Figure-1-:- Location map of the studied wells along with oil fields

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1 The Organic Geochemistry of the Middle Euphrates Region (Kifl, West Kifl, Musaiyab, Morjan, Ekheither and Afaq, Oil Fields), Middle Iraq. Amer Jassim Al-Khafaji 1, and Thamer Al-Ameri 2 College of science for women, Babylon University. Hillah. amersalman42@yahoo.com College of science, Baghdad University. Baghdad. thamer_alameri@yahoo.com Abstract: Rock Eval pyrolysis, total organic carbon (TOC) analysis are carried on for the Upper Jurassic and the Cretaceous Formations of core samples from the Kifl, Morjan and Ekheither oil wells for dating and evaluation of the source rocks. Najmah_Sargelu Formation had generated quantity of oil hydrocarbons according their TOC weight percent of with S2 : mgHc/g rock, high hydrogen index of the range mg Hc/g Rock, good petroleum potential of mg Hc/g rock, mature,tmax : C ), kerogen type II, and palynofacies parameters of up to 100 amorphous organic matters with algae deposited in dysoxic anoxic to suboxic anoxic basin, while the rocks of Butmah Formation are mature with 438 C with high TOC,Kerogen type IV hence is not generated hydrocarbons. But, Hartha and Zubair formations could be considered as oil reservoir according their high porosity (15 23%) and permeability (20 45 md) carbonate and sandstone rocks with structural anticline closure trending NW-SE. That oil have generated and expelled during two phases; the first is during Early Palaeogene that accumulated in traps of the Cretaceous structural deformation, while the second is during Late Neogene. Keywords; Oil field. Middle Euphrates region. Kifl, Ekheither and Morjan. Organic geochemistry. Sargelu. Introduction:- Most of the petroleum in the studied area is sourced from cyclically bedded Jurassic shales and carbonates (Callovian-Oxfordian- Kimmeridgian ages) that accumulated in restricted intra-shelf Mesopotamian Basin. The Mesopotamian Basin formed on the passive margin platform of the Tethys sea after Triassic rifting. The richest source rocks in this basin occur primarily as condensed sections deposited in the early phase of transgressive cycles. Circulation was restricted, allowing for preservation of large quantities of organic matter, mostly algal, under periodically anoxic bottom conditions in the basin centers. Evaporitic facies formed the seal for the hydrocarbons that accumulated in the high-energy shoal deposits, charged from the organic-rich shale and mudstone in the basin center. In latest Jurassic (Tithonian age) the seas eventually became shallower and evaporation rates increased, resulting in precipitation of evaporites that covered the organic-rich source and reservoir facies.(rewrite this article and add the Bajocian Bathonian,because this period of Geologic time is very formative. Material and Methods: This article is based on 332 core and cutting samples from mainly shale and limestone of Jurassic Late Bathonian Early Callovian Sargelu Formation up to Lower Cretaceous Lower Cenomanian Maudud Formation from selected oil wells in Middle Euphrates area. Collected rock sample from Kifl-1, Kifl-4, Morjan-1 and Ekheither-1 oil fields in the studied area. (Figure:1). Determination of total organic carbon (TOC), Rock Eval pyrolysis for the kerogen type, and organic maturation were based on the same rock samples and analyzed in the laboratories of the National Iraqi Oil Exploration Company and Geomark Research. Ltd. in Houston, TX, USA. Geology, Structural and sedimentary history: Iraq is located in the northern Arabian Platform including the western edge of the Zagros Mountain range, where the convergent tectonic boundary between the Eurasian and Arabian plates forms a fold and thrust belt. Tectonics and geology of Iraq have been influenced by the proximity of the Pre-Cambrian Arabian Shield to the southwest and the Zagros Province of the Tethyan geosyncline to the east (Al-Naqib, 1967). The high Bitlis-Zagros Mountains in the north and eastern part of the country are a folded belt in a NW-SE direction along the western part of Iran and northeast Iraq. 1

2 2 Figure-1-:- Location map of the studied wells along with oil fields They extend from Oman in the southeast to the Turkish border in the northwest (Adams and Barazangi, 1984). The folding probably started during the Upper Miocene-Lower Pliocene, and the belt is still considered to be one of the most active orogeny on earth (Stocklin, 1968; Kassler, 1973). Iraq can be divided into three tectonic zones: the unfolded (stable platform), folded, and the thrust zones. These units were differentiated during the late Tertiary (mainly Pliocene) Alpine orogeny (Dunnington, 1958). The Mesopotamian foredeep covers an intermediate structural position between the Alpine geosynclinal area of Zagros in N-NE part of Iraq and the Pre- Cambrian African-Arabian platform to the west. This zone is characterized by a great subsidence since Mesozoic time until late Cenozoic with slight folding of sedimentary cover up to 9 km (Laske et al., 1997; Seber et al., 1997), became thinner to the west of studied area. (Figure:2). The beginning of the Jurassic was marked by the development of platform along the Tethys Ocean. Carbonate deposition, often reefal, dominated these parts and was contemporaneous with the deposition of clastics and evaporates elsewhere. For the greater part, the deposited facies are shallow water origin with occasional restricted environment. The Liassic-Doggerian subcycle which was part of the Upper Triassic-Middle Jurassic cycle. The cycle began throughout the country by transgression during the Upper Triassic which marks the beginning of basin development. The regional break or regression above the Middle Jurassic Sargelu Formation indicates the end of the cycle. (Buday, 1980).

3 Figure-2 :- Structural Cross-section in the studied area, toward the Western Desert. At the Early Jurassic time various newly formed and rapidly subsiding grabens and depressions within Mesopotamian basin, formed the sites for deposition of organically rich facies. Restricted anoxic conditions ideal for the accumulation and preservation of the organic matter were possibly widely developed. The Euphrates Graben received a thick sequence of paralic to shallow marine clastics. The variety of the Mesopotamian Basin shale, evaporate and carbonate facies were laid down. The Mus Formation carbonates were deposited over a much wider area than Butmah Formation, indicating a major transgression in the Toarcian. Alan anhydrite Formation were deposited at the end of the Early Jurassic. (James, et. al, 2002). The Late Jurassic movements, the whole of the western part of the Arabian Plate was uplifted and heavily eroded. Most parts of Iraq were exposed during Early Cretaceous times. The basinal area of the Neocomain times was surrounded by submerged platforms. In addition a number of intra-basin submerged highs were established in Iraq. During the initial phase of the Early Cretaceous times, the Neocomian transgression allowed widespread carbonate deposition (Sulaiy, Yamama, and Ratawi). (Van Bellen, 1959, 2005). Source Rocks Geochemistry: Oil-and gas-prone source rock is identified and an assessment is made of original hydrocarbon potential for mature source rocks. The number of genetically distinct oil families (sources) existing in the area is determined, as well as probable migration pathways, thermal maturity and type degree of alteration. Table-1-:- Rock-Eval Pyrolysis Data for 332 rock samples in Kifl-3, Kifl-4, Morjan-1, West Kifl, and Ekheither-1 oil wells, carried out at EOC Baghdad,and at GeoMark Co. USA. Summary of Rock-Pyrolysis Data Kifl-3 No Depth Formation TOC S1 S2 S3 S2/S3 HI OI PI PP Tmax Aliji Aliji Aliji Tayarat Shiranish Hartha Hartha Hartha Moatsi Nahr Umr Nahr Umr Nahr Umr Shuaiba

4 Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Yamama Yamama Yamama Yamama Yamama Yamama Yamama Yamama Yamama Gotnia Gotnia Gotnia Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Sargelu Sargelu Sargelu Sargelu Adaiyah Butmah Butmah Butmah Butmah Butmah Kurrachine

5 Summary of Rock-Pyrolysis Data kifl-4 No Depth Formation TOC S1 S2 S3 S2/S3 HI OI PI PP Tmax Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Tanuma Tanuma Tanuma

6 Tanuma Mishrif Ahmadi Maudud Maudud Maudud Maudud Maudud Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Shuiaba Shuiaba Zubair Ratawi Ratawi Ratawi Ratawi Ratawi Ratawi Ratawi Ratawi Ratawi Ratawi Yamama Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Sargelu Sargelu Sargelu

7 Sargelu Sargelu Sargelu Sargelu Sargelu Sargelu Sargelu Sargelu Sargelu Sargelu Summary of Rock-Pyrolysis Data Morjan-1 No Depth Formation TOC S1 S2 S3 S2/S3 HI OI PI PP Tmax Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Aaliji Shiranish Shiranish Shiranish Shiranish Shiranish Shiranish Shiranish Shiranish Hartha Hartha Hartha Hartha Hartha Hartha Hartha Hartha Hartha Sadi Sadi Sadi Sadi Sadi Sadi Khasib Kifl Mishrif Nahr Umr Nahr Umr

8 Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Zubair Sulaiy Sulaiy Sulaiy Sulaiy

9 Gotnia Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Najmah Sargelu Sargelu Sargelu Sargelu Sargelu Summary of Rock-Pyrolysis Data Ekheither-1 No Depth Formation TOC S1 S2 S3 S2/S3 HI OI PI PP Tmax Shiranish Shiranish Shiranish Shiranish Shiranish Shiranish Shiranish Shiranish Shiranish Shiranish Shiranish Shiranish Hartha Hartha Hartha Hartha Hartha Hartha Hartha

10 Hartha Hartha Mishrif Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Nahr Umr Jurassic source rocks: Middle Jurassic source rocks are very important source rocks throughout South, Northeast and North Iraq due to the high TOC of the Sargelu and Najmah-Naokelekan formations that were deposited throughout the Jurassic basin. (Pitman, 2004, Al Ahmed,2006) concluded that most of the oil of Iraq was sourced from Jurassic source rocks. Lower to middle Jurassic source rocks are identified in the Butmah and Sargelu Formation of Iraq and in neighboring countries. Lower to Middle Jurassic is organically rich on a regional basis and several large and small depressions together formed a large, intermittently sidled basin during Jurassic times. Thickness and facies variations of the deposited organically-rich sediments in the Mesopotamian basin are expected because of its irregular bottom relief. Source rock richness gradually deteriorates towards northwestern and southwestern Iraq. ( Dunnington, 1958). Maturity evolution of the organically-rich Lower-Middle source rocks suggests widespread commercial oil and only local gas/condensate generation. Alan, Mus, Adaiyah and Butmah Formations: The Butmah Formation is expected to be organically-rich, but the most significant source rock intervals are to be found within the widespread Sargelu Formation. The drilled wells reached the Butmah Formation only in West Kifl -1and kifl-3. Its thickness is 460 m, 404m respectively. (Jassim, et. al, 2006). The total organic matters (TOC) content is 0.93 wt%, as an average. The kerogen type for organic matters in the formation are type IV kerogen type. Butmah Formation source rock became almost mature within the area study, Tmax reach up to 435 C in Kifl-3 oil field, and increase towards West Kifl-1. The lithofacies and faunal assemblage indicate the Butmah Formation was deposited in shallow water lagoonal and sabkha environment, so that the organic matter was not well preserved. A according to pyrolysis analysis, S2 is between was 1.0 to 1.4 in samples which were taken from Kifl-3, HI varies from (13 to 119) mghc/g TOC, and PI about 2.7, table -1 and figures (5,6 and 7). Several thin intervals within the Alan, Mus, Adaiyah and Butmah Formations are expected to be organically-rich, table - 1. In large parts of the Mesopotamian Basin, the Sargelu facies are excellent source rocks with TOC values varying between 1.5 and 17.5 wt%,( Al-Ahmed, 2006), and the dominate organic matter is algae amorphous debris. Sargelu Formation source rocks: The Sargelu Formation is the most important source rock in Iraq. It has gained special importance, as the best source rocks in Iraq, because it contains a high proportion of organic matters in sediments and it entered the stage of thermal maturity, in most parts of Iraq, except the western region. Upper Jurassic source rocks became almost mature. Oil migrated from the central part of Mesopotamia towards the Euphrates River and from the foothill towards the central Mesopotamian basin. Calculated maturity indicates that the Formation is mostly immature to early mature within the Salman zone. In western Mesopotamian the source 11

11 Figure3 : Plot of whole rock HI vs. OI showing various hydrocarbon-generative types. Peters, (1986), modified from VanKerevlen. Figure 4: Production index with maturity, sheet from GeoMark Co.Inst. Figure 5: Tmax with hydrogen index. Peters, (1986), 11

12 rocks are mid mature to late mature, gas window is observed, in the Eastern Mesopotamian basin Zone. (Pitman, 2004, Al-Ahmed, 2006). The total organic matter (TOC) values content of wt % as average is found in Kifl-3 oil well, 1.8 wt %, 0.8 wt% as an average in Kifl-4, Morjan -1 oil wells, respectively, (recent study), with 0.6wt% the total organic matters in West Kifl-1 oil well section,( EOC). According to tables (2-1 and 2-2 ), the amount of organic matters in Kifl area is good. Kerogen type in Kifl-3 oil well was type III oil and gas prone, type II and III in Kifl-4 prone oil, and kerogen type II in Morjan oil well which prone oil. (Figure 6), and table-1. The initial HI potential of Sargelu Formation was defined as 600 mg HC/g TOC based on the averge composition of kerogen in the source rocks. The present HI values in this formation range from less than 100 to more than 600 mghc/g TOC. Thermal maturity for Sargelu Formation in Kifl area, is as follows: the Tmax was from 425 to 429 in Kifl- 3 oil field, from 427 to 449 in Kifl-4, and 432 to 434 in Morjan oil well. So that the formation was immature to early mature in Kifl-3and to early mature in Morjan area and early mature to peak mature in Kifl-4 oil well. It`s prone oil because it was within the oil zone. The restricted outer shelf and basinal Sargelu formation contains a proportion of fair to good organic matter deposited in basinal euxinic marine environment, kerogen type II to II/III, the Formation almost mature, it has good quality as a source of hydrocarbons, and probably generate most of the oil in the area, which filled the reservoir formation after expulsion and migration. The maturation, and the petroleum potential (PP),and (S2) increase towards to the east towards the edge of the Mesopotamian basin. (Figures: 3,4,5 and 6) Najmah Formation source rock: The palaogeography during the Late Jurassic is controlled by the effects of Late Jurassic tectonic activity along the Arabian Plate margin prior to the opening of the southern Neo-Tethys. The inner shelf is represented by Najmah and Gotnia formations. It represents the calcareous neritic and lagoonal facies of the Late Jurassic. (Dunnigton, 1959). The Najmah Formation is important source rock in Iraq with its equivalent Noakelekan Formation. It has gained special importance, as the best source rocks with Sargelu Formation in Iraq, because it contains a high proportion of organic matters in sediments and has entered the stage of thermal maturity, in most parts of Iraq and has broad regional distribution covering most parts of Iraq with its equivalent Noakelekan Formation in the south of Iraq, except the western region. In term of geochemical, Sargelu and Najmah Formations are one geological unit, because they hold the similar geochemical properties and are successive in geological age. Table (1). The total organic matters (TOC): In Kifl-3 oil well was from 0.6 to 6wt%, a average was In Kifl-4 was 0.8wt% as average. 6.5 wt% was the average of TOC, from 0.5 to 6.7 wt%, in Morjan oil well section. Kerogen type: According to figures 7,8,9 and 10), and table 1, the kerogen type of Najmah Formation in Kifl-3 oil well section was kerogen type II, while it was kerogen type II and I for the formation in Kifl-4 and Morjan-1 oil well sections. The maturity of Najmah Formation was early to peak maturity in the area of study. Najmah Formation source potential quality is from fair to excellent because of the entireness of the formation in maturity range, II and I kerogen type, HI>500 mg HC/mg TOC, high TOC. Figures ( 5,6,7 and 8). Cretaceous source rocks: Cretaceous and Tertiary rocks are the principal reservoirs containing oil derived from Jurassic source rocks. Cretaceous reservoirs account for 76% of the petroleum reservoirs in the southern part of Mesopotamian Basin, and most of these reservoirs are at depth greater than 3 km. (Al- Gailani, 2003). 12

13 Fair quantities of land derived organic matter reached the depositional area of central and southern Iraq by multiple rivers of flood wadis from western Iraq. High proportion of the humic facies of several shaly intervals is evident during deposition of the clastic facies of the Zubair Formation. Shale of the Lower Cretaceous Yamama/ Sulaiy Formation are strongly sapropelic accumulations and represent good oil sources. Ratawi Formation in south Iraq comprises neritic shale and marl, these sediments contain oil prone sapropelic debris, Similar facies intermingled with humic or land-derived organic matter, prevail in the shallow marine to deltaic shales of Zubair Formation of central and southern Iraq. Zubair Formation consists of alternating porous and permeable sandstone beds and black, organically-rich shale beds, thus in situ oil generation and accumulation are possible. The Lower Albian Nahr Umr Formation contains several thick, organically-rich oil and gas prone shale in central and south Iraq. The Cenomanian Rumaila and Mishrif Formations, were founded to be partly organically-rich and classified as containing good quality oil-prone source rocks. Thus the source rock intervals provide seal and source potentials in the most parts of southern Iraq. (Jassim, et. al, 2006).Most of the Cretaceous source samples in studied area were immature. Chia Gara Formation: The Formation comprises, in Musaiyab-1 oil well, buff, dense marly limestone locally dolomitic, interbedded with black pyrite sandy shale, and black calcareous shale locally sandy, medium to fine Figure 6: Stratigraphic column of Kifl Oil Field with hydrocarbon generation parameters. 13

14 cemented by dolomite. Irregularly stained by dark, heavy oil at depth from 3367 to 3538m. The Formation was deposited in deep-water normal-marine environment. The Chia Gara Formation of Tithonian-Berriaisian age, has a TOC content of up to 6.91 wt%, it is the very good source rock in central and northern Iraq. (Al-Ameri, 2005). Yamama/Sulaiy Formation: The Sulaiy Formation was combined with the overlying Yamama Formation because of the difficulty of selecting a contact in the fairly continuous, neritic, pellital limestone sequence. The Mesopotamian Zone witnessed repeated open marine incursion leading to deposition of alternating shallow water carbonates and outer shelf. (Buday,1986). TOC in Morjan-1 oil well, clarified to be 0.5%wt to 1%wt for Sulaiy Formation. The TOC for Yamama Formation as average were, 0.91, and 0.86, in Kifl-3 and Kifl-4 oil wells sections. Kerogen type for Sulaiy Formation in Morjan-1, is type I, and type, and type II in the others oil wells Maturity; of the Sulaiy Formation is gradually ranges from immature to early mature, and Yamama Formation was immature, in the area of study. The lower part of Sulaiy was deposited in oceanic anoxic environment, that gave it good qualities to generate oil, and because of the small thickness, and thus the thin active thickness, and the fact that the formation was at the beginning of thermal maturity to immature, it is therefore likely to born small amount of oil. The Formation may generate some oil according to its maturity. Figures( 3,4,5 and 6). Conclusion:- According to geochemical analysis, including Pyrolysis, TOC, the Najmah/ Sargelu were the main source rocks with TOC reached to 17.5 wt%, with peak to moderate maturity and Kerogen type II, oil prone. The Nahr Umr, Zubair, Yamama, Sulaiy, Adiayah,and Butmah Formation might be regarded as source rock The maturity- at the beginning of mature to the immature, while, increasing maturity of source rocks to the east, for this, it is likely that most of the oils in the region, migrated from the deep basin at the east towards the study area. In Mesopotamian Basin, migration during and after the late Miocene was directed to the west and southwest, where the traps received an initial petroleum charge during this time too. At present day, there is a systematic decrease in thermal maturity from east to west across the region of studied area. too. At present day, there is a systematic decrease in thermal maturity from east to west across the region of studied area. References Al-Ahmed,Ahmead Askar (2006) Organic geochemistry, Palaenofacies, and hydrocarbon potential of Sargelu Formation (Middle Jurassic), northern Iraq. PhD thesis (unpublished), Baghdad University. Ayres, M.G., Bilal, M., Jones, R.W., Slentz, L.W., Tartir, M., and Wilson, A.O.,( 1982), Hydrocarbon habitat in main producing areas, Saudi Arabia: American Association of Petroleum Geologists Bulletin, v. 66, no. 1, p Bordenare M.L., ( 1993 ) ;Applied petroleum Geochemistry, Editions Technip,Paris, 534 p. Buday, T. and Jassim, S. Z., The regional geology of Iraq. Publication of GEOSURV, Baghdad. Chatton, M., and Hart, (1960);Revision of the Tithonian to Alpine Stratigraphy of Iraq I.P. C. Report. INOC. Baghdad. Dunnington, H.V., (1958) ; Mesozoic ( cretaceous ). In : Van Bellen, C., Dunnington, H.V., Wetzel R. and Norton D.M., Lexique Stratigraphique international, Asie, Vol.3,Fasc. 10a Iraq. Paris. 333P. James E. Fox And Thomas S. Ahlbrandt. (2002): Petroleum Geology and Total Petroleum Systems of the Widyan Basin and Interior Platform of Saudi Arabia and Iraq. U.S. Geological Survey Bulletin 2202 E. 14

15 Peters, K.E.,(1986); Guide lines for evaluating petroleum source rocks using programmed pyrolysis;aapgbull,v.70pp-318_329. Pitman, J. K., Steinshouer, D. and Lewan, M. D., Petroleum generation and migration in the Mesopotamian basin and Zagross fold belt of Iraq: results from basin modeling study. GeoArabia, 9, 4, p Saad Z. Jassim and Jeremy C. Goff, 2006, Geology of Iraq. Prague and Moravian Museum, Brno, 341p. Van Bellen, R.C., H.V. Dunnington, R. Wetzel, and D.M. Morton Lexique Stratigraphique International Asie, (Iraq), 333 pages. Reprinted by permission of CNRS by Gulf PetroLink, 15