Kashafrud Formation Research Articles

Estimation of porosity and volume of shale using artificial intelligence, case study of Kashafrud Gas Reservoir, NE Iran

The key problem in oil exploration and engineering is the lack of accurate and reliable data about the reservoir parameters of a field. Having a precise assessment of petrophysical properties can provide the ability to make decisions with a high degree of confidence about planning for production, exploitation, and further field development scenario. In this research, an artificial intelligence (AI)-based approach was developed to improve the estimation of reservoir parameters including porosity and volume of shale, which has a significant role in different stages of hydrocarbon exploration, in the Kashafrud Gas Reservoir in the northeast of Iran. For this purpose, we measured the petrophysical properties of 27 samples of the Kashafrud Formation. To increase the amount of data for employing a multilayer perceptron (MLP) artificial neural network (ANN), a geostatistical algorithm was used to increase the amount of laboratory measured data of porosity and volume of shale to 686 and 702, respectively. In addition, 2263 well-logging data from the same well were provided. The optimal MLP network with the topology of 6-7-1, and 6-8-1 was selected to estimate the porosity and shale volume with mean squared error (MSE) of 2.78731E−4, and 1.28701E−9, respectively. The training process was performed using two different sets of input data. In the first approach, all available well-logging data were used as input, ending up in high MSE. In the second approach, some selected well logs were used based on the results of sensitivity analysis which clearly improved the estimations. The ability of MLP networks made great improvements in the estimation of the both parameters up to 99.9%. The presence of valuable core data in this study significantly improved the process of comparison and conclusion. The final results prove that AI is a trusted method, also the potential of the ANN method for the reservoir characterization and evaluation associated problems should be taken into consideration. Due to the unavailability of core data along the whole wells, the application of intelligent methods, such as machine learning (ML) can be used to estimate the parameters in other oil or gas fields and wells.

Petrology and mineralogy of Middle Jurassic siliciclastic rocks of the Kopet-Dagh rift basin, NE Iran: A comparison with the Binalud intramontane basin

The Middle Jurassic Kashafrud Formation of the Kopet-Dagh Basin is a succession of fluvial to turbiditic siliciclastic rocks deposited in a rift basin that was initiated in the Late Bajocian and was filled with conglomerates, sandstones, and mudstones. The sandstones are mainly lithic arkoses and feldspathic litharenites. The sandstones of the Kashafrud Formation contain evidence of numerous diagenetic processes, including compaction and fracturing, cementation, dissolution, and formation of authigenic minerals. For evaluation of the thermal history and diagenetic processes, and the formation of clay minerals, a burial temperature range for the Kashafrud Formation of more than 100 °C has been assumed. Geochemical results point to felsic, mafic, and metamorphic rocks, as well as to Proterozoic recycled sandstones as source rocks. The chemical index of alteration and plagioclase index of alteration indicate a humid to semi-arid climate at the time of sedimentation. Based on petrographic and geochemical data, the main tectonic sources for the sediments of the post-orogenic Middle Jurassic Kashafrud Rift Basin were a recycled orogen and passive margin. The Early Jurassic to early Middle Jurassic Binalud Intramontane Basin, situated at the northern margin of the Binalud Mountains and formed during a late phase of the Early Cimmerian Orogenic Event, was also filled with sediments derived from the Cimmerian mountain belt. The two basins represent different tectonic settings, but both are connected to the closure of the Palaeo-Tethys, reflecting similar source rocks and similar climatic conditions.

Ichnology of the Middle Jurassic Deposits of NE Iran: Depositional Environment Interpretation

The Kopet Dagh Basin of northeast Iran formed in the Neotethys Ocean after the closure of Paleotethys in the south of Turan plate. A thick sequence of Jurassic to Miocene sediments has been deposited in this basin without any major break. The siliciclastic Kashafrud Formation (Middle Jurassic), overlying unconformably on Triassic rocks and ultrabasic rocks of turbidite and fluvio-deltaic facies, consists of sandstone, shale and conglomerate. Trace-fossil assemblages are presented in some units with different environments. The most important ichnofossils in this formation are Skolithos, Palaeophycus tubularis, Belorhaphe, Taenidium, Planoloites beverleyensis, Thalassinoides suevicus, Conichnus, Psilonichnus, Lophoctenium, Palaeophycus striatus, Rhizocorallium jenense and Scolicia.. It is interpreted, based on identified ichnofossils, the starat may have been deposited in fluvio-deltaic and deep water (turbidity conditions) environment.

Tectonically controlled sedimentation: impact on sediment supply and basin evolution of the Kashafrud Formation (Middle Jurassic, Kopeh-Dagh Basin, northeast Iran)

The Kashafrud Formation was deposited in the extensional Kopeh-Dagh Basin during the Late Bajocian to Bathonian (Middle Jurassic) and is potentially the most important siliciclastic unit from NE Iran for petroleum geology. This extensional setting allowed the accumulation of about 1,700 m of siliciclastic sediments during a limited period of time (Upper Bajocian–Bathonian). Here, we present a detailed facies analysis combined with magnetic susceptibility (MS) results focusing on the exceptional record of the Pol-e-Gazi section in the southeastern part of the basin. MS is classically interpreted as related to the amount of detrital input. The amount of these detrital inputs and then the MS being classically influenced by sea-level changes, climate changes and tectonic activity. Facies analysis reveals that the studied rocks were deposited in shallow marine, slope to pro-delta settings. A major transgressive–regressive cycle is recorded in this formation, including fluvial-dominated delta to turbiditic pro-delta settings (transgressive phase), followed by siliciclastic to mixed siliciclastic and carbonate shoreface rocks (regressive phase). During the transgressive phase, hyperpycnal currents were feeding the basin. These hyperpycnal currents are interpreted as related to important tectonic variations, in relation to significant uplift of the hinterland during opening of the basin. This tectonic activity was responsible for stronger erosion, providing a higher amount of siliciclastic input into the basin, leading to a high MS signal. During the regressive phase, the tectonic activity strongly decreased. Furthermore, the depositional setting changed to a wave- to tide-dominated, mixed carbonate–siliciclastic setting. Because of the absence of strong tectonic variations, bulk MS was controlled by other factors such as sea-level and climatic changes. Fluctuations in carbonate production, possibly related to sea-level variations, influenced the MS of the siliciclastic/carbonate cycles. Carbonate intervals are characterized by a strong decrease of MS values indicates a gradual reduction of detrital influx. Therefore, the intensity of tectonic movement is thought to be the dominant factor in controlling sediment supply, changes in accommodation space and modes of deposition throughout the Middle Jurassic sedimentary succession in the Pol-e-Gazi section and possibly in the Kopeh-Dagh Basin in general.

Structural evolution of the Kopeh Dagh fold-and-thrust belt (NE Iran) and interactions with the South Caspian Sea Basin and Amu Darya Basin

We present a detailed stratigraphic and structural study of the Kopeh Dagh fold-and-thrust belt in NE Iran, which is an investigation of the complex polyphased tectonic history of this belt and its links with the adjacent South Caspian Sea and Amu Darya basins. Based on numerous field surveys, a large amount of 2D and 3D seismic data, borehole data and more than 150 new biostratigaphic datings, a new detailed biostratigraphic chart and 4 main regional cross-sections illustrate the importance of lateral facies variations and structural inheritance in the present-day structure of the belt.After the Cimmerian orogeny corresponding to the closure of the Paleotethys Ocean in Late Triassic/Early Jurassic times, a Middle Jurassic post-collisional rifting event was associated with the deposition of one of the main source rocks of the Kopeh Dagh and the Amu Darya Basin (Kashafrud Formation). Following this rifting event, over 7 km of sediments were accumulated until the Tertiary above a regional post-Triassic unconformity. The occurrence of local uplifts during the Late Cretaceous-Early Paleocene is interpreted as a consequence of regional-scale modification of plate-slab coupling in the Neotethys subduction zone. The main inversion of the Kopeh Dagh occurred at Late Eocene times, when the far-field deformation developed in Eurasia as a consequence of the locking of the Neo-Tethys subduction. This folding phase is sealed in the western part of the belt by a major Eocene-Oligocene unconformity at the base of the thick sedimentary series belonging to the South Caspian Sea Basin. The bulk of sedimentary infill in the South Caspian Sea Basin is Oligocene and younger, and it is probably related to syn-compressional downward flexure of the resistant basement basin at the onset of the Alpine phase. In the eastern part of the Kopeh Dagh, this deformation is characterized by Middle Jurassic graben inversion with evidence of forced folding, short-cuts and as well by larger scale basement uplifts. In contrast, the northwestern part of the belt shows thrust faults involving basement and fault-propagation folds within the sedimentary sequence. The Kopeh Dagh presents tectonic structures that are parallel to the Paleotethys suture zone, which emphasizes the importance of the structural inheritance and inversion processes during the structural evolution of the belt. Finally, a change from a mostly dip-slip to a mostly strike-slip tectonics occurred during the Pliocene within the Kopeh Dagh as a consequence of a major tectonic reorganization in North-East Iran.

The record of the Late Palaeozoic active margin of the Palaeotethys in NE Iran: Constraints on the Cimmerian orogeny

The Cimmerian orogen resulted from the collision and accretion of several Perigondwanan blocks to the southern margin of Eurasia between the Late Triassic and Early Jurassic, following the closure of the Palaeotethys ocean. Remnants of this orogen discontinuously crop out in N (Alborz range) and NE Iran (Mashhad–Fariman area) below the syn- to post-collisional clastic successions of the Shemshak Group (Upper Triassic–Middle Jurassic) and the Kashaf Rud Formation (Bajocian). In NE Iran rock associations exposed in the Binalood Mountains, Fariman and Darreh Anjir areas include mafic–ultramafic intrusive rocks, basalts, silicoclastic turbidites and minor limestones, which have been interpreted in the past as ophiolitic remnants of the Palaeotethys ocean. Original stratigraphic, structural, geochemical and geochronological data, described in this paper, suggest a different interpretation. The volcano-sedimentary units of Fariman and Darreh Anjir complexes where deposited during Permian in a subsiding basin were siliciclastic turbidites, derived from the erosion of a magmatic arc and its basement, interfinger with carbonates and basaltic lava flows with both transitional and calc-alkaline affinity. The coexistence of magmatic rocks with different geochemical signature and the sedimentary evolution of the basin can be related to a supra-subduction setting, possibly represented by a fault-controlled intra-arc basin. The Fariman and the Darreh Anjir complexes are thus interpreted as remnants of a magmatic arc and related basins developed at the southern Eurasia margin, on top of the north-directed Palaeotethys subduction zone long before the collision of Iran with Eurasia. They were later involved in the Cimmerian collision during the Triassic. New radiometric ages obtained on I-type post-collisional granitoids postdating the collision-related deformational structures suggest that the suture zone closed before mid-Norian times. Deformation propagated later northward into the Turan domain involving the Triassic successions of the Aghdarband region.

Composition, porosity, and reservoir potential of the Middle Jurassic Kashafrud Formation, northeast Iran

In the Kopet-Dagh Basin of Iran, deep-sea sandstones and shales of the Middle Jurassic Kashafrud Formation are disconformably overlain by hydrocarbon-bearing carbonates of Upper Jurassic and Cretaceous age. To explore the reservoir potential of the sandstones, we studied their burial history using more than 500 thin sections, supplemented by heavy mineral analysis, microprobe analysis, porosity and permeability determination, and vitrinite reflectance. The sandstones are arkosic and lithic arenites, rich in sedimentary and volcanic rock fragments. Quartz overgrowths and pore-filling carbonate cements (calcite, dolomite, siderite and ankerite) occluded most of the porosity during early to deep burial, assisted by early compaction that improved packing and fractured quartz grains. Iron oxides are prominent as alteration products of framework grains, probably reflecting source-area weathering prior to deposition, and locally as pore fills. Minor cements include pore-filling clays, pyrite, authigenic albite and K-feldspar, and barite. Existing porosity is secondary, resulting largely from dissolution of feldspars, micas, and rock fragments, with some fracture porosity. Porosity and permeability of six samples averages 3.2% and 0.0023 mD, respectively, and 150 thin-section point counts averaged 2.7% porosity. Reflectance of vitrinite in eight sandstone samples yielded values of 0.64–0.83%, in the early mature to mature stage of hydrocarbon generation, within the oil window. Kashafrud Formation petrographic trends were compared with trends from first-cycle basins elsewhere in the world. Inferred burial conditions accord with the maturation data, suggesting only a moderate thermal regime during burial. Some fractures, iron oxide cements, and dissolution may reflect Cenozoic tectonism and uplift that created the Kopet-Dagh Mountains. The low porosity and permeability levels of Kashafrud Formation sandstones suggest only a modest reservoir potential. For such tight sandstones, fractures may enhance the reservoir potential.

Stratigraphy, depositional environments and geodynamic significance of the Upper Bajocian–Bathonian Kashafrud Formation, NE Iran

Abstract A strongly subsiding rift basin in NE Iran, the Kashafrud Basin, opened in the Late Bajocian with the accumulation of more than 2000 m of Upper Bajocian–Upper Bathonian siliciclastic sediments. These sediments comprise the Kashafrud Formation, which crops out along a NW–SE stretch of more than 200 km and occupies a width of 50 km, situated between the Koppeh Dagh and the Binalud Mountains. Ten sections of the formation were logged. Sedimentary environments range from non-marine alluvial fans and braided rivers in the lowermost part of the succession to deltas, succeeded by storm-dominated shelf, slope and deep-marine basin. Monotonous mudstones and turbidites prevail in the deep-marine part of the basin. The thickness and facies of the Kashafrud Formation vary strongly between localities, and reflect distance from the rift margins as well as submarine topography, which was shaped by block tectonics. The Kashafrud Basin is interpreted as the eastern extension of the South Caspian Basin, which entered the rifting stage in the late Early Jurassic and the spreading stage in the Late Bajocian.

Middle Jurassic palynomorphs of the Kashafrud Formation, Koppeh Dagh Basin, Northeastern Iran

Diverse and moderately well-preserved palynofloras occur in Middle Jurassic sediments of the Kashafrud Formation at the Senjedak section, southeast of Mashhad, northeastern Iran. Trilete and monolete spores and pollen dominate the assemblages, whereas dinoflagellate cysts, foraminiferal test linings, and fungal spores are minor components. Forty-seven species of spores (30 genera) and 15 species of pollen (eight genera) are identified. Representatives of Dictyophyllidites and Klukisporites are particularly abundant. Based on the stratigraphic distribution of miospores, three distinctive stratigraphically successive palynofloras informally termed in ascending order, Assemblages A, B, and C are identified within the Kashafrud Formation. These are compared with palynozones known from Iran and elsewhere. Based on the presence of certain miospore species, the Kashafrud palynofloras are collectively dated as Middle Jurassic (Bajocian-Bathonian), thus corroborating the faunal (ammonoid) evidence. The appearance of a key miospore species, Contignisporites burgeri , within the succession has been used to attribute a late Bajocian age and early Bathonian age to the lower and upper parts of the studied interval, respectively. Inferred natural relationships of the miospores imply derivation from a diverse parental flora of Pterophyta and gymnosperms, such as Coniferophyta, Cycadophyta, and Ginkgophyta, growing under warm, humid conditions during the Bajocian-Bathonian. The associated marine fauna (ammonites), marine palynomorphs (proximate dinoflagellate cysts, and acritarchs such as Micrhystridium ), and foraminiferal test linings, along with terrestrial palynomorphs (spores and pollen) collectively indicate an open marine, nearshore depositional setting for the Kashafrud Formation at the section studied.

NEW OCCURRENCES OF THE TRACE FOSSIL PALEODICTYON IN SHALLOW MARINE ENVIRONMENTS: EXAMPLES FROM THE TRIASSIC-JURASSIC OF IRAN

Abstract The graphoglyptid trace fossil Paleodictyon, characterized by a stratiform hexagonal net, is a diagnostic member of the deep-water Nereites ichnofacies and usually found in deep-sea flysch successions. Scattered records of the trace fossil from shallower, lower-shelf-to-upper-slope environments, particularly since the mid-Mesozoic, have been substantially augmented by new data from Upper Triassic and Jurassic sedimentary basins of Iran. Paleodictyon has been found on the soles of mid-to-lower-shelf event beds produced by storm-induced currents and on the soles of prodelta turbidite deposits in the Upper Triassic Nayband Formation of east-central Iran, the lower Middle Jurassic Shemshak Formation of north-central Iran, the Middle Jurassic Kashafrud Formation of the Koppeh Dagh, and the Middle Jurassic Dalichai Formation of the Binalud Mountains. It appears that the bathymetric range of Paleodictyon throughout the Phanerozoic was considerably wider than generally assumed. The observed dominance of ...

Jurassic deep-water fans in the Neo-Tethys Ocean: The Kashafrud Formation of the Kopet-Dagh Basin, Iran

The Middle Jurassic Kashafrud Formation of northeast Iran was deposited in the Kopet-Dagh Basin, linked to the Neo-Tethys Ocean. The 2 km thick succession commences with fluvio-marine boulder conglomerates that occupy bedrock valleys, but the bulk of the formation comprises a deep-water succession of interbedded sandstone and mudstone packages with trace fossils and sparse ammonites. Neogene collisional events deformed the strata to create the Kopet-Dagh mountains. The deep-water succession represents channel-lobe systems and associated levees and overbank areas on slope to basin-floor fans. Northward paleoflow suggests that rivers drained uplands along the Paleo-Tethys Suture zone, forming fan deltas on a narrow shelf, with associated sediment transport to deeper water. Coarse sands, extrabasinal pebbles, and plant fragments are present throughout the formation, and a thick boulder conglomerate unit lies within the turbidite succession. These observations suggest proximity to terrestrial sources throughout deposition. Sandstone packages are mainly less than 10 m thick (maximum 84 m), and numerous lensoid packages of thick-bedded sandstone tens of meters thick and up to 200 m wide represent submarine channel fills. Thick-bedded lenses and sheets show a relatively narrow range of paleoflow direction and represent major submarine conduits, whereas the more varied paleoflow direction of thin-bedded packages suggests that many were deposited on levees. The presence in the Kashafrud Formation of potential source rocks in the form of organic-rich mudstones and abundant plant fragments suggests that the formation may have contributed to hydrocarbon fields within overlying formations. Sandstone sheets and channel fills could form local reservoirs.