Salawati Basin Research Articles

Correlation of the Salawati and Tomori Basins, eastern Indonesia: a constraint on left-lateral displacements of the Sorong fault zone

Abstract The Salawati Basin of western New Guinea and the Tomori Basin of eastern Sulawesi, Indonesia, are two sedimentary basins located either side of the main fault strands in the Sorong fault zone strike-slip system. It is suggested that prior to displacement on the Sorong system the two formed a single sedimentary basin. Movement on the Sorong system occurred largely during the latest Miocene-Quaternary, contemporaneous with deposition of a clastic sedimentary succession. An older basinal sequence, essentially Miocene in age, is composed predominantly of carbonate sediments, and this may have formed part of the foreland basin sequence related to the east Sulawesi orogenic belt. Correlation of the Salawati and Tomori Basins implies a left-lateral displacement of about 900 km on part of the Sorong fault zone.

Neogene Carbonate Exploration Play Concepts for Northern New Guinea: New Iteration from Field Work and Seismic Stratigraphy Along the Northern New Guinea Fault Zone: ABSTRACT

Recent field reconnaissance, petrography, nanno and foraminifera age determinations, and seismic stratigraphy of the Sepik and Piore subbasins of northern New Guinea reveal the existence of an extensive, tectonically unstable, Miocene-Pliocene carbonate shelf system. These findings represent the first recorded evidence of northern Papuan limestones coeval in age to those of the hydrocarbon productive Salawati Basin of Irian Jaya. Moreover, these observations also demonstrate the significance of episodic activities of the northern New Guinea fault zone upon the changes in carbonate sedimentation and diagenesis. During the Neogene, algal biosparites to foraminiferal biomicrites defined the clean portion of a mixed clastic-carbonate shelf system of the northern New Guinea basin, which began at the central New Guinea cordillera and deepened northward. This shelf was interrupted by coral-coralline algal boundstone fringing- to patch-reef buildups with associated skeletal grainstones. Clean carbonates were spatially and temporally restricted to basement blocks, which episodically underwent uplift while terrigenous dilutes carbonates were more common in adjacently subsiding basement block bathymetric lows. These tectonic expressions were caused by the spatially transient nature of constraining bends of the evolving north New Guinea faults. As shown by seismic stratigraphy, by the late Miocene to the early Pliocene the uplift of themore » Bewani-Torricelli Mountains sagittally divided the shelf of the northern New Guinea basin into the Ramu-Sepik and the Piore basins. Continued regional sinistral transpression between the Pacific and the New Guinea leading edge of the Indo-Australian plates led to the reverse tilting of the Piore basin, the shallowing of the former distal shelf with concomitant extensive biolithite development (e.g., on subsiding volcanic islands) eventual uplifting of the Oenake Range, and en echelon faulting of the Bewani-Torricelli Mountains.« less

Geology and Hydrocarbon Potential of the Sepik-Ramu Area, Ramu Basin, Papua New Guinea: ABSTRACT

Improvements in seismic processing have made new interpretations of the structural and depositional history of the northwestern portion of the Ramu basin possible. Support for a wrench tectonic model for this area is observed in the reprocessed seismic data. Strike-slip movement along major fault zones has allowed compressional forces to be translated laterally and resulted in only minor deformation occurring in the Sepik-Ramu area. The major tectonic event is thought to have occurred during late Miocene-early Pliocene, and not during the middle Miocene, as earlier hypothesized. Consequently, Miocene deposition is postulated to have occurred uninterrupted by periods of erosion. A thick Miocene section is preserved in this region and is postulated to contain slope, reef, and shelf carbonates of early to middle Miocene age. This interpretation has led to the identification of a reef trend over 7 mi wide and at least 42 mi long containing numerous pinnacle reefs. The pinnacle reefs are analogous to those found in the Salawati basin of Irian Jaya, Indonesia. The reefs are overlain by deep-water shales, a combination that provides potential reservoirs and seals necessary for the entrapment of hydrocarbons. The presence of oil and gas seeps document the existence of a source. Thesemore » three factors justify hydrocarbon exploration in this area. The numerous potential drilling targets may lead to the discovery of significant quantities of hydrocarbons.« less

An investigation of the relationship between the geology of indonesian sedimentary basins and heat flow density

Geothermal data, collected from 929 wells drilled by oil companies in 20 Tertiary basins of Indonesia, have been related to the geology and tectonics of the area. It is found that the thermal conductivity increases with the depth of burial and degree of compaction in both transgressive and regressive sediments but decreases with increases in impurities and heterogeneous grain sizes. The temperature gradient is controlled mainly by the depth and temperature of a heat source beneath a basin. Very high heat-flow densities (> 125 mW m −2) found in central Sumatra, South Sumatra, Salawati Basin and Bintuni Basin may be caused by relatively shallow magmatic diapirism.

Hydrocarbon Exploration on Ancient Shelf-Slope Breaks: ABSTRACT

A general set of traps, reservoirs, and seals occurring on the shelf-slope break can be hypothesized based on the structural regime, provenance, and width and slope of the shelf. To evaluate this break is to look at the entire region--shelf and slope. With a wide or moderately wide shelf, gentle slope, and peneplaned provenance, carbonate sediments would dominate in marine environments. Logically, a reefal environment (reservoir) would be expected at the shelf slope. Conversely, with a narrow shelf and a positive continental borderland in close proximity, terrigenous clastics would be expected. Deltaic-like reservoirs could be expected on the shelf; turbidites would logically occur downslope. A broad shelf with a positive provenance could inspire various lithologic deposition (depending on the environment)--reefal at the shelf-slope area, deltaic or lagoonal behind, and turbidites in front. Examples of such former reservoirs are Empire-Abo reef trend of Texas-New Mexico; Cretaceous Stuart City shelf margin of Texas; Golden Lane-Pozo Rica trends of Mexico; Miocene pinnacles of the Salawati basin, Irian Jaya; and Kirkuk field on the Arabian Platform. Penultimate reservoirs are the linear sands of the San Joaquin and Ventura basins; Oligocene sands of south Louisiana; Triassic sands of the North Sea basin; Cretaceous Seaway sands in the Powder River basin; and the ancient Mississippi delta and cone. Latter reservoirs are found in the eastern shelf, Midland basin, and Bombay offshore basin, India. It is understood that for some of these reservoirs to become traps, the founding structural regime is modified, e.g., faulting, diapirism. Seals are classed as carbonate muds, evaporites, and faults. Source matter may be incorporated in marine shale and limestone deposited in anoxic environments. End_of_Article - Last_Page 946------------

Oil-Bearing Reefs in Salwati Basin of Irian Jaya, Indonesia

Recent exploration activity in the Salawati basin, along the northwestern tip of Irian Jaya, Indonesia, has resulted in significant oil discoveries. Reservoir and trap are provided by highly porous and permeable Miocene reef rocks, which have yielded oil at rates of up to 32,000 bbl per day from individual wells. The Salawati basin is a structural-stratigraphic basin containing more than 15,000 ft (4,600 m) of marine Tertiary sedimentary deposits. The basin is bounded on the north by the Sorong fault zone which separates the Australian continental plate from the Pacific oceanic plate. Basin development was initiated in the Miocene when local downwarping and increased water depths resulted in the deposition of a basinal limestone and shale sequence in the area. Toward the east and south margins of the basin these sediments are replaced by shallow-water carbonate rocks which form a well-defined shelf and associated shelf margin. The productive reef belt is just basinward of the shelf and shelf-margin area. The reefs, which reach heights in excess of 1,600 ft (490 m), range in areal extent from 2 to 48 sq mi (5 to 124 sq km). Porosities within the reefal carbonate rocks are as much as 43 percent and average 20 to 30 percent. Late Pliocene-Pleistocene normal faults which cut many of the reefs, combined with postreef structural tilt, have modified considerably the original configuration of the reefs and the associated oil accumulations. The knowledge gained from the current exploration program concerning reef morphology, porosity variations, tectonic history, and other factors which control the oil accumulations should expedite future exploration efforts in the basin.

Recent Knowledge of Hydrocarbon Potentials in Sedimentary Basins of Indonesia: ABSTRACT

Although the search for hydrocarbons in Indonesia was initiated about eight decades ago, exploration work is still at a high level. Recent studies have resulted in a new understanding of the prolific Tertiary sedimentary basins and, especially, knowledge concerning offshore sedimentary basins has been updated significantly. More important, however, is the current knowledge on the mechanism of basin formation which seems to enhance the validity and applicability of the new global tectonics to the geology of Indonesia. The Tertiary sedimentary basins in western Indonesia previously have been described as idiogeosynclines, situated around the periphery of a supposed landmass of pre-Tertiary age (the Sunda Shelf). Recent exploration surveys and subsequent drilling have shown that the southern part of the Sunda Shelf actually consists of many sedimentary basins and intervening uplifts. Major faults are common throughout the area and clearly control the distribution and shapes of the basins. Block faulting appears to have broken up the periphery of the Sunda Shelf at the beginning of Tertiary time. The chief crude-oil production in western Indonesia is from the regressive and deeper transgressive sand series of Oligocene-Miocene age, except in East Kalimantan where producing zones range from Eocene to Pliocene age. Prospects have changed considerably since oil and gas in economic amount have been proved within the interbedded limestone formation of Tertiary age and additional reserves are anticipated within stratigraphic traps. Oil and gas discoveries within deltaic sandstones, notably in East Kalimantan, have upgraded significantly the onshore and offshore potentials of the area. Carbonate rocks are becoming a prime objective in the search for oil, especially in the East Java-Madura basinal area. Although eastern Indonesia was chiefly the site of late Paleozoic and Mesozoic sedimentation, oil has been proved only within the strata of Tertiary age, notably in the Salawati basin. Of particular importance was the recognition of the tremendous potential that reefs, and in particular Tertiary reefs, possess as hydrocarbon reservoirs. A similar basin and environmental model is anticipated for the Bintuni basin. Scientific cruises within the last five years have indicated the presence of several potential basinal areas between the Sunda Shelf and the Sahul Shelf. The sedimentary basins in Indonesia can be classified into grabenlike basins, present foreland basins, and basins which are in front of the present magmatic arc. End_of_Article - Last_Page 1454------------