Triassic Formation Research Articles

Chirothere Footprint Sites from the Otter Sandstone Formation (Middle Triassic, late Anisian) of Devon,United Kingdom

Three chirothere footprint sites are documented from the Middle Triassic (Anisian) fluvial Otter Sandstone Formation of Sidmouth, Devon, UK. One site, on the foreshore below Peak Hill, has revealed numerous tracks, including a probable manus imprint, which are recorded here. Another site, also beneath Peak Hill, has produced a single probable manus track from a higher horizon. The third site, on the foreshore below Salcombe Hill Cliff, has yielded a small number of pes tracks similar to those from Peak Hill. The footprints at all sites are interpreted as belonging to a large Chirotherium ichnospecies, perhaps C. barthii Kaup. Unusually, the tracks are preserved in mudstone, often in convex epirelief, and are inferred to have been generated subaqueously. The apparent restriction of the footprints to the higher part of the Otter Sandstone Formation supports other evidence, such as a greater abundance of vertebrate skeletal material, subhorizontal rather than vertical rhizocretions, and a greater frequency of lacustrine facies, for a less arid climate and higher water table than lower in the sequence.

Trace fossils from the continental Upper Triassic Kågeröd Formation of Bornholm, Denmark

The Upper Triassic Kagerod Formation of Bornholm consists of clays, sandstones and conglomerates of floodplain and fluvial origin, but details of the depositional environment are poorly understood. Trace fossils are described for the first time from the red and green clays (floodplain with lake deposits) and cross-stratified sandstones (fluvial channel deposits) of the Upper Triassic Kagerod Formation on Bornholm, Denmark. The sparse ichnofauna consists of large, mud-filled shafts and tunnels in caliche-bearing conglomerate, determined as Camborygma and attributed to the burrowing activity of cray fish. The sandstones preservevertical U-shaped burrows passively filled with sand, assigned to Arenicolites and probably produced by insects. Furthermore, they contain winding, horizontal, oblique and vertical unbranched burrows with an active meniscate sand fill, referable to Taenidium and supposedly produced by burrowing beetles. The clays and the sandstones contain numerous caliche nodules of centimetre to decimetre size, some of which contain root traces in the form of rhizoliths. This trace-fossil association reflects deposition on a vast floodplain with shallow lakes and fluvial channels, under semiarid conditions.

A Review on Fossil Findings of Central Iran’s Permo-Triassic Deposits

In this research, a review was done on Permo-Triassic deposits in Central Iran including Abadeh, Hambast, and Elika formations. Following an overview about the circumstances of Central Iran Basin during Permotriassic time interval, the respective formations are introduced, and then, history of paleontology studies on these deposits will be depicted. Through analysis and comparison of previous studies, the following ages were estimated for the aforementioned formations: Early Dzhulfian for Abadeh Formation, Late Dzhulfian-Dorashamian for Hambast Formation, and Early Triassic (Scythian) for Elika Formation. Also, Permotriassic boundary in Central Iran is continuous, bearing the proposed sedimentation and fossil content. It is noteworthy that due to volcanic events at the boundary of these deposits in Central Iran, one might infer that occurrence of the aforementioned activities has been among the major causes of the respective extinction.

Stratigraphic framework and microfacies of the Triassic Lower Karamay Formation in districts I, III, NW Junggar, China

The Triassic Lower Karamay Formation (T2k1) is one of the main oil-bearing stratigraphic units in the northwestern margin of Junggar Basin (NW Junggar), China. Based on an integrated investigation of outcrops, well logs and seismic data of NW Junggar, the Lower Karamay Formation is subdivided into 2 sets, 6 beds and 13 layers. Also, it is considered that the alluvial fan, the braided river, the meandering river and the shore-shallow lacustrine were developed during the early period of Middle Triassic in Karamay districts I, III. The Lower Karamay Formation deposits the following 9 sedimentary subfacies: the lower fan, the middle fan, the upper fan, the braided channel, the overflow bank, the river flood of braided river, the meandering channel, the river flood of meandering river, the shore-shallow lacustrine. Seventeen microfacies such as the braided stream channel, the alluvial sand floodplain, the alluvial glutenite floodplain, the water channel, the channel bar etc. have been identified in subfacies as well. The thickness of strata is firstly up-thinning and then thickening upward to the top, it is a process from large-scale lacustrine transgression to partly lacustrine regression. Furthermore, the microfacies planar distributing law proves that the remaining oil may enrich along the margin of microfacies because of the planar microfacies changes. Therefore, this research is beneficial for searching remaining oil in NW Junggar and providing information to the project “The Secondary Exploration” of PetroChina.

Models for Saturation of the Tight Gas Sandstone Reservoir

The conventional model of formation saturation is restricted in well logging interpretation of tight gas sandstone because it is difficult to eliminate the influences of abrupt change of mineral component content. This paper studied the Triassic Xujiahe formation located in northeast Sichuan Basin, which has large variation of carbonate content between adjacent logging intervals. Based on Capillary Theory and analysis of element capture spectroscopy data, the paper proposed two models to limit the carbonate effect. It is proven that the employment of two models together in the evaluation of the tight gas sandstone reservoir in the studied area increased interpretation accuracy and has been proven effective.

Geothermal bathing and recreation centres in Poland

Ten geothermal bathing and recreation centres have been established in Poland from 2006 to 2013. The largest number of geothermal bathing and recreation centres is located in the Podhale region and in the Polish Lowlands. These structural units have the best geothermal conditions. The maximum reservoir’s temperatures in the main aquifer of the Podhale Geothermal System can reach ca. 120–128 °C in the deeper parts of the system. The most prospective and exploited aquifers occur within the Middle Triassic formations and in overlaying Middle Eocene formations at the depth of 1,000–3,700 m. At present, five operating centres are located in the Podhale region. They use geothermal waters with the temperature of 27–82 °C (the lowest and the highest wellhead temperature of water from wells which are connected for recreational purposes) and total dissolved solids (TDS) of 0.4–3 g/dm3. In the Polish Lowlands, the reservoir’s temperatures vary from 20 to 130 °C at depths of 1–4 km. The most prospective geothermal aquifers of the Polish Lowlands occur within the Lower Cretaceous and the Lower Jurassic formations. Five geothermal recreation centres are currently operating. The centres use waters with the temperature of 38–72 °C and a wide range TDS from 0.4 to 79 g/dm3. Geothermal waters of the Polish Lowlands are generally high in Na and Cl concentrations. The new centres will use the waters of Lower Jurassic aquifers, the outflow temperatures of which vary from 27 to 82 °C and a TDS from 6 to 140 g/dm3.

Neuro-fuzzy system to predict permeability and porosity from well log data: A case study of Hassi R׳Mel gas field, Algeria

Characterization of shaly sand reservoirs by well log data is a usual way of describing oil/gas field reservoirs. Over the last few years, several studies have been conducted in the field of petroleum engineering by applying artificial intelligence. This work represents a petrophysical-based method that uses well logs and core plug data to predict well log data recorded at depth in a shaly sand reservoir of Triassic Formation in Hassi R׳Mel field, Algeria. In the study of oil reservoirs, the prediction of absolute permeability is a fundamental key in reservoir descriptions and has a direct impact, in particular, on effective completion designs, successful water injection programs and more efficient reservoir management. The Triassic Formations of Hassi R׳Mel fields are composed of sandstones and shaly sands with dolomites. Logs from 10 wells are the starting point for the reservoir characterization. This paper presents a hybrid neuro-fuzzy model based on the use of data from four wells regarding porosity and permeability estimation. A fuzzy logic approach is used to calibrate the calculated permeability and core permeability; and a neural network was developed in this model, based on the data available from the field. Fuzzy analysis is based on fuzzy logic and is used to choose the best well logs with regard to core porosity and permeability data. A neural network is used as a nonlinear regression method to develop transformation between the selected well logs and core measurements. Porosity and permeability are predicted in these wells through linear regression; and back-propagation models are constructed and their reliabilities are compared according to the regression coefficients for predictions in un-cored sections. This investigative hybrid neuro-fuzzy method becomes a powerful tool for the estimation of reservoir properties from well logs in oil and natural gas development projects.

An exceptional record of the sedimentology and biostratigraphy of the Montney and Doig formations in British Columbia

Abstract The Talisman Altares 16-17-083-25W6M well in British Columbia penetrates the entirety of the Triassic Montney Formation and possesses core coverage of most of it, including the basal contact with the underlying Permian Belloy Formation and its upper contact with the base of the Triassic Doig Formation. The Montney Formation in British Columbia is punctuated by several flooding surfaces and is bound top and bottom by two sequence boundaries: one at the Belloy-Montney formation boundary and one at the Montney-Doig boundary. These two surfaces can be correlated throughout wells in British Columbia and into Alberta. Conodont data from British Columbia shows that the lower-middle Montney boundary is Smithian in age, and the middle-upper Montney boundary approximates the Smithian-Spathian boundary. These age determinations are significantly younger than previous estimates for the equivalent boundaries in Alberta, underscoring the inherent diachroneity of lower Mesozoic lithostratigraphic subdivisions in Western Canada. The Montney-Doig boundary occurs within the Spathian in this well, and is therefore older here than in other wells in northeastern British Columbia. It is also older than previous estimates for the age of the boundary that have ranged from the Anisian to the Ladinian.

Formation mechanism of reservoir oolitic dolomite in Lower Triassic Feixianguan formation, northeastern Sichuan Basin, southwest China

A series of marine natural gas fields were recently discovered in oolitic dolomites of the Lower Triassic Feixianguan formation, northeastern Sichuan Basin, southwest China. The mechanism forming these reservoir dolomites is debatable, limiting the ability to characterize these reservoir successfully. Based on the investigation of the representative Dukouhe, Luojiazhai, and Puguang areas, this issue was addressed by examining the distribution, petrology, and geochemistry of the dolomites, the most comprehensive study to date was provided. Dolomitization occurred at a very early stage of diagenesis, as shown by the petrological features of the rock fabric. Vadose silt, which is composed primarily of dolomitic clasts, is found in the primary and secondary pores of the oolitic dolomite. This indicates that the overlying strata were subjected to dolomitization when the Feixianguan formation was located in the vadose zone. Therefore, it may be inferred that the dolomitization which occurred before the formation was exposed to meteoric conditions. The spatial distribution and geochemical characteristics of the dolomite indicate that dolomitization occurred as a result of seepage reflux. The degree of dolomitization decreases with increasing distance from the evaporative lagoon. Furthermore, the type and porosity of the dolomite vary in different zones of the upward-shoaling sequence, with the porosity gradually decreasing from the highest layer to the lowest layer. This reflects a close relationship between dolomitization and seawater evaporation during the formation of the dolomite. Geochemical analysis provided further evidence for the relationship between the dolomitization fluid and the coeval seawater. The 87Sr/86Sr and δ13C isotopes, as well as the abundances of trace elements, Fe and Mn, indicate that seawater concentrated by evaporation acted as the dolomitization fluid. These results also show that dolomitization most likely occurred in a semi-closed diagenetic environment. Therefore, the main mechanism of oolitic dolomite formation is seepage reflux, which occurred at an early stage of diagenesis.

Facies analysis and depositional environment of the Geli Khana Formation (Middle Triassic), Northern Iraq

The Middle Triassic Geli Khana Formation is one of the important formations for the opportunity to study the Anisian–Ladinian facies and depositional environment in northern Iraq. Two sections (outcrop and subsurface) were selected to study the litho- and microfacies of the Geli Khana succession and to interpret its depositional environment. The formation is divided into five lithofacies (A–E) comprising dolomite, dolomitic, and marly limestones; calcareous shaly and marly limestones; limestone with dolomitic and marly limestones; black shales; and evaporites. Five microfacies were recognized, these include mudstone, silty mudstone, graded mudstone, oyster (bioclastic) wackstone, and laminated silty oyster packstone microfacies. Generally, the studied succession represents shallow reducing marine environment with peritidal carbonate facies in which three environments, supratidal, intertidal, and subtidal, were recognized. The deeper subtidal environment dominates in the northern parts of the basin while the shallower supratidal is common in the southern parts.

Ichnofabrics and their environmental interpretation from the fluvial deposits of the Middle Triassic Youfangzhuang Formation in Western Henan, Central China

Fluvial deposits from the Middle Triassic Youfangzhuang Formation in Henan Province, China contain a low-diversity trace fossils. Vertical dwelling burrows of opportunists dominate in active channel, whereas horizontal deposit-feeding, grazing, and vertical dwelling burrows occur in overbank deposits. Seven recurrent ichnofabrics were distingushed. The Palaeophycus tubularis ichnofabric preserves below scour interface between two fluvial cycles. The Skolithos linearis ichnofabric forms in middle to high-energy, soft substrates in the middle and upper parts of active channel deposits under semi-arid climate. The Skolithos linearis-Planolites montanus ichnofabric occurs in the sediments just a little above the Skolithos linearis ichnofabric and is formed in middle-energy, soft substrates in the upper part of active channel deposits. The Planolites montanus ichnofabric is mostly preserved in association with medium- to thick-bedded brown-red silty mudstones or siltstones in low-energy, perennial muddy bottom ponds in overbank settings. The Taenidium barretti ichnofabric is interpreted as periodically exposed ephemeral ponds or low-energy distal floodplain. The Skolithos isp. ichnofabric commonly occurs in middle to high-energy firm ground of proximal foodplain or crevasse-splay deposits. The root trace ichnofabric occurs in the crevasse splay deposits. The presence of thin palaeosols and the abundance of calcretization in mudstones indicate a seasonal climate ranging from humid to semi-arid, with high temperature, rainfall, and well-defined dry and wet seasons.

An Early Triassic basal actinopterygian fish (Osteichthyes) from D'Urville Island, New Zealand

A small partial actinopterygian (ray-finned) fish from the Lower Triassic Greville Formation of D'Urville Island is reported as the first formally noted and described Triassic actinopterygian from New Zealand. The specimen includes the upper lobe of a slender heterocercal caudal fin, with fringing fulcra and a series of dorsal caudal fulcra and epaxial basal fulcra. The fossil also preserves additional fin rays and a series of probable neural and haemal arch elements. The fossil is too incomplete to be precisely identified, but the heterocercal caudal fin with associated fringing and dorsal caudal fulcra are sufficient to diagnose the specimen as a phylogenetically basal ‘palaeoniscoid’-grade actinopterygian, the first to be reported from New Zealand.

Freshwater shark teeth (Family Lonchidiidae) from the Middle-Upper Triassic (Ladinian-Carnian) Paramillo Formation in the Mendoza Precordillera, Argentina

ABSTRACTA collection of over 550 elasmobranch teeth (Family Lonchidiidae) were obtained from fresh water fluvial deposits of the Middle–Upper Triassic (Ladinian–Carnian) Paramillo Formation, in northwestern Mendoza Province, Argentina. The new hybodontid species, Lonchidion paramilloensis, sp. nov., solely based on teeth, is within a 20-m-thick interval containing black shale interbedded with andesitic sills and intercalated with lensoidal calcarenites. The teeth have a characteristic labial peg with an accessory cusplet and a low gracile crown that is narrower labiolingually and more elongate laterally. The teeth are similar to some North American Late Triassic and Late Cretaceous species of the genus Lonchidion (e.g., L. humblei, L. griffisi, L. selachos), but are distinct in having a low primary cusp, up to seven pairs of lateral cusplets, a rounded-triangular-shaped labial peg with one accessory cusplet, and an absence of other crown ornaments. Color analyses of upper tooth crowns indicate an ichthyolith alteration index (IAI)/conodont alteration index (CAI) value of 6.0–6.5 (360–610°C). Considerable pitting and alteration of specimens indicates thermal alteration to 610°C and (or) chemical alteration.

Delineating the fluvial channel system in the Upper Triassic formation of the Elward area in the Syrian Euphrates Graben using 3-D seismic attributes

3-D seismic data were used to evaluate the reservoir in the Mulussa F formation in the Elward area and to discover new drillable locations by delineating the fluvial channel system and the features of its facies. Seismic attributes such as relative acoustic impedance, coherency volume and reflection strength were considered. The attribute maps revealed different types of channels such as braided, meandering and anastomosing channels. They also revealed fluvial features such as point bars, Ox-Bows and crevasse splays, which are considered potential points of hydrocarbon accumulation due to the abundance of sandy bodies. The map of relative acoustic impedance demonstrated that the sandstone beds have high impedance, whereas the shale beds have low impedance. In fact, well data indicated that the shaly beds were surrounded by sandy beds, and their thickness was in the range of 20–25 m within the Mulussa F formation. The coherency attribute showed some of the meandering tributary channels that were not seen on the relative acoustic impedance map. The abundance of fluvial channels in the Euphrates region indicates a large water discharge during the deposition of the Mulussa F formation because of the wet climate prevailing during the Upper Triassic.

Integrated Well-Test Strategy in Unconventional Tight Gas Reservoirs

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 16950, ’Integrated Well-Test Strategy in Unconventional Tight Gas Reservoirs: Learning and Experiences From an Actual Field Project,’ by Minquan Jin, SPE, Shell Exploration & Production; Wenxia Zhang, SPE, Shell China Exploration and Production; and Hongli Zhang, PetroChina Southwest, prepared for the 2013 International Petroleum Technology Conference, Beijing, 26-28 March. The paper has not been peer reviewed. Copyright 2013 International Petroleum Technology Conference. Reproduced by permission. Tight gas reservoirs and shale gas reservoirs are economically viable hydrocarbon prospects that have proved to be successful in North America. In such reservoirs, established methods of well testing and data analysis are often impractical. This paper presents an integrated well-test program developed for a tight gas reservoir in southwestern China. The program, designed and modified from conventional methods to meet the project-delivery timeline and cost constraints, makes use of a combination of various formation-evaluation techniques. Introduction The northwestern and central areas of the Sichuan basin have been identified as having basin-centered gas potential. In particular, there are several blocky sand intervals in the Late Triassic Xujiahe formation that contain a relatively immature, continuous gas accumulation. The tight-gas-reservoir project described in this paper is located in the central uplift area of this basin and is operated by Shell and PetroChina as a joint venture. In this tight gas block, the Xujiahe formation has a gross thickness of greater than 500 m and is found at 3000- to 4000-m drilling depth. The hydrocarbon system in the block is an overpressured section of tight gas sands that are sourced by imbedded and surrounding shales and coals. Gas and condensate can be produced from this objective section through massive multistage hydraulic-fracturing treatments. As with the exploration and development of any tight gas reservoir, the economic delivery of this project requires the integration of various well-testing methodologies to identify the economic feasibility of the reservoir. Well tests are normally conducted during various stages of the well life (Fig. 1). The objectives of well tests include the following: Identifying the hydrocarbon-bearing horizon Characterizing reservoir parameters Obtaining initial reservoir pressure Characterizing well damage and the extent of the damage Determining well deliverability and drainage area Evaluating well-completion efficiency Evaluating reservoir heterogeneities Estimating recoverable reserves Unlike conventional hydrocarbon prospects, however, the formation permeability in a tight gas reservoir is extremely low, and commercial production generally requires stimulation through extensive hydraulic fracturing. The mature and well-defined methods of well testing and data analysis, although applicable, are often impractical because of excessive test duration. Therefore, the true potential in tight gas reservoirs can be established only when well tests are combined with a well-hydraulic-fracturing program. We present an integrated well-test program developed and implemented for reservoir characterization and formation evaluation of this particular tight gas reservoir. The program makes use of a combination of various formation-evaluation techniques that include diagnostic fracture- injection tests (DFITs), perforation-inflow tests (PITs), pressure-buildup (PBU) tests, rate-transient analysis, and production logging.

Hydrocarbon potential and porosity types of the Geli Khana Formation (Middle Triassic), Northern Iraq

Hydrocarbon generation potential and porosity types of the Middle Triassic Geli Khana Formation in Jabal Kand-1 (JK-1) well and from outcrop section at Ora of northern Iraq are investigated. Total organic carbon, pyrolysis, and maturation assessment such as thermal alteration index (TAI) and vitrinite reflectance (Ro%) for 19 shale samples are conducted. The analyses showed a sufficient amount of organic matter (OM) occurs in JK-1 specifically. According to the obtained samples from the pyrolysis analysis of the studied samples, the existing organic matters in well (JK-1) are composed of a mixed of kerogen type II–III and III; while type IV in outcrop section which found in post mature state, indicating dry gas window. The estimated TAI for the studied section ranged between 3.3 in and 3.7 in JK-1 and 3.3–4 in Ora section. Additionally, the maturity derived information from vitrinite reflectance supported that the Geli Khana Formation is in dry gas window and post mature stage in both sections due to the average ratio of (Ro %) which is between 1.35 and 2 %. The porosity types in the carbonate successions of the formation include; fracture, moldic, intergranular, intramatrix, vuggy, intercrystalline, channel and fenestral birds-eye porosities. These types enhance the reservoir characteristics of the carbonate succession of the formation.

Quantitative Evaluation Model of Carbonate Reservoirs Based on Multi-Level Fuzzy Theory

The quantitative evaluation of carbonate reservoir is one of the key issues of oil and gas exploitation. However, due to the characteristics of carbonate reservoir, such as diverse physical distribution, complex pore-throat structure and strong heterogeneity, its quantitative evaluation is relatively difficult. Take the Lei 1 Member carbonate reservoir of Middle Triassic Leikoupo Formation in the Moxi gas field of Sichuan Basin as the example. The improved analytic hierarchy process is adopted based on 9 prioritized parameters which have direct influence on the quality of carbonate reservoir, namely porosity, permeability, water saturation, displacement pressure, average pore-throat radius, effective reservoir thickness, permeability variation coefficient, permeability rush coefficient and permeability range, to build a multi-level hierarchical structure model and quantitatively determine the relative importance quantitative indicators of all the parameters for reservoir quality. And fuzzy comprehensive evaluation method is used to build a quantitative evaluation model of carbonate reservoir. The evaluation results are well consistent with the actual gas capacity, which indicates that the mathematical model is available for quantitatively evaluating the carbonate reservoir and has relatively good feasibility.

Geology of the Island of Grand Manan, New Brunswick: Precambrian to Early Cambrian and Triassic Formations

Geology of the Island of Grand Manan, New Brunswick: Precambrian to Early Cambrian and Triassic Formations

A new hump-backed ginglymodian fish (Neopterygii, Semionotiformes) from the Upper Triassic Chinle Formation of southeastern Utah

ABSTRACT A new species of hump-backed semionotiform fish, Lophionotus sanjuanensis, gen et sp. nov., is described based on specimens recently and previously collected from the Upper Triassic Church Rock Member of the Chinle Formation of southeastern Utah. It is characterized by a deep body with a large postcranial hump, and dense tuberculation on the posterodorsal margin of the skull that continues into the dorsal ridge and dorsolateral flank scales. The vertical preoperculum bears a short and broad paddle-like ventral process. The infraorbital series expands ventral to the suborbital and contacts the anterior ramus of the preoperculum, although this character has also been observed in other deep-bodied semionotiform taxa. This taxon represents the first newly described semionotiform fish species from the western United States in over 45 years, and adds to knowledge of Triassic fishes biodiversity.

Revision of genus Sabrinella (Gastropoda) and a new minute vetigastropod from the Late Triassic Cassian Formation (N Italy)

Revision of genus Sabrinella (Gastropoda) and a new minute vetigastropod from the Late Triassic Cassian Formation (N Italy)