U.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY

Lambert Conformal Conical ProjectionUnits: Meters, Standard Parallels: 33 00 00, 45 00 00Meridian: −94 00 00, Latitude of Origin: 29 00 00False Easting: 0, False Northing: 0Original data accurate at scale of 1:500,000.Digital base from U.S. Geological Survey.

Manuscript approved for publication July 7, 1995

OIL AND GAS INVESTIGATIONSMAP 0M−226

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U.S. DEPARTMENT OF THE INTERIOR OIL AND GAS INVESTIGATIONSU.S. GEOLOGICAL SURVEY MAP OM–226

PAMPHLET

MAPS SHOWING HYDROCARBON PLAYS OF THE FLORIDA PENINSULA,USGS PETROLEUM PROVINCE 50

ByRichard M. Pollastro and Roland J. Viger

1998

PROVINCE INTRODUCTION ANDGEOLOGIC SUMMARY

The Florida Peninsula, USGS petroleumProvince 50 as defined by the 1995 USGSNational Oil and Gas Assessment (Gautier andothers, 1995), includes all of the State of Floridaeast of the Apalachicola River, and the adjoiningState waters; the part of the Florida Panhandlewest of the Apalachicola River is part of USGSpetroleum Province 49 (Mississippi-Louisiana SaltBasin). The Apalachicola River generally trendsnorth-south, separating Gadsden, Liberty, andFranklin Counties on the east from Jackson,Calhoun, and Gulf Counties on the west. USGSpetroleum Province 50 (hereafter referred to asProvince 50), inclusive of State waters, isapproximately 150 mi wide and about 400 milong, totaling about 70,000 mi2. It is bounded tothe north by the State boundary with Georgia andto the east, south, and southwest by theboundaries of the Florida State waters. The Statewater boundaries extend to 3 leagues (10.36statute miles) on the Gulf of Mexico side of Floridaand to 3 mi on the Atlantic Ocean side (the Gulf-Atlantic boundary line runs westward from theMarquesas Keys along latitude 24°35' N. and thenturns southward, just west of the Dry Tortugas,along longitude 83° W.).

The most prominent positive structuralelement within the province is the Peninsular arch,which is a crystalline basement high plungingsouth-southeast along the axis of the FloridaPeninsula (map A). Other smaller positivestructural elements generally define the boundariesof the associated South Florida basin, theApalachicola embayment, and the SoutheastGeorgia embayment (map A). The South Floridabasin is the most prominent of these features andhas the greatest petroleum potential.

The South Florida basin is a structurallysimple basin containing 25,000 ft or more ofsediment in the apparent depocenter that liesnorthwest of the Florida Keys under present-dayFlorida Bay. Sedimentation in the South Florida

basin kept pace with subsidence, producing nearlycontinuous carbonate-evaporite deposition fromthe Jurassic(?) to the present (fig. 1). The SouthFlorida basin covers some 50,000 mi2 andincorporates the southernmost one-third or moreof the peninsula of Florida including the FloridaKeys and the easternmost Gulf of Mexico.Onshore, the basin exhibits only subtle structureswith no major faults or vertical fractures.However, more complex structural elements arebelieved to exist in the offshore part of the basin,which, if present, may provide excellent potentialfor hydrocarbon accumulations. The basin has agenerally low (~1.0°F/100 ft) geothermal gradient;however, the gradient of some onshore oil fieldsmay reach 1.5°F/100 ft.

The Southeast Georgia embayment in thenortheastern part of the province contains asmuch as 6,000 ft of sedimentary rock. Becausethis area contains only shallow, thermallyimmature sequences and lacks potential petroleumsource rocks, its potential for undiscoveredpetroleum resources is estimated as slight. TheApalachicola embayment in the northwestern partof the province, however, has petroleum potentialin the Jurassic Smackover Formation, whichproduces in the Florida Panhandle in Province 49.

Six conventional hydrocarbon plays aredefined for Province 50. These plays weredeveloped for the 1995 USGS National Oil andGas Assessment (Gautier and others, 1995). Twoplays are confirmed: Upper Sunniland Tidal ShoalOil play (5001) and Lower Sunniland FracturedDark Carbonate Oil play (5002). The other fourare hypothetical: Dollar Bay Shoal-Reef DolomiteOil play (5003), Lower Cretaceous CarbonateComposite Oil play (5004), Extended UpperSunniland Tidal Shoal Oil play (5005), and WoodRiver Dolomite Deep Gas play (5006). Theeasternmost part of the SmackoverAlabama/Florida Updip Oil play (4911) alsoextends into Province 50 but has been assigned toProvince 49; therefore, this play is not shown ordefined here.

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EXPLORATION CELLS ANDFIELD OUTLINES

Each cell on the maps represents 0.25 mi2in which exploration has taken place. Cell datafrom this map were summarized from theDecember 1993 version of the Well HistoryControl System of Petroleum Information, Inc. ofHouston, Texas. Solid green squares indicateexplored cells with oil production; solid bluesquares indicate explored cells, but nohydrocarbon production. Field outlines wereestablished from a variety of sources including: (1)the exploration cells and (2) well data, structurecontour maps, and oil/water contact mapspublished by the Florida Geological Survey (Lloyd,1991).

PLAY DESCRIPTIONS

MAP A. UPPER SUNNILAND TIDAL SHOALOIL PLAY (5001)

Known only in the subsurface, the LowerCretaceous Sunniland Formation is the basal unitof the Ocean Reef Group (fig. 1). Onshore, theformation is relatively uniform in thickness andconsists of limestone, dolomite, and anhydrite.The upper part of the Sunniland Formationproduces heavy, marginally-mature crude oilsonshore from porous bioclastic debris mounds,banks, and pods on the eastern margin of theSouth Florida basin. The region of productivereservoir facies of the upper Sunniland Formationis defined in part by eight fields that have producedmore than one million barrels of oil (MMBO) andfive smaller fields; most of the smaller fields areabandoned or shut in. Combined, these fieldsform an arcuate northwest-southeast trend, the“Sunniland trend,” which is about 20 mi wide and150 mi long. Generally, the updip limit of theSunniland varies from about 50 to 60 mi northeastof the producing trend. The first upper Sunnilandoil field discovery was the Sunniland field in 1943;the largest is the West Felda field, discovered in1966, with total production through July 1993 ofover 44 MMBO. Cumulative production for allupper Sunniland Formation reservoirs through July1993 was about 100 MMBO.

The northern and updip play boundary forthe Upper Sunniland Tidal Shoal Oil play (5001) isdefined here by an area in which the upperSunniland consists of only micritic limestone andcontains no reservoir mounds within its intertidal,lagoonal-mudflat facies. Moreover, the lower partof the Sunniland dark carbonate source rocks isalso absent. The downdip southern boundary ofthe play is limited by an area where wells identify

an anhydrite-cemented, nonporous, sabkha-likefacies.

The existing reservoir facies in the upperSunniland Formation consist mostly of isolatedfossil-shell hash (skeletal grainstones). Thesebioclastic buildups represent probable stormdeposition as shoals in a regionally restricted,back-reef lagoonal area in the warm, shallowmarine shelf setting of the eastern South Floridabasin during the late Early Cretaceous (Mitchell-Tapping, 1984, 1987). These tidal shoals weredeposited on subtle bathymetric highs probablyrelated to underlying basement structure. Later,the upper parts of these porous shoal moundswere subaerially exposed, leached, and dolomitizedduring a low sea-level stand, further enhancing thereservoir quality of the upper porous zones.Individual debris mounds vary in thickness betweenabout 40 and 100 ft (Means, 1977; Montgomery,1987). Depth to the upper Sunniland tidal shoalreservoirs in the producing trend is from about11,200 to 11,600 ft. Most mounds are sealed byoverlying impermeable lagoonal mudstones andwackestones, some of which have beendolomitized. Porosities of primary (interparticle)and secondary (dissolution and dolomitization)origin range from 10 to 25 percent and average15–18 percent (Mitchell-Tapping, 1984, 1987).Impermeable micritic carbonate and nodularanhydrite beds within the upper Sunniland encloseand seal many of the individual porous reservoirmounds. Moreover, the entire SunnilandFormation is sealed above and below by thickanhydrite units (fig. 1). Most hydrocarbon traps arestratigraphic; however, some mixedstratigraphic/structural traps have beenrecognized.

Oils produced from the upper Sunnilandgrainstones are immature, having API gravitiesthat range from about 21° to 28° and average25°–26°; on average, the gas-to-oil ratio (GOR) isabout 85 (Palacas, 1984; Palacas and others,1984; Tootle, 1991). The source rocks are adark, micritic carbonate unit (informally referred toas the dark carbonate interval) in the lower part ofthe Sunniland Formation. These micriticcarbonates are commonly algal laminated andhave total organic carbon (TOC) ranging from<0.4 to 3.0 weight percent. Potential sourcerocks (as identified by >0.4 weight percent TOC)average 1.8 weight percent TOC. Greater than80 percent of the organic matter within thesesource rocks is composed of algal-amorphous (oil-prone) kerogen (Palacas and others, 1984). Thehydrocarbon-generating potential of the lowerSunniland dark carbonate facies ranges from poorin wells updip from the producing trend to goodjust downdip to excellent near the depocenter of

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the basin (Applegate and Pontigo, 1984).Onshore, the dark carbonate facies varies inthickness from zero at the updip limit of theSunniland to >150 ft in the producing trend. Oilproduced from reservoirs in the Sunniland trendwas probably generated downdip where theorganic matter in the dark carbonate facies isricher and more mature. The petroleum thenmigrated updip and accumulated in the porousgrainstone facies of the upper Sunniland (Palacasand others, 1984).

Exploration and development of the upperSunniland Formation has been minimal based onthe drilling history and well distribution within theplay area, which is shown by the limited number ofexplored cells on the maps. The eight upperSunniland fields containing >1 MMBO are BearIsland, Corkscrew, West Felda, Lehigh Park, Mid-Felda, Raccoon Point, Sunniland, and Sunoco-Felda (see map A for outlines and locations). Atleast three of these eight fields are located in theBig Cypress Swamp drainage and (or) NationalReserve, an area of critical environmental concern(Lloyd, 1991). Factors such as environmental andpolitical concerns and the present oil pricesprobably have discouraged full resourcedevelopment. Minimal exploration anddevelopment of petroleum resources because ofthese factors, coupled with the success of wellsdrilled in the past few decades, indicate that theUpper Sunniland Tidal Shoal Oil play has goodpotential for undiscovered oil accumulations ofmoderate size.

MAP A. EXTENDED UPPER SUNNILANDTIDAL SHOAL OIL PLAY (5005)

This hypothetical play is an extension to theeast and south of the productive Sunniland trendin the Upper Sunniland Tidal Shoal Oil play(5001). Thus, reservoirs and source rocks are thesame as those for play 5001. Shown on map A,this play forms a southwest-to-northeast arcuatetrend approximately 20 mi wide and 250 mi longfrom the State waters of the Dry Tortugasnortheast through the Florida Keys and along thesoutheastern Atlantic Coast of the FloridaPeninsula to Broward County. Bioclastic moundsof smaller size than those in currently productiveunits from the upper part of the SunnilandFormation accumulated on subtle structural highsin this updip, less thermally mature area of thebasin to the east and far south. Prominent positivestructural elements include the Pine Key arch andthe Largo high. Some heavy oil shows having lowAPI gravity (10°–14°) have been reported in wellsin the northern part of the play area; however,22° API gravity oil was reported in shows from

wells near the Marquesas Keys in the west andsouthernmost part of the play area (Faulkner andApplegate, 1986; Lloyd, 1991).

The Extended Upper Sunniland Tidal ShoalOil play (5005) is delineated by an area ofsuspected porous tidal-shoal facies forming ontopographic/bathymetric highs. The darkcarbonate source unit in the lower part of theSunniland Formation thins toward the east andsouth margins of the basin south of the play area,making it less favorable than the proven UpperSunniland Tidal Shoal Oil play (5001). TheSunniland in this area is also less thermally maturethan in play 5001. The eastern and southernAtlantic coastal boundaries of the play aredetermined by the 3-mi line, and the northern,Gulf of Mexico boundary by the 3-league (10.36mi) Florida State waters boundary.

MAP B. LOWER SUNNILAND FRACTUREDDARK CARBONATE OIL PLAY (5002)

The Lower Sunniland Fractured DarkCarbonate Oil play is based solely on the discoveryof the Lake Trafford field in Collier County. TheLake Trafford field (shown on map A) isrepresented on maps A–E by one productive cell.The dark carbonate unit of the lower part of theSunniland Formation is believed to contain theprimary source beds for oils produced in the tidalshoal grainstones of the upper part of theSunniland Formation (plays 5001 and 5005).Although no oil accumulations are proven ofminimum (>1 MMBO) size, the one discovery well(Mobil Oil Corporation) defining the Lake Traffordfield has produced commercial quantities of oilsince its discovery in March 1969, from fracturedlimestone at a depth of about 11,800 ft. Theproducing zone is commonly referred to as therubble zone of the dark carbonate unit in the lowerSunniland Formation (Means, 1977). The matrixporosity of the producing zone, as measured bywell logs, is about 9 volume percent, and the porespace is oil saturated. Core of the rubble zonefrom the discovery well has been described asburrowed, fractured, and stylolitized (Lloyd, 1991);these characteristics are thought to be responsiblefor enhancing the porosity and permeability forcommercial production. In March 1988, thediscovery well was shut in after oil productiontotaled about 278,000 barrels. Two offset verticalwells, located to the northwest and south of theproducing well, and a recent horizontal test wellwere dry holes. Based on the production historyof the one vertical well, horizontal wellspenetrating the rubble zone of the dark carbonateunit could potentially produce a few hundredbarrels of oil per day (BOPD). Owner/operator

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Brian Richter (oral commun., 1994) reports thatthe horizontal test missed the targeted pay zone.

The play boundary is defined by thickness(>60 ft) of the dark carbonate unit, as partlydetermined from cross sections and isopachs(Applegate and Pontigo, 1984), and from offshorewell summaries of Lloyd (1991). In addition tothickness, the area defined for the LowerSunniland Fractured Dark Carbonate Oil play wasfurther delineated from reference wells having acombination of good source-rock qualities andevidence of either the rubble zone or somefracturing present (Montgomery, 1987). This playis assigned fair potential for undiscovered oilresources. The most favorable part of the play isin an area northwest of the Lake Trafford field.Expected depths of production within the playarea are estimated between 10,000 and 13,000ft, with a median depth of about 11,800 ft.Potentially productive fractured reservoirs arewithin the lower dark carbonate zone of the lowerSunniland and are enclosed by impermeable,micritic, tidal flat, lime mudstones. The unit issealed below by the Punta Gorda Anhydrite.

Indigenous hydrocarbons are produced frombrown and medium-dark-gray micritic andargillaceous limestones with total carbonatecontent averaging 76 weight percent, and rangingfrom 50 to 98 weight percent. These micriticcarbonates are commonly algal laminated andhave TOC ranging from <0.4 to 3.0 weightpercent. Potential source beds (>0.4 weightpercent TOC) within the unit average about 1.8weight percent TOC. Oil produced from the onewell at the Lake Trafford field has an API gravityof about 26°, similar to the oil in the upperSunniland producers (API gravities ranging from21° to 28°). Inasmuch as oils in the upperSunniland are derived from sources in the lowerdark carbonate, the similarity in API gravities isexpected. Similarly, lower Sunniland oils areexpected to have a GOR range of that of upperSunniland oils from about 80 to 100.

MAP C. DOLLAR BAY SHOAL-REEFDOLOMITE OIL PLAY (5003)

The hypothetical Dollar Bay Shoal-ReefDolomite Oil play is based on (1) interpretations ofwell-log data from a series of onshore wellsreporting numerous shows (Winston, 1971) and(2) the paleoenvironmental reconstructions ofWinston (1971) and Mitchell-Tapping (1990) ofthe reservoir tidal shoal and patch reef facies; thedata of Faulkner and Applegate (1986) were alsoused in the definition of this play.

The youngest formation in the onshoreportion of the South Florida basin that shows

characteristics favorable for petroleum generationand accumulation is the Lower Cretaceous DollarBay Formation, the uppermost unit of the BigCypress Group (fig. 1). The unit lies about 1,500ft or more above the Sunniland Formation and isas much as 620 ft thick in some parts of the basin.Onshore, the unit ranges in thickness from about475 to 550 ft. Many wells penetrating the DollarBay Formation in south Florida have reportedlow-gravity (~17° API) oil shows or tarry residuesin both limestone biohermal deposits and an upperdolomite section; however, no commercialproduction has occurred from this play. Like theSunniland Formation, the Dollar Bay commonlyconsists of evaporite-carbonate cycles ofanhydrites, dolomites, and limestones. Theseevaporite-carbonate beds formed during atransgressive-regressive cycle; some thin beds ofcalcareous shale, salt, and lignite are also present(Applin and Applin, 1965; Mitchell-Tapping,1990). In certain areas of the basin, however,limestone is the predominant lithology of theformation. Speculative production in the DollarBay Formation will be from leached limestones inthe middle part of the formation, or from adolomite section in the upper part.

Reservoirs are believed by Mitchell-Tapping(1990) to exist in tidal shoal deposits and patchreefs in a tidal flat, lagoonal, restricted-marinesetting, and in a subtidal platform, open-marinesetting. Potential reservoirs include (1) porous,leached, and dolomitized grainstones in the upperparts of isolated debris mounds, (2) isolated patchreefs in the middle part of the Dollar BayFormation, and (3) a porous dolomite in the upperpart (Mitchell-Tapping, 1990). These potentialreservoirs have measured porosities ranging fromabout 10 to 30 percent and permeabilities on theorder of 5–60 millidarcies (mD). Traps are createdbecause these reservoirs are draped withimpermeable, micritic, tidal flat deposits, and insome cases argillaceous lime mudstones andanhydrite. The formation is underlain by thick,dense, nodular and nodular-mosaic anhydrites ofthe Gordon Pass Formation.

Oil and tarry residues recorded in Dollar Baywells are believed to originate within the formation(Palacas, 1978a, b; Winston, 1971). The organic-matter content of the Dollar Bay Formation rangesfrom very lean to fairly rich, with some bedscontaining more than 3 weight percent TOC; theaverage TOC of the Dollar Bay is about 0.6weight percent (Palacas, 1978a, b). Mostpetroleum explorationists infer that the Dollar BayFormation located updip and to the northeast ofthe Sunniland trend is thermally immature and hasprobably not generated hydrocarbons ofcommercial quality and quantity (Montgomery,

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1987). Others strongly disagree, however, andpredict that the Dollar Bay Formation has beenoverlooked and should be a considered a primaryoil target with good potential (Winston, 1971;Palacas, 1978a, b; Mitchell-Tapping, 1990).

Offshore, in the more central part of thebasin where the Dollar Bay lies at depths >10,000ft, the formation should be more thermally mature.Based on one major show, which consisted of 15ft of free oil, API gravity measured 17° at a depthof about 10,000 ft . Thus, API gravities of oilfrom this play are expected to be low, probablyranging from 15° to 20° (Mitchell-Tapping, 1990).Sulfur contents are similar to those of Sunniland-type oils (2–4 percent). Moreover, the inferredpresence of patch reefs and more complexstructures in the Federal offshore, and increasedthermal maturity for the Dollar Bay in the offshorepart of the basin, enhances the potential for newfield discoveries and commercial oil production.

MAP D. LOWER CRETACEOUS CARBONATECOMPOSITE OIL PLAY (5004)

The hypothetical Lower CretaceousCarbonate Composite Oil play comprises two unitsin the South Florida basin: the brown dolomitezone of the Twelve Mile Member of the LehighAcres Formation, and a potentially porousdolomite unit within the underlying Pumpkin BayFormation (fig. 1). Both units in this play arebelieved to contain oil derived mainly fromorganic-rich beds in the upper part of the PumpkinBay Formation.

The extent of the play is delineated by twoseparate areas: one centered in Lee County andintersecting the Sunniland trend, and the othercentered near the Marquesas Keys. The northernarea (Lee County and vicinity) includes the areaoutlined by Applegate (1987) of the porous browndolomite and the area within the Pumpkin BayFormation shown to contain live oil in porousdolomite (6–16 percent porosity). The section isthe thickest (as much as 1,200 ft thick) in theseareas, as measured from reference wells in Statewaters near Charlotte Harbor and onshore inCollier and Hendry Counties, and has good toexcellent source-rock potential from geochemicaland thermal maturity measurements (Means,1977; Applegate and others, 1981; Palacas andothers, 1981; Attilio and Blake, 1983; Faulknerand Applegate, 1986; Applegate, 1987;Montgomery, 1987). The northern segment alsocorresponds to an area of brown dolomite wherehigh porosity is caused by epigenic dolomitizationfrom an active geothermal lineament system (Saul,1987). Several oil shows are reported in thick,porous dolomite sections in the southern segment

of the play area (Faulkner and Applegate, 1986;Lloyd, 1991).

The informally named brown dolomite zonerefers to a dolomite unit commonly found withinthe Twelve Mile Member of the Lower CretaceousLehigh Acres Formation (Aptian). The browndolomite lies about 300 ft below the base of thePunta Gorda Anhydrite and about 1,000 ft belowthe Sunniland Formation (fig. 1). The unit is bestdeveloped where thickest (~100 ft) and mostporous (10–22 percent) onshore in CharlotteCounty and surrounding counties at a depth ofabout 12,000 ft . Good oil shows are reported,and because it is about 1,000 ft lower in thestratigraphic section than the SunnilandFormation, oils from the brown dolomite arepredicted to have higher API gravity (20°–50°?)and thermal maturity than Sunniland oils.

Reservoir rocks consist of sucrosic dolomiteand exhibit pinpoint to vuggy porosity in bedsfound at least 50 ft below the top of the TwelveMile Member of the Lehigh Acres Formation. Asmuch as 50 ft of porous dolomite has been foundonshore where the brown dolomite zone reaches amaximum thickness of about 100 ft. An areahaving highest potential onshore is defined mostlyby the porous zones shown by Applegate (1987)in Charlotte, Lee, Hendry, Collier, Highlands, andGlades Counties and adjacent State waters. Goodoil shows were observed in the Bass Collier 12-2well in Collier County in dolomite having sonicwell-log porosities ranging from 10 to 22 percentand core porosities as high as 18 volume percent.Good potential is also predicted offshore in bothState and Federal waters. In particular, oil stainswere noted in wells where about 350 ft of mostlyporous dolomite has been penetrated near theMarquesas Keys (Faulkner and Applegate, 1986;Lloyd, 1991).

The thickest and deepest interval in theSouth Florida basin with significant reservoirpotential is the Lower Cretaceous Pumpkin BayFormation. The formation is mostly limestoneexcept at its northern limit, where it has beenfound to be mostly dolomite. Within Province 50,the Pumpkin Bay is as thick as 1,200 ft in offshoreFlorida State waters of Charlotte Harbor; theformation is projected to thicken westward in theFederal offshore and into the basin depocenter(Faulkner and Applegate, 1986). Onshore, thePumpkin Bay Formation is found at depths fromabout 12,500 to 14,000 ft. Core porosities forthe Pumpkin Bay are as high as about 20 percent,and its sonic well-log porosities measure slightlyhigher. Porosities are generally lower in thePumpkin Bay Formation than in potentialreservoirs found in younger units. Generally, thebest potential for the Pumpkin Bay Formation is

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predicted in the Pulley Ridge area of Federaloffshore waters in the Gulf of Mexico (Faulknerand Applegate, 1986). Projections suggest thatthe formation is as much as 1,500 ft thick in thisarea and that good reservoirs exist within a thickporous dolomite zone (300–350 ft thick; pinpointto vuggy porosity as great as 25 percent) in themiddle to upper part of the formation, at depthsfrom about 12,500 to >15,000 ft.

Source-rock studies by Palacas and others(1981) suggest that organic rich beds in the upperPumpkin Bay Formation are likely source rocks foroils that could be reservoired both within themiddle and upper part of the Pumpkin Bay and inthe porous brown dolomite zone. Palacas andothers (1981) identified organic-rich, argillaceouscarbonate beds with high (0.43–3.2 weightpercent) TOC in the upper Pumpkin Bay andconcluded that these beds had the greatestpetroleum-generating potential of all rocks olderthan the Punta Gorda Anhydrite.

The TOC contents of these rocks, however,varies within the basin. Most rocks within theTwelve Mile Member of the Lehigh AcresFormation contain insufficient organic matter(average ~0.3 percent TOC) to have generatedcommercial amounts of petroleum. Some richersource beds occur within this unit, however, havingmarginal (~0.5 percent TOC) to good sourcepotential. Particularly, greater than 2.0 percentTOC is contained in a relatively thin (~1 ft thick)limestone bed in the West Felda field.

The thermal maturation level for oilgeneration is greater in this play than that for theupper and lower Sunniland plays (5001 and5002). Thus, oils of this play are expected to bemarginally to moderately mature and to havehigher API gravities (25°–50°) and higher GORthan Sunniland oils.

MAP E. WOOD RIVER DOLOMITEDEEP GAS PLAY (5006)

In the hypothetical Wood River DolomiteDeep Gas play, the Upper Jurassic(?) and LowerCretaceous Wood River Formation averages about1,700 ft thick and is the lowest sedimentary unit inthe South Florida basin (fig. 1). The few wells thathave penetrated this formation show that a 100-to 150-ft-thick clastic unit forms the basal part ofthe Wood River Formation and consists of dark-red shale and fine- to coarse-grained arkosicsandstone and calcareous sandstone (Applegateand others, 1981). These basal clastics possiblyrepresent fan, fan-delta, and fluvial-lacustrine ormarine deposits. Below the basal clastic sequencein Collier County is a rhyolite porphyry with anage of 189 Ma. Overlying these clastic rocks is a

thick sequence of anhydrite, dolomite, andlimestone with occasional interbedded saltstringers, indicating marine transgression(Applegate and others, 1981).

One well, the Mobil-Phillips Seminole C inHendry County, produced measurable gas andwater flows at depths of about 15,700 ft fromperforations in a dolomite zone averaging about 8percent porosity. Moreover, logs from the wellindicated higher porosities and increasedresistivities just above the perforated section,possibly indicating the presence of gas (Applegateand others, 1981; Palacas and others, 1981).Although formation damage occurred in the wellbore, this well had potential for commercial gasproduction (J.G. Palacas, oral commun., 1994)and the occurrence of a potentially commercialwell indicates a possible source of deep gas.Marine beds, generally regarded as potentialpetroleum sources, are predominant, and thedepositional environment, especially in thesouthern areas, probably favored reef growth; thusa source, a seal, and a reservoir should be present.

Organic geochemistry studies of wellsamples from the Wood River Formation indicatethat the hydrocarbon-generating potential of theunit ranges from poor to excellent (Palacas andothers, 1981; Faulkner and Applegate, 1986).The scarcity of wells penetrating the Wood RiverFormation, however, makes any evaluationinconclusive. Potential reservoirs in the WoodRiver are porous (8 percent or greater) dolomitesenclosed by anhydrite, salt stringers, and (or)micritic limestone at depths from about 15,000 to19,000 ft onshore and in State waters. The playarea includes areas of the southern part of thebasin where reef growth is favored. It is possiblethat gas in the Wood River in the area of theSunniland trend may have originated in deeperparts of the basin and migrated updip, perhaps asa single, large accumulation.

REFERENCES CITED

Applegate, A.V., 1987, Part II—The BrownDolomite zone of the Lehigh AcresFormation (Aptian) in the South Floridabasin—A potentially prolific producinghorizon offshore: Florida GeologicalSurvey Information Circular No. 104, pt.2, p. 46–66.

Applegate, A.V., and Pontigo, F.A., Jr., 1984,Stratigraphy and oil potential of the LowerCretaceous Sunniland Formation in southFlorida: Florida Bureau of GeologyReport of Investigations No. 89, 40 p.

Applegate, A.V., Winston, G.O., and Palacas,J.G., 1981, Subdivision and regional

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stratigraphy of the pre-Punta Gorda rocks(lowermost Cretaceous–Jurassic?) in SouthFlorida: Gulf Coast Association ofGeological Societies Transactions, v. 31,p. 447–453.

Applin, P.L., and Applin, E.R., 1965, TheComanche Series and associated rocks inthe sub-surface in central and southFlorida: U.S. Geological SurveyProfessional Paper 447, 84 p.

Attilio, D.E., and Blake, Bruce, 1983, Petroleumpotential, exploration possibilities of SouthFlorida basin, Florida Keys: Oil and GasJournal, v. 81, p. 148–153.

Faulkner, B.M., and Applegate, A.V., 1986,Hydrocarbon exploration evaluation ofPulley Ridge area, offshore South Floridabasin: Gulf Coast Association ofGeological Societies Transactions, v. 36,p. 83–95.

Gautier, D.L., Dolton, G.L., Takahashi, K.I., andVarnes, K.L., eds., 1995, 1995 Nationalassessment of United States oil and gasresources—Results, methodology, andsupporting data: U.S. Geological SurveyDigital Data Series DDS–30, one CD-ROM.

Lloyd, J. M., 1991, 1988 and 1989 Floridapetroleum production and exploration:Florida Geological Survey InformationCircular No. 107, p. 1–62.

Means, J.A., 1977, Southern Florida needsanother look: Oil and Gas Journal, v. 75,no. 5, p. 212–225.

Mitchell-Tapping, H.J., 1984, Petrology anddepositional environment of the Sunnilandproducing fields of south Florida: GulfCoast Association of Geological SocietiesTransactions, v. 34, p. 157–173.

———1987, Application of the tidal mudflatmodel to the Sunniland Formation ofSouth Florida: Gulf Coast Association ofGeological Societies Transactions, v. 37,p. 415–426.

———1990, New oil exploration play in Florida—The upper Fredericksburg Dollar BayFormation: Gulf Coast Association ofGeological Societies Transactions, v. 40,p. 607–621.

Montgomery, S.L., 1987, Success and sensibilityin South Florida: Petroleum Frontiers, v.4, 52 p.

Palacas, J.G., 1978a, Distribution of organiccarbon and petroleum source rockpotential of Cretaceous and lower Tertiarycarbonates, South Florida basin,preliminary results: U.S. GeologicalSurvey Open-File Report 78–140, 35 p.

———1978b, Preliminary assessment of organiccarbon content and petroleum source rockpotential of Cretaceous and lowerTertiary carbonates, South Florida basin:Gulf Coast Association of GeologicalSocieties Transactions, v. 28, p. 357–381.

———1984, Carbonate rocks as sources ofpetroleum—Geological and chemicalcharacteristics and oil-source correlations:Proceedings of the 11th World PetroleumCongress, 1983, v. 2, p. 31–43.

Palacas, J.G., Anders, D.E., and King, J.D.,1984, South Florida basin—Primeexample of carbonate source rocks ofpetroleum, in Palacas, J.G., ed.,Petroleum geochemistry and source rockpotential of carbonate rocks: AmericanAssociation of Petroleum Geologists,Studies in Geology, v. 18, p. 71–96.

Palacas, J.G., Daws, T.A., and Applegate, A.V.,1981, Preliminary petroleum source-rockassessment of pre-Punta Gorda rocks(lowermost Cretaceous–Jurassic?) in SouthFlorida: Gulf Coast Association ofGeological Societies Transactions, v. 31,p. 369–376.

Saul, W.L., 1987, Brown Dolomite zone of theLehigh Acres Formation, LowerCretaceous, South Florida: Lafayette, La.,University of Southwestern LouisianaMaster’s thesis, 95 p.

Tootle, C.H., 1991, Reserves estimated,production listed for Florida’s 22 oil fields:Oil and Gas Journal, v. 89, p. 84–87.

Winston, G.O., 1971, The Dollar Bay Formationof Lower Cretaceous (Fredericksburg) agein South Florida, its stratigraphy andpetroleum possibilities: Florida Bureau ofGeology Special Publication No. 15, 99 p.

STRATIGRAPHIC UNIT

Corkscrew SwampFormation

Rookery BayFormation

Panther CampFormation

Dollar BayFormation

Gordon PassFormation

Marco JunctionFormation

Rattlesnake HammockFormation

Lake TraffordFormation

Sunniland Formation

Punta Gorda Anhydrite

Able Member

West FeldaShale Member

Pumpkin Bay Formation

Bone Island Formation

Wood River Formation

Gla

des

Gro

up

LO

WE

R C

RE

TAC

EO

US

Leh

igh

Acr

esF

orm

atio

n

Big

Cyp

ress

Gro

up

Nap

les

Bay

Gro

up

Oce

an R

eef

Gro

up

UP

PE

RJU

RA

SS

IC(?

)

LITHOLOGY

Dolomite,anhydrite,limestone,

salt stringers,and basal clastics

Limestone,anhydrite,dolomite

Limestone,anhydrite,dolomite

Calcareousshale

Brown

dolomite

zone

Twelve MileMember

Brown dolomite,limestone,dolomite

Limestone, dolomite,anhydrite

Anhydrite and salt,limestone, dolomite

Limestone,anhydrite

Limestone, dolomite,anhydrite

Anhydrite,limestone, dolomite

Limestone, dolomite,anhydrite

Anhydrite,limestone, dolomite

Limestone, dolomite,anhydrite

Limestone, dolomite,anhydrite8

Limestone, dolomite,anhydrite

Limestone, dolomite,anhydrite

Basal

clastics

PE

RIO

D

Figure 1. General stratigraphic section for the South Florida Basin[modified from Faulkner and Applegate (1986) and Lloyd (1991)].

8