Programed oil generation of the Zubair Formation, Southern Iraq oil fields: results from Petromod software modeling and geochemical analysis

1D petroleum system modeling was performed on wells in each of four oil fields in South Iraq, Zubair (well Zb-47), Nahr Umr (well NR-9), West Qurna (well WQ-15 and 23), and Majnoon (well Mj-8). In each of these fields, deposition of the Zubair Formation was followed by continuous burial, reaching maximum temperatures of 100°C (equivalent to 0.70%Ro) at depths of 3,344–3,750 m of well Zb-47 and 3,081.5–3,420 m of well WQ-15, 120°C (equivalent to 0.78%Ro) at depths of 3,353–3,645 m of well NR-9, and 3,391–3,691.5 m of well Mj-8. Generation of petroleum in the Zubair Formation began in the late Tertiary, 10 million years ago. At present day, modeled transformation ratios (TR) indicate that 65% TR of its generation potential has been reached in well Zb-47, 75% TR in well NR-9 and 55-85% TR in West Qurna oil field (wells WQ-15 and WQ-23) and up to 95% TR in well Mj-8, In contrast, younger source rocks are immature to early mature (<20% TR), whereas older source rocks are mature to overmature (100% TR). Comparison of these basin modeling results, in Basrah region, are performed with Kifle oil field in Hilla region of western Euphrates River whereas the Zubair Formation is immature within temperature range of 65–70°C (0.50%Ro equivalent) with up to 12% (TR?=?12%) hydrocarbon generation efficiency and hence poor generation could be assessed in this last location. The Zubair Formation was deposited in a deltaic environment and consists of interbedded shales and porous and permeable sandstones. In Basrah region, the shales have total organic carbon of 0.5–7.0 wt%, Tmax 430–470°C and hydrogen indices of up to 466 with S2?=?0.4–9.4 of kerogen type II & III and petroleum potential of 0.4–9.98 of good hydrocarbon generation, which is consistent with 55–95% hydrocarbon efficiency. These generated hydrocarbons had charged (in part) the Cretaceous and Tertiary reservoirs, especially the Zubair Formation itself, in the traps formed by Alpine collision that closed the Tethys Ocean between Arabian and Euracian Plates and developed folds in Mesopotamian Basin 15–10 million years ago. These traps are mainly stratigraphic facies of sandstones with the shale that formed during the deposition of the Zubair Formation in transgression and regression phases within the main structural folds of the Zubair, Nahr Umr, West Qurna and Majnoon Oil fields. Oil biomarkers of the Zubair Formation Reservoirs are showing source affinity with mixed oil from the Upper Jurassic and Lower Cretaceous strata, including Zubair Formation organic matters, based on presentation of GC and GC-MS results on diagrams of global petroleum systems.     

Salinity mapping model and brine chemistry of Mishrif reservoir in Basrah oilfields,Southern Iraq

Cation and anion concentrations and boron isotopic ratio of brines in the Mishrif Formation (U. Campanian-Tuoronian) from North Rumaila, South Rumaila, Majnoon, Zubair, and West Qurna oilfields southern Iraq were investigated. The aims of this study are to define the type, origin of the oilfield waters, and its flow model in the subsurface oil traps. Mishrif brines are characterized by having higher concentrations of sodium (50,500–84,200 ppm), chlorine (102,100–161,500 ppm), and boron (21.9–31.1 ppm) with lower sulfate contents (187–1350 ppm) relative to the modern seawater. Samples have slightly depleted in δ ¹¹B (35.4‰) relative to seawater fall near the seawater intrusion of the diagram Cl/Br Vs δ ¹¹B and occupied the field of evaporated seawater on the diagrams of Cl vs B and 1/Br vs δ ¹¹B. The brine of Na-chloride type is characteristics of the Mishrif reservoir in all oilfields except WQ which defined by facies of Na-Ca-chloride type. A weak acidic brine of a salinity six-time greater than seawater plays a role in generating the formation pressure and controlling the fluid flow. The reservoir rock-fluid interactions were interpreted using boron isotopes which eventually reveal an ongoing dilution process by the present seawater intrusion and injection water used for the secondary production under conditions of high-temperature digenetic reactions. The ¹¹B in the oilfield water is resulted from uptake of the tetrahedral borate after precipitation of calcium carbonate, while ¹⁰B is sourced from the thermal maturation of organic matters.     

Evaluation of groundwater quality in the Dibdibba aquifer using hydrogeochemical and isotope techniques (Basrah Province,Iraq)

Acta Geochimica - The Dibdibba aquifer is considered to be the main source in the Al-Zubair area because agriculture depends on it to provide grazing water in the area. The groundwater well samples...     

Geochemistry of sediments of the Al-Batin alluvial fan,Southern Iraq

The Al-Batin alluvial fan covers a broad area of southern Iraq. It was the main battlefield of two devastating wars in 1991 and 2003, during which huge amounts of depleted uranium (DU) were used. This study aims to assess the geochemistry of this fan sediment including the potential effects of the DU used. Sixty-three samples were collected from sediments including three samples from sediments under tanks attacked by DU ammunition. Major elements were measured by XRF (fusion bead method), whereas ICP-MS was used to measure the trace elements. The results suggest that the most dominant major minerals are in the order of: quartz?>?secondary gypsum?>?calcite?>?feldspar, clay minerals?>?iron oxide, and show abnormal concentrations of Sr, Cr, Ni, and V. This study also determined an area with high concentration of U in the north east part of the fan. Statistical analysis and spatial distribution of important elements suggests that two major factors affect mineral formation. The first factor reflects the influence of minerals in the source area of the sediments (Arabian Shield): quartz, carbonate, clay minerals, feldspars, as well as iron oxides and elevated concentrations of V, Ni, and Cr. The second factor points at authigenic formation of secondary gypsum and celestite and elevated U concentration under the control of a hot arid climate and the specific groundwater situation. However, the origin of the sediments is geogenic, while the anthropogenic impact seems to be minor. Spatial distribution of U and the ^235/238U ratio did not show any peaks in the places where tanks have been destroyed. This is contrary to media speculations and some scientific reports about the permanent risks of DU in the area, which creates public concern about the potential risk of living in this area.     

Surpac软件在三维地质建模中的应用

介绍了Surpac软件在数字矿山地质建模上的应用.以某矿山为例,根据矿区的原始资料,利用Surpac软件,建立了矿区数据库、实体模型、块体模型,清晰直观地反映了矿体的空间分布特征.研究涵盖了特异（高）值的分析与处理,块体属性的建立及其大小参数等的确定,矿体模型、岩性模型等在指导矿山工程布置上的运用等方面.最后,着重比较了Surpac与传统方法的储量计算结果,数据表明Surpac模型可靠,计算正确,可用于资源评估、资源动态管理、采矿设计及计划编制等工作.     

Cretaceous petroleum system of the Khasib and Tannuma oil reservoir, East Baghdad oil field, Iraq

Gas chromatography, palynomorph constituents, and maturation are analyzed for oil samples of the Campanian Khasib and Tannuma Formations in the wells of East Baghdad oil field for biomarker studies, while palynomorph constituents and their maturation, Rock Eval pyrolysis, total organic carbon (TOC) analysis are carried on for the Upper Jurassic and the Cretaceous Formations of core samples from the same wells for dating and evaluation of the source rocks. The gas chromatography of these oils have shown biomarkers of abundant ranges of n-alkanes of less than C₂₂(C₁₇–C₂₁) with C₁₉ and C₁₈ peaks to suggest mainly liquid oil constituents of paraffinic hydrocarbons from marine algal source of restricted palaeoenvironments in the reservoir as well as low nonaromatic $ {\hbox{C}}_{15}^{+} $ peaks to indicate their slight degradation and water washing. Oil biomarkers of $ \Pr ./{\hbox{Ph}}{.} = {0}{.85,}{{\hbox{C}}_{31}}/{{\hbox{C}}_{30}} < 1.0 $ , location is in the triangle of C₂₇–C₂₉ sterane, C28/C29 of 0.6 sterane, oleanane of 0.01, and CPI = 1.0, could indicate anoxic marine environment with carbonate deposition of Upper Jurassic–Early Cretaceous source. The recorded palynomorph constituents in this oil and associated water are four miospore, seven dinoflagellates, and one Tasmanite species that could confirm affinity to the Upper most Jurassic–Lower Cretaceous Chia Gara and Ratawi Formations. The recorded palynomorphs from the reservoir oil (Khasib and Tannuma Formations) are of light brown color of $ {\hbox{TAI}} = 2.8 - 3.0 $ and comparable to the mature palynomorphs that belong to Chia Gara and Lower part of Ratawi Formations. Chia Gara Formation had generated and expelled high quantity of oil hydrocarbons according their TOC weight percent of 0.5–8.5 with ${S_2} = 2.5 - 18.5\,{\hbox{mg}}\,{\hbox{Hc/g}}\;{\hbox{rock}} $ , high hydrogen index of the range 150–450 mg Hc/g Rock, good petroleum potential of 4.5–23.5 mg Hc/g rock, mature ( $ {\hbox{TAI}} = 2.8 - 3.0 $ and $ {\hbox{T}}\max = 428 - 443{\hbox{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 palynomorphs of the rocks of Khasib Formation are of amber yellow color of TAI = 2.0 with low TOC and hence not generated hydrocarbons. But, this last formation could be considered as oil reservoir only according their high porosity (15–23%) and permeability (20–45 mD) carbonate 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’s.     

Eco-environmental change detection by using remote sensing and GIS techniques: a case study Basrah province, south part of Iraq

This study examines the temporal and spatial dynamics of eco-environment degradation processes and change detection as evident from land use survey datasets (1990–2003) for the Basrah province, Iraq was taken as a case. Using a combination of techniques of RS, GIS, and GPS, the study identifies five prominent eco-environment degradation processes, namely: desertification, secondary salinization, urbanization, vegetation degradation, and loss of wetlands. Rates of conversion were calculated and distribution patterns were mapped with the aid of GIS. The results suggest that wind erosion was the dominant cause of eco-environment degradation in more than half of the study area. Coupled with this were increases in salinization processes, affecting 17.6% of the land area in 2003. Overall, severe eco-environment degradation was noticed to be the dominant eco-environment degradation grade (61.9% of total area), followed by moderate eco-environment degradation (18.9% of total area) in 2003. Incorporation of both natural and anthropogenic factors in the analysis provided realistic assessment of the risk of land degradation. The study area, in general, is exposed to a high-risk of eco-environment degradation.     

Palynofacies, palaeoenvironment, and source rocks evaluation of Ratawi Formation, Southern Iraq

Palynological analysis were done on 12 rock samples for Ratawi Formation from Rumailah well 131 and eight samples for the same formation from Zubair well 47, South Iraq, to extract sedimentary organic matters. Microscopic examination led to diagnose large numbers of spores, pollen, dinoflagellates (proximat, cavate, and chorate), foraminifera, melanogen, hylogen, and amorphogen. Three palynological facies were determined on the bases of percentages of sedimentary organic matter and palynomorphs from two sections. Analysis of these palynofacies clarified Ratawi Formation as deposited from environments ranging from delta and lagoon (suboxic–dysoxic) to shelf facies (anoxic near the shore–suboxic) with the presence of some layers deposited from semideep open marine environment (bathyal). Organic geochemical analysis of total organic carbon and Rock Eval pyrolysis were done to determine quantity, quality, and degree of maturation of the kerogen. Poor to medium proportion of total organic carbon of kerogen types II and III within a catagenesis stage are recorded in these rocks, and hence, poor hydrocarbon generation could be suggested for these strata.     

Fully coupled modeling of seabed subsidence and reservoir compaction of North Sea oil fields

This paper focuses on the aspects of fully coupled continuum modeling of multiphase poroelasticity applied to the three-dimensional numerical simulations of the Ekofisk oil reservoir in the North Sea (56°29′–34′N, 03°10′–14′E). A systematic presentation is chosen to present the methodology behind fully coupled, continuum modeling. First, a historical review of the subsidence phenomena above an oil and gas reservoir is given. This will serve as a background against which the relevance of the present approach to compaction and subsidence modeling will be demonstrated. Following this, the governing equations for a multiphase poroelasticity model are briefly presented. Particular attention is paid to the analysis of the pore-compressibility term usually used in an uncoupled approach for characterising the host-rock deformation. A comparative numerical analysis is carried out to contrast and highlight the difference between coupled and uncoupled reservoir simulators. Finally, a finite-element numerical model of the Ekofisk field is presented and a significant result is a contour map of seabed subsidence which is in general agreement with the shape of the subsidence contours based on past bathymetric surveys. Analysis of the simulation reveals that, due to the downward movement of the overburden, oil migration occurs from the crest of the anticline in which the field is situated, towards the flank. The pore-pressure depletion in the reservoir is significantly delayed due to the replenishment of the reservoir energy via the formational compaction. Horizontal movement in the reservoir, which is neglected in traditional modeling, can be significant and comparable in magnitude to the vertical subsidence. Electronic Publication     

三维地质建模软件发展现状及问题探讨

分析了三维地质建模软件可以明显地提高工作效率与工程质量,建立勘探区的三维地质模型,检查原始数据的正确性,通过各种“虚拟切割”手段检查各种地质要素间的相互关系。探讨了三维地质建模软件开发中所存在的几个问题,包括软件开发团队应适时转为公司机制,审慎选择开源工具,三维地质建模的三维模型数据标准,在勘探规范中增加三维地质建模要求,二、三维联动编辑,选准产品的用户群的与盈利模式等。     

Hydrochemical and isotopic investigation of groundwater of Al-Batin alluvial fan aquifer,Southern Iraq

Major ions and important trace elements in addition to δ¹⁸O and δ²H were analysed for 43 groundwater samples sampled from the Al-Batin alluvial fan aquifer, South Iraq. The most dominant ions (with respect to molarity) were: Na⁺ > Cl^? > SO₄ ^2? > Ca²⁺ > Mg²⁺ > NO₃ ^? > HCO₃ ^?, with total dissolved solids (TDS) averaging 7855 mg/L. High concentrations were found for the trace elements U, Mo, V, B, Sr, and Cr. This study suggests a hydraulic connection exists near the fan apex between the uppermost part of the Al-Batin aquifer and the underlying Dammam aquifer by means of the Abu-Jir fault system. Except for the effects of extensive irrigation, fertilizer use, and poorly maintained sewers, the groundwater chemistry is mainly controlled by geological processes such as dissolution of evaporites and the enrichment of dissolved ions as a result of the high evaporation and low recharge rate. Furthermore, it is shown that the Kuwaiti fuel–oil burning during Gulf War in 1991 contributed to the enrichment of V and Mo in the studied aquifer. The spatial distribution of most ions appears to generally increase from the south-west towards the north-east, in the direction of groundwater flow. The stable isotopes show heavier values in groundwater with a gradually increasing trend in the direction of groundwater flow due to the decreasing depth to groundwater and thus increasing of evaporation from both groundwater or irrigation return water. Additionally, the stable isotope signature suggests that rainfall from sources in the Arabian Gulf and the Arabian Sea is the major source of recharge for the Al-Batin aquifer. Except for two samples of groundwater, all samples were not suitable for potable use according to the WHO standards. Most of the groundwater is suitable for some agricultural purpose and for livestock water supply. Apart from the high salinity, boron represents the most critical element in the groundwater with respect to agricultural purposes.     

Environmental changes in the wetlands of Southern Iraq based on palynological studies

Palynological techniques are useful in reconstructing past environments, especially when other sources of information are lacking. We have embarked on a palynological study of the wetlands in Southern Iraq in an attempt to determine the nature and extent of past plant communities and other conditions prior to the drying of the wetland in the 1990s. Ten 1-m depth cores were collected from selected locations in marshes and shallow open water wetlands in Mesopotamian wetlands of Southern Iraq. Pollen diagrams from three short cores from the Hawizeh wetlands serve as a reference because this site has not been drained. The palynomorphs in these cores were Gramineae, Chenopodiaceae, Typha, Isonandra lanceolata, Bursarea, Artocarpus, Ireantea, Arenga, Crinum, Palmae, Navia, Tofieldia, Ipomorea, Xyris, and Morus. Fungal spores including Polyporisporites, Pluricellaesporites palyadosporites, Fusiformisporites, Spegazzinites indicus, Diporisporites, Plochmopellinites, Lycoperdon, Miliolinites, Dryadosporites constrictus, and Trichothyrites padapakarensis were noteworthy. Charcoal was scattered through the cores and indicate activities associated with human settlements. Many other forms of cuticles, filaments, insects, algae, and foraminifera test linings were also recorded. A second set of pollen samples were analyzed from 160 soil samples from eight cores collected from the wetland area which was dried during the 1990s. These data show a mixture of pollen and spores that could be used to evaluate past vegetation, climatic, and ecological changes. Preliminary results indicated that chenopodiaceous have increased while germinate types have declined which probably reflected desertification and a trend towards a more aeolian landscape during the 1990s. It is hoped that these studies will be useful in establishing conditions of the wetlands prior to destruction and will assist in setting restoration goals in the future. Case studies of one deep borehole (153 m) near Amara city for evaluating late Quaternary history and dig of 3 m depth to evaluate ancient desertification by wetland dryness were taken for correlation and connection with this recent sediment.     

Facies, depositional environment and diagenetic processes of the early Mid-Miocene Jeribe Formation, Central and Southern Iraq

The Jeribe Formation (Early Middle Miocene) in the central and southern Iraq consists mainly of shallow marine carbonates. Many microfacies have been identified: mudstone, wackestone, packstone, and grainstone with seven submicrofacies. Four major depositional cycles were determined. Microfacies developments and their distribution are controlled by cyclicity and relative sea level fluctuations. The Allochems in the Jeribe Limestone Formation are dominated by bioclasts. Peloids, ooids, and intraclasts are less abundant. The fossils are represented by benthonic forams and very rare planktonic forams. Calcite and dolomite are the predominant mineral components of Jeribe Formation. The carbonates of Jeribe have been affected by a variety of diagenetic processes such as compaction, dissolution, cementation, neomorphism, dolomitization, anhydritization, and silicification. By using the lithofacies association concepts, the depositional model of the Jeribe Formation environment was built. The Jeribe was deposited in open to restricted platforms which indicated lagoonal environment with warm and restricted-open circulation and the lower part (in well Hemrin-2) was deposited in foreslope environment.     

基于GOCAD的宁芜盆地云台山地区三维地质建模

阐述了利用GOCAD软件进行三维地质模型构建的思路及主要步骤,重点介绍其模拟地质界面的3种主要方法。以宁芜盆地云台山地区为例,利用GOCAD模拟了该区地层、岩体及断裂。在构建地形、地层及构造面时,利用剖面建模法以及离散光滑插值技术,快速构建研究区的表面模型。由面模型向体模型转化时,选用GOCAD的SGrid代替Solid功能,更加方便准确地反应了真实地质情况。     

基于Vulcan软件的山东莱州留村金矿区三维建模及资源量估值北大核心CSCD

留村金矿位于山东莱州市城区西南12 km的留村断裂带上,是发育于古老变质岩中的小型石英脉型金矿。为深入研究该矿区地层、构造与矿体在地下的延伸分布情况,加快后续数字化矿山建设,山东黄金集团应用Vulcan矿业软件对矿区开展三维地质建模。在收集相关地质实物资料的基础上,通过建立地质数据库、数据转换、地质解译等系列功能操作建立了矿区地表、岩体、构造及矿体模型,并对其进行任意剖割划分,实现了矿区地层岩性、地质构造、矿体的三维可视化,促进了本区矿体赋存规律的研究以及三维空间的成矿预测。同时利用软件强大的数据处理功能对资源量进行估值,本次估值的金资源量为1984.18 kg,与原详查报告中提交的金资源量2009.34 kg误差仅为1.25%。经估值后的每个矿块段都被赋予了精确的资源量数据,为后续矿山采矿设计与排产计划提供了准确的数据支撑,助力实现数字化、智能化矿山建设。     

3D geomodeling of the Lower Cretaceous oil reservoir, Masila oil field, Yemen

Oil was first discovered in the Masila area of Yemen in the late 1990s, with about 90% of the reserves found in the Lower Qishn Clastic Member of the Qishn Formation. The porosity determinations of the Lower Qishn Clastic are relatively high and the permeability ranges from 103 to 374?md. This paper tries to evaluate the hydrocarbons in the porous zones encountered in the Lower Cretaceous formations, which were penetrated by the eight wells in the study area. The water saturation shows low values, while the hydrocarbon saturation is in a reverse relation, i.e., the hydrocarbon increases where the water saturation decreases. Different cross-plots such as Rho-PHIN, Rho-DTN, and M-N were used in lithological identification for the two studied formations (Saar and Qishn) in the studied wells. Formation evaluation and presentation forms of the obtained petrophysical parameters have frequently proven that the formations have high hydrocarbon saturation in this area and contain many pay zones. On of the main targets of this paper is to build a detailed 3D geological modeling of the Lower Cretaceous Sequence conducted through an integrated study.     

Petroleum geochemistry of oil samples from shallow boreholes at Sakran site,western Iraq

Findings of the oil source affinity for oil sample collected from shallow borehole already drilled for ground water purposes at the Sakran area, NE Haditha city, western Iraq, is performed in this study by biomarker studies with addition to the analysis of gravity map. Petroleum geochemistry study is carried out on oil sample. The terpane and sterane biomarker distributions, as well as the stable isotope values, are used for determining the validity of oil to correlate its source. The results showed that the oil belongs to the Jurassic age, with high sulfur content (2.75 %) and value of C28/C29 up to 0.75. The tricyclic terpanes values as well as hopanes indicated a source rock affinity of carbonates, whereas the pristine/phytane ratio indicated marine algal source of kerogen type II. All these information could confirm that the source rock affinity was the Sargelu Formation (Jurassic), in which their age’s equivalent to the source in East Baghdad Oil Field and Tikrit Oil Field, with a difference from the oil family near the Akkas field, located to the west of the area. Chemical analyses of water sample collected from the borehole showed the following results: TDS?=?12,700 mg/l, EC?=?215,900 μs/cm, pH?=?6.8, DO?=?28 mg/l, and temperature?=?24 °C. Hydrochemical functions such as rNa/rCl (<1), (rNa–rCl)/rSO₄ (<0) and rSO₄/rCl (<1) indicate that the water is of marine origin, partially mixed with meteoric water. Analysis of the gravity map revealed two anomalous areas; the western one represents large anomaly with EW trend similar to the Anah graben to the north. The second one consists of many anomalies trending N–NW direction. The main local anomaly is identical with the seeps from the drilled borehole covering large area. The boundaries and trends of the main geological structures have been defined by gradient analysis procedure to the gravity data. The closed gravity anomalies with their large extensions reflect the importance of the results for further studies and promising area for oil reservoirs.