U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL

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

U.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEYOIL AND GAS INVESTIGATIONSMAP OM–226PAMPHLETMAPS SHOWING HYDROCARBON PLAYS OF THE FLORIDA PENINSULA,USGS PETROLEUM PROVINCE 50ByRichard M. Pollastro and Roland J. Viger1998PROVINCE INTRODUCTION ANDGEOLOGIC SUMMARYbasin 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.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 GulfAtlantic 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 Florida1

EXPLORATION CELLS ANDFIELD OUTLINESan 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 (MitchellTapping, 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 (oilprone) 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 ofEach cell on the maps represents 0.25 mi 2in 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 DESCRIPTIONSMAP 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 identify2

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, MidFelda, Raccoon Point, Sunniland, and SunocoFelda (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.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/operatorMAP 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 from3

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.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 organicmatter 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,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 shows4

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, A

Oil play (5003), Lower Cretaceous Carbonate Composite Oil play (5004), Extended Upper Sunniland Tidal Shoal Oil play (5005), and Wood River Dolomite Deep Gas play (5006). The easternmost part of the Smackover Alabama/Florida Updip Oil play (4911) also extends into Province 50 but has been assigned to Prov