جستجوی مقالات مرتبط با کلیدواژه « محیط رسوبی » در نشریات گروه « علوم پایه »

One of the most important carbonate gas reservoirs in the Zagros and Persian Gulf sedimentary basins is the Dalan Formation. This research investigates the microfacies, lithostratigraphy, and sequences of carbonate-evaporite deposits in the Lower member of the Dalan and the Nar member belonging to the Guadalupian series with a total thickness of 2402 meters in four wells namely A, D, E, and G located in the eastern part of the Qatar-Persian arc in the Persian Gulf. The study of 340 thin sections prepared from the drilling cutting pieces with 2-meter intervals of well E, and a review of documents related to other wells led to the identification of 20 species belonging to 14 genera of foraminifera and the foraminiferal assemblages consisting of 65 species belonging to 25 genera. A foraminiferal biozone was recognized in well E, assigned to the Wordian? - Capitanian: Pachyphloia- Globivalvulina- Hemigordius, Assemblage Zone.  Additionally, 11 microfacies were determined, mainly distributed in five environments (sabkha, intertidal, lagoon, shoal, and shallow marine). Based on the stacking patterns facies and the gamma-ray log trends, two 3rd-order transgressive–regressive (T-R) sequences were determined. These sequences correspond to the sequences of the reservoir unit’s equivalent formations in the southern and eastern Tethyan basin including Saudi Arabia, UAE, Oman, Iraq and South China.

The studied section is located in the 113Km east of Birjand (25Km Asadiyeh City) and east of Pating Village. The mentioned sequence, aged Late Cretaceous, is totally 246m in thickness and mostly consists of thick and medium bedded limestones along rock units. The lower boundary has been limited by basal red conglomerate and the upper boundary has been covered by red-colored sandstone unit. In This research, based on both field and laboratory studies, the main components of carbonate rocks include both skeletal and non-skeletal grains and totally 7 carbonate microfacies have been determined which have been deposited within 3 facies belts including tidal flat, Semi-restricted lagoon and shoal. According to the obtained evidences from the microfacies analysis, the suggested depositional model for the Pating section is a homoclinal ramps type carbonate platform. All of the microfacies are mainly deposited in the inner part of the ramp slope. The obtained geochemical data from carbonate samples analysis indicate a calcitic original mineralogy and dominance of a closed diagenetic system for the studied sequence. Also, according to the geochemical data, a temperate climatic condition could be considered for the formation environment of this sequence which is confirmed by the Late Cretaceous Palaeogeographic global map. The studied limestone samples have been widely affected by different diagenetic processes that the most important of which are micritization, cementation, mechanical and chemical compaction, dissolution, neomorphism, replacement, fracturing and vein-filling cements that have been formed in a variety of marine, meteoric, shallow burial and uplift diagenetic environments.

The Cretaceous system includes carbonate sediments and covers a large part of Zagros. Gadwan and Darian formations are located in the upper part of Khami group. These formations have been investigated by many researchers in several terms. The purpose of this study is to investigate the biostratigraphy of Gadwan and Darian formations, as well as to identify sedimentary facies to reconstruct their paleo-environment.

In this study, thin sections were prepared from cores and cutting and examined with a microscope. A microscopic study was done to identify microfossils (Loeblich and Tappan 1988). Also, skeletal and non-skeletal elements and microscopic characteristics were determined (Flügel, 2010). These were named according to Dunham's method (1962).

Biostratigraphy in Well A: 1) Choffatella decipiens - Pseudocyclammina littus -Trocholina elogatus assemblage Zone. It is introduced from the depth of 4740 m (the lower limit of Gadvan Formation) to 4623 m.
2) Mesorbitolina texana - Choffatella decipiens assemblage Zone. This zone is introduced from the depth of 4623 m to 4552 m.
Biostratigraphy in Well B: 1) Choffatella decipiens - Pseudocyclammina littus -Trocholina elogatus assemblage Zone. Zone No. 1 is introduced from the depth of 4860 m (the lower part of Gadvan Formation) to 4744 m.
2) Mesorbitolina texana - Choffatella decipiens assemblage Zone. This zone is introduced from the depth of 4744 m to 4677 m.
Facies of Darian Formation (Well A): MF1) Mudstone. This facies is associated with deep basin microfacies.
MF2) Planktonic Foraminifora Wackestone. This microfacies represents the low-energy environment.
MF3) Bioclastic Planktone Foraminifora Packstone. The presence of micrite indicates a low energy zone.
Facies of Gadvan Formation: MF4) Bentic Foraminifera Bioclast Packestone. It indicates a high salinity and indicates a lagoon.
MF5) Bioclastic Wackestone. It indicates low-energy environment of the middle ramp.
MF6) Mudstone. This microfacies represent a lagoon environment.
Facies of Darian and Gadvan formations (Well B)
Facies of Darian Formation: MF1) Mudstone. The facies formed in the outer ramp.
MF2) Planktonic Foraminifora Wackestone. The facies deposited in a low-energy in the external ramp.
MF3) Bioclastic Plankton Foraminifora Wackestone. The facies deposited in the outer ramp.
MF4) Orbitolina Peloid Packstone. The facies indicate an environment with high salinity in shallow waters and in the lagoon environment.
MF5) Bioclastic Wackestone. The facies deposited in the middle ramp.
MF6) Mudstone. The facies composed of micrite and has less than 10% bivalves and bryozoans.

Sedimentary environment: 

These facies were deposited in the marine environment and in the outer and middle ramp and a small part of the inner ramp.

In order to study the depositional environment of Gadvan and Dariyan formations in Gachsaran oil field, thin sections have been studied. Based on the biostratigraphy data, the age of Barremian to Aptian for Gadvan and late Aptian for Dariyan was considered. Microfacies study of Dariyan and Gadvan formations led to recognition of 6 microfacies in 3 facies belt, Inner ramp, Mid-ramp, Outer ramp in marine environment. Also, based on variation of microfacies, the studied area predicted as hemoclinical carbonate ramp.

Since the Garau Formation is important as a source rock in the Zagros sedimentary basin, in this research, tried to identify and introduce microfacies, sedimentary model, and sedimentary geochemistry of this formation in Aligudarz section located in the southeast of Lorestan.

Aligudarz section (southeast of Lorestan) is located in the high Zagros zone and in the geographical range of north latitude 33°04′05″ and east longitude 49°00′17″. To identifying microfacies and sedimentary environment, 235 thin sections were prepared and studied. Also, 40 samples were analyzed by atomic absorption spectrometer (AAS) to determine the range of values of major and minor elements (Ca, Mg, Sr, Na, Mn, and Fe).

The Garau Formation thickness in Aligudarz section is 483 m, and lithology consists mainly of limestone, shale and shaly limestone. The lower boundary of the Garau Formation with brrecia limestones is equivalent to the Gotnia Formation in the form of unconformity and the upper boundary is not clear due to its location in the syncline core. Study of this section microscopic sections led to the identification of 7 microfacies in the deep-sea facies belt. Based on the major and minor elements and the ratio of these elements to each other, original mineralogy composition has been mainly aragonite and have been affected by two types of dissolution in closed and open systems. And also has anoxic conditions or an increase in the effect of meteoric diagenesis. The original mineralogy composition has been mainly aragonite and have been affected by two types of dissolution in closed and open systems. Due to anoxic conditions or an increase in the effect of meteoric diagenesis.

Thickness of this section is 483 meters, and lithology consists mainly of limestone, shale and shaly limestone. The lower boundary of the Garau Formation with brrecia limestones is equivalent to the Gotnia Formation in the form of unconformity and the upper boundary is not clear due to its location in the syncline core.The most important biological components identified in different parts of the Garau Formation include radiolarian, planktonic foraminifera (Globigerinelloides, Hedbergella, Leupoldina). Among the most important non-carbonate compounds are iron oxides.The Garau Formation is formed in the deep-sea facies belt belonging to a ramp-type carbonate platform. The original mineralogy has been mainly aragonite and have been affected by two types of dissolution in closed and open diagenetic systems, possibly due to anoxic conditions or an increase in the effect of meteoric diagenesis

Bio-cementation is a new process in which urea hydrolyzing bacteria decompose urea into ammonia and produce calcium carbonate crystals in higher pH due to the production of an alkaline environment. The aim of this study was to investigate the production of calcite using S. pasteurii in precipitation medium and optimization the factors affecting on this reaction. In addition, in this study, the effect of carbon sources in precipitation medium was studied. In this study, according to the results of quantitative XRD analysis, it was found that 1% urea with 94% calcite, 2.4% vaterite and 2% calcium with 92.3% calcite, 4.9% vaterite productivity, respectively, were the best condition for the highest calcite productivity in precipitation medium. Particle size analysis using FESEM revealed that particles produced in 1% urea were often in the range below 100 nm. With increasing urea concentration, the frequency of particles below 100nm in size decreased. The particle size distribution showed that the particles of less than 100nm were lower in 2% urea compared to 1%.FESEM analysis showed that with increasing calcium chloride particles of less than 50nm decreases significantly. The same was true of urea, and it was found that the particle size of the crystals increased at high concentrations of the reactants. In addition, the effect of the presence of carbon sources in the precipitation medium on the production of calcium carbonate crystals was also investigated, which was not significantly different from their absence ( glucose and sucrose). Maltose sugar decreases calcite and increases other crystals.

A large part of the hydrocarbons of the Abadan plain region is located in the Bangestan Group, including the Ilam Formation. Ilam Formation of Santonian age is considered as one of the important oil reservoirs of Abadan plain, whose upper boundary is conformable with Gurpi Formation and its lower boundary with Laffan Formation, and it is mainly composed of limestone with regular layering and between thin layers of shale. The purpose of this study is to determine the role of microfacies and influential diagenetic processes in the reservoir part of Ilam Formation. Petrographic studies on the number of 142 thin section samples related to the drilling debris led to the identification of 7 microfacies related to the three belts of lagoon, Shoal and open marine facies. Among the most important diagenetic processes of Ilam Formation, we can mention cementation, micriteization, compaction, dolomitization, Hematization, glauconitization, pyritization, dissolution, and various types of porosity. In general, the results relating the distribution of reservoir characteristics of Ilam Formation with the study of sedimentary microfacies and influential diagenetic processes show that the best reservoir prone microfacies are wackestone to bioclast packstone and wackestone containing planktonic foraminifera. Also, among the effective diagenetic processes in the reservoir section, we can mention the dissolution and resulting porosity (vuggy porosity), porosity resulting from fracture, recrystallization (caused by microscopic porosity) and dolomitization.

The Campanian-Maastrichtian sequence in the Shiraz region of Inner Fars includes Gurpi and Tarbur formations. In order to study petrography and evaluate the evolution of the sedimentary environment and sequence stratigraphy of these sediments, two stratigraphic sections of Koh-e Qhale and Koh-e Shahrek Abarj in Marvdasht city of Fars province were selected and analyzed. Based on field studies, manual samples, and a detailed microscopic study of 250 thin sections prepared from the studied formations, it was identified that 14 facies (11 carbonate microfacies and three lithofacies) were deposited in a shelf carbonate platform. By studying about 1400 meters of Maastrichtian sediments, depending on the location of the sections under study, three third depositional sequences were identified and separated in terms of sequence stratigraphy. During the Campanian period and the formation of the LST systems tract towards the northeast of the studied area (Koh-e Qhale section), the clastic sediments of the lower part of the Tarbur formation and in the deeper parts of the sedimentary basin of the Gurpi formation were deposited equivalently. At the time of the highstand systems tract (HST facies) and high carbonate production rate in the steep part of the sedimentary environment, interlayered reef deposits (rudist packstone and rudist grainstone) were deposited between the limestones of the Tarbur Formation.

In this research, the process of lithological changes and diagenetic processes of Asmari formation with Oligo-Miocene age has been investigated. For this purpose, 400 samples were selected and collected from a section of the Masjid Suleiman oil field and the surface section of the Asmari anticline in the Dezful depression and the Gurpi anticline in the Izeh zone. Petrographic studies revealed 18 sedimentary microfacies that were deposited on a ramp-type carbonate platform. Among the significant diagenetic processes in the region are the process of micritization, bioturbation and the influence of burrowing organisms, cementation (types of cement related to marine, meteoric and burial diagenesis environments), dissolution (meteoric and burial dissolution), dolomitization (in different phases), silicification, pyritization, phosphatization, mechanical compaction, chemical compaction, fracture and porosity. Based on the identification of the sequence boundaries and following the facies depth changes, the carbonate sequence of the Asmari formation in the subsurface section and the Asmari anticline section are introduced in the form of 3 sedimentary sequences of the third order shallowing upwards, which are the former Aquitanian, the late Aquitanian and Bordigalin belong. Among the dominant porosities in the Asmari Formation, we can mention the hole, mold and fracture porosities.

Asmari Formation (Rupelian-Burdigalian) is one of the most well-known formations in Iran. In order to investigate the stratigraphy and sedimentary environment, a section of this formation was selected in Khamir salt mountain section in Bandarlengeh embayment. In this number, 70 limestone microscopic thin sections and 3 marl samples (XRF) were evaluated to identify the microfacies and the sedimentation conditions.The petrographic study led to the identification of 10 microfacies belonging to the facies belts of tidal, lagoon, carbonate bar, open marine, which were deposited in the homoclinal carbonate ramp environment. The composition of marl facies oxides also indicates the presence of carbonate minerals, quartz and clay minerals, which along with field observations and alternating calcareous facies suggest that this facies was deposited in an open marine environment. Finally, it seems that the facies and fossil diversity of the Asmari Formation in the mentioned section is such that during the Aquitanian stage, this formation was located closer to the coast line and during the Rupelian and Chattian-Burdigalian times, it was located at a further distance from the coast line.

Shally units are one of the most problematic parameters in the process of drilling oil reservoirs. The current study is related to the instability of the wellbore due to the presence of clay minerals bearing shally units of the Pabdeh-Gurpi formations in Aghajari oilfield. Investigation and identification of shales were done using the XRF laboratory and NGS logs. The results showed that the NGS method is sensitive and applicable to identify Illite mineral merely. According to Fe2O3 content, the upper part of the oxidant conditions, but towards the Gurpi, is dominated by reduction condition. The role of other elements in the formation of clay minerals was discussed. Based on the amount of iron, manganese and vanadium, the samples are classified as the Quinby_Hunt and Wilde class lll (non-sulfide resuscitation but Eh recovery and medium to low pH). The range of changes in the Th/U ratio (4-1.5) signified an environment with changes from sea to intermediate states.

In this paper it is attempted to reconstruct the depositional environment of the Jeirud Formation in Aro section. The Jeirud Formation (Late Devonian) is composed of about 45 meters of clastic sedimentary units in the southwest of Firoozkuh city, southern Alborz area. To carry out this research a field work was done during which a precise and detailed sedimentary log of the section was prepared and 52 samples from different lithologies of the formation were collected. Thin sections were prepared from all conglomeratic and sandstone samples, besides some thin sections were prepared from mudrocks and just 1 sample of paleosoil and then all were petrographically studied. In the study area, both basal and top boundary of the Jeirud Formation is disconformable with Mila and Mobarak formations respectively. All facies in the section include clastics (conglomerates, sandstones, mudstones and a paleosoil horizon). The facies were classified based on Miall classification so that conglomeratic facies comprise Gcm and Gmm; sandstone facies comprise Sh, Sp and Sm and mudrocks include Fl and Fm facies. Combined field and lab studies resulted in identification of two sedimentary facies associations including channel fill and flood plain facies associations. The reconstructed sedimentary environment of the Jeirud Formation in the Aro area represents a braided river depositional environment. The lower parts of this formation represent a finning-upward sequence which indicates deposition within a braided river channel subenvironment (conglomerates and sandstones) and the upper part is dominated with mudrocks with a paleosoil horizon representing deposition in a flood plain subenvironment.

To prepare sedimentological data, 98 surface sampling stations have been designed from the seabed in the continental shelf in the southern part of the Caspian Sea and along the coast of Iran. Indicators such as the type and amount of sediment load transported to the sedimentation environment, the energy of waves and sea currents, as well as how the slope of the seabed changes, play a role in the production and diversity of the sedimentary facies. 9 sedimentary facies are the most abundant in the surface deposits of this area and on average, in the sediments of the continental shelf, there are 1% by weight of coarse-grained particles, 25% by weight of medium-grained particles and 74% by weight of fine-grained particles. The composition of sedimentary facies in this area is controlled by indicators such as the size of sedimentary particles, the amount of sedimentary load carried to the environment, the energy of waves and sea currents, and how the slope of the seabed changes. In the marine environment of the study area, sub-sedimentary environments, Backshore, Foreshore, Shoreface, Offshore transition zone and offshore can be identified. The two facies of slightly gravelly Mud and Mud are more abundant than other facies.

The carbonate interval of the Asmari formation along with sandstone deposits were deposited in most areas of the Zagros sedimentary Basin, including the Ahvaz area, in Oligo-Miocene. In this study, the effects of depositional and post-depositional environments on the reservoir quality of zone A7 of the Asmari Formation in well No. 4 in Ahvaz oil field were studied. The study of the sequences of the Asmari Formation in this section led to the identification of 11 carbonate facies, one evaporite facies, one mixed carbonate-siliciclastic facies, and one siliciclastic facies. Sedimentary environments of tidal zone, lagoon, coral reef and open sea were introduced for the depositional environment of identified facies. Due to the absence of sudden changes, it seems that the studied deposits were deposited in a ramp-type carbonate platform that was influenced by siliciclastic sediments from the Zagros river systems. The immature sedimentary texture of the sandstone facies indicates the proximity of the origin of the quartz sources to the carbonate basin. Among the diagenetic processes that have affected the examined sequences, the following processes can be mentioned: micritization, cementation, neomorphism, physical and chemical compaction, dissolution, fracture development and filling, dolomitization, and anhydritization. These diagenetic processes occurred in post-depositional marine, meteoric and burial diagenetic environments. Many fractures were filled with petroleum, which indicates that fractures, along with dolomitization, chemical compaction, and fenestral pores, are among the most important post-sedimentation complications to increase reservoir quality. While cementation and anhydritization resulted in reducing the reservoir quality by closing the pore spaces .

The Zagros sedimentary Basin has long been considered by geologists because of the presence of the hydrocarbon reservoirs and source rocks. Variable sedimentology and facies studies in this basin especially in Jurassic and Cretaceous successions have displayed their high potential as hydrocarbon source rocks. The Sargelu Formation is one of these successions that consist of abundant thin-shelled bivalves. Pelagic disarticulated bivalves concentrations in the deep marine sediments have been introduced as filaments that have recorded in variable middle Jurassic sediments around the world. In this study diversity and abundance of the Posidonia-dominated faceis have applied to differentiation of the sub-environments and reconstruction of the palaeoecological conditions of the Sargelu Formation. Because of the importance of the Sargelu sediments as source rocks, the achieved results are useful for reconstruction of the paleogeographical condition and hydrocarbon exploration in the Zagros Basin.  

The studied outcrops of the Sargelu Formation throughout Zagros fold-thrust belt including the Lorestan Zone consists of Tange-Havandeh, Kezi, Dowdan, Bizel, Tange-Mastan and Homajgah. To evaluation and determination of the sedimentary facies and sedimentary environment of the Sargelu sediments, a detailed sedimentary parameters include sediment/package/layers thickness, bedding boundaries (gradational, sharp, erosional), sedimentary structures, variable grain size, type and preservation mode of macrofossils (fragmented, whole, disarticulated, articulated) were recorded in the field. Based on microscopic asses on 500 thin-section, eight carbonate facies were identified in the Sargelu sediments in the studied area. Carbonate facies were classified/named according to Dunham (1962) classification. Identification of the facies/facies associations and their sedimentary environments were based on Wilson (1975) and Flugel (2010) scheme. 

Based on the microscopic and field analysis, eight facies have been identified in the Sargelu sediments that were related to two facies associations including basin to outer ramp of a distally steepened ramp system. Mud-dominated, fine-grained facies (calcareous shale, mudstone, pelagic bivalve wackestone/floatstone) including pelagic and hemi-pelagic deposits were deposited in the basin environment below SWB, characterized by long time of the low sedimentation rate, low water circulation and low oxygen level, displayed by high abundance of the organic material in this sediments (Pomar et al, 2012; Bayet-Goll et al, 2018; Sharafi et al, 2016, 2019). Outer ramp association consists of thin- to medium-bedded dark limestone including abundant Posidonia-dominated shell concentration with sharp-based, chaotic to preferentially parallel bed orientation of the skeletal elements and fining up-ward fabrics. These special features display periodically activity of the turbidity currents during deposition of the shell concentration and higher sedimentation rate and relatively favorable environmental conditions (with respect to the oxygen and nutrients) for the benthic communities, displayed by abundance bioturbation in these sediments.

Facies analysis of Sargelu Formation exposed in Lorestan Zone led to identification of two facies associations, representing basin to outer ramp of a distally steepened ramp system. Basin deposits in central Lorestan Zone include pelagic and hemi-pelagic deposits, displayed by mud-dominated, fine-grained facies. These sediments were deposited in an anoxic to dysoxic, relatively deep, sea-floor environment as revealed by the presence of: a) organic-rich shales and limestones, b) undisrupted lamination in most facies, c) absence benthic fauna. In contrast, Posidonia pelagic bivalves are interpreted as the result of the proliferation of this bivalve during periods of favorable environmental conditions on the sea floor. Thin to medium beds of graded wackestone/packstone to rudstone/floatstone and accumulations of thin shells of Posidonia pelagic bivalves indicate sporadic reworking of the sea floor by turbidity currents. Disarticulation, fragmentation, and reorientation of Posidonia pelagic bivalves can be indicative of reworking, by turbidity currents which periodically interrupted periods of lower-energy suspension sedimentation.

The carbonate deposits of the Taleh Zang Formation are exposed extensively in the southeastern to northern Lorestan zone, SW Iran. The thickness of the shallow water carbonate Taleh Zang Formation in Ritt Anticline is 84.5 meters. It overlies on top of the turbidity Amiran Formation and it is overlain by the clastic-dominated Kashkan Formation. Petrographic examinations revealed seven facies deposited in tidal flat, lagoon, shoal and open marine. Detailed analysis of sedimentary facies indicates that in the Late Paleocene interval, the depositional system of the Taleh Zangi Formation was a ramp carbonate platform. Changes in the depositional facies and cycle stacking patterns indicate one transgressive-regressive sea-level cycle from the bottom to the top of the section, which is equivalent to the last eustatic sea level rise in the Late Paleocene (Thanetian).  This depositional sequence is separated by type 2 and 1 sequence boundaries at its lower and upper boundaries, respectively. Elemental geochemical evidence indicates a closed to weakly open digenetic system, with low water-rock interaction for carbonates of the Taleh Zang Formation. The relatively open digenesis system in this formation could be due to the influence of meteoric fluids in the erosional discontinuity at the border between the two formations, the Taleh Zang and Kashkan formations.

Paleocene-Eocene succession in the Shiraz region includes Sachun and Jahrom-Pabdeh formations. In order to study petrography, sedimentary environment, and sequential stratigraphy, 4 stratigraphic sections of Beiza, Sadra (auxiliary), Sarvestan, and Shahneshin were selected and analyzed. Based on field studies, manual samples, and detailed microscopic study, 800 thin sections prepared from the studied samples were identified as 23 microfacies and lithofacies deposited in a homoclinal carbonate ramp model. This model the time evolved to steepened ramp sedimentary environment model. By studying about 1700 meters of Paleocene-Eocene sediments, 9 depositional sequences were identified and separated depending on the location of the sections under study in sequence stratigraphy. During the Paleocene and FSST systems tract formation toward to southwest of the study area (Sarvestan section) evaporites sediments in the lower part of Sachun formation correlative deposited the equivalent of Pabdeh formation in the outer ramp. The evolution of steepened carbonate ramps in shallow parts of the carbonate platform of Jahrom Formation and in deeper parts of the Pabdeh formation was deposited in the Middle Paleocene to Middle Eocene period. In the HST systems tract and high carbonate production rate (Highstand Shedding) in the sloping part of the environment calciturbidite has been deposited as a layer between the Pabdeh Formation. Studies show that the facies of Sachun Formation in the study area gradually changes from west to evaporitic-marly facies to marl, limestone, dolomitic limestone, and purple shale facies.

The sedimentary succession of Cenomanine-Turonian, which is introduced by Sarvak Formation, is the most important hydrocarbon (reservoir) formation of Abadan plain. Reservoir facies of this formation show variable temporal and spatial distribution in this time period due to tectonic and sedimentary conditions. In this study, using subsurface seismic data and well data (petrophysical logs and core thin sections), and also comparison with surface outcrops data of Izeh zone, facies, sedimentary environments and diagenetic changes of Sarvak Formation have been studied and analyzed in the framework of sequence stratigraphy. Investigation lateral and vertical variations of facies belts and sequences indicated sedimentation of Sarvak Formation on a rimmed carbonate shelf and intra-platform basins. By examining the changes and geometries of sedimentary-seismic facies along with well, paleontological and petrophysical data and comparison with outcrops, four third-order sedimentary sequences have been separated in the Sarvak Formation (Cenomanian – Turonian interval) with an average age of about 4 million year. These sequences include K120, K130, and K135 in the early Cenomanian, mid Cenomanian, and late Cenomanian respectively, and the K140 sequence is in the early to mid-Turonian. This study showed that distribution and migration of system tracts are consistent with the reservoir zones of Sarvak Formation. The best reservoir facies are in Highstad Systems Tract (HST) which are grain-supported, high porosity and permeability and are subjected to diagenetic processes such as dissolution and karstification. The K135 Sequence forms the best hydrocarbon-containing reservoir facies of shoal, rudist, and channel type in the area.

In order to reconstruction of sedimentary conditions and paleogeography of Qom Formation, one stratigraphic outcrop in the Northeast of Mahneshan has been studied. In this study, microfacies analysis and microfossil investigations have been carried out on Forty-seven samples from one hundred sixty-two meters of sedimentary rock layers. Qom Formation in this section, is composed of carbonate, clastic and volcanoclastic layers that covers the andesitic strata of the Karaj Formation with a disconformity boundary and overlayed by clastic strata of the Upper Red Formation with gradual boundary. Microfacies analysis led to identification of one lithofacies (grain supported conglomerate) and three microfacies (1- Algal coral bioclast packstone, 2- Carbonate volcaniclastic and 3-Pelagic wack/packstone) that are related to the open carbonate shelf, submarine channels and submarine volcano in this section. Fossil investigations lead to identification if seventeen species of foraminifera fossils and two biostratigraphical zones. Based on foraminiferal index fossils (Borelis melo curdica, Meandropsina iranica, Praeorbulina glomerosa), Burdigalian-Langhian have been proposed as relative age for these strata. Facies change throw the stratigraphic column show deepening upward trend (during Langhian) in this study that can be correlated with paleogeographic events and relative sea level rise in Langhian age in this area.

The purpose of this research is to determine the sedimentary environment of alluvial terraces south of Khorramabad to Poldokhter using structural elements and limiting surfaces. In line with this goal, 4 sections were identified and studied. The cuttings are located at distances between 60 and 80 kilometers south of Khorram Abad towards Poldokhter. The studies conducted on these sections lead to the identification of 10 rock facies, including 4 gravelly rock facies (Gm, Gms, Gp, Gt), 4 sandy rock facies (Sm, Sp, St, Sh) and 2 rock facies. Flower (Fsm, Fm), 13 structural elements including (GB, HS, C/S, LHF, LCS, CVs, DIs, TCS, OF, CH, SB, SHF, LIS) and 6 limiting levels of rank 1 to 6 became. According to rock faces, limiting surfaces and structural elements under channel environments, channel bars, point bar, wide cuts (crevasse splay), natural embankments (levee).) and flood plain subenvironment were determined for the alluvial terraces south of Khorramabad to Poldokhtar. Structural elements CH, GB, C/S, LHF, SHF were observed in the studied alluvial barracks in abundance, which indicates a river environment with low twist for the studied alluvial terraces, which alternates between at times, it was attacked by strong and destructive floods, and the coexistence of flood channels indicates that they are periodic.

The Ilam formation is one of the important carbonate oil reservoirs of the Zagros and Dezful embayment basins. In order to identify the microfacies and depositional conditions and diagenesis processes, 100 microscopic thin sections from one well of this reservoir in one of the Dezful embayment oil fields were evaluated. Porosity and permeability data were used to check reservoir quality. The petrographic study led to the identification of 9 microfacies belonging to the facies belts of lagoon, barier, middle ramp and outer ramp, which were deposited in the homoclinal ramp environment. The most important diagenesis processes identified in Ilam reservoir include cementation, dissolution, fracture, micriteization, stylolitization, and dolomitization. Based on the qualitative classification of the reservoir and Lucia's petrophysical diagrams, the lagoon facies and the middle ramp have an average reservoir status, and the carbonate barier facies and the outer ramp have a weak reservoir status. The reservoir quality of the lagoon and middle ramp facies is related to the existence of interconnected and channel porosities. Due to strong cementation and the presence of unrelated porosity such as mold porosity, the carbonate barier facies has low permeability and has a poor reservoir status. In general, the Ilam Formation in the studied field is in a weak state in terms of reservoir, which can be important in addition to the facies controllers in relation to the lack of expansion of fracture and dolomitization and the excessive expansion of cementation in these facies. Therefore, the Ilam Formation in the studied field has a weak reservoir performance due to diagenetic processes, despite having more shallow sequences than deep ones.