Lower Hackberry Research Articles

Abstract: Foraminiferal Biofacies, Local Zonation and Paleobathymetry of the Hackberry Sequence (Middle Oligocene Frio) of Southwestern Louisiana 

ABSTRACT The Hackberry Sequence is a Middle Oligocene (Frio) wedge of deepwater sediments characterized by the Hackberry foraminiferal assemblage. Reevaluation of foraminiferal faunas through high-resolution biostratigraphic studies has increased the known diversity to over 200 species, one of the richest microfaunas in the Gulf Coast Paleogene. Careful evaluation of these diverse assemblages allows recognition of ten foraminiferal biofacies within the Hackberry Sequence. Each biofacies, characterized by distinctive assemblages of key and secondary foraminiferal taxa, has been recognized from recent work in the downdip portion of the Hackberry in Cameron and Calcasieu parishes of southwestern Louisiana. The time of Hackberry deposition also serves as the point of origin or arrival for many long-ranging foraminifera within the Gulf Coast Basin fossil record. Hackberry foraminiferal biofacies are useful for subdividing this sequence into a local zonation scheme, each indicative of a particular paleobathymetric regime. Analysis suggests that the basal to lower biofacies were deposited in depths ranging from lower to middle bathyal. Transported downdip shelf sands in the lower Hackberry are marked by influxes of inner shelf taxa, especially Amphistegina floridana and Elphidium rota. This suggests a correlation of the lower Hackberry to the updip Chickasawhay Formation. Middle and upper Hackberry biofacies range from middle bathyal to deep middle neritic, indicating a gradual in-filling and environmental shallowing throughout deposition of the Middle Oligocene Hackberry Sequence. The biostratigraphic and paleoenvironmental nature of the Pre-Hackberry unconformity is also addressed.

Evolution of Salt and Hydrocarbon Migration: Sweet Lake Area, Cameron Parish, Louisiana: ABSTRACT

ABSTRACT The interpretation of seismic, gravity, and well data in northern Cameron Parish, Louisiana suggests that lateral salt flow has influenced the area's structural evolution, depositional patterns, and hydrocarbon migration. Sweet Lake field has produced over 46 MMBO and 15 BCFG from middle Miocene deltaic sands. The productive structural closure is a faulted downthrown anticline controlled by the underlying salt feature. Sweet Lake field overlies a allochthonous salt mass that was probably once part of an ancestral salt ridge extending from Hackberry to Big Lake. Nine wells encountering top of salt and several seismic lines define a detached salt feature of more than 44 square kilometers (17 square miles) at depths from 8,560'-18,000'. Salt withdrawal in the East Hackberry-Big Lake area influenced the depositional patterns of the Oligocene lower Hackberry channel systems. Progradation of thick middle Oligocene Camerina (A) andMiogypsinoides sands into the area caused salt thinning and withdrawal, resulting in the development and orientation of the large Marginulina-Miogypsinoides growth fault northwest of Sweet Lake. Additional evidence for the southeast trend of the salt is a well, approximately 10 kilometers (6 miles) southeast of Sweet Lake, which encountered salt at approximately 19,800'. High quality 2-D and 3-D seismic data will continue to enhance the regional understanding of the evolving salt structures in the onshore Gulf Coast and the local understanding of hydrocarbon migration. Additional examples of lateral salt flow in the onshore area will be recognized and some may prove to have subsalt hydrocarbon potential.

Depositional Patterns and Structural Styles--Hackberry Salt Dome, Cameron Parish, Louisiana: ABSTRACT

ABSTRACT The West and East Hackberry fields of north-central Cameron Parish, Louisiana, are associated with a large southeast-plunging salt ridge. Episodes of salt movement influenced the depositional patterns and reservoir trap styles of the Oligocene- and Miocene-age sedimentary section. The Oligocene lower Hackberry channels were influenced by the salt structure, resulting in the Manchester-Holmwood channel system flanking the east and south sides of the salt dome and the Choupique channel system flanking the west side of the salt dome. The depositional patterns and structural bed dips of the younger Oligocene Camerina A to Marginulina section demonstrate a major period of salt movement and erosion. The resulting truncation of the Camerina A sandstones, sealed by overlying shales, provides the dominant trap style for the majority of the reservoirs. This same general period of salt movement influenced the orientation of the Oligocene Marginulina to Miogypsinoides expansion fault system to the east. The Sweet Lake salt dome, downthrown to this expansion system, probably represents a southeast extension of this ancestral salt ridge.

Deep-Seated Salt Sheet: Eastern Calcasieu Parish, Louisiana

ABSTRACT Interpretation of recent seismic and well data in the Gillis-English Bayou and West Manchester area of Calcasieu Parish, Louisiana, supports a complex structural history involving allochthonous salt, erosion and faulting. Since its discovery in 1934, Gillis-English Bayou has produced over 195 BCFG and 18 NMBL from Oligocene and Miocene age sands. Unlike the aerially small, shallow salt dome fields along trend, Gillis-English Bayou covers approximately eighteen square miles, by area the largest field in the parish. West Manchester, to the south, has produced over 120 BCFG and 2 MMBL from Oligocene Lower Hackberry sands. The associated salt sill underlies at least thirty square miles at depths of 15,000 to 20,000 and can be indirectly related to hydrocarbon accumulation in the area. Associated with this vertical and lateral movement of salt is a significant Vicksburg erosional event underlying West Manchester Field. In this area of thick Vicksburg sediments, over 1,200 of section is absent.

North Sabine Lake Field: Complex Deposition and Reservoir Morphology of Lower Hackberry (Oligocene), Southwest Louisiana: ERRATUM

North Sabine Lake Field: Complex Deposition and Reservoir Morphology of Lower Hackberry (Oligocene), Southwest Louisiana: ERRATUM

Geology and Coproduction Potential of Submarine-Fan Deposits Along the Gulf Coast of East Texas and Louisiana

Summary Four reservoirs containing dispersed gas were examined for their coproduction potential. Reservoirs in Port Acres field (Texas) and Ellis field (Louisiana) produce from the Hackberry member of the Oligocene Frio formation, and two reservoirs in Esther field (Louisiana) produced from the lower Miocene Planulina zone. Log-pattern and lithofacies maps, together with stratigraphic position, suggest that the reservoirs are in ancient submarine-fan deposits. Dip-elongate, channel-fill sands are characteristic; reservoir sands pinch out along the strike. Growth faults, common in the submarine slope setting, form updip and downdip boundaries, producing combination traps. In Ellis field, coproduction accounts for 300 Mcf/D [8.5 × 103 m3/d] of gas. Port Acres field contains the largest remaining reserves, but other technical and economic factors limit coproduction potential there. Recent drilling has extended primary production and delayed coproduction in the Esther field. Introduction During conventional production from a water-drive gas reservoir, mobile gas is removed from the gas cap. A considerable amount of dispersed gas remains in the water, however, after the field has watered. out.1 This dispersed gas can be recovered through coproduction (the simultaneous production of gas and water). During coproduction, large amounts of water are pumped to the surface, lowering reservoir pressure and causing dispersed gas to expand; the gas then moves to the coproducing well and is produced with the water.2 If the reservoir has sufficient residual pressure and the pumped water can be disposed of easily, extended production of a field may be economically viable.1 To avoid costly well re-entry or drilling of new wells, coproduction is best initiated in a watered-out reservoir before the wells have been plugged. Four reservoirs with coproduction potential were selected for detailed study. The resrvoirs are in Port Acres, Ellis, and Esther fields (Fig. 1). The lower Hackberry and Nodosaria 3 reservoirs, in Port Acres and Ellis fields, respectively, are productive from the Hackberry member of the Frio formation, and the two Planulina zone reservoirs in Esther field are productive from lower Miocene sands. Several factors that determine the suitability of a reservoir for coproduction - such as porosity, permeability, and reservoir volume3 - relate to the geology of the reservoir. Therefore, for each reservoir selected for study, all available data were used to interpret the depositional setting of the reservoir sand, the trapping mechanisms, and the volume of the reservoir. Original gas in place and remaining reserves were calculated, and the coproduction potential of each field was assessed. Hackberry Trend The Frio formation (Oligocene) is a major progradational wedge of predominantly sandy sediment that extends from Texas to Louisiana. Previous workers divided the Frio into three units by log character. In this interpretation, the Hackberry member is laterally equivalent to middle Frio sediments.4 The upper boundary of the Hackberry sequence is marked by Marginulina texana, and for the purpose of this paper, the lower Hackberry will include the Nodosaria blanpiedi zone, although there is some dispute over the lower boundary of the Hackberry5 (Fig. 2). The Hackberry member was probably deposited as a submarine-fan complex6; it is composed mainly of turbidite, or gravity-flow, deposits. The Hackberry embayment, containing Hackberry submarine fans, extends from southeast Texas eastward to south-central Louisiana4 (Fig. 1). The updip limit of Hackberry sediments is the Hartburg flexure, which is more or less coincident with the oldest growth faults in the Frio.5 The unit thickens basinward to more than 3,000 ft [900 m].7 The lower Hackberry is relatively sand-rich, with nearly continuous sand sequences up to 800 ft [240 m] thick; the upper Hackberry is almost entirely mud. Depositional channel-sand axes of the Hackberry trend northwest/southeast in Texas and north/south in Louisiana.4 Hackberry reservoir sands are highly lenticular and dip-elongate; they are an important producing trend in the gulf coast.5 A model of submarine-fan subenvironments8 linked with spontaneous-potential (SP) log patterns representing the different subenvironments4 (Fig. 3) was used to interpret the environments present in the Port Acres and Ellis Hackberry reservoirs.

North Sabine Lake Field: Complex Deposition and Reservoir Morphology of Lower Hackberry (Oligocene), Southwest Louisiana

Gas and condensate production at the North Sabine Lake field is from sands of the Hackberry wedge of the Oligocene Frio Formation. These lower Hackberry sands were deposited in a preexisting submarine canyon. Multiple sand bodies are present, and five patterns of sand deposition are recognized from SP logs: (1) incised channel fill, (2) braided fan channel, (3) intermediate suprafan, (4) proximal suprafan, and (5) overbank. Although three faults surround the field, the primary trapping mechanism is stratigraphic. The development and production history of the field indicate that many small sand lenses have coalesced to form a single large reservoir; however, differences in permeability have caused variations in water influx and in the levels of gas-water contacts. Sand lenses that are not connected to the larger reservoir are of limited size and have produced small amounts of hydrocarbon. Development of the field has been complicated by casing damage probably caused by reservoir compaction.

Deeply Buried Tertiary Sand Bodies in Northern Gulf of Mexico: Examples from Lower Hackberry (Oligocene) and Houma Embayments (Miocene): ABSTRACT

Ninety-three electric logs were used to analyze deep-seated sand bodies in two fields in the Hackberry embayment of southeastern Texas and the Houma embayment of southern Louisiana. The geometry and occurrence of these sand bodies can be related to the regional structural and sea level history of the study areas. The Hackberry embayment originated by shelf-edge retreat after a major drop in sea level. Large amounts of sediment were then supplied by the Frio delta systems that built out to the shelf margin. The Houma embayment originated during a slight increase in the rate of sea level rise, while the Miocene deltaic systems built out over the continental shelf, triggering mass movement on the continental slope. Both areas are characterized by large-scale synsedimentary faulting and salt tectonics. Large arcuate growth faults form the updip boundary of each embayment. Displacement across faults is from 900 to 2,000 ft (300 to 650 m). In both embayments, the sand bodies are overlain by thick shale masses that contain similar flysch-type faunas. The sands have a blocky appearance on the SP curves of electric logs, are slightly more than 100 ft (35 m) thick, and can be correlated for only a few miles. The structures show typical rollover, or reverse drag, into the main growth faults. In the Hackberry embayment, it can be shown that some intervals on the expanded downthrown side of the fault contain additional section, whereas marker beds below and above continue across the fault. These expansi ns developed during a time interval represented by 400 ft (130 m) of section and are interpreted as erosional and depositional events across the growth fault. Comparison with present-day large-scale rotational slumps on the continental slope off the Mississippi delta shows that the overall characteristics of the Tertiary sands are similar to such modern slump masses; therefore, these sands are interpreted as having originated in a similar fashion. Thus, it appears that these analogous sand bodies accumulated as a result of comparable processes, even though the associated changes in sea level in the two areas differed considerably. End_of_Article - Last_Page 1425------------

Habitat of Hydrocarbons in Hackberry (Oligocene, Middle Frio), Texas and Louisiana: ABSTRACT

This paper reinterprets the stratigraphic position, depositional environments, and depositional systems in the middle Frio (Oligocene) Hackberry, and their relation to hydrocarbon accumulations. This stratigraphic unit is present in the subsurface of southeastern Texas and southwestern Louisiana, in an area known as the Hackberry embayment. The unit consists of a lower Hackberry sandstone-shale sequence, overlain by middle and upper Hackberry marine shale (the Hackberry shale wedge). The lower Hackberry sandstone-shale sequence overlies a truncated lower Frio section, but in some interdomal areas and in downdip locations lower Hackberry sediments rest conformably on lower Frio Nonion struma beds. Planktonic foraminifers indicate that the erosional surface between lower and middle Frio coincides with a worldwide relative sea level fall approximately 30 Ma, in planktonic foraminiferal zone P21. Dip-oriented submarine channel and fan systems related to this erosional surface contain lower Hackberry reservoir sands in downdip positions. The marine shale wedge that overlies the lower Hackberry sandstones was deposited during a relative sea level rise, when rates of subsidence exceeded rates of deposition. Some strike-oriented discontinuous marine sand reservoirs are present within the shale wedge. Production is found in the lower Hackberry in structural traps in reservoirs related to nearshore and fluvio-deltaic deposition (traction-transport systems), and, in downdip locations, in stratigraphic-structural traps in submarine channel-fan systems (gravity-transport systems). Unexplored objectives related to submarine channel-fan systems may be present below thick, growth-faulted younger Frio sections. End_of_Article - Last_Page 468------------

Enhanced Gas Recovery From Watered-Out Reservoirs: ABSTRACT

Major additions to future gas reserves will depend partly on development of resources that are presently unconventional. Recently, coproduction of gas and water has been proposed as a method to increase ultimate gas recovery from reservoirs that have begun to water out or were abandoned because of high water production. The enhanced recovery method involves producing large volumes of water and reducing reservoir pressure to the point where dispersed gas, trapped in the water-invaded zone, is mobilized and flows to the well bore. Research involving the coproduction method was funded by the Gas Research Institute. Integration of geological and engineering studies indicates that the Port Arthur field in Jefferson County, Texas, is a prime area for research to test the coproduction techniques. Prior to abandonment, the field produced from lower Hackberry (Oligocene) sandstones at depths less than 12,000 ft (3,600 m). The field contains 11 reservoirs with a maximum net sandstone thickness of over 450 ft (135 m). Individual sandstones are 10 to 120 ft (3 to 36 m) thick, but gas columns are usually less than 20 ft (6 m) thick. The reservoirs are relatively narrow and elongate and are oriented nearly perpendicular to the local structure, a simple roll-over anticline. These reservoirs, interpreted as submarine channel and fan deposits, are internally heterogeneous owing to the vertical imbrication and dip-alignment of the sand lenses. Optimum reservoir facies occur as thick, massive sandstones with uniformly high porosities and permeabilities that average 28% and 60 md, respectively. Reservoir quality is more variable and diminishes somewhat away from the channel axes in the more thinly bedded sandstones with intercalated shales. Upward decreases in porosity and permeability characterize the zones of gas accumulation. The C sandstone was selected for detailed investigation because of high abandonment pressure, excellent reservoir quality, high productivity, and good lateral continuity. Reservoir simulation studies suggest that 5.5 bcf of gas and some condensate could be recovered from the C sandstone under natural flow conditions by producing slightly more than 9 million bbl of water over a 5-year period. Brine disposal would be accomplished by injection into thick Miocene sandstones that occur at shallow depths. If successful, the recovery efficiency of the C sandstone would be increased from 42% (primary) to 53% of the original gas in place. An economic analysis of the enhanced recovery project indicates a favorable payout under prevailing gas prices. Project economics are even more attractive if gas prices increase or if gas production from other abandoned reservoirs is commingled with production from the C sandstone. End_of_Article - Last_Page 475------------

Morphology of Turbidite-Channel Reservoirs, Lower Hackberry (Oligocene), Southeast Texas: ABSTRACT

ABSTRACT Hackberry sandstones produce gas at depths of from 9500 to 11,500 ft (2900 to 3500 m) in the western part of the Hackberry embayment. Adjacent shales contain a microfauna generally believed to represent bathyal depths. The Hackberry sandstones have long been known to be turbidites in the form of dip-trending, channel-like bodies. Recent cores from fields in southeast Texas provide more details concerning reservoir character and morphology. Hackberry reservoirs are found in narrow channels only 3000 to 4000 ft (914 to 1219 m) in width. Channel sandstones thicken abruptly to 200 to 300 ft (61 to 91 m). Middle-channel locations are characterized by stacked, massive sandstones which represent the A division of the turbidite sequence. Stacked channel beds are apparently on the order of 10 ft (3.5 m) in thickness, but no intervening shales separate bed sets. The channel-margin sections consist of interbedded sandstone and shale. The beds are on the order of 3 to 5 ft (1 to 1.5 m) in thickness and consist of massive and laminated sandstones that form turbidite sequences of the A and AB type. The immediately adjacent overbank sections are composed dominantly of shale but contain thin sandstones and siltstones that are massive to laminated and rippled and form more complete turbidites of the ABC type. All of the sandstones have graded texture and are volcanic-chert arenites of moderate quartz content. The channels appear to be of constructional origin, and log correlations above and below the channel facies suggest that they are inserted in the sedimentary section rather than filling eroded channels. The several facies illustrated by cores have characteristic responses on borehole logs which permit recognition of channels and overbank sections by logs alone. These distinctive log characteristics may permit the prediction of channels in exploratory and development drilling.