Sequence Stratigraphy and Depositional Environment of the Zubair Formation in Rumaila Oilfields, Southern Iraq: Microfacies and Geochemistry (original) (raw)
Related papers
The Petroleum System of Zubair Formation in Selected Oil fields- Southern Iraq Supervised by
2012
The Lower Cretaceous Zubair Formation is the most important reservoir in south of Iraq and adjacent countries, as well as the shale intervals may be the possible source rock. The main parameters of the possible source rock within Zubair Formation are satisfying, in terms of quantity, quality, and thermal maturity. Thirty eight samples (15 cores 23 cuttings) are analyzed to determine the pyrolysis parameters in addition to the inverted data from The Oil Exploration Company and South Oil Company in Iraq, as well as nine rock samples (6 core and 3 cuttings) are introduced to GC/MS analysis. On the other hand, six oil samples have been analyzed to determine the carbon isotopes, biomarkers, composition and correlation. Quantitative analysis is done with Gas Charmotagraphy/Mass Spectrometry (GC/MS). All these data are mainly obtained from Nassiriah, Gharraf, Rafidain oil fields in Euphrates Subzone, as well as from Rumaila North, Rumaila South, Zubair, and West Qurna oil fields in Zubair Subzone. Early-peak oil generation has been indicated from the vitrinite reflectance (Ro) to the chosen samples in the Zubair Subzone (Ro range 0.5-0.7%), while in Euphrates Subzone, the maturity is indicated as immature-early oil generation due to shallow depths of Zubair Formation, as well as the terrestrial supply of organic matters . On the other hand, the optical investigation revealed that the formation is within the mature zone dependent of the thermal alteration and spores color indices. From the total organic carbon (TOC) values point of view, shale intervals within Zubair Formation are generally good to excellent as source rocks, except in the lower parts, namely the Lower Shale Member in Zubair Subzone, which has fair amounts of the total carbon content. While the kerogen types are mainly type III gas - oil prone, mix type II/III oil-gas prone, and type II oil prone, which the later concentrated in the upper and lower sandstone members. The dominant type of organic matters was the amorphous organic matters (AOM), which is principally related to oil prone source rock. The Rock-Eval Pyrolysis shows that the organic geochemical properties presented an effective and/or potential source rock depending on the values of S1, S2, and S3 and their derivatives. This source rock has started the oil expulsion, where the S1/TOC values were mainly more than 0.2 mgHC / gTOC. The source related biomarkers suggested that the reservoir oils of Zubair Formation and the source rock extracted oils indicate the same origin, depositional environment, sulfur content, and maturity level. The depositional environment of the source rock is indicated as the anoxic, shallow marine offshore facies of the prodelta shale intervals, which is located within the multistory sand bodies. The modeling explains that the Zubair Formation, wholly, has been entered the onset, partially, the peak, and rarely the end of oil generation in the studied Subzones. This conclusion depends on the calculated temperatures, geothermal gradients, and vitrinite reflectance calibration. Hence the migration pathway has been estimated to be primarily, the highly permeable and porous reservoir carrier beds, which allowed the oils to migrate horizontally up dip into the west, northwest, and southwest of the Mesopotamian zone, and secondarily Tachadid-Al-Qurna fault, which may allow the oils to move east-west in all directions. The reservoir rock within the multistory sand bodies had well properties in terms of porosity and permeability. The porosity ranges 18-30%, and the permeability ranges 100-1000md. The seal rock in the upper and lower parts of the formation is precisely efficient, which contain high mud content with low permeability sometimes approximately up to zero value.
Stratigraphic Analysis of the Nahr Umr Formation in the Luhais Oil Field, South Iraq
Iraqi Geological Journal
The Nahr Umr Formation, which is Albian-Early Turonian in age, was investigated in the Nahr Umr Formation succession at two wells of the Luhais oil field in southern Iraq. The study defined sedimentary facies, types, and distribution of porosity and their relationship to sedimentary facies, as well as different types of diagenetic processes. It also included the distribution of facies in the Nahr Umr Formation in relation to suggested depositional settings. Thin sections of the cores from the two chosen boreholes (Lu 39 and Lu 43) in the Luhais Oil Field were used to study the petrography and lithofacies of the Nahr Umr Formation. The five fundamental facies identified in this study are poorly and well-sorted, quartz arenite sandstone, in additional to clayey sandstone poorly sorted, sandy shale, and shale, it represented many sub-environments present in the delta plain depositional environment, the distributary channel depositional environment, and the delta front depositional envi...
The Petroleum System of Zubair Formation in Zubair Subzone, Southern Iraq
2020
The Lower Cretaceous Zubair Formation is the most important reservoir in the south of Iraq and adjacent countries, as well as the shale intervals, may be the possible source rock. The parameters of the possible source rock within Zubair Formation are accepted, regarding quantity, quality, and thermal maturity. From the total organic carbon values standpoint, shale intervals of Zubair Formation are generally good source rocks, except in the lower parts. While the kerogen types are generally type III gas-oil prone, mix type II/III, and type II oil-prone. The main type of organic matters was amorphous organic matters, which is principally related to oil-prone source rock. The Rock-Eval Pyrolysis shows that the organic geochemical properties presented an effective and/or potential source rock depending on the values of S1, S2, and S3 and their derivatives. The source rock has started the oil expulsion, where the S1/TOC values were mainly more than 0.2 mg HC / g TOC. The modelling explains that the Zubair Formation, wholly, has been entered the onset, partially, the peak, and rarely the end of oil generation in the studied Subzones. This conclusion depends on the calculated temperatures, geothermal gradients, and Vitrinite reflectance calibration.
Bulletin of the Geological Society of Malaysia
The carbonate platform is the environment of Khasib, Tanuma and Sa’di formations which were deposited within open shelf settings at the Majnoon oil field in eight microfacies. The deposition, based on the analysis of microfacies, took place within shallow open marine, shoal environment, deep marine and basin environments. Five third order cycles of succession consist in MJ-12 oil well and three third order cycles in the MJ-15 oil well. They represent successive episodes of sea level rise and standstills. The succession in the study area was formed in a high subsidence environment, reflecting the high subsidence as the main controlling factor in the sequence creation. Because of a significant transgression, the Khasib, Tanuma, and Sa’di formations were deposited on an extremely subsidential carbonate base, where sea level succession involved episodes of rise and standstills.
— The Carbonate-Clastic succession in this study is represented by the Nahr Uamr and Mauddud Formations deposited during the Albian Sequence. This study includes facies analysis and stratigraphic development for this succession in 5 boreholes within Nasiriyah oil field. There are several types of microfacies were recognized in the succession of the Mauddud Formation. Their characteristic grain types and depositional texture enabled the recognition of six facies associations (depositional environments) were distinguished in the Mauddud Formation, they are: shallow open marine, restricted, reef, slope, deep open marine and basinal. Two types of rocks are observed within the Nahr Umr Formation; the first is the upper part which characterized by shale dominated rocks and the second (lower part) is characterized by sand dominated rocks. Four facies associations (depositional environments) were distinguished in the Nahr Umr Formation, they are: delta plain, prodelta, bay fill, and distributary channels. The microfacies analysis and reconstructed the paleoenvironments of the Albain basin in the studied area; there are three stages of the deposition:-during the first stage the sea level was rise which led to progress prodelta facies (retrogradation) and onlapping the unconformity. This part is represented by TST stage in all studied boreholes. The prodelta facies was changed to distributary channel facies up-wared to mark the mfs between these two facies. This refers to deposition during the high stand period as two cycles. The sea level was reactivated to progress after the last step of Nahr Umr deposition, to start the Mauddud Formation deposition. At second stage the facies change was shown three steps of the sea level rise (TST) to deposition the restricted, reef-back reef and shallow open marine/slope. Overlying the slope facies to the shallow marine and then deposited the shallow marine refer to maximum flooding surfaces after deposition the last ones. Therefore, the shallowing upward succession which deposition later was represented the high stand stage (HST). The final stage is represented by reactivated the sea level rise to deposition the basinal facies within the Mauddud Formation. The continued rise in sea level during the period of transgression (TST) is a preparation for the Ahmadi basin, which is characterized by deposition in a deep environment and conformable lower contact with the Mauddud Formation. Keywords— Petrophysical Properties, Reservoir development, Albian Succession and Nasiriyah Oil Field.
Iraqi journal of science, 2022
The Shiranish Formation is cropped out in several areas in northern Iraq. A stratigraphic and facies study was conducted within the Duhok region to determine the sedimentary environment. Three microfacies, reflecting the various subenvironments within different shelf parts of the deep sea, have been identified within the Shiranish Formation. Four depositional environments are identified: slope, the toe of slope, deep shelf, and deep-sea or cratonic deep basin. The Shiranish Formation in the Duhok region, Northern Iraq, was deposited in an open shelf carbonate platform. The Shiranish Formation sequence is divided into six third-order cycles in the study area. These asymmetrical cycles reflect an imbalance between the relative level of the sea and the production of carbonate, and each one reflects a rise in the sea level following a period of standstill. There is a twosequence boundary type SB-2 that defines the surface. The Shiranish sequence developed in a high-subsidence area that played the main role in the evolution of the formation. It was deposited on a carbonate platform with high subsidence due to major transgression, wherever the successive sea-level rise and stillstand episodes persist.
Geochemical Study for the Upper Shale Member - Zubair Formation in Rumaila Oilfield, South Iraq
International journal of mining science, 2018
Geochemical study considered as Important means to solve some mystery which accompanied sedimentation process through distribution study major element content as well secondary element distribution whereas those element reflect affecting environmental conditions in type of original sediments, sedimentation speed and digenetic process that occur on sediments after compaction , so attempt of find relation between the geochemical datum relationship with digenetic process it possible to reflect depositional conditions. Classic sediments chemical composition is the net results of a number of geological factors, these comprise , source rocks, the rate of sediments supply, the intensity of their chemical weathering and sorting (both textural and mineralogical) through transportation and deposition. This is first geochemical study of Zubair formation-Upper shale member in Rumaila oilfield. Ten subsurface samples were collected from two wells in south and north Rumaila oilfield at depth (3145-3281) m. These samples were distribution for five samples in south Rumaila (RS) and five samples in north Rumaila oilfield(RN) covered almost Upper shale member from (USM20 to USM65). The main aim of this study is to understand the geochemical nature of the sediment by determine the major oxides for the sediments (Al₂Oᴣ, SiO₂, CaO, Fe₂Oᴣ, MgO, K₂O, TiO₂ and SO3), with special focus to the chemical behaviour of the trace elements
Facies and depositional environments of the Devonian–Carboniferous succession of Iraq
Geological Journal, 2008
Facies associations and depositional environments of the Late Devonian-Early Carboniferous succession in Iraq have been studied in several boreholes from north and northwestern Iraq. The >400 m-thick succession comprises the Kaista, Ora, Harur and Raha formations which are composed generally of mixed siliciclastic-carbonate facies. The Kaista Formation consists of sandstones intercalated with siltstones and calcareous shale that were deposited in a mixed fluvial-marine environment. The Ora Formation is composed dominantly of black shale with subordinate sandstone and dolomite deposited in a shallow-marine, sub-tidal shelf environment. The Harur Formation is composed mainly of dolomite with subordinate shale and was deposited in a deep sub-tidal environment. The Raha Formation consists mainly of marine shales intercalated with sandstones and concluded the Kaskaskia megasequence. The depositional setting is considered as a subsiding basin with a wide geographic distribution. It extended from the Ora region in the extreme north of Iraq to west and southwestern Iraq and reflects an epicontinental or epeiric sea setting on a homoclinal ramp inclined to the southeast. devonian-carboniferous facies analysis, iraq 387 Figure 4. (A) Isopach map showing the facies distribution and thicknesses of the Kaista Formation in northwestern Iraq. The formation is dominated by sandstones with a few shales and carbonates. (B) Isopach map showing the facies distribution and thicknesses of the Ora Formation in northwestern Iraq. The formation consists predominantly of marine shales with minor carbonates, and towards Syria it becomes dominated by sandstones. (C) Isopach map showing the facies distribution and thicknesses of the Harur Formation in northwestern Iraq. The formation consists predominantly of shallow marine carbonates.
Petrology and depositional evolution of the Paleozoic rocks of Iraq
Marine and Petroleum Geology, 2009
The study integrates petrographical and lithological data from deep exploration wells and outcrops in northern Iraq to better understand the sedimentary environments present in the basin and to evaluate the depositional evolution of the Paleozoic rocks in Iraq. The studied Paleozoic successions are represented by five sedimentary cycles of intracratonic sequences. These are dominated mainly by siliciclastic and mixed sedimentary packages, and are separated by major and minor unconformity surfaces.
Microfacies and Depositional Environment of Mishrif Formation, North Rumaila Oilfield, Southren Iraq
International Journal of Mining Science, 2019
Mishrif Formation is the most significant carbonate reservoir unit in Iraq, it includes up to 30% of total Iraqi oil reserves (Aqrawi et al., 2010). The formation is composed of thick carbonates of middle Cenomanianearly Turonian age (Chatton and Hart, 1961), that deposited on a basin-wide shallow water platform, accommodation space was supplied by a major eustatic seal-level rise in the middle Cenomanian (Haq et al., 1987; Gale et al., 2008). The Mishrif and underlying Rumaila formations were originally described in southern Iraq in well Zb-3 in Zubair oilfield (Aqrawi et al., 2010). The contact between the Mishrif and Rumaila Formations is gradational, the Mishrif Formation is unconformably overlain by the Khasib Formation (Aqrawi 1995). The microfacies of Mishrif Formation were classified based on Folk's (1962) and Dunham's (1962), adjusted by Embry and Klovan (1972) and revised by Wright (1992), this classification is depending on the mud-or grainsupported textural types. 1.1. Study Area North Rumaila oilfield is a giant oil field located in southern Iraq which is approximately 32 Km from Kuwait border and about 50 kilometer west of Basra city, between coordinate 47°16'46''-47°26'14'' Easting and 38°28'34''-38°42'30.8'' Northing. The longitudinal axis of the North Rumaila oilfield is 30 km, while the width is 20 km. It is covered an area about 600 km 2. Zubair, Tuba oilfields located at the east, while West Qurna oilfield located at the north and Ratawi oil field in the west of North Rumaila oilfield, it is consists of subsurface anticlines which are trending N-S (Karim, 1992), it is separated by saddle form south Rumaila oilfield subsurface anticlines (Fig. 1).