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PETROPHYSICAL PROPERTIES AND RESERVOIR DEVELOPMENT OF ALBIAN SUCCESSION IN NASIRIYAH OIL FIELD, SOUTHERN IRAQ
الخواص البتروفيزيائية والتطور المكمني لتتابع الالبيان في حقل الناصرية النفطي، جنوبي العراق

Authors: Marwah H. Khudhair مروة حاتم خضير --- Aiad A. Al-Zaidy أياد علي الزيدي
Journal: Iraqi Bulletin of Geology and Mining مجلة الجيولوجيا والتعدين العراقية ISSN: 18114539 Year: 2018 Volume: 14 Issue: 2 Pages: 61-69
Publisher: Ministry of Industry and Minerals وزارة الصناعة والمعادن

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Abstract

The carbonate-clastic succession in the studied wells is represented by the Nahr Umr and Mauddud formations deposited during the Albian Sequence. This study includes petrophysical properties and reservoir characterization of this succession in 5 wells within the Nasiriyah oil field. According to values and shape of gamma ray logs and shale values, the studied formations were subdivided into five zones named; A, B, C, D, and E. Three types of rocks were identified in these zones according to their total porosity: Type I: High-moderate active porosity rocks; Type 2: High-moderate inactive porosity rocks and Type 3: Low-non porous rocks. According to the relationship of resistivity-porosity and hydrocarbon saturation two reservoir horizons have been identified in this study within the Nahr Umr Formation. The Mauddud Formation, on the other hand, does not show any hydrocarbon in the studied succession, due to the overwhelming presence of shale strongly affected by diagenetic processes such as cementation and compaction. Horizon 1 appears in the upper sand member of Nahr Umr Formation, encountered in wells No.1, No.2, and No.3. This type of rocks is characterized by high-moderate porosity (effective porosity) with low volume of shale and high deep resistivity. The thickness of this type ranges from 21 m to 48.5 m. Horizon 2 is represented by breaded river lithofacies, occurring in all the studied wells except No.3. It is divided into two sub-horizons in well No.5. This type of rocks is 12.25 – 57 m thick and characterized by high-moderate porosity with low volume of shale and high deep resistivity.

يتمثل التتابع موضوع الدراسه الحالية بتكويني نهر عمر ومودود المترسبين خلال دورة الألبيان وتضمنت الدراسة البتروغرافية والتحليل السحني والخواص المكمنية لهذا التتابع في خمسة آبار ضمن حقل الناصرية النفطي. قسم التتابع الى خمس أنطقة (A، B، C، D و E) بالاعتماد على شكل وقيمة أشعة گاما وحجم السجيل الموجود وقسمت هذه الأنطقة الى ثلاث أنواع من الصخور بالاعتماد على المسامية الكلية هي: 1) عالي-متوسط المسامية الفعالة، 2) عالي الى متوسط المسامية غير الفعالة، و 3) قليل الى عديم المسامية. تم تقييم الخواص المكمنية لتكويني نهر عمر والمودود من خلال مناقشة التغيرات في المساميات الثانوية والفعالة والنفاذية بالاعتماد على المقاومية والمسامية. تم حساب الاشباع الهايدروكاربوني وتحديد مستويين مهمين في المقاطع المدروسة ضمن تكوين نهر عمر، بينما لم يظهر تكوين مودود أيشواهد لوجود الهيدروكاربونات ويرجع ذلك ربما الى نسبة السجيل العالية وتأثر التكوين بالعمليات التحويرية وخاصة السمنتة وعملية التراص. يقع المستوى الأول في الجزء الأعلى للوحدة الرملية ضمن الآبار ناصرية-1، ناصرية-2 و ناصرية-3 ويتميز بوجود صخور ذات مسامية فعالة عالية الى متوسطة ونسبة سجيل ضئيلة ومقاومية عميقة عالية ويتراوح سمكه بين 21 – 84.5 متر. يتميز المستوى الثاني بقيم مسامية فعالة عالية وقيم سجيل ضئيلة ومقاومة عميقة عالية ويتراوح سمكه بين 12.25 – 57 متراً ويتمثل بسحنة بيئة النهر الضفائري في جميع الآبار المدروسة عدا البئر ناصرية-3.


Article
Facies Analysis and Stratigraphic Development of the Zubair Formation in the Mesopotamian Zone, Southern Iraq

Authors: Hani H. Al-Rubaye --- Ali D. Gayara --- Aiad A. Al-Zaidy
Journal: Iraqi Journal of Science المجلة العراقية للعلوم ISSN: 00672904/23121637 Year: 2019 Volume: 60 Issue: 2 Pages: 290-307
Publisher: Baghdad University جامعة بغداد

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Abstract

The Barremain-Aptian succession represented by the Clasits deposits of Zubair Formation. This formation is the most significant sandstone reservoir in Iraq which deposited in fluvio- deltaic, deltaic and marine environments during the Barremain to Early Aptian age. The area of study is located in the Mesopotamian Zone at Southern part of Iraq which represented by five oil fields (Nasira, Luhais, Suba, Tuba and West Qurnah). The petrographic study showed that quartz mineral is the main component of the sandstone in Zubair Formation with minor percentage of feldspar and rare rock fragments to classified as quartz arenite. The formation consists of mainly interbedded sandstone, shale, siltstone and sometimes thin beds of carbonate. Shale thickness increase towards east and decrease the sandstone towards the east southern of Iraq. Zubair characterized in the lower member by mud - dominated delta front associated facies. They seem to vertically separate relatively multi-storied mode and multi-lateral changes deltaic channel sand bodies resulting in compartmentalized reservoir architecture. The presence of the delta front associated facies overlaying the unconformity surface (SB1) refers to the transgressive system tract (TST). This stage was ended by the deposition the fluvial channel facies to mark a high-stand system tract (HST). The fluctuation point between the TST and HST is represented a maximum flooding surface. The middle member of Zubair Formation is characterized by moderate to well sorted quartz arenite sandstone with appearance bands of the shale overlaying the sand body. This succession was deposied in the delta plain environment with steps of sea level rise during the transgressive stage. There are two sequences as TST in this part which end with the maximum sea level rise (MFS) to mark the upper part of the Zubair Formation. The next stage was appeared high concentrations of organic matters and pyrite mineral which indicating that the sedimentary environment has been reduced to the marshes environment during the HST. The upper part of the Zubair Formation showed a shallower environment with shale dominated rocks associated with high organic matters and pyrite. This indicates to the finning up-ward mode during highstand stage when the deposition environment changed from delta plain fluvial channel to delta front mouth bar. The sea level rise marked the end of this stage when deposition the upper part of Zubair Formation, and the beginning of deposition of shallow marine carbonate of the Shuaiba Formation as shallow carbonate marine.

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