Early Miocene Qom Formation of the Gooreh Berenji Region (Jandaq Area, Central Iran)
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GeoArabia, Vol. 12, No. 4, 2007 Oligocene-Miocene Qom Formation, central Iran Gulf PetroLink, Bahrain Microfacies and sedimentary environments of the late Oligocene- early Miocene Qom Formation of the Gooreh Berenji region (Jandaq area, central Iran) Alireza Shakeri, Jalal Douraghinejad and Mehran Moradpour ABSTRACT The late Oligocene-early Miocene Qom Formation in the Central Iran Basin contains oil and gas in the Alborz and Sarajeh fields. Organic geochemical analyses in previous studies indicated that the hydrocarbons migrated from deeper source rocks, likely of Jurassic age. In the Central Iran Basin, the Qom Formation is 1,200 m thick and is bounded by the Oligocene Lower Red Formation and the middle Miocene Upper Red Formation. In previous studies, the Qom Formation was divided into nine members designated from oldest to youngest: a, b, c1 to c4, d, e and f, of which “e” is 300 m thick and constitutes the main reservoir. Our study focused on a Qom section located in the Gooreh Berenji region of central Iran which is 294 m thick. The lower part of the formation was not deposited, and only the following four members of early Miocene age (Aquitanian and Burdigalian) were identified between the Lower and Upper Red formations: “c2”? (mainly greyish to greenish gypsiferous marls); “d” (thin- to thick-bedded anhydrite with intercalation of thin-bedded sandstone); “e” (argillaceous or sandy limestone); and “f” (fine-grained coral and bryozoan boundstone). In contrast to the Central Iran Basin, the “e” member in Gooreh Berenji is only 15 m thick and does not have a good reservoir potential. A detailed petrographic analysis of the Gooreh Berenji section resulted in the identification of 13 microfacies (MF) that were interpreted in terms of their depositional environments according to the following categories: MF1 (sabkha), MF2 (intertidal river channel), MF3 (lower intertidal), MF4 (peritidal), MF5 (supratidal), MF6 and MF7 (shallow restricted lagoon), MF8 and MF10 (proximal open-marine), MF9 (leeward lagoon), MF11 (shoal), MF12 (reef and patch reef formed within lagoon), and MF13 (open-marine). The Qom Formation constitutes a regional transgressive-regressive sequence that is bounded by two continental units (Lower and Upper Red formations). The transgression started from the south in the late Oligocene and by the early Miocene the sea covered all of central Iran. In the Gooreh Berenji area, carbonate deposition occurred on a shallow-marine ramp. The presence of a wide range of lagoonal facies indicates that reefal facies (“f”) developed in a narrow elongated strip away from the shoreline. INTRODUCTION The Central Iran Basin is located in the western part of the Lut microplate, and is bounded to the north by the Alborz Mountains and to the southwest by the Sanandaj-Sirjan Zone (Stöcklin and Setudehnia, 1971) (Figure 1). The basin lies within the Turkish-Iranian Plateau that reaches elevations of 1.5 to 2.0 km and forms part of the Alpine-Himalayan collisional system (Sengör and Kidd, 1979; Dewey et al., 1986; Allen et al., 2004). Hydrocarbons were discovered in this basin in the early 1950s in the Alborz and Sarajeh fields by the National Iranian Oil Company (NIOC, 1963) in the Oligocene-Miocene argillaceous limestones of the Qom Formation. This formation is in part equivalent to the petroliferous Asmari Formation in the southern Iranian fields. Whereas the Alborz field has now been nearly depleted and abandoned, the Sarajeh field continues to produce large volumes of gas and condensates. 41 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/12/4/41/4570238/shakeri.pdf by guest on 26 September 2021 Shakeri et al. 46°E 48° 50° 52° 54° 56° 58° 60° 62° Caspian TURKMENISTAN Tabriz Sea N 38°N Mianeh 0 200 38° Takab A l b km o r z M Bl-3 o u Zanjan n t a i n s Mashhad 36° Bl-2 Semnan 36° Tehran Figure 7 Sanandaj Bl-1 Razan Figure 4 Qom Figure Hamedan 3 Figure 2 34° Alborz Ardestan Jandaq 34° Field Sarajeh Sanandaj-SirjanKashan Zone Anarak Field AFGHAN- IRAQ Zagros Fault Zone Naein Z a g r o s M o ISTAN Esfahan 32° IRAN 32° Sirjan Lut Block u TURKEY Caspian n t a i Kerman Sea 3030° 30° SYRIA Location N n Shiraz Med 0 km 300 Sea Map PAKIST IRAQ IRAN AN JORDAN KUWAIT 29 28°39 40 41 28° BAHRAIN City Qom Formation distribution QATAR EGYPT Arabian Locality Central Iran Shield UAE OMAN sedimentary basin SAUDI ARABIA Bl-3 Exploration blocks Dasht-e Kavir (Great Desert) Red SUDAN Sea 26° YEMEN 52° 54° 56° 58° 60° 62° ERITREA Figure 1: The distribution of Oligocene-Miocene Qom Formation in the central Iran sedimentary basin. Also shown are exploration blocks 1 to 3 and the transverse section (blue line, Figure 3) (modified from Darvishzadeh, 1992). Fault 34°08' 34°07' Lower Red Formation Qom Formatio n d 34°06' Upper Re Formation 54°02' 54°03' 54°04' 54°05' 54°06' 54°07' Figure 2: Satellite image of the study area showing the location of the Gooreh Berenji section, the Jandaq area (modified from Google Earth, 2006). The Qom Formation is separated from the Oligocene Lower Red Formation by a NE-trending fault. In this section, the Qom Formation is of Miocene age and is overlain by the mid-Miocene Upper Red Formation. 42 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/12/4/41/4570238/shakeri.pdf by guest on 26 September 2021 Oligocene-Miocene Qom Formation, central Iran Gooreh Berenji Kuh-e Nardaghi Section (Qom area) In order to further understand the lithofacies, and the general environment and depositional characteristics Litho- of the Qom reservoir, we sampled a 294-m-thick logy section of the Qom Formation located at Gooreh (meter) Member Lithology Formation 300 km Berenji in the central part of Dasht-e Kavir (the Great 0 Upper Red Desert of central Iran), 40 km northwest of Jandaq Formation 10 city (Figures 1 and 2). This paper describes the results 20 of a sedimentological and petrographic study of 30 172 samples from the studied section. Thin sections 40 were stained by Alizarine red solution and detailed 50 f microscopic analyses were carried out to identify the 60 different microfacies (Figure 6) so as to interpret their 70 depositional settings. We also correlated the Gooreh f Berenji section to a more complete section at Kuh-e 80 Nardaghi, located 300 km away in the Central Iran 90 e Basin (Figure 3). 100 110 d HYDROCARBON HABITAT OF THE 120 CENTRAL IRAN BASIN 130 140 The Alborz oil and Sarajeh gas fields are located in 150 the northwestern part of the Central Iran Basin, about 160 140 km southwest of Tehran, between the cities of 170 Qom and Kashan (Figures 1 and 4). Both fields occur 180 QOM FORMATION in northwest-trending anticlines having a surface 190 expression that is complicated by thrust, and possibly 200 strike-slip faults. 210 220 e Alborz Oil Field 230 The surface expression of the Alborz field is a large 240 Undifferentiated member (c2?) asymmetrical anticline with a height of 900 m. The 250 steeply dipping northwestern plunge is partly covered 260 by gravel plains. At the surface, the Qom salt plug 270 occurs at the northern end of the anticline (Figure 4). 280 d Despite this complexity, reflection seismic maps have 290 proven quite accurate. The field is located 17 km Lower Red 300 Formation southwest of the Mil oil seep. The main reservoir 310 reaches depths between 2,677 and 2,977 m above sea 320 level. About 15 wells have been drilled in the field. They 330 encountered extremely high pressures, which caused 340 difficult drilling problems, including lost circulation at many levels and low formation strength in the upper 350 Coral Bryozoa section. 360 Red Algae 370 Limestone The main Qom reservoir zone, “e”, is 97 m and 79 m 380 Sandy Limestone thick in the Alborz-6 and Alborz-8 wells, respectively, 390 Fossiliferous and the porosity varies from 0.5% to 15.0% (NIOC, 1959; 400 limestone Tabibian et al., 1995). The oil in the “e” reservoir is light Marl 410 and paraffinic with a gravity of 39° API (NIOC, 1964; Gypsiferous marl 420 Fossiliferous Baghbani et al., 1995). The “c1” member (130 m thick) gypsiferous marl 430 constitutes a separate reservoir zone that contains 24° Anhydrite 440 API oil (NIOC, 1964; Tabibian et al., 1995). Sandstone 450 Shale/Claystone 460 Siltstone Figure 3: Correlation of the Qom Formation between 470 Covered a-c 4 the Gooreh Berenji and Kuh-e Nardaghi locations. 43 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/12/4/41/4570238/shakeri.pdf by guest on 26 September 2021 Shakeri et al. 50°40' 50°50' 51°00' 51°10' 51°20' Surface section Contour interval 35°10' Subsurface section 35°10' Morreh Kuh (96) (meter) Locality 0 m Road 100 200 Oil field 200 Gas field 300 400 500 600 hran 700 Te 35°00' N 35°00' 0 10 To 400 800 km 900 1,000 1,100 40 1,200 0 60 0 0 60 34°50' 34°50' 80 0 Kaj Gazaran 1,000 Rostam-1 (710) 800 Alborz Alborz-8 (358) Qomrud Karvansara Sangi (1,213) Alborz-7 (578) 34°40' Dochah (970) 34°40' Qom Kamar kuh (1,000) Alborz oil field 1,000 Nardaghi (1,328) Sarajeh Sarajeh gas field Dobaradar (1,259) 1,200 To Arak Jamkaran Khurabad 34°30' 34°30' Khurabad (1,090) Sarajeh-3 (1163) 1,000 Pasangan village 80 Tighe-e Reza abad (947) 0 Shurab (928) Kahak (923) Kahak Esfahan To 60 Shurab 0 Qobadbazan To E sfahan 40 34°20' 0 34°20' Neyzar (300) 50°40' 50°50' 51°00' 51°10' 51°20' Figure 4: Isopach map of late Oligocene-early Miocene Qom Formation in the middle part of the Central Iran Sedimentary Basin (Qom area) contoured at 100 m intervals (modified from Baghbani et al., 1995).