Midyan Havzası’nın Stratigrafik Evrimi ve Hidrokarbon Potansiyeli (KB Suudi Arabistan)

Öz

Önemli miktarlarda hidrokarbon üretiminin yapıldığı Midyan Havzası, Suudi Arabistan’nın kuzeybatısında yer alır ve Arap Kalkanı olarak bilinen Proterozoyik yaşlı kristalin temel tarafından çevrilmiştir. Bu havza, Erken Miyosende (23,03 My) Kızıldeniz, Süveyş ve Akabe Körfezleri’nin açılması ile oluşmuş yarı-grabenlerde çökelmiş petrol ve doğal gaz potansiyelleri yüksek kalın sedimanter istifler içerir. Açılmanın erken aşamasında çökelen istifler, karasal alüvyon yelpazesi çökelleri, playa evaporitleri ve bunların üzerine gelen bol fosilli sığ deniz karbonatlarından oluşur. Midyan Havzası’nın Erken Burdigaliyen zamanında derinleşmesi nedeniyle, sığ deniz karbonatları üzerine uyumlu olarak Burqan Formasyonu’nun derin deniz yelpazeleri içindeki hidrokarbon üretiminin yapıldığı klasik türbidit istifleri gelir. Kızıldeniz, Süveyş ve Akabe Körfezleri açılmasının en etkili oduğu zirve döneminde (yaklaşık, 19 My) Sina Yarımadası düşey yönde 4 kilometreden daha fazla yükselmiş ve yüksek dağ zirvelerinde Alp-tipi buzul çökelleri oluşmuştur. Açılmanın geç ve son aşamasını temsil eden istifler sığ deniz ortamında çökelmiş marnlar ve evaporitlerle temsil edilir. Bu çalışmanın amacı, Burqan Formasyonu içindeki türbidit istiflerinin hidrokarbon potansiyellerini ortaya çıkarmak ve değişen iklim koşullarını temsil eden buzul çökellerinin farklı fasiyeslerini incelemektir. Arazide ölçülmüş sedimantolojik kesitler yardımıyla farklı jeolojik süreçlerin, Burqan Formasyonu içindeki petrol ve gaz rezervuarını oluşturan kökensel yönden farklı kumtaşlarının geometrileri, devamlılıkları ve rezervuar kaliteleri üzerindeki etkileri araştırılmıştır. Sina Yarımadası üzerinde oluşan Alp-tipi buzul çökelleri, gerçek buzul (moren), buzul-fluviyal ve buzul-denizel çökeller arasındaki düşey ve akış yönündeki yanal değişimleri anlamak için önemli bir olanak sağlar. Masif, boylanmamış morenler havzanın kuzeyindeki derin, U-şeklindeki buzul vadilerinin içinde çökelmiştir. Bu çökeller vadilerin akışı yönünde içinde cilalanmış ve çizilmiş bloklar içeren buzul-fluvial çökellere geçer. Havzanın en derin olduğu güneydoğu bölgesinde buzul-denizel çökeller pelajik şeyller ve türbiditlerle birlikte çökelmiştir. Midyan Havzası’nın, stratigrafik evrimini anlamak, çökelme ortamlarını yorumlamak ve hidrokarbon potansiyelini ortaya çıkarmak için istiflerin devamlı olduğu bölgelerde çok sayıda kesit ölçülmüş ve kumtaşlarının rezervuar özelliklerini ortaya koymak için örnekler alınmıştır.

Anahtar Kelimeler

• Aqaba Körfezi
• denizel buzul
• fluviyal buzul
• gerçek buzul
• Midyan Yarımadası
• Sina Yarımadası
• Süveyş Körfezi

Stratigraphic Evolution of the Midyan Basin and its Hydrocarbon Potential (NW Saudi Arabia)

Öz

The hydrocarbon-producing Midyan Basin is located in northwestern Saudi Arabia and is surrounded by the Proterozoic igneous basement of the Arabian Shield. It includes thick hydrocarbon-producing sedimentary sequences deposited in half-grabens that formed during rifting of the Red Sea and the gulfs of Suez and Aqaba in the Early Miocene (23.3 Ma). The early syn-rift succession consists of arid alluvial fan sediments and playa evaporates, followed by shallow marine carbonates. The late syn-rift sequences consist of progradational deep sea turbidites and Alpine-type glacial deposits indicating strong vertical uplift during the climax of the rifting (19 Ma). The post-rift succession overlies the late syn-rift successions and consist of shallow marine marls and evaporites. The aim of this study is to examine the hydrocarbon potential of the turbidite sandstones and the formation of various types of glacial deposits in the Burqan Formation. This study also encompasses the importance of various geologic processes in order to understand their significant influence on the geometry, continuity and reservoir quality of oil and gas producing genetically different sandstones in the subsurface of the Burqan Formation in the Midyan Basin. The Alpine-type glacial deposits provide an excellent opportunity to study the presence of continuous vertical and lateral facies variations between true glacial, glacio-fluvial and glacio-marine deposits in the direction of sediment transportation. Unsorted moraines deposited in the deep and U-shaped glacial valleys occupy the northwestern part of the basin. They pass gradually into glacio-fluvial sandstones that contain large polished and striated boulders. In the southeastern part of the deep basin, the glacio-marine deposits are associated with deep sea turbidites and pelagic shales. Many stratigraphic and sedimentologic sections were measured from well-exposed outcrops in every part of the basin to establish various depositional environments. A large number of sandstone samples was collected to examine their reservoir quality.

Anahtar Kelimeler

• Glacio-fluvial
• glacio-marine
• Gulf of Aqaba
• Gulf of Suez
• Midyan Peninsula
• Sinai Peninsula
• true glacial

Teşekkür

A large part of this study was carried out when the first author was employed for 30 years as Senior Geological Consultant at Saudi Aramco of Saudi Arabia and recently in Turkish Petroleum. We are grateful to these organizations for providing us with all the necessary facilities both in the field and in the office. We greatly acknowledge Prof. Dr. Nizamettin Kazancı, Prof. Dr. Cemal Göncüoğlu, Prof. Dr.Graham Evans and Prof. Dr. M.Namık Yalçın who kindly read and edited the paper by making some corrections and valuable suggestions. Some figures were drafted by Dr. Murat Şentürk and Mahir Kaya. We appreciate their contributions.

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