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Palyological study of Milla, Illbeyk, Zard Kuh and Faraghan at Zard Kuh,. Chal –I – shel areas and Darang well, No. 1 in Zagros Basin, southern Iran, NIOC Geol.
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H. Teymourzadeh, Seyed H. Vaziri, D. Jahani, Nader K.G. Vand, A. Yahyaei, A. Afzali. Exploration of characteristics and lithostratigraphy of the Kangan and upper Dalan formations in Lavan gas field, Northern Persian Gulf. International Journal of Academic Research Part A; 2014; 6(5), 311-320. DOI: 10.7813/2075-4124.2014/6-5/A.43 Library of Congress Classification: G1-922

EXPLORATION CHARACTERISTICS AND LITHOSTRATIGRAPHY OF THE KANGAN AND UPPER DALAN FORMATIONS IN LAVAN GAS FIELD, NORTHERN PERSIAN GULF 1

2

3

Haleh Teymourzadeh *, Seyed Hamid Vaziri , Davood Jahani , 4 5 Nader Kohansal Ghadimvand , Ahmad Yahyaei 1

2,3,4

PhD. student Science and Research Branch of the Islamic Azad University (Tehran SRBIAU), Geology Department, Faculty of Basic Sciences, North Tehran Branch, Islamic Azad University, Tehran, 5 Iranian Offshore Oil Company (IOOC), Tehran, Science and Research Branch, Islamic Azad University (IAU) (IRAN) E-mails: [email protected], [email protected], [email protected], [email protected], [email protected] DOI: 10.7813/2075-4124.2014/6-5/A.43 Received: 02 Feb 2014 Accepted: 30 Aug, 2014

ABSTRACT In this paper, one subterraneous of Kangan and upper Dalan formations of Lavan well number 3 was studied. Based on petrographic studies, Kangan Formation in the study area is predominantly made up of dolomitic limestone lithology and upper Dalan Formation is made up of dolomitic and lithology in its upper part. The well is visible between layers of anhydrite in both formations. The border between Dalan and Kangan formations is disconformity and is specified by the absence of Durashamian fauna. Kangan Formation upper border is transitional by Shales Dashtak Formation and the lower boundary of upper Dalan Formation is also limited by Nar anhydrite part. Based on reservoir subdivisions, Kangan lithostratigraphic Formation is divided into two units of K1 and K2, while the upper Dalan Formation has K3,K4 units. According to petrographic studies, 5 types of dolomite have been identified in Kangan Formation and 3 types of dolomite have also been identified in upper Dalan Formation (dolomites have been composed of Sabkha and mixed-zone models). Effective diagenesis processes in Kangan and upper Dalan formations including biological disturbance, micritization, density, cementation, geoptal fabric, breakup, dolomitization, fracture, silicification, and pyritization have affected Kangan and upper Dalan formations in the form of marine diagenesis and meteoric environments. Referring to petrographic studies and facies identified, 13 facies and 9 facies have been identified in Kangan and the upper part of upper Dalan formations, respectively. The presented sedimentary environment is of isocline ramp in Kangan and the upper Dalan formations. Key words: Kangan Formation, Dalan Formation, Reservoir Zone, Facies 1. INTRODUCTION Kangan and upper Dalan formations (equal to upper Khuf formation in the Saudi Arabia) have the largest gas reserves in the Middle East and also the world (Insalaco et al., 2006); therefore, better understanding of the reservoir characteristics of the mentioned formations and the presentation of a better picture of the depositional environment are very important. Consequently, more detailed petrographic studies and identification of facies and diagenesical processes along with the identification of petrophysical studies have been used. Area Geography and Access Roads Lavan is a coral island; it dates back to the fourth geological period; and it has been located at a distance of about 16 km of the Iranian coast (across Magham port). With the geographical coordinates of 53˚14' 17"E longitude and 26˚ 50' 00"N latitude, this island is the largest island in Persian gulf water after Qeshm and Kish islands and it is also the farthest island from the center of Hormozgan province (Figure 1).

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2. METHODOLOGY a. Petrograpyic Studies Petrographic studies in this research are based on the determination of carbonate and non-carbonate components and their frequency in order to identify microscopic facies, sedimentary environment, and also to consider diagensis processes to determine diagenesis history of upper Dalan and Kangan formations.

Fig. 1. Geographical Situation of Lavan Island b. Petrophysical Studies Using petrophysical logs, geological reports, and also repository data of the studied formations, this study has been used for the interpretation of reservoir characteristics.

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Fig. 2. Lithological Column of upper Kangan Formation in well No.3 of Lavan Gas field, Persian Gulf 2.1. Lithostratigraphy of Kangan Formation Based on the investigation of the microscopic section (720 thin sections from 153m rock sequence of Kangan Formation) and the employment of the core data and reservoir characteristics, Kangan Formation with the middle Triassic one from top to bottom can be divided into two reservoir units of K2 (at the top) and K1 (at the bottom) (Figure 2). K1: This reservoir unit is 99 m thick; regarding reservoir and lithological characteristics and facies, they differ from each other in the different parts. The bottom part of this unit (K1) often includes dolomudstone to grain rich facies and grainstone ones with significant porosity and reservoir quality. The upper part of this reservoir unit is often of calcareous lithology and mudstone facies. It must be noted that the lower part of this reservoir unit is fully dolomite; they are mostly mudstone facies; and they have no reservoir quality. The middle part of this reservoir unit has the best reservoir quality; medium to high reservoir quality has been considered for this dolomudstonefacies. This reservoir unit with dolomudstonefacies has average porosity and permeability. This unit is divided into 4 subunits (Table 1). K2: This unit is 55 m thick with considerable reservoir quality. This sequence includes grain rich facies and also mud and microbialifacies. Most microbialies are in the base of this reservoir unit. The bottom part of this reservoir unit can be divided into to 3 subunits. 2.2. Litostratigraphy of the Upper Dalan Formation Upper Dalan Formation is of calcareous dolomite lithology in elementary parts (in the several upper meters); the rest is dolomitic. It is notable that core samples have been only taken from the upper part of the

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upper Dalan Formation (equivalent with K3,K4 units) and the rest is non-core samples (Figure3) (of 83 m rock sequences of Dalan Formation, 394 thin sections were obtained). Lithology in upper Dalan Formation is dolomite at first; and then, it turns into calcareous and dolomitic calcareous towards the lower parts and the middle layers are anhydrite. Resevoir Unit K3, K4: This reservoir units are 45m thick and 38m thick respectively. This contains thick sequences of mud rich; the dominant grain base part of this section is anhydrite which has not been picked up and has low reservoir quality. The main facies of this section which has reservoir quality includes grainstone and oolitic / bioclasti packstone with format porosity and middle crystalline; it must be noted, however, some of mudstones also have good middle crystals porosity. The middle part of reservoir section consists of atternation of dolomitic mud rich facies and grain rich facies with remarkable reservoir quality.

Fig. 3. Lithological Column of upper Dalan Formation in well No.3 of Lavan Gas field, Persian Gulf Diagenesis Processes in upper Dalan and Kangan Formations Diagenesis includes all physical, chemical, and biological processes which take place after sedimentation until reaching to metamorphism by increasing temperature and pressure on the sediments (Tucker, 1991). Biological perturbations, micritization, geoptal fabric, solution, density, cementation, neomorphism, pyritization, silicification, porosity, and dolomitization are of diagenesis processes in the mentioned formation (Figure 4).

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Table 1. Kangan and Dalan formations’ Subunits Reservoir quality Moderate to Low Low Low

Lithology

Thickness (m)

Sub unit

Rich calcareous grain facies and dolomitic to mudstone facies

14/6

K1c

16/4

K1b

38

K1a

A mixture of the dolomite and grain rich calcareous to mud rich facies Calcareous mudstone facies with low porosity

Reservoir unit

Formation name

K1 High

Dolomudstone and dolo grainstone facies with nodules and anhydrite layers.

30

K1a

Moderate To High

Grainstone or calcareous grain rich facies

19

K2d,c

10

K2b

25

K2a

High Moderate High High Moderate to Low Moderate to Low

Kangan Including calcareous grain rich facies and small amount of anhydrite nodules Calcareous grain rich facies Dolomitic mud to dominant grained facies Dolomitic mud rich facies to rich grain facies Dolomitic mud rich facies to grainstone facies

14 15 16

K3c K3b K3a

Dolomitic mudstone facies to grainstone facies

38

K4a,b

K2

K3 Dalan K4

Biological perturbation will determine the path of diagenesis; therefore, it is very useful in assessing the reservoir potential (Flugel, 2004) such that biological disturbance causes heterogeneity in sediments and thereby, creating porosity and permeability and ultimately, determining hydrocarbon migration path (Libelo et al., 1994). Biological perturbation is mostly seen in lagoon environment of at wackstones and packstones in both formations. Micritization is of the common diagenesis processes in both formations, which is mostly seen in allochems such as ooids and fossils. This process is common in reservoir rock lagoon facies. Geoptal fabric is a good indicator for determining the layer’s upper part. These structures record surface horizon at the time of sedimentation and in some cases, they show the initial slope. This fabric is rarely seen in the gastropods of Kangan Formation. Cementation includes processes which lead to the sedimentation of minerals in primary and secondary cavities and requires the supersaturation of pore fluids in relation with these minerals (Flugel, 2004). Solution process has been studied in the reservoir, especially in the grainstone facies. Allochem solution, and in particular ooids is accompanied by causing template porosity. In upper Dalan and Kangan formations, template and cavity porosities have been created due to solution in fresh water feriatic environments such that some of these porosities have been filled with anhydrite, calcareous, and horse saddle dolomite sediments. Silica diagenesis is in the form of chalsedony quartz crystals. The source of silica is generally calcareous rocks, sponge needle, diatoms, and radiolarians. This type of silica was rarely seen only in some parts of the upper Dalan Formation. Dolomitization in the reservoir rock is of the most important diagenesis processes. Based on petrographic studies, 5 types of dolomite (Adabi, 2009) have been identified including dolomicrite, dolomicroespare, dolospare, dolomitic cement, and horse saddle dolomite in Kangan Formation and 3 types of dolomite containing dolomicrite, dolospare, and dolomitic cement in upper Dalan Formation. 2.3. Facies and Sediment Environment Based on field observations and reviewing petrology and determining the percentage of each skeletal and non- skeletal elements, cement, and matrix at each microscopic section, 13 facies can be specified for Kangan Formation and 9 faceis can be specified for Dalan Formation (facies of the mentioned formations are similar; but Dalan Formation lacks argilic mudstone facies). 4 types of sedimentary environment of supratidal-intertidal zone, subtidal zone, lagoon, carbonate shoals have been detected and some openmarine in Kangan Formation. (Figures 5,6) as follows. It must be noted, however, naming different types of sedimentary contexts has been performed based on Dunham’s category (Dunham, 1962) and the specified microfacies have been compared with Flugel’s high ramp microfacies belts (Flugel, 2004). Based on studying microscopic facies and in comparison with standard facies (Flugel, 2004), two main sedimentation environments including the middle and inner ramp were considered for upper Dalan and Kangan formations. On the other hand, the lack of turbidite deposits and the extension of the tidal zone along with ooid barrier’ facies in the reservoir rock indicate the stability of carbonate platform of the isocline ramp(Figure 4).

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Fig. 4. Carbonate platform of the isocline ramp model for Dalan and Kangan formations in well No.3 of Lavan Gas field 2.4. The Evaluation of the Obtained Porosity and Permeability Using Laboratory Methods on Core Samples The most part of K4 and K1 reservoir units lacked reservoir quality. K1 subunit has the upper reservoir; but, reservoir unit K3 has better reservoir quality than K1’s; K2 reservoir unit has low thickness; but, it has the best reservoir quality in total. The evaluation of porosity and permeability around permo – Triassic boundary shows that there are grain stone facies with intracalst and ooid at the top of the upper Dalan formation.

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Fig. 5. A: Biological perturbations at mudstone facies; B: Micritization process in the Oolithic grainstone Facies; C: Geoptal fabric in a fossil gasteropoda; D: Marginal fiber Cement; E: Iso dimensional Calcite Cement Filled the Interior Space between the grains in an Oolithic grianstone; F: Micritization process in Ooids and bioclast elements in a bioclast grainstone facies.

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Fig. 6. A: Crystallized anhydrite facies with stretched anhydrite Crystals;(Needel shape) B: Dolomitid mudstone facies with anhydrite nodules; C: Mudstone facies with anhydrite Scattered Crystals; D: Mudstone facies with anhydrite scattered crystals (Anhydrites have been replaced by the Initial gypsum formats); E: Dolomudstone fenstral facies; F: Wackestone facies with iron particle. Table2. The Adaptation of reservoir zones, facies environment, and reservoir quality in different parts of the upper Dalan and Kangan reservoir units Reservoir Units

K1

K2

K3

K4

Reservoir Subunits

zone

K1d

Non Reservoir

K1c

Reservoir

K1b

Non Reservoir

Facies Shoal Lagoon Intertidal Lagoon Intertidal-Supratidal

K1a

Reservoir

Shoal Lagoon

Upper K2c

Non Reservoir

Shoal

K2b Lower K2c

Reservoir

Shoal Lagoon

K2a

Non Reservoir

K3c

Reservoir

K3b

Non Reservoir

K3a

Reservoir

Lagoon Lagoonal margin Lagoon Lagoon Leeward Shoal Lagoon

K4b

Reservoir

Lagoon

K4a

Non Reservoir

Lagoon Lagoonal margin

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Petrophysics (ReservoirQuality) Very Low Very Low to Low Very Low Intermediat Good to very Good Very Low to Low Intermediate Good to very Good Very Low Intermediate Very Low to Low Low-Intermediate Intermediate Good to very Good Very Low

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In the lower section of Kangan Formation, there are grainstone facies containing interaclast and Oncoid which show high energy conditions at the beginning of Triassic when sea water progresses; on the other hand, meteoric and widespread marine cementation in these facies have eliminated all primary porosities. Trombulite / stromatolitefacies have been placed on these facies without reservoir quality and calcareous lithology. In the following lines, towards higher parts of Kangan Formation, high energy deposition of the facies along with substantial mold porosity and higher reservoir quality are seen. 3. CONCLUSION Upper Dalan and Kangan formations are a carbonate – evaporate sequence. Kangan formation with its lower Triassic age includes two reservoir units of upper Kangan (K1) and lower Kangan (K2). Upper Dalan Formation which has the same age of upper Permian also includes the reservoir unit (K3,K4). The boundary between the upper Dalan and Kangan formations is as an uncertain boundary and an isocline disconformity such that Kangan Formation carbonates with the age of the middel Triassic have been placed on Dalan Formation carbonates with the age of jolfian(Wuchapingian). In the meantime, the lack of Durashamin epoch is characterized as the lack of a hiatus. The emergence of trumbolitefacies at the base of Kangan Formation implies the extinction above ermotriassie border. Based on paleontological studies in Dalan Formation, no fossil was identified regarding Durashamin epoch; therefore, the lack of Durashamin sediments is seen due to either the lack of sedimentation or erosion in the area. Regarding the expansion of the upper ooid ridges and sediment tidal zone and the lack of turbidite sediments and the gradual transformation of the facies, sedimentary environments of Kangan and upper Dalan formations have been considered as an isocline ramp. Reviewing the permotriassic boundary from the perspective of facies, diagenesis, and reservoir quality shows that Kangan Formation facies, after permotriassic borders, are of very low reservoir quality due to the precipitation of calcite cement, while at the top part and near the border, the upper Dalan Formation has a significant porosity and permeability in grainstone facies. REFERENCES 1. Adabi M.H., 2009. Multistage dolomitization of Upper Jurassic Mozduran Formation, Kopet- Dagh Basin N.E. Iran. Carbonates and Evaporites. P. 16-32. 2. Archie G. E., 1952, Classification of carbonate reservoir rocks and petrophysicalconsiderations: mericanAssociation of Petroleum-Geologists Bulletin, v. 36, p.278-298. 3. Bordenave M.L., 2002. Gas prospective areas in the Zagros Domain of Iran and in the Gulf Iranian waters, AAPG, 10p. 4. Bordenave M.L., 2008. The origin of permo- Triassic gas accumulation in the Iranian Zagros fold belt and contiguous offshore areas: A review of the Paleozoic Petroleum System. Journal of Petroleum Geology, 31(1): 3-42. 5. Dasdupta S. N., Hong, M. R., & Al- Jallal, I. A., 2001. Reservior characterization of Permian Khuff- C carbonate in the supergiant Ghawar Field of Saudi Arabia. T he leading Edge (July), 706-717. 6. Dunham R. J., 1962, Classification of carbonate Rock. (Ed. Eyw. E. Hamm). Mem, Am. Ass. Petrol. Geo, 1:pp. 108-121. 7. Flugel E., 2004, Microfacies of carbonate rocks: analysis, interpretation and application. 976p. Springer Verlag Berlin, Heidelberg, New York. 8. Gaillot J., 2006, The Late Permian- Early Triassic Khuff Formation in the Middel- East, sequence biostratigraphy and palaeoenvironments by means of calcarrous algae and foraminifers. 687 pp., Ph. D. University of Lille, 3 volumes. 9. Ghazban, Fm, 2007. Petrleum geology of the Persian Gluf. Thran University and National Iranian Oil Company Pub. 707p. 10. Ghavidel- Syooki, M., 1990. Palyological study of Milla, Illbeyk, Zard Kuh and Faraghan at Zard Kuh, Chal –I – shel areas and Darang well, No. 1 in Zagros Basin, southern Iran, NIOC Geol. Lab. Paleo. Rep. No.380 proc. Lst Intern. Symp. On diapirism with special reference to Iran1: 141-241. 11. Haynes S.J. & Mc Quillan H., 1974. Evolution of Zagros suture zone southern Iran. Geol. Soc. A m. B ulle. 84, 739-744. 12. Harrison J.V., 1930. The geology of some salt plugs in Laristan (southern Persian). Geol Soc. London Quart Jour., 86: 463-522. 13. Insalaco E., A. Virgone, B. Courme, J.Gaillot,M.Kamali, A. Moallemi, M. Lotfpour,and S. Monibi, 2006, Upper Dalan Member and Kangan Formation betweenthe Zagros Mountains and offshore Fars, Iran: Depositional system,biostratigraphy and stratigraphic architecture: GeoArabia, v. 11, p. 75-176. 14. Murris R.J., 1980. Middle East stratigraphic evolution and oil habitat. American Association of Petrolum Geologists Bulletine, 64: 597- 618. 15. Purser B.H., 1973. The Persian Gluf Holocen carbonate sedimentation and diagenesis a shallow apicontnental sea. Hedelberg, Berlin,SPRINGER- Velag Pub, 471p.

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16. Sephr M. & Cosgrove J.W.,2004. Structural framework of the Zagros Flod- T RUST Belt, Iran. Marine and Petroleum Geology,21: 829-843. 17. Szabo F. & Kheradpir A., 1978. Permian and Triassic Stratigraphy Zagros Basin, Southwest Iran. Jour. Pet. Geo., 1: 57-82. 18. Szabo F. & Kheradpir A. & Khalili M., 1977. Permian and Triassic study of Fars Northwest and adjacent areas. Report No. 1249, (unpub). 19. Sharland P., Archer D. & Casey R., 2001. Arabian Plate sequence stratighraphy. Blackwell, Oxford. 320p. 20. Stockline J., 1968. Structual history and tectonics of Iran; a review. AAPG Bulletin, 52(7): 1229-1258. 21. Tucker K. E., and R.G. Chalcraft, 1991, Cyclicity in the Permian Queen Formation-U.S.M. Queen Field, Pecos County, Texas, in A. J. Lomando, and P. M. Harris, eds., 5Mixed carbonatesiliciclasticsequen-ces: Tulsa, Oklahoma,Society of Economic Paleontologists and Mineralogists, p. 385-428. 22. Yahyaei I., Afrooz I., 2008. Geological complation Report “Lavan Well-03”, Report No-16,Iranian Offshore OilCompany, 68p. 23. Wignal P.B., 2005. Permian. In: Selly, R.C; Cocks, L.R. & Plimer, I.R, Encyclopedia of Geology, Elsevier Academic Press, 3345 p.

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