Showing papers on "Petroleum reservoir published in 1974"

Formation velocity and density—the diagnostic basics for stratigraphic traps

Abstract: A multiplicity of factors influence seismic reflection coefficients and the observed gravity of typical sedimentary rocks. Rock velocity and density depend upon the mineral composition and the granular nature of the rock matrix, cementation, porosity, fluid content, and environmental pressure. Depth of burial and geologic age also have an effect. Lithology and porosity can be related empirically to velocity by the time‐average equation. This equation is most reliable when the rock is under substantial pressure, is saturated with brine, and contains well‐cemented grains. For very low porosity rocks under large pressures, the mineral composition can be related to velocity by the theories of Voigt and Reuss. One effect of pressure variation on velocity results from the opening or closing of microcracks. For porous sedimentary rocks, only the difference between overburden and fluid pressure affects the microcrack system. Existing theory does not take into account the effect of microcrack closure on the elasti...

Petroleum Microseepage at Cement, Oklahoma: Evidence and Mechanism

Abstract: Striking mineralogic and chemical changes occur in outcrops of a Permian redbed sequence overlying oil-productive parts of the prolific multireservoir oil accumulation at the Cement anticline, Oklahoma. Gypsum beds along the flanks are altered abruptly to erosion-resistant carbonate rocks at the crest of the fold in the Keechi Hills. Associated sandstones, typically red and friable in the surrounding region, are altered to pink, yellow, and white on the flanks of the anticline and to hard carbonate-cemented gray sandstone at the crest. The zone of cementation, confined to sandstone intervals, extends to a depth of at least 2,500 ft. Calcitized gypsum exceptionally deficient in C13 and light-carbon/heavy-oxygen cements directly overlie petroleum-productive zones near regions where fluids have superior vertical avenues of communication (faults and an unconformity at shallow depths and of limited extent along the crest). Away from these avenues of leakage, the influence of hydrocarbons on the isotopic composition of the carbonate cements decreases systematically. Color changes in the sandstones are related to reduction and dissolution of iron in the presence of hydrocarbons. Much of the hydrocarbons leaked from Missourian reservoirs beneath the crestal unconformity. Dense crude oil from stratigraphically discontinuous reservoirs along the basinward flank of the structure are associated with low-salinity pore water. Paraffinicity and salinity of waters decrease systematically with increasing depth of burial; these salinity variations, initially effected by ingress of water squeezed from expandable clays in the bordering basin, may have played a role in the selective solution of low-molecular-weight fractions. Water, vertically expelled along the crest, was desalted in passing from sandstone to shales. Large volumes of sandstone thereby were cemented off in shallow Permian rocks in places over the crest; the uncemented sandstones are petroleum-productive do n the flanks.

Displacement Stability of Water Drives in Water-Wet Connate-Water-Bearing Reservoirs

Abstract: Displacement of oil by water from water-wet connate-water-bearing reservoirs is unstable if the mobility ratio across the shock front is greater than one, provided the wavelength of the instabilities is smaller than the reservoir dimensions. Capillary forces determine the wavelength, and the one that predominates contributes the maximum to the energy dissipation. Experiments in a transparent model have confirmed these results.

Direct methods in reservoir simulation

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Underground storage of natural gas in Illinois--1973

Abstract: Natural gas is stored in underground reservoirs at 37 locations in Illinois. These reservoirs contain more than 580 billion cu ft of gas, about one-third of which is working gas and two-thirds is cushion gas. Potential usuable capacity of these reservoirs is estimated to be 1.2 trillion cu ft. At 11 of the storage projects, gas is stored in depleted, or partially depleted, gas reservoirs. One depleted oil reservoir is used for storage, and in the remaining projects, gas is stored in aquifers that originally contained no hydrocarbons in commercial quantities. At 4 locations, 2 reservoirs at different depths are in various stages of exploration, testing or development for storage. Two projects have been abandoned. Rocks of all systems from Cambrian to Pennsylvanian are used for storage of gas in Illinois. However, most of the storage volume is in sandstone aquifers of Cambrian and Ordovician age. (50 refs.)

Genesis and Distribution of Desmoinesian (Pennsylvanian) Sandstone Reservoir, Sleepy Hollow Field, Red Willow County, Nebraska

Abstract: Sleepy Hollow oil field, Red Willow County, Nebraska, discovered in 1960, has produced nearly 30 million bbl of oil from a "basal" Desmoinesian (Pennsylvanian) sandstone. The trap for this substantial oil accumulation is complex, related to (1) sandstone characteristics and distribution, and (2) gentle late Paleozoic structure. Examination of reservoir core samples from 23 Sleepy Hollow field wells reveals sedimentary characteristics which, when combined with observations of the stratigraphic sequences in and adjacent to the sandstone, suggest that the following sequence of sedimentary events governed the distribution of this reservoir rock. The Precambrian surface that had been exposed at least since Early Pennsylvanian time was incised by fluvial channels that were choked with granite detritus (quartz and feldspar in various stages of weathering). During the Middle Pennsylvanian marine transgression of the Precambrian surface, quartz fragments derived from the granite wash were reworked by westward longshore drift in the shallow sea but rarely were transported more than a few miles from the drainage system from which they were derived. Accumulation of relatively pure quartz sand is presumed to have occurred as a result of the removal of feldspar through weathering of the exposed crystalline rocks and by winnowing by shallow-marine currents. After several episodes of shoreline and shallow-marine sand deposition and accompanying winnowing of clay, lobate sand bodies coalesced to form the present continuous reservoir. Sand deposition did not occur north and south of Sleepy Hollow because of the absence of a nearshore high-energy environment for clastic deposits. Sand deposition did not occur east of Sleepy Hollow because of the relative position of the fluvial channel and the direction of longshore drift.

Petroleum Geology of Sweetgrass Arch, Alberta

Abstract: The Sweetgrass arch is a positive structural feature extending from central Montana into southeastern Alberta. Rock units ranging in age from Precambrian Beltian to Late Cretaceous Montanan are exposed along the 350-mi axis. Three major elements can be highlighted: the South arch, which culminates in the Beltian exposures on the south end; the Kevin-Sunburst dome and the Sweetgrass Hills which dominate the center along the International Boundary; and the Bow Island arch which plunges northward into southern Alberta. Early exploration for hydrocarbons naturally was focused on the search for structural traps; such a large positive trend would be expected to have many faulted and domal anomalies. Active development work over the years proved that the stratigraphic trap predominated as the setting for hydrocarbon accumulation. Even the large closed structural anomaly of the Kevin-Sunburst dome does not entirely cause the entrapment of oil and gas there, but irregular porosity development in Mississippian carbonate rocks, and lensing and pinchout of Cretaceous sandstones more accurately account for the accumulations. The largest oil reserves on the arch are in a group of channel sandstones in the Lower Cretaceous basal Mannville Group, extending from the Cutbank field of Montana northward through the Taber, Hayes, and Bantry fields of Alberta. The middle Mannville Glauconitic-Moulton sandstones produce from a string of sandbars trending northward from the Darling area on the International Boundary through the Taber area and in scattered trends in the Jenner, Countess, and Hussar fields of Alberta. Large gas reserves are found in thin blanket sandstones of Late Cretaceous age, principally in the Medicine Hat and Second White Specks zones in the Alderson, Medicine Hat, Bantry, and Princess areas. Minor gas deposits are also in the Lower Cretaceous Bow Island Formation in long, narrow sandbars in the Pakowki Lake and Bindloss areas. A 300-ft-thick interval of silty and sandy shale in the Milk River Formation has been known to contain gas for some time, but, because of its low productive rate, only recently has this enormous deposit been developed. Since 1970 a small drilling boom has been under way to put this huge reserve on the market. The Milk River pool may be the largest single gas field in areal extent in western Canada.

A Geophysical and Geological Investigation of Potentially Favorable Areas for Petroleum Exploration in Southeastern Arizona

Abstract: The objective of this study has been to determine areas potentially favorable for oil and gas exploration in southeastern Arizona. Surface geological investigations in the mountain ranges indicate that a thick sequence of marine sedimentary Paleozoic and Mesozoic (Cretaceous) rocks was deposited in the Pedregosa basin in southeastern Cochise County and adjacent shelf areas. According to Wengerd (1962), Kottlowski (1971), Greenwood (1969), and Greenwood and Kottlowski {1974), these marine strata deposited in this basin are similar in many aspects to those in petroleum-productive areas in southeast New Mexico and west Texas. They contain organic-rich basin facies of rocks that were probable sources for oil and gas. The margins of the Pedregosa basin offer structural, stratigraphic, unconformity, and paleogeomorphic traps. However, such adverse factors as the wide thickness variance of Cenozoic valley fill (100 feet or less to almost 12,000 feet), very little information as to the absence or presence of potentially petroleum-productive undeformed Paleozoic and Mesozoic rocks beneath Cenozoic rocks in the valleys, and extensive evidence in the mountains that the area has had an extremely complex geologic history, have discouraged exploration in the past.

Possible Ordovician Carbonate Reservoirs in Mississippi

Abstract: To mid-1973, carbonate rocks of Ordovician age in north Mississippi had produced 7,813 bbl of 35° gravity oil from one well and 123,752 MCF of gas from another. In spite of the poor results of exploration of Ordovician strata, large reservoirs may be present in these oil- and gas-bearing limestones and dolomites, and structural and stratigraphic conditions may favor commercially profitable accumulations of oil and gas. Porosity is found in fractured and vuggy dolomite, in sucrosic dolomite, in secondarily dolomitized limestone, in coquinoid or reef limestone, in oolitic limestone, and in chert residuum from post-Ordovician, Early Silurian, lixiviation.

Dynamics of petroleum reservoirs under gas injection

Abstract: The four chapters cover: history of gas injection, material-balance methods, immiscible gas-oil displacement, and gas-oil displadement with mass transfer. (DLC)

Petroleum Geology of the Moluccas, Eastern Indonesia*

Abstract: The greater Moluccas are bounded by the Pacific and Indian Oceanic plates and the greater Australian and Sunda continental crustal plates or shelves. The effect of their opposing movement is a giant counterclockwise sworl. The island arcs within this pattern include parts of subduction zones between the opposing plates. The Sorong transform, left lateral fault resulted from these forces, and remnants of the Irian Jaya shelf terrain are offset at least 700 kilometers westerly to the Sula Islands. Fossil subduction zones are present in the form of melanges, including a persistent zone extending in an “S” pattern from Timor through Ceram, Buru, and Sulawesi. The age of emplacement of this zone in part is post-Lower Miocene to pre-Middle Pliocene. Sedimentary rocks of Miocene to Permian age occur notably in Timor and the Sula Islands. In most localities, they are deformed and indurated to the extent of making them economic basement. Plio-Pleistocene linear sedimentary basins follow the “S” trend and reach a maximum of 3000 meters in thickness in northeast Ceram and Timor. Rocks include deep water claystones, shelf and lagoonal clays, bar and beach sands, and barrier coral reefs. Oil seeps occur on Ceram, Timor, and Buton (asphalt), mostly from Plio-Pleistocene rocks. Oil is produced at Bula, Ceram, from Pleistocene bar and shoreline sands in stratigraphic traps. A recent development at Bula is prolific production from an extremely permeable Pleistocene coral reef. The data suggest that oil accumulation per unit volume of sediments is abnormally high in the Plio-Pleistocene. Reasonable extrapolation indicates that major oil fields may be found in prospecting the “S” trend. Most likely traps will be stratigraphic with accumulations in beach, bar and reef limestones, and possibly turbidite sands. Prospects also exist in other than Plio-Pleistocene in other portions of the Moluccas. Prospecting for these subtle, elusive traps may be rewarding, if geologists exchange certain negative prejudices for a positive optimistic approach in combination with good imaginative geology.

Thrust faults of Rough Creek fault system in Western Kentucky and related petroleum occurrences

Abstract: Recent investigations in Union County, Kentucky, have facilitated recognition of certain previously unreported geologic features associated with the Rough Creek fault zone, a prominent E.-trending belt of normal and reverse faults in the Illinois Basin near its SE. margin. These features include (1) major thrust faults with planes that dip south at angles that range from as low as 25/sup 0/ to as high as 70/sup 0/, as indicated by repeated stratigraphic section in oil test holes and by surface exposures; (2) local structural relief of as much as 4,000 ft in the vicinity of the fault zone; and (3) E.-trending grabens bounded by normal faults that die out with depth in the near-surface Pennsylvanian rocks. Approximately 48 million bbl of oil have been produced from the fields bordering and within the Rough Creek fault zone in W. Kentucky. Untested structural and probable stratigraphic traps associated with the fault zone should yield additional petroleum discoveries.

Laboratory studies of sandstone reservoirs gas displacement from having strong water drive

Abstract: Investigations by the Petroleum Technology Section of the Bureau of Mineral Resources have shown that a substantial residual gas saturation is trapped behind the flood front in gas-producing reservoirs having a strong water-drive; the volume of gas trapped may be as high as 44 per cent of pore space, and lies within the same range as residual oil saturation in a flooded-out oil reservoir. Core samples from gas-productive reservoirs in three Australian sedimentary basins have been subjected to laboratory tests to measure this effect. The tests comprised capillary pressure measurements, water-flooding by dynamic-displacement and imbibition at ambient and elevated temperatures, and repeat gas recovery measurements in core samples exhibiting variations in irreducible water saturation. The results show a loose correlation between porosity and residual gas behind the flood front in these samples. Temperature appears to have little effect on the residual gas saturation. Gas recovery, however, is strongly dependent on the irreducible water saturation established prior to flooding.

Stratigraphic Trap Accumulation in Southwestern Kansas and Northwestern Oklahoma

Abstract: An oil- and gas-bearing inlier of Morrowan sandstones presents a paradoxical situation in that water, oil, and gas are present in an inverted structural relation, some of the gas being structurally lower than oil and water. A map of the pre-Pennsylvanian topography reveals that a modified trellis drainage system was developed on subaerially exposed Mississippian strata. Southwestward-tilted resistant limestones of the Chesterian Series stood out as subparallel cuestas; intervening erosional valleys developed on interbedded nonresistant shales. Morrowan strata were deposited under conditions of cyclic marine southwest-to-northeast transgression, which was interrupted by several minor regressions. Sands were deposited during the regressive phases, and shales during transgressive phases. Small-scale structural noses and closures on the Inola limestone are largely the result of differential compaction of shales deposited over buried pre-Pennsylvanian topography. Detailed mapping affords a logical explanation for each producing well and all but a few dry holes in the Second Morrow sand of the Harper Ranch field of Clark County, Kansas. The anomalous distribution of some gas accumulation is explained by Gussow's principle, modified to apply to a stratigraphic trap.

Fracture porosity and permeability in stratigraphic traps

Abstract: Geologic history of Cardium rocks suggests that structural compression is important in controlling in direction of fracture sets; uplift and erosional unloading are most important in producing the network of fractures at depth that are essential to fractured reservoirs. The important control exerted by lithology over fracture porosity and permeability in fine-grained rocks begins early in their history. It commences with depositional, diagenetic and tectonic events which create a rock susceptible to brittle failure by fracturing and capable of maintaining an open network of fractures. Many basins probably contain a spectrum of subtle traps ranging from stratigraphic pools in coarse-grained rocks to fine-grained stratigraphic reservoirs in which fracture porosity and permeability are well developed. Exploration for stratigraphic traps should include a search through fine-grained reservoir rocks, having in mind the increased reservoir permeability that fractures can provide.

The Discovery and Development of the Petapahan Oil Field, Central Sumatra

Abstract: The Petapahan oil field is located about 60 km west of Pekanbaru, the capital of Riau Province and just north of Tapung Kiri River in central Sumatra The field covers approx 3,200 acres At the end of 1973, 17 wells had been drilled in the field with 2 dry holes Of the remaining 15 wells, 12 are on production and 3 are shut in, awaiting production testing Production of 33' API gravity oil is obtained from 3 separate sandstone reservoirs at the rate of approx 40,000 bpd Cumulative production to Dec 31, 1973 was 147 million bbl of oil Oil was discovered in 3 separate sands in the lower Miocene Sihapas Group The sands, designated as A, B, and C, are divided on their differences in reservoir characteristics with 12 ft (35 m), 30 ft (9 m), and 114 ft (35 m) of respective net pays The Petapahan structure extends northwest-southeast along the S flank of a deep Tertiary basin The 2 lithologic units of interest in the Petapahan field are (1) the lower Miocene Sihapas Group which is composed predominantly of porous quartzose sandstone with silt and shale interbeds, and is the reservoir unit; and (2) the overlaying lowermore » to middle Miocene Telisa Formation is predominantly shale with thin sandstone interbeds; it is the effective cap rock and is also considered the likely source bed for oil generation« less

Poison Draw Field, Converse County, Wyoming

Abstract: Poison Draw field produces oil and gas from a reservoir in the lower Teckla Sand Member of the Lewis Shale. Because of its low formation pressure, the lower Teckla Sand is subject to severe invasion of drilling mud and formation damage. Careful protection of the sand by proper mud programs and logging as soon after penetration as possible are the keys to thorough and confident evaluation of the reservoir. The Poison Draw pool is a stratigraphic type of trap. It is defined by an updip loss of permeability near the sand pinchout, lateral permeability barriers formed by lithologic variations and a downdip oil-water contact. The trap is located on the northeastern regional limit of the lower Teckla Sand. The reservoir sand was deposited in a shallow open marine environment on the seaward edge of a prodelta sequence. Bottom currents from the northwest swept the sediments southeast forming NW.-SE. trending sand bodies containing thin porous sand lenses which form the Poison Draw reservoir rock. The field contains 99 producing wells which through Dec. 1974 have produced 2.9 million bbl of oil and 1.6 billion cu ft of gas. The primary recoverable reserves are estimated to be over 9 million bbl ofmore » oil and 15 billion cu ft of gas. A secondary flood should double the oil production to an ultimate recoverable reserve of 18 million bbl of oil.« less

Geology of the Badak field, east Kalimantan, Indonesia

Abstract: The Badak Field was discovered in January 1972. It is located on the coast of E.Kalimantan (Borneo), about 35 kilometers northeast of the provincial capital of Samarinda. Oil and gas were found in a multitude of deltaic sandstone beds of middle Miocene to Pliocene age, between 4500 and 11,000 feet. The structure is a broad anticline with flanks dipping less than 10 degrees, areal closure of roughly 40 square kilometers and vertical closure up to 1000 feet depending on the depth. The majority of the closed reservoirs contain gas and condensate and the structure appears to be filled to its spill point. Oil occurs in some sands in the crest of the anticline and in oil rings below gas in several reservoirs. At this date exploration for oil rings on the flanks of Badak anticline is still in progress. Recoverable reserves in the Badak Field are estimated to be in excess of six trillion SCF of hydrocarbon gas and fifty five million barrels of hydrocarbon liquids.

A Brief Study of Reservoir Rock Wettability in the Iranian Oil Fields

Abstract: Reservoir study revealed that the wettability of rocks can have a profound influence on the displacement of oil by water from the oil-producing reservoir rocks. Therefore, a correct prediction of the efficiency of waterflood secondary recovery is based on the evaluation of a reservoir rock wettability. The wettability characteristics of a reservoir in the two largest fields in southwestern Iran (Ahwaz and Marun) were evaluated. Results indicated that the reservoir rocks in both fields are water wet but with different intensities.