Z. Alishavandi; H. Rahimpour-Bonab; A. Kadkhodaei; M. Arian
Abstract
The Sarvak Formation deposited in the North to Northeastern margin of the Arabian Platform during the Mid-Cretaceous (Albian-Turonian), and is extensively encountered in the Folded Zagros of southwestern Iran. It is the most important reservoir unit after Asmari Formation in Iran. Petrography of microscopic ...
Read More
The Sarvak Formation deposited in the North to Northeastern margin of the Arabian Platform during the Mid-Cretaceous (Albian-Turonian), and is extensively encountered in the Folded Zagros of southwestern Iran. It is the most important reservoir unit after Asmari Formation in Iran. Petrography of microscopic thin sections in studied wells led to determination of nine microfacies that deposited in 3 sub-environments; restricted lagoon, lagoon-open marine and shoal in an interior part of carbonate ramp. Petrographic studies revealed that since deposition, the Sarvak Formation experienced several diagenetic realms including marine, meteoric, burial and telogenetic diagenetic environments. Location of the studied wells shows that the relative depth of the Sarvak Formation ramp decreases from the east to the west. Also, the results show that the Sarvak reservoir quality affected by various diagenetic processes such as micritization, dissolution, dolomitization, cementation, stilolitization and fracturing. These diagenetic successions are mainly restricted to the upper and lower parts of the Cenomanian-Turonian disconformity. Meteoric water infiltration below this disconform boundary and related karstification led to development of moldic and vuggy porosity a long with reservoir quality increase. Based on the sequence stratigraphic study, three third-order sequences were recognized in the middle Cenomanian to middle Turonian part of the formation. The results of this research show that the reservoir quality distribution in this unit is primarily controlled by depositional facies so that the rudist microfacies (grainstone, floatstones and rudstones) have the best primary reservoir qualities though, it has also been drastically improved by dissolution in paleoexposure surface
R Sadeghi; A Saidi; M Arian; M Ghorashii
Abstract
In this study, separation of paleostress phases in the Khalkhal region has been doneusing paleostress analysis based on heterogeneous fault slip data and related slip lineations.The data have been measured and collected from the Jurassic, Cretaceous and Eocene units.To determine the sense of shear or ...
Read More
In this study, separation of paleostress phases in the Khalkhal region has been doneusing paleostress analysis based on heterogeneous fault slip data and related slip lineations.The data have been measured and collected from the Jurassic, Cretaceous and Eocene units.To determine the sense of shear or slip, indices such as stratigraphic separation across the faults, kinematic indicators on fault surfaces, conjugate fractures, and tensile cracks were used.The data were analyzed with the help of inversion method. The results indicate that strike-slip regime is dominant in the region. Constraining the stress phases and comparison with the field and seismic data revealed that the third stress regime is characterized by avertical σ2and a NE-SW extension related to the modern stress regime, which is also compatible with the seismic data. The first and second phases of stress prevailed along NW-SE and N-S directions related to the paleostress regimes.Various investigations, including rose diagram analysis of faults and arrangement of structures show that the faults in the region are dominantly strike-slip and strike-slip with normal component, and the shape of the stress field in the region is prolate.
K Rezaeeparto; H Rahimpour Bonab; A Kadkhodaie; M Arian; E Hajikazemi
Abstract
Dariyan Formation (Aptian-Albian) is one of the main reservoir units in the South West of Iran which is equivalent to Shuaiba Fm,. Since the first step in the evaluation study of reservoir rock is studying the microfacies, depositional environments and diagenesis processes, in this research we have discussed ...
Read More
Dariyan Formation (Aptian-Albian) is one of the main reservoir units in the South West of Iran which is equivalent to Shuaiba Fm,. Since the first step in the evaluation study of reservoir rock is studying the microfacies, depositional environments and diagenesis processes, in this research we have discussed these parameters in Dariyan reservoir in Salman oil field A, B, C, D and E wells. On the basis of petrographic studies classification of carbonate rocks by Dunham’s method and nomination of microfacies by Flugel’s classification was done and 7 basic microfacies have been identified: Mudstone, Mudstone to fossiliferous wackestone, Orbitolinid wackestone to packstone, Bioclast packstone to grainstone with restricted microfauna, Echinoderm wackestone to packstone, Planktonic wackestone to packstone, Mudstone to Planktonic/echinoderm wackestone, that belong to open marine sedimentary environment, shoal and lagoon. The study of vertical and lateral facies changes and comparing them with modern and ancient sedimentary environments show that Dariyan Formation in this area is deposited in a leeward mud dominated carbonate ramp. Due to numerous diagenetic processes observed in the formation, of their direct impact on the quality of the reservoir to the conclusion that micritization, cementation, compaction (mechanical), neomorphism, and pyritification to block the pores and pore through in the reservoir porosity and permeability decrease while, compaction (chemical), dolomitization, and fracture caused voids and communication between them. Finally, the porosity and permeability of the reservoir increased and led to higher quality.
M.R Rahmani; R Moussavi – Harami; M Arian
Abstract
Dariyan formation is one of the oil reservoirs in the south pars field. This formation has been studied in wells SPO-1, SPO -2 and Spo-3. Thickness of Dariyan formation in mentioned wells are 109, 113 and 114 meters respectively. Based on the studies of thin sections from the Dariyan formation of three ...
Read More
Dariyan formation is one of the oil reservoirs in the south pars field. This formation has been studied in wells SPO-1, SPO -2 and Spo-3. Thickness of Dariyan formation in mentioned wells are 109, 113 and 114 meters respectively. Based on the studies of thin sections from the Dariyan formation of three above mentioned wells, nine carbonate and one detrital facies have been identified within four facies associations including tidal flat (Mudstone), lagoon (Bioclast mudstone to wackstone, Bioclast peloid wackstone to packstone, Bioclast peloid packstone to grainstone, Algal boundstone), Mid ramp (Echinoid mollusk wackstone to packstone, Orbitolina wackstone to packstone, Framestone, Floatstone) and outer ramp (Shale). Facies studies indicate that Dariyan formation has been deposited in a homoclinal ramp.The Dariyan formation has been affected by four diagenetic stages, including marine, meteoric, burial and uplift. The most important identified diagenetic processes are micritization, bioturbation, geopetal, physical and chemical compaction, cementation, neomorphism, replacement, dissolution, fracturing and filling. Among the all diagenesis process, dissolution and fracturing are the major processes improving reservoir quality. In Contrary, physical compaction and especially cementation are the main processes redusing reservoir quality. Dissolution process with generating secondary porosity consists of vuggy and moldic, has important effect on increasing of porosity. Most of the dissolution features have been produced during the meteoric diagenesis and less through burial diagenesis. Dissolution process with develop the vuggy pores caused to connect them in some case and also affected on fractures , stylolites and previous diagenetic cements in upper and lower members of daryian formation which eventually has been increased permeability and reservoir quality. Also, Fracturing, the main other diagenetic process with connect the some individual vuggy and moldic pores together has effective role to increase the permeability and reservoir quality in upper and lower parts of Dariyan formation.
Gh Razaghian; A Beitollahi; M Pourkermani; M Arian
Abstract
Iran is in the middle part of the seismic belt of Alps-Himalayas with dissimilar geological, structural and seismological features. In the present article, zonation maps of the earthquake occurrence rate (Rate) and the largest observed earthquakes (Mmax) have been prepared for all the regions of Iran. ...
Read More
Iran is in the middle part of the seismic belt of Alps-Himalayas with dissimilar geological, structural and seismological features. In the present article, zonation maps of the earthquake occurrence rate (Rate) and the largest observed earthquakes (Mmax) have been prepared for all the regions of Iran. The parameter (Rate) shows the number of occurred earthquakes in the year in the region of Iran. Subsequently, according to the zonations, classification of different regions with different seismic activities will be achievable. The zonation map of earthquake occurrence frequency (Rate) in the present article shows that trend of the main classified zonations, according to the calculations, is similar with the geological and structural features of the region. It seems that zonation of Zagros and certain parts of the east of Alborz and Kopedagh with the maximum rate of earthquakes are drastically different with the zonation of central parts of Iran, Makran and eastern part of Iran with low seismic activities. In addition to zonation maps of the earthquake occurrence rate, zonation of the largest observed earthquakes (Mmax) has been provided in this region as well. According to the map, different regions of the Central part of Iran and Alborz with large seismic activities are different with other regions of Iran. Having compared the two zonation maps in this article, it is possible to classify the seismic activities of different regions. The seismic data and the basis of the article are according to the National and International Seismology catalogue for a period of 1900 to 2008.