Petroleum geology
Bita Arbab; Davood Jahani; Bahram Movahed
Abstract
The Aptian Shuaiba deposits, in southeastern of Persian Gulf due to having resistivity less than 6 to 1 ohm.m, is considered as low resistivity pay zone. On the basis of experimental studies 8 microfacies defined which settled in a carbonate platform of homoclinal ramp model that belong to outer, ...
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The Aptian Shuaiba deposits, in southeastern of Persian Gulf due to having resistivity less than 6 to 1 ohm.m, is considered as low resistivity pay zone. On the basis of experimental studies 8 microfacies defined which settled in a carbonate platform of homoclinal ramp model that belong to outer, middle, inner ramp. Existence micro porosity in the microfacies is main reason for lowering resistivity. Various digenetic process are seen such as micritization and pyritization which have noticeable impact on declining resistivity. Lønøy method applied to address pore throat sizes which contain Intercrystalline porosity, Chalky limestone, Mudstone micro porosity. Pore systems are at class 3 Lucia. NMR logs and core data have been used for defining reliable water saturation and reservoir characterization. Results explain that decreasing of resistivity in pay zone is related to texture and grain size variation not being existence of moved water .Irreducible water estimate for this reservoir between 30 to 50 %.
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 ...
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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 ...
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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.
M. H. Adabi; R. Abbasi; H. Ghalavand
Abstract
In this investigation Dariyan Formation with the age of Lower Cretaceous (Aptian- Albian) were studied for geochemical and sedimentology characteristics in the surface section at Kuh-e Siyah Anticline and subsurface section Sabzpushan well number 1. Based on petrographical studies 12 microfacies identified ...
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In this investigation Dariyan Formation with the age of Lower Cretaceous (Aptian- Albian) were studied for geochemical and sedimentology characteristics in the surface section at Kuh-e Siyah Anticline and subsurface section Sabzpushan well number 1. Based on petrographical studies 12 microfacies identified which are belonging to 5 facies belt, such as: intertidal, lagoon, shoal, shallow open marine and deep open marine. The observed facies patterns indicated a carbonate ramp depositional environment. Important diagenetic processes were observed in Dariyan Formation including cementation, physical and chemical compaction and replacement processes such as pyritization and silicification. Prosities in these sections are secondary, including vuggy, fracture and channel types. Major and minor elements and carbon and oxygen isotopes studies are indicated that aragonite was original carbonate mineralogy for this Formation. The plots of elemental values also are illustrated that mainly burial diagenetic processes have been affected this formation in semi- close to semi- open system. A temperature calculation based on the heaviest oxygen isotope value indicates that the very early, shallow burial temperature was around 28.5°C during Dariyan carbonate deposition.
F. Safari; M. Yazdi-Moghadam; F. Sajjadi
Abstract
To recognize different species of the genus Orbitolina and determine the age of the Dariyan Formation, the upper limy part of the Dariyan Formation in Dashtak section was sampled and studied. Based on the size, shape and complexity of embryonic apparatus, five species belonging to subgenus Mesorbitolina ...
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To recognize different species of the genus Orbitolina and determine the age of the Dariyan Formation, the upper limy part of the Dariyan Formation in Dashtak section was sampled and studied. Based on the size, shape and complexity of embryonic apparatus, five species belonging to subgenus Mesorbitolina were recognized as below: Orbitolina (Mesorbitolina) lotzei, Orbitolina (M.) parva, Orbitolina (M.) texana, Orbitolina (M.) subconcava, Orbitolina (M.)sp. cf .M. pervia According to stratigraphic distribution of the mesorbitolinids, the upper part of the Dariyan Formation can be ascribed to the late early Aptian-late Aptian. The early/late Aptian boundary coincides with first occurrence of O. (M.) parva