middle Oxfordian paleogeographyshowing the partially opened Gulf of Mexico as Yucatan rotatedcounterclockwise, formation of incipient proto-Caribbean oceaniccrust as South America drifted away from North America, anddeposition of the San Cayetano Formation and related rocks along the passive margin of Yucatan Platform. Dashed black lines areuncertain geologic boundaries; dashed red line is the BahamaFracture Zone (modified from Pszczolkowski, 1999). E, Escambray terrane; P, Pinos terrane; SO, Sierra de los Organos terrane; SR,Southern Rosario terrane; NR, Northern Rosario terrane; BFZ,Bahama Fracture Zone.

basin (g. 8; Pindell, 1993). As sea-oor spreading continued,the drift of South America from North America led to thedevelopment of a passive margin along the south edge of theNorth American plate. The passive-margin strata associatedwith the proto-Caribbean plate are now known from the manyTSU exposures on Cuba, and these strata are important for the

interpretation of petroleum source rocks, reservoirs rocks, andseal rocks in the subsurface of northwestern Cuba.

Passive-margin conditions existed from about Oxfordianthrough the Late Cretaceous, during which time severalpotential petroleum source rocks were deposited alongthe passive margin (g. 10), including mudstones of theCenomanian-Turonian, which are known source rocks in theU.S. Gulf Coast.

Movement of the Caribbean Plate

In about Aptian-Albian time, subduction polarityreversed along the western margin of the proto-Caribbean


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Figure 9. Reconstruction of Tithonian paleogeographyshowing further counterclockwise rotation of Yucatan and

the opening of the Gulf of Mexico and formation of proto-Caribbean oceanic crust. Tithonian source rocks are animportant component of the Jurassic-Cretaceous Compos-ite Total Petroleum System in the North Cuba Basin. Dashedblack lines are uncertain geologic boundaries; dashed redline is the Bahama Fracture Zone (modified from Pszc-zolkowski, 1999). BFZ, Bahama Fracture Zone.


Figure 10. Reconstruction of Hauterivian-Bar-remian paleogeography showing complete

opening of the Gulf of Mexico, further opening of the proto-Caribbean oceanic basin, and devel-opment of the passive margins of the BahamaPlatform and Yucatan Platform with sedimentsnow named as terranes. Dashed black lines areuncertain geologic boundaries; dashed red lineis the Bahama Fracture Zone (modified fromPszczolkowski, 1999). SO, Sierra de los Organos terrane; SR, Southern Rosario terrane; LE, LaEsperanza terrane; NR, Northern Rosario terrane;P, Placetas terrane; C, Camajuani terrane; R,Remedios terrane.


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plate, allowing Caribbean crust to enter the area betweenNorth and South America (Pindell and others, 2005) bysubducting proto-Caribbean crust rather than Pacic crust.By Maastrichtian time the westward drift of North Americacaused the Caribbean crust to collide with the southern partof the Yucatan Platform (g. 11), forming the Sepur clastic

wedge in the resulting foreland basin (Angstadt and others,1985) (g. 12). During this time the Guaniguanico terrane wasdeposited east of the Yucatan passive margin (g. 12). Manyof the formations composing the Guaniguanico terrane arepart of the petroleum systems of the North Cuba Basin, as theterrane was disrupted and incorporated into Cuba (g. 13).By early Paleocene, continued movement of the Caribbeanplate caused the leading edge of the plate to break away andmove northward (g. 14), whereas the main Caribbean platecontinued to move northeast prior to the formation of theCayman Trough. The opening of the Yucatan Basin (Case,1975; Rosencrantz, 1990; Pindell and others, 2005) andsubsequent Paleogene spreading of the Yucatan Basin causedCuba arc-forearc rocks to collide with the passive margin ofthe Bahama Platform (g. 15). This explanation is somewhatsimplied because the opening of the Yucatan Basin involvedmovement of a complex assemblage of crustal blocks, faults,and sea-oor spreading (Pindell and others, 2005).

Collision of Cuba Arc-Forearc with the BahamaPlatform

The opening of the Yucatan Basin in the Paleogeneresulted in the northward translation of Cuba arc and forearc

rocks (g. 15) away from the leading edge of the Caribbeanplate. By middle Eocene, the arc-forearc collision with thepassive margin of the Bahama Platform culminated, resultingin suturing and welding of the Cuba fold and thrust belt andthe Cuban foreland (g. 16) onto the North American plate.The collision resulted in a series of north-verging thrust sheetsand metamorphic complexes that constitute the main geologicelements of the island of Cuba. The thrust sheets for the mostpart represent strata that formed the southern passive marginof North America admixed with the arc-forearc rocks thatarrived from the west and southwest along the leading edge ofthe Caribbean plate.

Tectonic Summary

A summary of the tectonic development of the northernCaribbean is shown in gure 17. In the Late Cretaceous,

Figure 11. Reconstruction of Late Maastrich- tian paleogeography showing migration of theCaribbean plate and arc-forearc from the south,and subduction of proto-Caribbean oceaniccrust, with passive margin deposition along the Bahama and Yucatan Platforms (modifiedfrom Pszczolkowski, 1999). Ca, CacarajicaraFormation; Am, Amaro Formation; Pr, PenalverFormation; SJM, San Juan and Martinez Basin;Cf, Cienfuegos Basin.


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watercarbonates

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Olithostromes


Figure 12. Reconstruction of the Guaniguanico terrane along the Yucatan passive margin anddevelopment of the active margin west of theEl Pinar fault zone of northwestern Cuba (fromSchafhauser and others, 2003).

Figure 13. Stratigraphy of the Guaniguanico terrane reflects the presence of Jurassic and Cretaceous source rocks along the eastmargin of the Yucatan Platform that were incorporated into Cuba as the arc-forearc complex translated northward toward the BahamaPlatform in the Paleogene (modified from Pszczolkowski, 1999). SC, San Cayetano Fm.; AC, Arroyo Cangre Fm.; ES, El Sabalo Fm.; J,Jagua Fm.; F, Francisco Fm.; SV, San Vincente Member of Guasasa Fm.; G, Guasasa Fm.; AR, Artemisa Fm.; PL, Polier Fm.; L, Lucas Fm.;ST, Santa Teresa Fm.; GB, Guajaibon Fm.; PN, Pons Fm.; MR, Moreno Fm.; PS, Penas Fm.; CT, Carmita Fm.; PA, Pinalilla Fm.; CA, Cacaraji-cara Fm.; AN, Ancon Fm.; MN, Manacas Fm..


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Figure 14. Reconstruction of Early Paleocene paleogeography showing position of the Caribbean plate relative to the proto-Caribbeanplate, consumption of oceanic crust by subduction of the proto-Caribbean by the advancing Caribbean plate (modified fromPszczolkowski, 1999). Vb, Vibora Basin; Cf, Cienfuegos Basin; Tf, La Trocha Fault.

Figure 15. Structure of the Yucatan Basin (light gray area). The Yucatan Basin opened in the Paleogene and caused the Greater Antil-les (Cuba) arc-forearc rocks (dark gray area) along the leading edge of the Caribbean plate to move northward and collide with the pas-sive margin of the Bahama Platform (from Holcombe and others, 1990). The Cayman Trough opened subsequent to the Yucatan Basin.


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the leading edge of the Caribbean plate, possibly havingoriginated in the Pacic realm, arrived at the Yucatan Platform,consuming proto-Caribbean oceanic crust as it migratedto the east and northeast. In the late Paleocene the YucatanBasin opened by spreading and began to fold and thrust thepassive margin sediments and obduct arc-forearc rocks ontothe Bahama Platform. This process continued into the Eocene,and by the end of the middle Eocene the arc-forearc wascompletely sutured onto the North American plate.

The signicance of the tectonic history of the northernCaribbean is that organic-rich, passive margin-sedimentsdeposited during Late Jurassic to Paleogene time wereprogressively buried beneath successive thrust sheets andforeland basin sediments as the Cuban arc-forearc collidedwith the passive Bahama Platform margin. In addition to thefold and thrust belt, the collision resulted in the formationof a foreland basin whose accommodation space was lledprimarily with Paleogene clastic rocks, further adding to theoverburden and thereby might have assisted in the thermalmaturation of the Mesozoic organic-rich rocks. Thus, the

tectonic history is a direct cause for the development ofpetroleum systems in the North Cuba Basin.

Looking specically at the area that is now the NorthCuba Basin, the tectonic history had a direct inuence onthe elements of the petroleum system. In gure 18 A , thearea was dominated by Mesozoic rift basins. These, in turn,were overlain by Upper Jurassic and Cretaceous shallowand deep-water carbonate sediments, several of which areorganic-rich (g. 18 B ). In the Paleogene, the initiation of the

fold and thrust belt caused some of these source rocks to beburied sufciently to reach the generative thermal windowsfor oil (g. 18 C ). Further thrusting resulted in the formationof the Cuban foreland, and some of the extensional structuresassociated with rifting were inverted (g. 18 D ). By the middleEocene suturing was complete, and the foreland continuedto accumulate clastic sediments, further burying potentialsource rocks into the generative windows for oil and gas (g.18 E ). A summary of the main tectonic events and the relationto petroleum system elements of the North Cuba Basin ispresented in gure 19.

Figure 16. Middle Eocene reconstruction showing the opening of the Yucatan Basin, the collision and suturing of the Greater Antillesarc-forearc with the Bahama platform, leading to the development of the Cuban fold and thrust belt and foreland basin (modified fromPszczolkowski, 1999, and Pindell and others, 2005). Dashed black lines are faults.


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THRUST BELTFORELAND

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Figure 17. Tectonic model for the development of the Cuban fold and thrust belt and foreland (from Gordon and others, 1997).


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N.W. S.E.

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Continental basementSynriffPostriff carbonate platformPostriff deep water facies

Tertiary syntectonic deposit

Tertiary post-tectonic depositActive faultsNon-active faults

E .

D .

C .

B .

A .


Figure 18. Sequential development of the northwest Cuban fold and thrust belt and the foreland associated with the fold belt. A,Proto-Caribbean synrift (Early to Middle Jurassic) development of rift basins; B , post-rift subsidence; C , end of Greater Antilles orogenyin early Eocene; D , infilling of basin, which began as foreland in previous phase; E , passive subsidence caused by sediment influx fromCuba (after Moretti and others, 2003b).


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CONIACIANTURONIAN

Main Tectonic EventsAffecting N.W. Cuba

Geologic Age

Petroleum System Elements

N E O G E N E

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Figure 19. Summary of tectonic events affecting the northwestern Cuba area and the main elements of the Jurassic-CretaceousComposite Total Petroleum System. Letters A-E refer to time intervals represented by diagrams shown in figure 18. Dashes reflectuncertainty of timing of geologic events.


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Jurassic-Cretaceous Composite TotalPetroleum System

A TPS is an integration of the tectonic, sedimentary, andthermal history of an area (Pindell, 1991) and is dened to

encompass all uids that have been generated from geneticallyrelated pods of thermally mature petroleum source rocks(Magoon and Dow, 1994). In the North Cuba Basin, threemajor types of oils are present, which reects the presenceof potential source rocks. However, it is not possible on thebasis of currently (2008) available geochemical information toisolate and dene separate petroleum systems. Accordingly, asingle petroleum systemThe Jurassic-Cretaceous CompositeTotal Petroleum Systemwas dened for the North CubaBasin (g. 20).

Source Rocks

As indicated above, geochemical analyses andinterpretations of samples of potential petroleum sourcerocks, oils, and gases have quantitatively dened severalsource rocks and potential petroleum systems of the NorthCuba area (Maksimov and others, 1986; Lopez-Quintero andothers, 1994; Lopez-Rivera and others, 2003a, b; Moretti

and others, 2003a,b; Magnier and others, 2004). These are:(1) Lower to Middle Jurassic rift-related mudstones; (2)Upper Jurassic and Lower Cretaceous deep-water organic-rich carbonate mudstones; (3) Upper Cretaceous deep-watercarbonate mudstones; and possibly (4) Paleogene mudstones.Of these, the Upper Jurassic and Lower Cretaceous deep-water

carbonate mudstones are considered to be volumetrically themost signicant petroleum source rocks in the basin (Morettiand others, 2003a,b). Paleogene source rocks and uids alsohave been reported, but these uids are not considered to bevolumetrically signicant because of the low level of thermalmaturation of these sediments (Magnier and others, 2004)relative to the generative windows in the foreland basin. Eachof these potential source rocks are described briey in thefollowing paragraphs.

Lower to Middle Jurassic Rift-RelatedMudstones

Field investigations in western Cuba have revealedthe presence of Lower to Middle Jurassic rift-related faciescomposing the San Cayetano Formation (g. 7; Haczewski,1976). The formation is exposed in western Cuba, having beenplaced in that position by the compressional tectonics betweenthe Cuban allochthonous assemblage and the passive margin

Figure 20. Boundary of the Jurassic-Cretaceous Composite Total Petroleum System (yellow line) and three assessment units (AU)defined in this study (red lines). Red symbols refer to numbered Deep Sea Drilling Project wells.


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of North America during the Paleogene. The San CayetanoFormation might have been part of the passive margin ofthe Yucatan Platform during rifting (g. 8), and the terranesubsequently was detached, moved northeastward, and weldedonto the Cuban assemblage during the opening of the YucatanBasin in the Paleogene.

The San Cayetano Formation formed during the riftingof South America from North America. From Late Triassicthrough early Late Jurassic time, rifting resulted in attenuatedcontinental crust and the formation of grabens, half grabens,and other rift related structures. The structures have beenimaged seismically (Lopez-Rivera and others, 2003b) and aresimilar to coeval structures reported from the U.S. Gulf Coast(Salvador, 1987; 1991). The rift facies have been describedfrom several thrust-bounded rock packages in western Cubawhere the facies of the San Cayetano Formation and theFrancisco Formation have been examined in detail.

The involvement of the San Cayetano Formation in thetectonic slices makes a determination of its original thicknessdifcult, but estimates of thickness range to as much as 5,000 m.Facies descriptions of the formation are typical for rift basins,with rapid facies changes and difcult correlations. Haczewski(1976) dened several facies of the San Cayetano, includinguvial, possibly nearshore marine and estuarine sandstonesand mudstones, lagoonal mudstones, and a series of slope-basin turbidite facies including sandstones and mudstones; allsandstones are potential reservoirs in the subsurface.

Signicant to the issue of petroleum source rocks arethe lagoonal facies and the deep-water black shales thatwere examined in outcrop. Analyses of black shales of theSan Cayetano and Francisco formations from western Cubaby Moretti and others (2003b) demonstrated that the shalesare organic-rich and are thermally overmature with respectto oil generation. Measurements were made of total organiccarbon (TOC), a standard measure of the weight percent oforganic matter in a rock that represents only that organiccarbon remaining after maturation and possible expulsionof petroleum. Remnant TOC values for the black shalesrange from 0.7 to 3.3 weight percent. Average initial TOC isestimated at approximately 3 weight percent, but initial TOCcould have been higher. The black shales were interpreted tocontain oil-prone marine Type IIS organic matter by Morettiand others (2003b). These data indicate that similar rift-relatedblack shales in the subsurface, which are known to exist

throughout most of the southeastern Gulf of Mexico, might bepetroleum source rocks (g. 21).At present (2008), no petroleum produced from oil

elds in Cuba has been genetically tied to rift-related blackshales. Theoretically, these uids would be geochemicallydistinct from uids originating in the deep-water carbonatefacies of the Upper Jurassic and Cretaceous strata. Withoutspecic data, a separate rift-basin petroleum system cannot bedened in the North Cuba Basin, but this may be designatedas a distinct petroleum system in the future. The rift-relatedblack-shale facies might be present over a large part of theassessment area (g. 21), and given that the shales may

be thermally mature to overmature, petroleum might havebeen generated from these shales, migrated, and formedaccumulations related to the rift basins. This concept isconsidered a possibility in several exploration play denitionsfor the North Cuba Basin (Moretti and others, 2003b).

Similar rift basins are present in the U.S. Gulf Coastwhere the rift facies are collectively referred to as the EagleMills Formation, and in east-central Mexico where thefacies are called the Huayacocotla and Hulzachal formations(Salvador, 1991). Although the Eagle Mills Formation isinformally referred to as a red-bed facies based on limiteddrilling, Salvador (1991) states that organic-rich mudstonesand local coal beds are typical of these facies, indicating thatsource rocks might be present in these rifts. However, thepresence of source facies would be strongly dependent uponpaleoclimate.

In summary, data from northwestern Cuba indicate thatsome rift-related black shale might have contained sufcientorganic matter to have served as petroleum source rocks,

but much uncertainty remains. Seismic data interpretationshave shown the presence of numerous rifts in the assessmentarea, indicating that these rifts might have petroleum sourcerocks. Modeling shows that the shales in the rift grabens inthe North Cuba Basin might have generated petroleum in theJurassic, and that these uids might have been sealed withinreservoirs of the rift basins or might have migrated out and upinto reservoirs of the post-rift sequences (Moretti and others,2003b; Vassalli and others, 2003). Another issue is that theuids originating from these shales might be gas at presentrather than oil because the shales are thermally overmaturefor oil.

Figure 21. Present-day distribution of postulated synrift Jurassicsource rocks; original extent most likely was further south prior to thrust shortening. Dashed lines reflect uncertainty of source-rockextent (from Moretti and others, 2003b).


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Upper Jurassic-Lower Cretaceous Deep-MarineCarbonates

Deep-marine, ne-grained, organic-bearing carbonatemudstones of the Upper Jurassic and Lower Cretaceousinterval are considered to be the most signicant petroleum

source rocks in the North Cuba Basin (gs. 22, 23). Thesesource rocks crop out in western Cuba, and source-rockdata from outcrops were summarized by Moretti and others(2003b). Upper Jurassic rocks, specically Upper Oxfordianand Tithonian deep-water carbonates, were depositedbasinward of shallow-water carbonate platforms that rimmedthe southeastern Gulf of Mexico in the Late Jurassic (Salvador,1991; Pindell and Kennan, 2001). The basinal carbonatesare ne grained, with alternations of dark organic-bearinglamina with grayer, less organic-bearing carbonate lamina;TOC values average about 3 weight percent, with somemeasurements as high as about 7 weight percent (table 2).

Upper Oxfordian deep-marine carbonates are the primarysource rocks in the northern U.S. Gulf Coast for petroleumin the Jurassic Smackover Formation reservoirs (Sassen andothers, 1987). Tithonian deep-marine carbonates are theprimary petroleum source rocks in the Mexican southern Gulfof Mexico (Magoon and others, 2001), and these rocks arethe source for petroleum in many of the major Mexican GulfCoast oil elds. Tithonian shales might contain signicantgas resources in the U.S. Gulf Coast as well, mainly from theBossier Formation (Wagner and others, 2003).

Upper Cretaceous Deep-Marine Carbonates andMudstones

Deep-marine carbonate mudstones from the Cenomanian-Turonian interval are known source rocks in the U.S. GulfCoast region. These rocks might be present in the passivemargin section of Northwest Cuba that was overridden by thethrust sheets in the Paleogene (g. 24). Moretti and others(2003b) have shown that samples of Cenomanian mudstones,in addition to Albian and Aptian samples, had TOC valuesabove 1 weight percent. They suggested that TOC valuescould be as high as 3 weight percent, with hydrogen index(HI) values greater than 600, both parameters indicatingan excellent potential source for oil. The thickness of theCenomanian interval in northwest Cuba is unknown, and it

is possible that some of the Cenomanian section was eroded.The Cenomanian source rocks, which are included withrocks of Aptian and Albian age, were analyzed as havingType II and Type IIS organic matter (Moretti and others,2003b), indicating a marine oil-prone source rock. They alsointerpreted the source rocks as having a hypersaline-anoxicorigin (table 2), similar to the results reported by Navarrete-Reyes and others (1994). Thermal maturation of Aptianthrough Cenomanian rocks was modeled by Moretti and others(2003b), and the results indicate that these rocks are thermallyimmature in the foreland basin and carbonate platform areas,but are thermally mature in the fold and thrust belt.

Figure 22. Present-day distribution of Upper Jurassic deep-watercarbonate source rocks (shaded blue); original extent most likelywas further south overlying proto-Caribbean crust prior to thrustshortening in the Paleogene. Dashed lines reflect uncertainty ofsource-rock extent (from Moretti and others, 2003b). Contours arewater depths, in meters.

Figure 23. Present-day distribution of Lower Cretaceous deep-water carbonate source rocks (shaded green); original extent mostlikely was further south prior to thrust shortening in the Paleo-gene. Dashed lines reflect uncertainty of source-rock extent (fromMoretti and others, 2003b). Contours are water depth, in meters.


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Table 2. Geological attributes of four main groupings of potential petroleum source rocks in the Jurassic-Cretaceous Composite Total Petroleum System in the North Cuba Basin.

TectonicSetting

Synrift

Post-RiftPassive Margin

Post-RiftPassive Margin

Foreland Basin

Source Rock Group

Lower-Middle Jurassic

Upper Jurassic -Barremian

Aptian - Cenomanian

Paleocene - Eocene

Organic MatterType

Type II

Type II, IIs

Type II, IIs

?

GeneralDepositionalEnvironment

Siliclastic Shales

Deep Marine Carbonates

Deep Marine Carbonates

Siliclastic Shales

SpecificDepositionalConditions

Deep Marine (?)

Hypersaline/Anoxic

Hypersaline/Anoxic

?

General Level of PresentThermal Maturity

Total Organic CarbonRemnant

(Weight %)

0.7 - 1.5

up to 7.6

up to 3.1

?

Thrust Belt

B - M

M

M

I

Foreland

O - M

M

I

I(?)

Deep Marine

M(?)

I

I

I

Original(Weight %)

~ 3

~ 3

~ 3

?

l

1,000 1 , 0 0 0

1 , 0 0 0

1 , 0

0 0

1,0 0 0

2 , 0 0 0

1,0 0 0

20 0

2 0 0

2 0 0

2 0 0

2 0

0

2 0 0

86W 84W 82W 80W

22N

24N

26N

BAHAMAS

CUBA

Gulf of Mexico

Caribbean Sea

FLORIDA

YUCATAN

PLATFORM

0 200 Kilometers

0 200 Miles

OMTYPE II, IIS

OMTYPE II

OMTYPE II (I-II)

ENVIRONMENTMarine, Anoxic

ENVIRONMENTMarine, Anoxic

ENVIRONMENTMarine, Subanoxic, Suboxic

High Confinement Low Confinement Higher Terr. Lower Terr.Input:

Carbonate >> Shale Carbonate >> Shale Carbonate


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SULFUR, in percent

A P I G R A V I T Y

, i n d e g r e e s

40

35

30

25

20

15

10

5

00 1 2 3 4 5 6 7 8 9 10

Tertiary Lower Cretaceous Upper Jurassic

V. Blanca 101

0

0

10

20

30

40

2 4 6 8 10

TOC, in percent

S 2 m g

H C / g

Synrift Rhaetian-OxfordianPost-rift KimmeridgianPost-rift TithonianDSDP-535 BeriasianPost-rift A ptian/Albian

0

0

10

20

30

40

2 4 6 8 10

TOC, in percent

S 2 m g

H C / g

Synrift Rhaetian-OxfordianPost-rift KimmeridgianPost-rift TithonianDSDP-535 BeriasianPost-rift Aptian/Albian


Geochemical data indicate that several oils from differentsource rocks are present in the North Cuba Basin, and thatthere are several oil families based on geochemical data(table 3). However, the oils are located in complex structureswithin the fold and thrust belt and are distributed somewhatrandomly. In addition, the oils are difcult to differentiate andmap into distinct families on a regional basis. For this reason,a composite TPS was dened in the North Cuba Basin.

Petroleum Generation

Moretti and others (2003b) discussed the results ofthermal modeling aimed at determining the timing ofpetroleum generation in several source-rock intervals in theNorth Cuba Basin. For the synrift source rocks, modelingresults indicate that the synrift source rocks are overmaturewith respect to oil generation within the thrust belt andforeland basin areas. Within the deep offshore area, synriftsource rocks are interpreted to be just within the oil generationwindow. For the Upper Jurassic and Lower Cretaceous ne-grained carbonate source rocks, modeling indicates probablethermal maturity within the thrust belt and possibly also inthe deeper parts of the foreland; however, in the majority of

the foreland and platform areas, modeling indicates the rocksare thermally immature for oil generation. This conclusionis corroborated by the ndings from the Deep Sea DrillingProject (DSDP) Site 535 well (discussed below). Modelingalso indicates that gas generation may have occurred withinthe thrust belt and the deeper parts of the foreland (Moretti andothers, 2003b).

Figure 27. Plot of percent sulfur and API gravity for some Cubanoils in Upper Jurassic, Lower Cretaceous, and Paleogene rocks(from Magnier and others, 2004).

Figure 28. Plot of Rock-Eval data from Cuba onshore source rocksamples and samples from DSDP well 535 showing distribution of total organic carbon (TOC) values (from Magnier and others, 2004).S2 mg HC/g, value of milligrams of hydrocarbon/gram of sourcerock from the Rock-Eval S2 peak..

Figure 29. Map showing boundaries of the Jurassic-CretaceousComposite Total Petroleum System (yellow line) and the threeassessment units defined in this study.

range of API gravities (9-43 degrees), and a wide range ofsulfur contents (g. 26) most likely because of biodegradation(Campos-Jorge and others, 1994).

Data on sulfur content and API gravity indicate that someof the Cuban oils have been biodegraded, resulting in thelower API gravities and higher sulfur contents (Campos-Jorge

and others, 1994), but this is not true for all Cuba oils (g. 27).As for hydrocarbon potential, many samples from northernCuba plot with TOC values greater than 1 weight percent,and therefore could be petroleum source rocks (g. 28).Geochemical data also indicate that many of the Cuban oilsoriginated from source rocks that were deposited as carbonatesediments under anoxic and hypersaline depositionalenvironments, possibly in deep water. A few oils indicate asiliciclastic Paleogene source (g. 29).


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West0

1

2

3

4

5

6

CampecheEscarpment

Reeftalus

Triassic?rift basin

536 MCU

early Mesozoiccarbonate platform?

535

540

MCU

Late Jurassic

Rifted and attenuated

continental crust(transitional crust)

EarlyCretaceous

MCU

FloridaEscarpment

East

5374

5

6

7

S e c o n

d s

S e c o n

d s

MCU

CatocheKnoll

Rifted continental crust

26

24

22N 88W 86 84 82 80

537536

538

535 539540

Cuba

3,

1 ,0 0 0

2 0 0

2 0 0

1,0 0 0

Middle Cretaceouscarbonate platform

margin

B B

AA

BB

0 ~12 Miles

~12 Kilometers

Oil Family

B

C

Well Sample

- -

Yumuri 37Yumuri X

Via Blanca 103Boca Jaruco 359

Varadero 103Varadero 306

Yumuri 31Via Blanca 101

Boca Jaruco 370Marabella Mar 1

Cantel 33

Marabella Mar 2Cantel 30

Cantel 229Martin Mesa 1

Martin Mesa 24

Sample Depth

- -

12802321198918261690161314871380130625501140

1898477424824733

- -

135036002054185717201645

1467(?)1410135625651172

1912683488

807(?)773

Reservoir Age

- -

Upper JurassicUpper JurassicUpper JurassicUpper JurassicUpper Jurassic

Lower CretaceousLower CretaceousLower CretaceousLower CretaceousLower CretaceousUpper Cretaceous

PaleocenePaleocenePaleocene

Lower EoceneLower Eocene

Formation

- -

CifuentesCifuentesCifuentesCifuentesCifuentesCifuentes

RondaCarmitaCarmitaParaisoCarmita

VegaSerpentiniteSerpentinite

ManacasManacas

API

- -

6.3- -

21.1- -9.6

10.410.433.7- -

11.0- -

26.612.014.123.218.6

SULFUR

- -

5.967.646.206.768.98.94.62.9

3.535.69- -

- -1.17- -

1.380.69

Nickel

- -

705430286866- -9

2345- -

- -- -41125

Vanadium

- -

1111025047

109105- -142376- -

- -- -41125

(ppm)(ppm)(percent)(meters)A


Petroleum Migration

The most signicant geologic uncertainty in the Jurassic-Cretaceous Composite TPS is the efcacy of lateral petroleummigration. Clearly, petroleum source rocks are present, andsome have reached generative thermal maturity. However,the source rocks had to be thermally mature at depth to haveproduced the oil in Cuba, at DSDP Site 535, and in wellsalong the south margin of the Bahama platform. The degreeto which petroleum migration has occurred beyond the foldand thrust belt to permit trapping and pooling of signicantvolumes of petroleum is highly uncertain. Petroleum wasgenerated as thrust loading and burial of source rocks in thePaleogene resulted in thermal maturity. Fluids generatedwithin the thrust belt migrated vertically to the 20-plus knownelds, and uids might have migrated laterally into reservoirswithin the foreland basin and to the carbonate platformmargin. That some lateral migration has occurred is shownby the oil in cores at DSDP Site 535 well. Lateral migrationmight not have been possible for petroleum generated withinthe synrift strata, because the presence of evaporites suchas halite and anhydrite within the Middle Jurassic section

and the ne-grained carbonates that were deposited duringthe Berriasian ooding event would have served as seals tolimit the lateral movement of synrift petroleum (Magnier andothers, 2004). Lateral migration of petroleum from UpperJurassic and Lower Cretaceous source rocks would not havebeen as constrained as that generated from source rocks withinthe synrift section. Structural barriers such as faults also mighthave limited lateral migration. Parnell and others (2003)interpreted some petrologic information from oil-bearingsamples from the fold and thrust belt to indicate that theremight have been multiple episodes of oil migration related tothe multiple thrust events.

Significance of DSDP Site 535 Well,Southeastern Gulf of Mexico

In 1981 several wells were drilled in or near the Jurassic-Cretaceous Composite TPS in the North Cuba Basin duringLeg 77 of DSDP (g. 2). The main objective was to sampleshallow Cretaceous carbonate rocks thought to exist in thearea. Six wells were drilled, and cores from one of the wells,Site 535, contained what were interpreted as oil stains andasphalt-lled fractures (Herbin and others, 1984; Katz,1984; Palacas and others, 1984a; Patton and others, 1984).These shows of petroleum bear directly on the denitionand mapping of the composite petroleum system in thenorthwestern part of Cuba.

Figure 30. Location of wells drilled on Leg 77 of the Deep Sea DrillProject. Site 535 well is shown on an interpreted seismic section (B-B). The Jurassic and Cretaceous sedimentary section at this locationis thermally immature for petroleum generation, so oil reported fromcore in this well must have migrated to this locality. Gray shade isbasement rock (from Buffler and others, 1984). MCU, MiddleCretaceous unconformity.

Table 3. Geochemical parameters of some onshore oils from the North Cuba Basin (after Moretti and others, 2003 a, b). ppm, partsper million.[ppm, parts per million; - -, no data.]


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Site 535(Water depth = 3,455 m)

LithologyAge

Cenomanian

late Aptianearly

Aptianearly

Barremian __ lateHauterian

Hauterian

Valanginian

lateBerriasian

Recent _late

Pleistocene

Unit I:Mud and clay withminor sand

1.65

2.84

2.80

3.27

3.07

3.40

3.36

3.20

3.41

4.70

Unit II:Laminated, banded andbioturbated limestonewith some coarsebioclastic layers

Unit III:Alternating white togray massivelimestone and gray to black la minatedand bioturbatedmarly limestone*

Unit V:Alternating white togray massivelimestone and gray

to black la minated to bioturbat ed marlylimestone*

Unit IV:Alternating graylaminated tobioturbatedmarly limestone*

Velosity(km/s)

0

100

200

300

400

500

600

700

S u

b - b

o t t o m

d e p t h

,

i n m e t e r s

Total Depth = 714 m*Graphic symbols for this part of the column are schematic and do not represent true thickness of alternating lithologies 1,200

1,000

800

600

400

200

00 50 100 150 200 250 300 350 400 450

H y

d r o g e n

i n d e x

( m g

H C / g o r g a n

i c c a r b o n

)

Oxygen index (mg CO2 /g organic carbon)

I (oil prone)

II (oil/gas prone)

Stained

III (gas prone)

Holocene/late PleistoceneCretaceous


The well at DSDP Site 535 was drilled in a waterdepth of 3,455 m. Coring recovered approximately 714 mof sedimentary rock, mostly carbonates (gs. 30, 31). Thecores began in Holocene and upper Pleistocene siliciclastic

sediments, and at a sub-sea depth of 287 m drilling foundpossible Cenomanian carbonates, followed by Aptian,Barremian, Hauterivian, and Valanginian carbonates. Drillingwas terminated in upper Berriasian carbonate rocks (g.31). These cores have been examined in detail for petroleumsource-rock potential (Herbin and others, 1984; Katz, 1984;Palacas and others, 1984a; Patton and others, 1984; Rullkotterand others, 1984; Summerhayes and Masran, 1984).

The Cretaceous rocks cored at DSDP Site 535 weredescribed as deep-water carbonates, mainly laminated tononlaminated limestones with increasing percentages oforganic material providing a darker color to the rock. The

rocks ranged from white nonlaminated limestones to white andgray to dark gray laminated limestones (Herbin and others,1984). Several studies analyzed the cores for TOC, which isan indicator of petroleum source rock potential. In general, thedarker laminated limestones contained more organic carbonthan the lighter laminated limestones. The majority of the

cored interval, from the late Barremian to the Cenomanian,was interpreted to have good to excellent petroleum sourcerock potential (g. 27). In general, TOC values above 0.5-1 weight percent are considered adequate for a petroleumsource. This condition was met in the gray to dark greylaminated limestones but not in the laminated to nonlaminatedwhite limestones (Katz, 1984).

The organic matter analyzed from these Cretaceouslimestones is nearly all marine-derived, oil-prone Type IIorganic matter (Herbin and others, 1984). Little Type III, orwoody nonmarine, gas-prone organic matter was observed inthe cores. All of the studies cited herein show a preponderanceof Type II and Type IIS marine organic matter (g. 32).

The limestones cored at DSDP Site 535 were interpretedto be thermally immature with respect to petroleumgeneration, because measurements of vitrinite reectancein all cores from Site 535 were less than 0.5 percent. Othergeochemical parameters such as biomarkers also indicatethermal immaturity of the petroleum (Palacas and others,1984a). The immaturity of the organic matter in the limestonesis signicant in that the oil stains and asphalt observed in thecores (g. 33) must have originated from a uid that migratedfrom a source rock that is mature in some other, deeper part ofthe basin. The fold and thrust belt is the likely source (Pattonand others, 1984). Because oil was observed at Site 535, itis an indication that oil likely migrated from deeper parts ofthe basin, possibly from the eastern, deeper part where the

Figure 31. Interpretation of carbonate strata cored at Deep SeaDrilling Project Site 535 (from Herbin and others, 1984).

Figure 32. Modified van Krevelen diagram for potential hydro-carbon-bearing source rocks at Deep Sea Drilling Project Site535. Potential source rocks contain predominantly Types II and IIIorganic matter (from Katz, 1984). Mg HC/g, milligrams of hydrocar-bons per gram of organic carbon; mg CO2/g, milligrams of carbondioxide per gram of organic carbon.


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Age Lithology

Holocene

late Albian?

middle Albian?

early Albian?

late Aptian?early Aptian?

Barremianlate Hauterivian

early Hauterivian

late Valanginian

early Valanginian

late Berriasian

?

? ?

?

Unit I: Mud and clay

Unit II: Laminated, banded and bioturbated limestone with some coarse bioclastic layers

Unit IV: Alternating gray laminated to bioturbated marly limestone

Unit V: Alternating white to gray massive limestone and gray to black laminated to bioturbated marly limestone

Unit III: Alternating white to gray massive limestone and gray to black laminated and bioturbated marly limestone

50-3, 2734 cm (unstained sample)

53-3, 037 cm (unstained sample)58-2, 103108 cm (unstained sample)

58-4, 345 cm and 1920 cm (oil-stained and asphalt samples)61-1, 046 cm (unstained sample)Oil-stained and asphalt samples (not analyzed)

0

100

200

300

400

500

600

700

Limestone Marl, marlylimestoneMud and clay Ammonites

S u

b - b

o t t o m

d e p t h

, i n m e t e r s


Lower Cretaceous limestones are thermally mature enough togenerate and expel petroleum.

Although the origin of the oil stains and asphalt atSite 535 is problematic, several studies indicate that the oilcame from mature carbonate source rocks in the deeper partof the North Cuba Basin. The source rocks may be from

thermally mature, deep-water limestones that are downdipor deeper than the rocks at Site 535, or the source may befrom rocks stratigraphically deeper than these Neocomianrocks, including possible Jurassic sources (Palacas and others,1984a). Moretti and others (2003b) concluded that the oilanalyzed from DSDP Site 535 originated from a source withinthe North Cuba Basin and showed geochemical similaritiesto some oils analyzed from the Cuban onshore elds, but wasdistinct from similar age oils reported from the South FloridaBasin (Palacas and others, 1984b).

Analyses of cores samples of Cretaceous limestones fromDSDP Site 535 thus demonstrate that Cretaceous deep-waterlimestones have good to excellent petroleum source rockpotential, and that these lithologies should be present to theeast in the deeper parts of the North Cuba Basin. If thermallymature, these organic-bearing carbonates would makepotential sources for oil not only in the North Cuba ThrustBelt AU but also in the North Cuba Foreland Basin AU andNorth Cuba Platform Margin Carbonate AU.

Significance of the Doubloon Saxon #1 Well,Bahama Platform

In 1986 a deep well was drilled to test the oil and gaspotential of the southwest edge of the Bahama Platformnear Cuba (Walles, 1993). The well was drilled to a depth of

6,631 m and remains (2008) the deepest test on the BahamaPlatform. Several other wells have been drilled there over theyears, but the area remains lightly explored for oil and gas(g. 34). The Doubloon-Saxon #1 well was drilled on theedge of the carbonate platform, nding carbonate rocks tototal depth. Unlike the carbonates in DSDP Site 535, therewere few intervals of potential petroleum source rock, andall potential sources were higher in the Upper Cretaceoussection. However, oil shows were recorded throughout muchof the Lower Cretaceous carbonate section (g. 35). TheCretaceous rock below a depth of about 5,000 m consisted ofalternating carbonates and anhydrite beds. Walles (1993), in apost-drilling summary of this well, concluded that anhydritebeds above this depth were removed by dissolutionthat is,ushing of the carbonate rock and dissolution of evaporatewas by meteoric waters brought down along faults relatedto the collision of Cuba with the Bahama Platform. He alsoconcluded that above a depth of 5,000 m, dissolution ofanhydrite beds resulted in a loss of seals to any potential

Figure 33. Stratigraphic column for Deep Sea Drilling Project Site 535 core showing location of oil-stained intervals in core that wassampled and analyzed by the U.S. Geological Survey (from Palacas and others, 1984a).


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A

A

NGREAT ISAAC #1

ANDROS IS. #1

TD 5443m

TD 4448mGULF 826-Y

TD 4720m

CAY SAL #1

TD 5766m

DOUBLOON-SAXON #1

TD 6631 m

CAYO COCO #2

TD 3222m

LONG IS. #1

TD 5355m

24N

22N

20N

84W 82W 80W 78W 76W 74W

60 Kilometers

0 60 M iles

FLORIDA

CUBA

BAHAMAPLATFORM

WEST

FLORIDA

SHELF

Atlantic

Ocean

Gulf

of Mexico


Figure 34. Map showing locations of oil and gas exploration wells in the southwestern part of the Bahama Platform (from Walles,1993). Cross section A-A shown in figure 35

hydrocarbon accumulations, greatly reducing the potentialfor commercial oil accumulations to exist. Much dead oilwas observed in the cores above 5,000 m, but deeper rockscontained live oil. Above 5,000 m, Walles (1993) believedthere to be no structural trapping of oil and gas at this wellsite.

The presence of petroleum along the southwest edge ofthe Bahama Platform, however, is signicant for the denitionof the Jurassic-Cretaceous Composite TPS in the NorthCuban Basin. In addition to the Doubloon-Saxon #1 well,petroleum was observed in several other wells in the BahamaPlatform (g. 35). Although no commercial oil accumulationshave been reported, the presence of oil demonstrates thatpetroleum was generated and migrated into carbonate rocksof the platform. In addition, because apparently there are nopotential petroleum source rocks in the Bahamian Platformcarbonates, which is unlike similar age carbonates of the SouthFlorida Basin (Palacas and others, 1984b), the oil must have(1) originated from deeper stratigraphic intervals (possiblyof Jurassic age) within the platform; or (2) the oil originatedlateral to the platform, possibly within the Cuban fold andthrust belt. Oil shows in the Doubloon-Saxon #1, Cayo Coco,and Cay Sal wells (gs. 34, 35) indicate that petroleum uidsmigrated into the carbonates from below, possibly from aJurassic source, or laterally from Jurassic or Cretaceoussources or both within the fold and thrust belt. There are nopublicly available geochemical data that would bear directly

on the origin of the Bahamian oils or on possible migrationpaths. Seals appear to be the main geologic risk above 5,000 mdepths.

Live oil at depth is signicant because if there arestructures at depth or diagenetic traps, then oil or gasaccumulations along the margin of the Bahama Platform are

possible or even highly probable, given the depth where oilhas been observed and the low geothermal gradients commonto carbonate platforms.

SummaryJurassic-Cretaceous CompositeTotal Petroleum System

A large body of geochemical data strongly indicates thatseveral petroleum source rock units are present in the NorthCuba Basin (Moretti and others, 2003b). The source rocksmay

petroleum system in cuba

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