دیاژنز

Open Access Article

1 - Factors controlling different types of anhydrite textures and their relation to reservoir quality in the Asmari reservoir in Ahvaz oil field
نسترن آزادبخت

Various diagenetic processes have affected reservoir quality of the Asmari Formation in Ahvaz Oil Field in wells No. 19 with a thickness of 357 meters. It is composed of limestone dolomite, dolomitic limestone, sandy dolomitic limestone, sandstone, siltstone and sha More

Various diagenetic processes have affected reservoir quality of the Asmari Formation in Ahvaz Oil Field in wells No. 19 with a thickness of 357 meters. It is composed of limestone dolomite, dolomitic limestone, sandy dolomitic limestone, sandstone, siltstone and shale. Study of 1100 thin sections from available cores at this well as well as the well’s numeral data, porosity and permeability of cores, indicates that the most important diagenetic processes is anhydritic cement with different types of textures. It appears as poikilotopic, porefilling and pervasive, nodular, fracture filling, sparce crystals, and evaporite veins. During different steps of diagenesis, these texture show replacement and pore filling porosity that have affected different facies to some degrees. Results of this study show that anhydrite cement occurs mainly in dolomitic and sandstone facies and to some extent, affected the reservoir quality. This is due to the effect of sulphate rich brines during dolomitization. Where the presence of anhydrite cements in limestone facies is sparse and rare, it has little effect on reservoir quality. However, pore filling and pervasive anhydrite texture filling all pore-space in dolograinstone and dolopackstone grain-supported facies during shallow burial intensively reduced reservoir quality. Dissolution of cements at later stage of diagenetic processes (creating secondary porosity) improved reservoir quality. In addition, solution of texture poikilotopic anhydrite in sandstone facies and repercipitated as patchy anhydrite with poikilotopic texture, results in reduction of porosity but it doesn’t make any changes in throat pores. Hence patchy anhydrite with poikilotopic texture that reduces porosity converts the sample from Lucias class 2 to class 1. Manuscript profile

Open Access Article

2 - The relationships between diagensis, fracture, distribution of matrix porosity, and well productivities in Bangestan reservoir of Ahwaz field
Mehdi Khoshnoodkia محمد حسين آدابي Mahboubeh Hooseni-barzi Mehdi Khoshnoodkia

Ahwaz Bangestan reservoir (Ilam and Sarvak formations with approximately 1000 meter thickness) were deposited in the Upper Cretaceous period, which is deposited in different sedimentological and tectonic situations. Ahwaz Bangestan reservoir is divided into four reservo More

Ahwaz Bangestan reservoir (Ilam and Sarvak formations with approximately 1000 meter thickness) were deposited in the Upper Cretaceous period, which is deposited in different sedimentological and tectonic situations. Ahwaz Bangestan reservoir is divided into four reservoir zones (C-E-G-I) which are separated by zones of dense limestone (A-B-D-F-H). This reservoir is formed due to repeating shallowing upward of shoal-bar to lagoonal facies with distribution of rudist debris, with the exception of younger sequence which belongs to deeper environment. Back shoal facies show frequent depositional changes in vertical and horizontal directions in zones C3-E-F-G-I, the changes which can be seen in reservoir. Furthermore, the effect of basement faults, with trend nearly N-S in Ahwaz Bangestan reservoir, resulted in changes of ancient paleogeography. These changes had an important effect on diagentic changes, depositional setting, and finally productivity in conventional and carbonate fractured reservoirs. Matrix porosity is fabric selective in zones C3-E-G-and I. So, grainstone, and packstone facies have better reservoir quality than wackestone and mudstone facies. Diagensis and meteoric waters affected the top of every exposure cycles, and caused the best reservoir quality in grainstone, and packstone facies and productivity of wells. But, zone C1 of Ahwaz Bangestan reservoir (chalky limestone) experienced dominantly solution and leaching, which caused an increase in matrix porosity, but little changes in permeability. Furthermore, the open fractures developed in zones E, F and G which are located in the central and southern parts of the field. Existence of open fractures are confirmed by mud losses, analysis of sedimentary structure and dynamic reservoir data. Increase of mud losses in some area of limestone zones (D, F, and H) could be an indication of vertical relationship of two reservoirs and absence of sedimentological barrier in these areas. Manuscript profile

Open Access Article

3 - Sedimentological studies and Petrophysical interpretation: An approach to reservoir characterization of Sarvak formation in the Dalpari oil field
علی اصغر عنایتی

The Ilam and Sarvak Formations of Bangestan Grouop are the second important potential reservoirs after Asmari formation in the zagros basin. Integration of petrographical factors and Petrophysical parameters resulted in better understanding of reservoir qualities of More

The Ilam and Sarvak Formations of Bangestan Grouop are the second important potential reservoirs after Asmari formation in the zagros basin. Integration of petrographical factors and Petrophysical parameters resulted in better understanding of reservoir qualities of these formations. In this study , 250 thin sections were collected and subjected to microfacies and petrography studies. As a result eight microfacies from three sedimentary environments were identified: Lagoonal (L1 ,L2 ,L3),Barrier (B1 ,B2) and Open marine (O1 ,O2 ,O3) and in three different of digenetic environments such as marine, meteoric and burial. This Study shows Sarvak Formation is being formed on Carbonate Rimmed shelf platform. Petrophysical interpretations by using of IP software shows Sarvak reservoir is divided into 3 zones (4, 5, 6). This study reveals that zone 4 contains the best reservoir quality in compare with the others by having (17m) oil column. porosity (more than 8%) and water saturation less than(14%) in this field. There is also decreasing of water saturation in Pay zone 4, but no significant changes has been observed through out zones 5&6. In zone 4, shale volume increases in zones 5&6 (Vsh more than 25%). Crossplot K-Th and K-Pe reveals that Chlorite_Montmorilonite are the dominant clay minerals in this reservoir. Manuscript profile

Open Access Article

4 - Sedimentological studies and Petrophysical interpretation: An approach to reservoir characterization of Sarvak formation in the Dalpari oil field
Abolhasan Ahan kar Abolhasan Ahan kar

The Ilam and Sarvak Formations of Bangestan Grouop are the second important potential reservoirs after Asmari formation in the zagros basin. Integration of petrographical factors and Petrophysical parameters resulted in better understanding of reservoir qualities of t More

The Ilam and Sarvak Formations of Bangestan Grouop are the second important potential reservoirs after Asmari formation in the zagros basin. Integration of petrographical factors and Petrophysical parameters resulted in better understanding of reservoir qualities of these formations. In this study , 250 thin sections were collected and subjected to microfacies and petrography studies. As a result eight microfacies from three sedimentary environments were identified: Lagoonal (L1 ,L2 ,L3),Barrier (B1 ,B2) and Open marine (O1 ,O2 ,O3) and in three different of digenetic environments such as marine, meteoric and burial. This Study shows Sarvak Formation is being formed on Carbonate Rimmed shelf platform. Petrophysical interpretations by using of IP software shows Sarvak reservoir is divided into 3 zones (4, 5, 6). This study reveals that zone 4 contains the best reservoir quality in compare with the others by having (17m) oil column. porosity (more than 8%) and water saturation less than(14%) in this field. There is also decreasing of water saturation in Pay zone 4, but no significant changes has been observed through out zones 5&6. In zone 4, shale volume increases in zones 5&6 (Vsh more than 25%). Crossplot K-Th and K-Pe reveals that Chlorite_Montmorilonite are the dominant clay minerals in this reservoir. Manuscript profile

Open Access Article

5 - Interpretation of sedimentary environment and factors affecting reservoir quality in upper Sarvak Formation in one the oil fields of Abadan plain
Mohammad Hossein Saberi Bahman Zarenezhad الهام اسدی Nasim Rahmani

The Sarvak Formation of the Albian-Turonian Formation is one of the most important hydrocarbon reservoirs in south and southwest of Iran. In this study, in order to assess the reservoir quality, from a petrographic study and porosity and permeability data, an important More

The Sarvak Formation of the Albian-Turonian Formation is one of the most important hydrocarbon reservoirs in south and southwest of Iran. In this study, in order to assess the reservoir quality, from a petrographic study and porosity and permeability data, an important well in one of the oil fields of Abadan plain has been used. Based on microscopic studies, 13 microfacies have been identified in the form of Four facies tidal flat, lagoon, shoal and open marine for Sarvak Formation deposits in the studied oil field, indicating that the upper part of the Sarvak Formation is deposited in a homoclinal carbonate ramp. Among the identified diagenetic processes, dissolution, cementation, dolomitization, fracturing, compaction, neomorphism, micritization, bioturbation, pyritization, hematitization, phosphatization and silicification are mentioned. Diagenetic processes of Sarvak Formation occurred in three marine, meteoric and burial environments. Among the dissolution and fracturing diagenetic processes, the most important role has been in increasing the reservoir quality, and cementation and compaction have been the most important factors in reducing reservoir quality. Sequence stratigraphy studies identified third order sedimentary sequences of the age of Turonian, Late Cenomanian, and Middle Cenomanian, and studied the facies and diagenetic processes within its framework. Correlation of porosity and permeability data of the core showed that the reservoir quality in this formation was influenced by facies and diagenetic processes. So that the microfacies containing the rudist have the highest reservoir quality. Due to the diagenetic processes, sedimentary and porosity and permeability data, the facies shoal and open marine to the land have the best reservoir quality. Manuscript profile

Open Access Article

6 - Interpretation of sedimentary environment and factors affecting reservoir quality in upper Sarvak Formation in one the oil fields of Abadan plain
Arad Kiani Mohammad Hossein Saberi Bahman Zare nejad Elham Asadi Nasim Rahmani

The Sarvak Formation of the Albian-Turonian Formation is one of the most important hydrocarbon reservoirs in south and southwest of Iran. In this study, in order to assess the reservoir quality, from a petrographic study and porosity and permeability data, an importan More

The Sarvak Formation of the Albian-Turonian Formation is one of the most important hydrocarbon reservoirs in south and southwest of Iran. In this study, in order to assess the reservoir quality, from a petrographic study and porosity and permeability data, an important well in one of the oil fields of Abadan plain has been used. Based on microscopic studies, 13 microfacies have been identified in the form of Four facies tidal flat, lagoon, shoal and open marine for Sarvak Formation deposits in the studied oil field, indicating that the upper part of the Sarvak Formation is deposited in a homoclinal carbonate ramp. Among the identified diagenetic processes, dissolution, cementation, dolomitization, fracturing, compaction, neomorphism, micritization, bioturbation, pyritization, hematitization, phosphatization and silicification are mentioned. Diagenetic processes of Sarvak Formation occurred in three marine, meteoric and burial environments. Among the dissolution and fracturing diagenetic processes, the most important role has been in increasing the reservoir quality, and cementation and compaction have been the most important factors in reducing reservoir quality. Sequence stratigraphy studies identified third order sedimentary sequences of the age of Turonian, Late Cenomanian, and Middle Cenomanian, and studied the facies and diagenetic processes within its framework. Correlation of porosity and permeability data of the core showed that the reservoir quality in this formation was influenced by facies and diagenetic processes. So that the microfacies containing the rudist have the highest reservoir quality. Due to the diagenetic processes, sedimentary and porosity and permeability data, the facies shoal and open marine to the land have the best reservoir quality. Manuscript profile

Open Access Article

7 - Investigation of petrographical and geochemical characteristics of carbonate deposits of the Jamal Formation in the Chah-Riseh section, northeast of Isfahan
Behrad Zebhi Kamand محمد علی صالحی Ezat Heydari Ali Bahrami

10.52547/ispg.39691.11.21.54

The Middle Permian Jamal Formation have been investigated for sedimentological and geochemical aspects in the Chah-Riseh section, northeast Isfahan. According to the field studies the Jamal Formation with 251 m thickness divided into eight lithostratigraphic unit. Lower More

The Middle Permian Jamal Formation have been investigated for sedimentological and geochemical aspects in the Chah-Riseh section, northeast Isfahan. According to the field studies the Jamal Formation with 251 m thickness divided into eight lithostratigraphic unit. Lower boundary of this formation with an unconformity is underlained by the Sardar Formation which belongs to the Carboniferous period and upper boundary with an unconformity reaches to the Lower Triassic Sorkh-Shale Formation. Facies and microfacies studies of the Jamal Formation led to the identification of two petrofacies and 14 carbonate microfacies. According to the recognized carbonate allochems, petrofacies and microfacies of the Jamal Formation and some evidence such as transitional microfacies changes, we can consider a depositional environment of a shallow mixed siliciclastic-carbonate ramp platform. Petrographically, four types of dolomites are recognized in the Jamal Formation. The dolomitization model for the type I dolomite is considered forming in tidal flat and burial dolomitization for types II, III and IV. Geochemical studies including major and trace elements analysis comprised of elements such as Ca, Mg, Sr, Mn and Fe. Using ratios of the elements and also by plotting some of these elements cross carbon and oxygen isotopes in various diagrams have been used in determining the original mineralogy of carbonate deposits and efficient diagenetic system on the Jamal Formation. The results indicate that the dominant diagenetic environment effected on the carbonate deposits of Jamal Formation was occurred in a semi-closed system and the original mineralogy was aragonite. Evaluation of major and trace elements contents of the four types dolomites, confirmed different characteristics of theses dolomite resembling crystal sizes in petrographic studies. Carbon and oxygen isotopes data of dolomites also defined their diagenetic situations. Manuscript profile

Open Access Article

8 - The history of deposition and post-deposition and their effects on the reservoir quality of Asmari Formation in Ahvaz oilfield
Akbar Heidari Milad Faraji Narges Shokri

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 re More

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 . Manuscript profile

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