Petroleum Source Rocks of the Onshore Interior Salt Basins, North ...

Petroleum Source Rocks of the Onshore Interior Salt Basins, NorthCentral and Northeastern Gulf of MexicoMancini, Ernest A., 1 Li, Peng; 1 Goddard, Donald A.; 2 and Zimmerman, Ronald K. 31 Center for Sedimentary Basin Studies and Department of Geological Sciences, University of Alabama, Box 870338,Tuscaloosa, Alabama 35487-03382 Center for Energy Studies, Louisiana State University, Baton Rouge, Louisiana 708033 Louisiana Geological Survey, Louisiana State University, Baton Rouge, Louisiana 70803IntroductionGeologic SettingAbstractUnderstanding the burial and thermal maturation histories of the strata in the onshoreinterior salt basins of the north central and northeastern Gulf of Mexico area is critical in petroleumsource rock identification and characterization. The burial and thermal maturationhistories of the strata in these basins and subbasins are consistent with the rift-related geohistoryof these features. Source rock analysis and thermal maturity modeling indicate that lime mudstoneof the Upper Jurassic Smackover Formation served as an effective regional petroleumsource rock in the North Louisiana Salt Basin, Mississippi Interior Salt Basin, Manila Subbasinand Conecuh Subbasin. The Upper Cretaceous marine shale was an effective local petroleumsource rock in the Mississippi Interior Salt Basin and a possible local source bed in the NorthLouisiana Salt Basin given the proper organic facies. Lower Cretaceous lime mudstone was aneffective local petroleum source rock in the South Florida Basin, and these rocks were possiblelocal source beds in the North Louisiana Salt Basin and Mississippi Interior Salt Basin given theproper organic facies. Uppermost Jurassic strata were effective source rocks in Mexico, andtherefore, were possible source beds in the North Louisiana Salt Basin given the proper organicfacies. Lower Tertiary shale and lignite have been reported to have been source beds in south Louisianaand southwestern Mississippi, but these beds have not been subjected to favorable burialand thermal maturation histories required for petroleum generation in the North Louisiana SaltBasin, Mississippi Interior Salt Basin, Manila Subbasin, and Conecuh Subbasin.Petroleum reservoirs in the interior salt basins and subbasins of the onshore northern Gulf ofMexico have produced 4 billion barrels of oil and 21 trillion cubic feet of natural gas. The lime mudstonebeds of the Upper Jurassic Smackover Formation are the main petroleum source rocks from whichthis oil and gas have been generated. The Smackover Formation has been documented to be an effectiveregional source rock in the northern Gulf of Mexico (Oehler, 1984; Sassen et al., 1987; Claypool andMancini, 1989).The purpose of this paper is to provide data and information regarding the organic and thermalmaturation characteristics of potential petroleum source rocks and in particular the Smackover limemudstone beds from the onshore interior salt basins and subbasins in the north central and northeasternGulf of Mexico. These data are a combination of new information and data compiled from previousstudies, especially those of Sassen et al. (1987), Sassen and Moore (1988), Claypool and Mancini(1989), and Mancini et al. (2003).The geologic history of the North Louisiana Salt Basin, Mississippi Interior Salt Basin, ManilaSubbasin and Conecuh Subbasin (Fig. 1) is directly linked to the evolution of the Gulf of Mexico basin(Wood and Walper, 1974). The Gulf of Mexico is a divergent margin basin dominated by extensionalGulf Coast Association of Geological Societies Transactions, Volume 55, 2005486

Mancini et al.TexasEast TexasSalt BasinSabineUpliftNorth LouisianaSalt BasinAA'LouisianaMississippiMonroeUpliftBB'AlabamaMississippiInteriorSalt BasinGeorgiaManila Sub-BasinC DConecuhRidgeD'C'ConecuhSub-BasinWigginsArchFloridaN400 km250 miFigure 1. Location map of interior salt basins and subbasins in the north central and northeastern Gulf ofMexico area.tectonics and wrench faulting (Pilger, 1981; Miller, 1982; Klitgord et al., 1984; Van Siclen, 1984; Pindell,1985; Salvador, 1987; Winker and Buffler, 1988; Buffler, 1991). The origin of the Gulf of Mexicobasin consists of phases of crustal extension and thinning, of rifting and sea-floor spreading, and of thermalsubsidence (Nunn, 1984).Sawyer et al. (1991) proposed the following as a model for the evolution of the Gulf of Mexicoand related onshore interior salt basins and subbasins based on the distribution of crust type. A Late Triassic-EarlyJurassic early rifting phase is typified by half-grabens bounded by listric normal faults andfilled with nonmarine red bed sediments and volcanics. A Middle Jurassic phase of rifting, crustal attenuationand the formation of transitional crust is characterized by a pattern of alternating basementpaleotopographic highs and lows and the accumulation of thick salt deposits. A Late Jurassic phase ofsea-floor spreading and oceanic crust formation is typified by an extensive marine transgression as aresult of crustal cooling and subsidence. Subsidence continued into the Early Cretaceous and a carbonateshelf margin developed along the tectonic hinge zone of differential subsidence between thicktransitional crust and thin transitional crust.This depositional pattern was interrupted by a time of igneous activity and global sea-level fallduring the Late Cretaceous (mid-Cenomanian) that produced a major drop in sea level and resulted inthe exposure of the shallow Cretaceous platform margin that rimmed the Gulf (Salvador, 1991). Thismid-Cenomanian unconformity is well developed in the northern Gulf of Mexico area.The Mesozoic and Cenozoic sediments of the northern Gulf of Mexico accumulated as a seaward-dippingwedge in differentially subsiding basins (Martin, 1978). Basement cooling andsubsidence resulted in an infilling of the accommodation space. Structural elements that affected thedeposition of these sediments included basement features associated with plate movement and featuresformed due to the movement of Jurassic salt. The graben system that developed is a result of rifting, andits geometry is a reflection of the direction of plate separation (MacRae and Watkins, 1996). The Lower487

Petroleum Source Rocks of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of MexicoCretaceous shelf margin corresponds to a major basement hinge. This feature dominated carbonate depositionthroughout the Early Cretaceous.The chief positive basement features that influenced the distribution and nature of Mesozoicdeposits are the Sabine Uplift, Monroe Uplift, Wiggins Arch, Choctaw Ridge, the Conecuh Ridge, thePensacola Arch, and the Decatur Ridge. The Choctaw, Conecuh, Pensacola, and Decatur Ridge complexesare associated with the Appalachian fold and thrust structural trend that was formed in the latePaleozoic by tectonic events resulting from convergence of the North American and African-SouthAmerican continental plates. The Sabine Uplift, Monroe Uplift and Wiggins Arch are associated withcrustal extension and rifting (Miller, 1982; Sawyer et al., 1991). These features may be remnants of therifted continental margin of North America. Paleotopography had a significant impact on the distributionof sediment, and positive areas within basins and along basin margins provided sources forMesozoic terrigenous sediments (Mancini et al., 1985). The North Louisiana Salt Basin and MississippiInterior Salt Basin, which are major negative structural features are classified as the interior fractureportion of a margin sag basin using the classification of Kingston et al. (1983). These extensional basinswere associated with early rifting linked with wrench faulting and were actively subsiding depocentersthroughout the Mesozoic and into the Cenozoic.Movement of the Jurassic Louann Salt has produced an array of structural features (Martin,1978). Salt-related structures include diapirs, articlines, and entensional fault and half graben systems.Structural features resulting from halokinesis include the regional peripheral fault trend and numeroussalt domes and anticlines. The regional peripheral fault trend consists of a series of en echelon extensionalfaults and half grabens that are associated with salt movement. Structural deformation related tosalt movement was initiated probably during the Late Jurassic (Dobson and Buffler, 1997).Sedimentation in the northern Gulf of Mexico was associated with rifted continental margin tectonics.Syn-rift Triassic graben-fill red-beds of the Eagle Mills Formation (Fig. 2) were depositedlocally as the oldest Mesozoic strata above pre-rift Paleozoic basement during the early stages of extensionand rifting (Tolson et al., 1983; Dobson, 1990).The syn-rift Middle Jurassic Werner Formation and Louann Salt are evaporite deposits thatformed during the initial transgression of marine water into the Gulf of Mexico (Salvador, 1987). Basementstructure influenced the distribution and thickness of Louann Salt, resulting in thick salt in theinterior salt basins, and salt being absent over basement paleohighs (Wilson, 1975; Cagle and Khan1983, Dobson, 1990; Dobson and Buffler, 1991). The updip limit of thick salt and the location of theextensional faults associated with the regional peripheral fault trend coincide with a basement hinge lineand occur in the northern part of these salt basins and subbasins (Mancini and Benson, 1980; Dobson,1990; Dobson and Buffler, 1991).The distribution of the Late Jurassic post-rift deposits of the Norphlet, Smackover, Haynesvilleand Cotton Valley have been affected by basement paleotopography (Mancini and Benson, 1980; Dobson,1990; Dobson and Buffler, 1991). The Norphlet Formation consists of alluvial fan and plain, fluvialand wadi, eolian sheet, dune and interdune and marine shoreface siliciclastic sediments (Mancini et al.,1985; Dobson, 1990). The Smackover Formation, which was deposited on a ramp surface during themajor Jurassic marine transgression in the Gulf, includes intertidal to subtidal laminated and microbiallime mudstone, subtidal peloidal wackestone and packstone, subtidal microbial boundstone, and subtidalto intertidal peloidal, ooid, oncoidal packstone and grainstone interbedded with fenestral limemudstone (Mancini and Benson, 1980; Benson, 1988; Dobson, 1990). This transgression has beenattributed to emplacement of oceanic crust in the Gulf and the resulting thermal subsidence due tocrustal cooling (Nunn, 1984; Winker and Buffler, 1988). The Haynesville Formation consists of subaqueousto subaerial anhydrite, shelf to shoreline limestone, shale, and sandstone and eolian, fluvial,and alluvial sandstone (Tolson et al., 1983, Mann, 1988; Mancini et al., 1997). The Cotton Valley Groupincludes fluvial-deltaic and delta destructive sandstone and shale (Moore, 1983; Tolson, et al., 1983;Dobson, 1990). Deposition of the Early Cretaceous Knowles Limestone has been interpreted as the precursorto the development of the Lower Cretaceous carbonate shelf margin (Dobson, 1990).488

Mancini et al.SystemSeriesStageGroupFormationMississippiAlabamaMemberOligoceneRupelianVicksburg(see text for formations)PriabonianJacksonYazoo Clay(see textfor members)PaleogeneEocenePaleoceneUpper CretaceousBartonianLutetianYpresianSelandianDanianMaastrichtianCampanianSantonianConiacianClaiborneWilcoxMidwaySelmaTuronianTuscaloosaCenomanianMoodys Branch FormationCockfield FormationCook Mountain FormationKosciusko Sand"lower Lisbon"Zilpha ShaleWinona Fm.Tallahatta Fm. Tallahatta Fm.WilcoxHatchetigbee FormationTuscahoma FormationNanafalia FormationNaheola Formation"Jackson Gas Rock" Porters Creek Clay(Cane River)undifferentiatedMidway undiff.(see text for formations)Eutaw FormationUpper Tuscaloosa FormationMarine ShaleLower Tuscaloosa FormationMoodys BranchGosport Sand"upper Lisbon""middle Lisbon"(see textfor members)Tombigbee SandCretaceousAlbianWashita-FredericksburgundifferentiatedDantzler FormationAndrew FormationPaluxy FormationLower CretaceousAptianBarremianHauterivianBerriasianTithonianCottonValleyMooringsport FormationFerry Lake AnhydriteRodessa FormationJames Limestone/Pine Island ShaleSligo Formation/Hosston FormationSchuler FormationDorcheatShongalooJurassicUpperJurassicMiddleJurassicKimmeridgianOxfordianCallovianBathonianBajocianHaynesville FormationSmackover FormationNorphlet FormationLouann SaltBuckner Anhydrite"Brown Dense"Pine Hill AnhydriteAalenianWerner AnhydriteTriassicLwr. JurassicHettangian?Rhaetian?Eagle Mills FormationFigure 2. Stratigraphy for the north central and northeastern Gulf of Mexico area.489

Petroleum Source Rocks of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of MexicoThe Early Cretaceous in the northern Gulf of Mexico consists of fluvial-deltaic to coastal silicilasticsedimentation updip and the development of a broad carbonate shelf with a low-relief margindowndip at the boundary between thick transitional crust and thin transitional crust (Eaves, 1976; Winkerand Buffler, 1988; McFarlan and Menes, 1991; Sawyer et al., 1991). The development of a carbonateshelf margin during the Early Cretaceous, which does not conform to the basement structure, is the resultof a combination of a change in the slope of the basement that is marked by a crustal hinge zone andJurassic sediment depositional patterns (Dobson, 1990; Sawyer et al., 1991). The hinge zone has formedas a result of differential subsidence across the crustal boundary between thick transitional crust and thintransitional crust (Corso, 1987). Although Jurassic Norphlet, Smackover and Haynesville depositionalpatterns are greatly affected by basement paleotopography, sediments, such as the Lower CretaceousKnowles Limestone, reflect an infilling of the basement low areas and a general progradation of the rampmargin (Dobson, 1990). This progradation has been interpreted by Dobson (1990) to produce a changefrom a carbonate ramp to a rimmed platform margin. The hiatus between the Cotton Valley Group-Knowles Limestone and the Hosston Formation is represented by most of the Valanginian Stage. Thisunconformity and hiatus are recognized throughout the Gulf Coast (McFarlan and Menes, 1991).The Lower Cretaceous shelf margin was exposed during the early Late Cretaceous by a majorlowering of sea level. This sea-level fall has been attributed to a combination of igneous activity andglobal sea-level fall (Salvador, 1991). A Late Cretaceous marine transgression followed this regionalerosional event, and this transgression in combination with the Laramide orogeny affected depositionfrom the Late Cretaceous to the Cenozoic (Salvador, 1991). Throughout the Cenozoic, the western Gulfwas the site of significant fluvial, deltaic and coastline siliciclastic sediment influx, while the easternGulf experienced principally carbonate deposition (Salvador, 1991).Potential Petroleum Source RocksThree active petroleum source rocks have been reported from the onshore north central andnortheastern Gulf of Mexico area. The Upper Jurassic (Oxfordian) Smackover lime mudstone beds havebeen described as serving as source rocks in the North Louisiana Salt Basin, the Mississippi Interior SaltBasin, and the Manila and Conecuh Subbasins (Oehler, 1984; Sassen et al., 1987; Sassen and Moore,1988; Claypool and Mancini, 1989; Mancini et al., 2003). The Upper Cretaceous (Cenomanian-Turonian)Tuscaloosa marine shale beds have been reported as serving as source rocks in Mississippi (Koonset al., 1974). The Lower Cretaceous (Albian) Sunniland lime mudstone beds have been described asserving as source rocks in south Florida (Palacas, 1978; Palacas et al., 1984). In addition, Sassen (1990)reported that lower Tertiary (Paleocene/Eocene) Midway, Wilcox, and Sparta shale beds are sourcerocks in southern Louisiana and that Paleocene/Eocene Wilcox lignite beds may be a petroleum sourcein southwestern Mississippi. Upper Jurassic (Tithonian) shale and carbonate beds are source rocks inMexico (Mancini et al., 2001).From source rock and oil characterization studies and from burial and thermal maturation historymodeling, Mancini and Claypool (1989), Mancini et al., (1999), and the results from this work, haveshown that the Paleocene/Eocene shale and lignite beds have not been subjected to favorable burial andthermal maturation histories required for petroleum generation in the North Louisiana Salt Basin(Fig. 3), Mississippi Interior Salt Basin (Fig. 4), Manila Subbasin (Fig. 5), and Conecuh Subbasin(Fig. 6). The Upper Cretaceous Tuscaloosa marine shale beds were an effective local petroleum sourcerock in parts of the Mississippi Interior Salt Basin and a possible local source bed in the North LouisianaSalt Basin given the proper organic facies but not in the Manila and Conecuh Subbasins. Theuppermost Jurassic strata and the Lower Cretaceous lime mudstone and shale beds were possible localsource beds in parts of the North Louisiana Salt Basin and Mississippi Interior Salt Basin given theproper organic facies. These beds probably were not source beds in the Manila and Conecuh Subbasinsbecause the proper organic facies do not appear to be present.490

PaluxyMancini et al.A)SubseaDepth0-1500-3000A1702701875 1702701974 1702720557 1701320349 1701320054 1706920079 1706900047 1706900174 1706900475 1706920017 1706900541 1711500016 1711520029TuscaloosaWilcoxMidwayNavarro-TaylorAustinA'SubseaDepth0-1500-3000-4500-4500-6000Ferry LakeRodessaJamesPine Island-6000Washita-Fred.-7500SligoRuskMooringsport-7500-9000-10500GlenRoseUndiff.-9000-10500-12000Cotton Valley-12000-13500-13500B)AA'SubseaSubseaDepthDepth1702701875 1702701974 1702720557 1701320349 1701320054 1706920079 1706900047 1706900174 1706900475 1706920017 1706900541 1711500016 1711520029-1500 -1500-2500 -25003000300030003000300030003000300030003000300030003000-3500 -3500EM-4500 -45004000400040004000400050005000500050005000500050005000500050005000500050006000600060006000600070007000700070007000700070007000700070007000700070008000800080008000800040004000400040004000400040004000-5500 MM-550060006000600060006000600060006000-6500 -6500-7500 -7500LM-8500 -8500800080008000800080008000800080009000900090009000900090009000900090009000900090002000-9500 -9500MG-10500 -105001000010000100001100011000110001000010000100001000010000100001100011000110001100011000-11500 -11500120001200012000120001200012000-12500 -125001300013000-13500 -13500-14500 -14500-15500-16500EM = Early MatureMM = Mid MatureLM = Late MatureMG = Main Gas Generation-15500-16500-17500 -17500Figure 3. Regional cross section and thermal maturity profile (A-A´) for the North Louisiana SaltBasin: A. Regional cross section and B. Thermal maturity profile at present. See Figure 1 forlocation of cross section.491

)(Petroleum Source Rocks of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of MexicoA)BLogLogDepthDepth2308320011 2305120020 2305120036 2316300049 2316320150 2308920043 2304920005 2304920004 23049200320 0VicksburgJacksonMoody's BranchB'Cook Mountain2000 Sparta2000Cane River2000(-1871)2000(-1673)2000(-1736)2000(-1790)2000(-1629)2000(-1802)2000(-1721)2000(-1731)2000(-1700)4000 4000MidwayWilcox4000(-3871)4000(-3673)4000(-3736)4000(-3790)4000(-3629)4000(-3802)4000(-3721)4000(-3731)4000(-3700)Gas Rock6000 Selma60006000(-5871)6000(-5673)Marine ShaleTuscaloosaLower TuscaloosaLower Cretaceous8000 Paluxy80008000(-7673)6000(-5736)8000(-7736)6000(-5790)8000(-7790)6000(-5629)8000(-7629)Eutaw6000(-5802)8000(-7802)6000(-5721)8000(-7721)6000(-5731)8000(-7731)6000(-5700)8000(-7700)10000 1000010000(-9736)10000(-9790)10000(-9629)10000(-9802)10000(-9721)10000(-9731)10000(-9700)12000 Sligo/Hosston1200012000(-11790)12000(-11629)MooringsportFerry LakeRodessa14000 Pine Island 1400014000(-13629)12000(-11802)14000(-13802)12000(-11721)14000(-13721)12000(-11731)14000(-13731)12000(-11700)14000(-13700)Cotton Valley16000 1600016000(-15629)16000(-15802)16000(-15721)16000(-15731)16000(-15700)18000 1800018000(-17802)18000(-17721)18000(-17731)18000(-17700)Haynesville20000 20000NorphletSmackover20000(-19731)20000(-19700)Louann Salt22000 2200022000(-21731)22000(-21700)24000 2400024000(-23700)B)26000 26000BSubseaSubsea2308320011 2305120020 2305120036 2316300049 2316320150 2308920043 2304920005 2304920004 2304920032DepthDepth-4000 -4000B'500050005000500050005000500050005000-5000 -5000600060006000600060006000600060006000-6000 -600070007000700070007000-7000 EM-7000700070007000700080008000800080008000800080008000-8000 -80009000900090009000100001000010000900010000900090009000-9000 -9000MM100001000010000-10000 -1000011000110001100011000110001100011000-11000 -11000120001200012000120001200012000-12000 -12000130001300013000130001400014000140001300013000-13000 -13000LM1400014000-14000 -140001500015000150001500015000-15000 -15000-16000EM = Early MatureMG-16000MM = Mid Mature-17000 LM = Late Mature-17000MG = Main Gas Generation-18000 -18000Figure 4. Regional cross section and thermal maturity profile (B-B´) for the Mississippi InteriorSalt Basin: A. Regional cross section and B. Thermal maturity profile at present. See Figure 1 forlocation of cross section.16000160001700018000160001700018000160001700018000160001700018000492

(9 09 09 09 09 075 075 075 075 075 06 06 06 06 06 045 045 045 045 045 03 03 03 03 03 015 015 015 015 015 0Mancini et al.A)CSubseaSubseaDepthDepth102520042 102520112 100320009 100320020 1003200260 0C'-1500 -1500(-13 9)(-1293)(-1454)(-1308)(-1403)-3000 -3000(-28 9)(-2793)(-2954)(-2808)(-2903)-4500 Selma-4500(-43 9)EutawTuscaloosa-6000 -6000(-58 9)(-4293)(-5793)Lower Tuscaloosa(- 454)(-5954)(-4308)(-5808)(- 403)(-5903)Marine Shale-7500 Lower Cretaceous-7500(-73 9)(-7293)(-7454)(-7308)(-7403)-9000 -9000(- 8 9)(-8793)(-8954)(- 808)(-8903)105 0(-10293)-10500 Paluxy-10500105 0(-10454)Rodessa Pine Island105 0(-10308)Mooringsport105 0(-10403)12 0(- 1793)-12000 -12000Sligo/Hosston12 0(- 1954)12 0(- 1808)Ferry Lake12 0(- 1903)135 0(-13293)-13500 -13500135 0(-13454)135 0(-1 308)135 0(-13403)Cotton Valley-15000 -1500015 0(-14954)15 0(-14808)15 0(-14903)-16500 Haynesville-16500165 0(-16454)165 0(-16308)165 0(-16403)Upper Smackover Lower Smackover-18000 -1800018 0(-17808)Buckner18 0(-17903)-19500 -19500Norphlet195 0(-19403)-21000 -21000B)CSubsea 102520042 102520112 100320009 100320020 100320026 SubseaDepthDepth-6000 -6000C'700080007000-7000 -7000EM-8000 -8000800070008000700080007000800090009000-9000 -900090009000900010000-10000 -1000010000100001000011000-11000 -1100011000110001100012000-12000 MM-1200012000120001200013000-13000 -13000130001300013000-14000 -14000140001400014000-15000 -15000150001500015000-16000 -16000160001600016000-17000 -17000170001700017000-18000 -18000LM-19000 -19000-20000EM = Early MatureMM = Mid MatureLM = Late Mature-20000-21000 -21000Figure 5. Regional cross section and thermal maturity profile (C-C´) for the Manila Subbasin: A.Regional cross section and B. Thermal maturity profile at present. See Figure 1 for location ofcross section.18000180001900020000493

((Petroleum Source Rocks of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of MexicoA)DSubseaSubseaDepthDepth113120001 109920002 109920007 103520008 1053200070 0D'1500(-1407)1500(-1449)1500(-1225)1500(-1133)1500(-1194)-1500 -1500-3000 -3000Selma3000(-2907)-4500 EutawTuscaloosa-4500Ferry Lake4500(-4407)Marine ShaleLower Tuscaloosa-6000-7500Lower CretaceousPaluxyMooringsportRodessa-6000-7500Upper SmackoverLower SmackoverSligo/Hosston-9000 -90006000(-5907)7500(-7407)3000(-2949)4500(-4449)6000(-5949)7500(-7449)9000(-8949)3000(-2725)4500(-4225)6000(-5725)7500(-7225)9000(-8725)Pine Island3000(-2633)4500(-4133)6000(-5633)7500(-7133)9000(-8633)3000(-2694)4500(-4194)6000(-5694)7500(-7194)9000(-8694)Buckner-10500 -10500Cotton Valley10500(-10449)10500(-10225)10500(-10133)10500(-10194)12000(-11949)12000(-11725)12000(-11633)12000(-11694)-12000 -1200013500(-13449)NorphletHaynesville13500(-13133)13500(-13194)-13500 -13500-15000 -15000B)D113120001 109920002 109920007 103520008 105320007SubseaSubseaDepthDepth-6000 -6000D'-8000 EM-800080008000800080008000-10000 -1000010000100001000010000-12000 -12000MM12000120001200012000-14000 -140001400014000-16000 -16000EM = Early MatureMM = Mid MatureLMLM = Late Mature-18000 -18000Figure 6. Regional cross section and thermal maturity profile (D-D´) for the Conecuh Subbasin:A. Regional cross section and B. Thermal maturity profile. See Figure 1 for location of cross section.494

Petroleum Source Rocks of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of MexicoTable 1. Organic geochemical analyses of core samples, North Louisiana Salt Basin.S am ple D epth TOC 2 T m a x3S1 4 S2 5 S3 6123456789101112N o . W e ll P a r is h (feet) U nit 1 (% ) (ºC ) (m g /g ) (m g /g ) (m g /g ) P I 7 PC 8 H I 9 O I 10 TAI 11 K e r o g e n 121 George Franklin #1 Richland 11,690.50 Sm k 0.16 334 0.06 0.08 0.35 0.43 0.00 50 218 3 Am2 George Franklin #1 Richland 11,770.00 Sm k 0.25 344 0.13 0.09 0.16 0.59 0.02 36 64 3 Am3 Colvin #2 Lincoln 10,856.00 Sm k 0.32 333 0.16 0.15 0.38 0.52 0.03 47 119 3 H4 M cGehee #1 Lincoln 13,439.00 Sm k 0.78 286 0.20 0.10 1.10 0.67 0.02 13 141 3+ Am /H5 M cGehee #1 Lincoln 13,602.00 Sm k 0.38 314 0.09 0.04 0.36 0.69 0.01 11 95 3+ Am /H6 Bearden #1 U nion 10,170.00 Sm k 0.14 288 0.11 0.04 0.16 0.73 0.01 29 114 3- H7 B-1 H am iter Bossier 10,568.00 Sm k 0.19 318 0.13 0.06 0.24 0.68 0.02 32 126 3- H8 W aller #1 Claiborne 10,390.00 Sm k 0.18 323 0.06 0.04 0.48 0.60 0.01 22 267 3- Am9 Sherm an #1 Claiborne 10,216.00 Sm k 0.24 430 0.20 0.14 0.18 0.59 0.03 58 75 3- Am /H10 D illon H eirs Caddo 7,015.00 CV 0.41 432 0.32 0.35 1.12 0.48 0.05 85 273 2 Am11 F. W appler Caddo 8,683.00 CV 0.75 370 0.17 0.58 0.54 0.23 0.06 77 72 2+ Am12 F. W appler Caddo 8,793.00 CV 0.62 336 0.09 0.05 0.72 0.64 0.01 8 116 2+ Am /H13 F. W appler Caddo 8,801.00 CV 1.80 441 0.30 2.71 0.42 0.10 0.25 151 23 2+ H14 F. W appler Caddo 9,351.00 CV 0.62 375 0.19 0.20 0.60 0.49 0.03 32 97 2+ H15 L. Enloe Claiborne 10,714.00 Sm k 0.19 308 0.21 0.10 0.94 0.68 0.03 53 495 3- H /W16 Bankston Franklin 14,656.00 CV 0.35 293 0.17 0.09 0.65 0.65 0.02 26 186 3 Am17 D avis Bros. Jackson 10,944.00 Boss 0.46 331 0.14 0.12 0.09 0.54 0.02 26 20 3- H18 D avis Bros. Jackson 12,956.00 Boss 0.43 304 0.10 0.08 0.22 0.56 0.01 19 51 3- H19 D avis Bros. Jackson 12,976.00 Boss 0.61 313 0.11 0.07 0.02 0.61 0.01 11 3 3- H20 C. Atkins N atchitoches 11,203.00 GR 0.10 288 0.09 0.03 0.36 0.75 0.01 30 360 3- Am21 H uffm an-M cN eely N atchitoches 17,480.00 CV 0.11 325 0.06 0.04 0.18 0.60 0.01 36 164 3+ Am22 J. Bentley Rapides 12,911.00 Sligo 0.23 365 0.10 0.10 0.23 0.50 0.02 43 100 3- Am /H23 J. Bentley Rapides 12,948.00 Sligo 0.45 408 0.00 0.07 0.35 0.00 0.01 16 78 3- Am /H24 Chicago M ill Tensas 14,876.00 H oss 1.69 519 0.04 0.09 0.16 0.31 0.01 5 9 3- H25 Chicago M ill Tensas 15,520.00 H oss 4.09 524 0.04 0.20 0.05 0.17 0.02 5 1 3- H26 Chicago M ill Tensas 15,560.00 H oss 0.51 333 0.06 0.06 0.07 0.50 0.01 12 14 3- H27 N . M anning U nion 16,016.00 p-salt 0.26 311 0.03 0.03 0.15 0.50 0.00 12 58 3 Am28 N . M anning U nion 16,057.00 p-salt 0.18 252 0.01 0.00 0.29 1.00 0.00 0 161 3+ Am29 N . M anning U nion 16,074.00 p-salt 0.13 252 0.01 0.00 0.12 1.00 0.00 0 92 3+ Am30 Frazier U nit W ebster 10,874.00 Sm k 0.24 318 0.18 0.13 0.59 0.58 0.03 54 246 3- H31 Frazier U nit W ebster 11,250.00 Sm k 0.21 411 0.06 0.10 0.24 0.38 0.01 48 114 3- H32 H . D avis W ebster 11,043.00 Sm k 0.28 380 0.02 0.03 0.15 0.40 0.00 11 54 3 Am /H33 H . D avis W ebster 11,243.00 Sm k 0.16 305 0.01 0.01 0.15 0.50 0.00 6 94 3 Am34 CZ 10-11 W inn 13,690.00 CV 0.57 276 0.03 0.03 0.22 0.50 0.00 5 39 3+ Am35 CZ 10-11 W inn 13,804.00 CV 0.47 252 0.03 0.01 0.21 0.75 0.00 2 45 3+ Am /H36 CZ 10-11 W inn 13,924.00 CV 0.48 252 0.01 0.01 0.02 0.50 0.00 2 4 3+ Am37 CZ 10-11 W inn 13,946.00 CV 0.30 354 0.03 0.05 0.13 0.38 0.01 17 43 3+ AM /I38 CZ 5-7 W inn 15,608.00 Boss 0.28 307 0.02 0.04 0.00 0.33 0.00 14 0 3+ I39 CZ 5-7 W inn 16,418.00 Boss 0.34 355 0.05 0.07 0.11 0.42 0.01 21 32 3+ I40 CZ 5-7 W inn 16,431.00 Boss 0.34 329 0.06 0.10 0.37 0.38 0.01 29 109 3+ W /I41 Pardee W inn 16,200.00 Boss 0.35 322 0.21 0.29 0.29 0.42 0.04 83 83 3+ Am /I42 Pardee W inn 16,400.00 Boss 0.35 328 0.19 0.16 0.16 0.54 0.03 46 46 3+ AM /IU n it: S m k = S m ack o v er, C V = C o tto n V alley, B o ss= B o ssier, G R = G len R o se, H o ss= H o ssto n , p -salt= p re-salt.TO C=total organic carbon.T m a x =tem perature index.S1=free hydrocarbon.S2=residual hydrocarbon potential.S3=CO 2 produced from kerogen pyrolysis.P I= S 1/ (S 1 + S 2 ).PC=0.083 (S1+S2).H I=hydrogen index.O I=oxygen index.T A I= th erm al alteratio n in d ex .K erogen: AM =am orphous, H =herbaceous, W =woody, I=inertinite.496

Mancini et al.Table 2. Organic geochemical analyses of core samples, Manila and Conecuh Subbasins.g g y pSatu-Trans- Temp Hydro- rate/ Pris-13 C13 CWell Car- Organic S1+S2 forma- Max Kero- TAI Bitu- car- HC/ Aro- tane/ Satu- Aro-Permit County/ Rock Depth bonate Carbon Yield tion Yield H gen 1-5 men bons org matic Phy- rate maticNo. Area 1 Unit 2 (feet) (%) (%) (mg/g) Ratio ( o C) Index Type 3 Scale (ppm) (ppm) C 4 Ratio tane CPI (%) (%)355 Esc Tus 5,814 2.30 1.18 1.11 0.05 416 89 Am(Al 2- 634 338 2.90 3.50 >1 >1 -26.40 -24.50427 Esc Tus 6,080 51.00 2.63 7.38 0.02 431 273 Am(Al 2- 1,440 630 2.10 1.90 >1 >1 -26.30 -25.302182 Cla Tus 5,271 15.60 2.75 7.75 0.01 415 277 Am(Al 2- 1,050 540 2.00 2.30 1 -26.20 -24.603299 Bal Hay 15,00 -- 0.05 -- -- -- -- -- -- -- -- -- -- -- -- -- --735 Cla Smk 11,15 85.10 0.29 0.28 0.46 425 51 Am(Al 2- 395 164 5.60 3.60 >1 1 -27.40 -24.301438 Cla Smk 10,98 99.00 0.11 0.08 0.12 426 63 Am(Al 2- 48 28 2.50 2.80 1 >1 -27.50 -26.803648 Cla Smk 13,48 59.20 0.28 0.27 0.19 433 78 Am(Al 2 235 164 5.90 3.30 >1 >1 -26.50 -24.601352 Mon Smk 9,221 -- 0.04 -- -- -- -- -- -- -- -- -- -- -- -- -- --1592 Mon Smk 14,24 75.00 0.54 0.47 0.17 433 72 Am 2+ 449 266 4.90 2.10 1 -24.00 24.904673 Mon Smk 14,59 94.20 0.05 0.03 0.50 -- 40 -- -- -- -- -- -- -- -- -- --1584 Bal Smk 16,22 -- 0.42 -- -- -- -- Am 2 -- -- -- -- -- -- -- --2075 Bal Smk 18,33 89.20 0.49 0.30 0.43 -- 34 Am 3- 327 322 6.60 16.10 1 1 -26.40 -25.902587 Bal Smk 19,86 95.80 0.20 0.04 0.25 -- 15 Am(Al 3+ 37 27 1.40 5.20

Petroleum Source Rocks of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of MexicoW ell Name County/State 1Table 3. Analyses y of potential p Smackover source rocks, , Mississippi Interior Salt Basin.(feet) (w t% ) Kerogen 2 3%R o T max (°C) 4 HI 5Depth TOCWeissinger Lumber Issaquena + 8,451 0.36 Am/Al 2 430 66Flora Johnson #1 Newton + 11,775 0.26 Am/Al 0.55 431 134Masonite 25-14 Clarke + 14,586 0.24 Am/Al 0.9 429 91USA Rubie Bell #1 Scott + 14,902 0.48 Am/Al 0.9 431 137Bishop-Cooley #1 Wayne + 15,541 1.35 Am/Al 1.5 427 27R. M. Thomas #1 Smith + 16,554 0.27 Am/Al 1.5 432 62Grief Bros. #1 Jasper + 17,015 0.44 Am/Al 0.55 433 54McFarland #1 Jones + 19,865 0.28 Am/Al 1.5 410 25Crain et al. 1-4 Rankin + 20,179 0.24 Am/Al 2 420 50Crown Zellerbach #1 Simpson + 23,981 4.55 Am/Al 2 367 23Jackson #1 Choctaw ++ 10,532 0.3 Am/Al 0.45 -- --Bolinger 3-4 Choctaw ++ 10,610 0.07 Am/Al 0.45 -- 42Stewart 6-5 Choctaw ++ 12,245 0.24 Am/Al 0.45 -- 22Britton #1 Washington ++ 16,101 0.08 Am/Al 1.5 -- 12Chatom 2-01 Washington ++ 16,167 0.19 Am/Al 1.5 -- 10Foster 10-6 Washington ++ 19,359 0.25 Am/Al 1.5 -- 41 State: + M ississippi, ++ Alabama.2 Kerogen: Am=Amorphous, Al=Algal (microbial).3 %R o : Vitrinite reflectance (% R o ) was determined by converting TAI values to R o values using theconversion chart ofGeochem Laboratories.4 T max : temperature index.5 HI: hydrog en index.Conclusions1. The Upper Jurassic Smackover lime mudstone beds served as an effective regional petroleumsource rock in the north central and northeastern Gulf of Mexico area.2. The Upper Cretaceous Tuscaloosa marine shale was an effective local petroleum source rock inthe Mississippi Interior Salt Basin and a possible local source bed in the North Louisiana SaltBasin given the proper organic facies.3. The uppermost Jurassic and Lower Cretaceous shale and lime mudstone beds were possiblepetroleum source rocks in the North Louisiana Salt Basin and the Mississippi Interior Salt Basingiven the proper organic facies.AcknowledgmentsThe burial and thermal maturation history modeling for this project was accomplished using BasinMod® 1D software application of Platte River Associates, Inc. This research was funded by the U.S.Department of Energy, Office of Fossil Energy through the National Energy Technology Laboratory.However, any opinions, findings, conclusions or recommendations expressed herein are those of theauthors and do not necessarily reflect the views of the U.S. Department of Energy.498

Mancini et al.Table 4. Analyses of Smackover crude oil samples, Mississippi Interior Salt Basin.y p , ppField County Depth ?API Sulfur 3 C 15+ HC 4 C 15+ C 15+ C 15+ C 15+ NSO Saturate/ Pristane/ CPI13 C13 C(ft) gravity (%) (%) asphaltene 5 saturate 5 aromatic 5 comp. 5 aromatic phytane sulfate aromatic(%) (%) (%) (‰) (‰)Pachuta Creek 1 Clarke + 13,065 37.6 -- 73.4 4.9 49.8 39.7 5.6 1.25

Depth Subsurface (feet)Depth Subsurface (feet)02000400060008000100001200014000020004000600080001000012000A) API 1702701974JK200 150 100 50 0Age (my)Age (my)C) API 0102520112JK14000200 150 100 50 0Age (my)PalPalNNFmt= 0Fmt = 0UndiffNavarroTaylorAustinEagel FordTuscaloosaMooringsportFerry LakeRodessaJamesPine IslandSligo/HosstonCotton ValleySmackoverNorphletUndiffSelmaEutawTuscaloosaMarine TuscaloosaL. TuscaloosaL. CretaceousPaluxyMooringsportFerry LakeRodessaPine IslandSligo/HosstonCotton ValleyHaynesvilleBucknerU. SmackoverL. SmackoverNorphletFigure 7. Burial history profiles for wells: A. API Number 1702701974, North Louisiana Salt Basin, B. API Number 2304920032, Mississippi InteriorSalt Basin, C. API Number 0102520112, Manila Subbasin, and D. API Number 0105320007, Conecuh Subbasin. See Figures 3 to 6 for location of wells.Depth Subsurface (feet)Depth Subsurface (feet)01000020000300000500010000B) API 2304920032J K Pal N200 150 100 50 0D) API 0105320007AgeAge(my)(my)J K Pal N1500016000200 150 100 50 0Age (my) Age (my)FmUndiffVicksburgJacksonMoody's BranchCook MountainSpartaCane Rivert = 0Fmt = 0WilcoxMidwaySelmaEutawTuscaloosaMarine ShaleMassive SandPaulxyMooringsportFerry LakeRodessaPine IslandSligo/HosstonCotton ValleyHaynesvilleSmackoverNorphletLouann SaltUndiffSelmaEutawTuscaloosaMarine TuscaloosaL. TuscaloosaL. CretaceousPaluxyMooringsportRodessaPine IslandSligo/HosstonCotton ValleyHaynesvilleBuckerU. Smackover/L. SmackoverNorphletPetroleum Source Rocks of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of Mexico500

Cumulative Hydrocarbon / TOC (mg/g TOC)Cumulative Hydrocarbon / TOC (mg/g TOC)5004003002001002502001501005002000200A) API 1702701974JJ150150K100Age (my)K100Age (my)5050PalPalNNHQ0HQ0in-situOilin-situGasin-situResidueexpelledOilexpelledGasin-situOilin-situGasin-situResidueexpelledOilexpelledGasFigure 9. Hydrocarbon expulsion plots for wells: A. API Number 1702701974, North Louisiana Salt Basin, B. API Number 23-049-20032, MississippiInterior Salt Basin, C. API Number 0102520112, Manila Subbasin, and D. API Number 0105320007, Conecuh Subbasin. See Figures 3 to 6 for location ofwells.Cumulative Hydrocarbon / TOC (mg/g TOC)Cumulative Hydrocarbon / TOC (mg/g TOC)50040030020010020015010050B) API 2304920032C) API 0102520112 D) API 010532000702000200JJ150150K100Age (my)K100Age (my)5050PalPalNNHQ0HQ0in-situOilin-situGasin-situResidueexpelledOilexpelledGasin-situOilin-situGasin-situResidueexpelledOilexpelledGasPetroleum Source Rocks of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of Mexico502

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