Güneydoğu Anadolu Bölgesi’nde Rezervuar Kayacı Olan Dolomitlerin Kümelenmiş İzotop Sinyalleri

Year 2022, , 925 - 943, 31.08.2022

Deniz Atasoy , Aylin Geçer , Arzu Aktosun , Aynur Geçer Büyükutku

https://doi.org/10.35414/akufemubid.1105170

Abstract

Yeni nesil bir jeotermometre yöntemi olan kümelemiş izotop tekniği derin gömülmüş kayaçların diyajenetik süreçlerinin iyi anlaşılması kabiliyetine sahiptir. Bu yöntem kullanılarak, Kambriyen-Eosen yaş aralığındaki altı birimden, ~1-3.2 km gömülme derinliğine sahip toplamda 28 adet dolomit üzerinde ölçüm yapılmıştır. Bu çalışmada, bölgesel olarak seçilmiş Güneydoğu Anadolu rezervuarlarının karot ve sondaj kesintilerinden elde edilen dolomit örneklerinin paleosıcaklıkları ve dolomitleşme sularının δ18O değerleri belirlenmiştir. Kümelenmiş izotop yöntemi ile 37.2-161.9oC aralığında değişen sıcaklık değerleri ve +0.9-9‰ aralığında değişen dolomitleşme sularının δ18O değerleri bulunmuştur. Bu çalışma petrografik destekli olarak, paleosıcaklık ve dolomitleşme sularının δ18O d dağılımlarının dört farklı grup altında toplandığını kanıtlarıyla ortaya çıkarmıştır. İlk grup, Hoya Formasyonu için 43±7oC olarak erken dolomitleşme sıcaklığını ve Mardin Grubu-ED için 53 oC kısmi yeniden kristallenme sıcaklıklarını yansıtmaktadır. Bu değerler depolanma yüzeyindeki yoğun buharlaşma ve/veya sığ gömülme olayıyla ilişkilidir. İkinci grubu oluşturan Cudi Grubu dolomitleri, 64.3oC-93.8oC arasında değişen sıcaklık ve 9‰’e varan δ18Osu değerleri sağlamaktadır. Bu değerler, oldukça yoğun buharlaşmış deniz sularının meydana getirdiği yeniden kristallenme olayını temsil etmektedir. Üçüncü grubu oluşturan Mardin Grubu-GD ve Koruk Formasyonu dolomitlerinin kümelenmiş izotop sinyalleri 134.5oC-8‰’e varan sıcaklıklık ve δ18Osu değerlerine dönüştürülmüşlerdir. Bu değerler derin gömülme koşulları altında tamamlanmış yeniden kristallenme olayı ile karakterize edilmektedirler. En yüksek sıcaklık ve δ18Osu değerlerine sahip son grubun değerleri ise 140oC ve +6.5‰’i aşmaktadır. Bu sonuçlar kalın ve masif dolomit oluşumlarından sorumlu olan hidrotermal suların varlığını gösterdiği şeklinde yorumlanmaktadır. Sonuç olarak, bu araştırma petrol rezervuarlarını meydana getiren dolomitleşme olayının şifrelerini çözmeye yardımcı olan kümelenmiş izotop yönteminin yüksek potansiyelini ortaya çıkarmaktadır.

Keywords

Cudi grup, Dolomit, Dolomitleşme, Kümelenmiş izotoplar, Mardin grup, Paleotermometre

Supporting Institution

TÜBİTAK

Project Number

2214A PROGRAMI PROJE NO: 1059B141700284

Thanks

Çalışmacılar bu araştırmanın yayınlanmasına olanak sağlayan Türkiye Petrolleri A.O’na teşekkür etmektedirler. Birinci yazar kümelenmiş izotop tekniğinin öğrenilmesi ve uygulanması aşamasında University of Miami-Duraylı İzotop Laboratuvarı’nda başta Peter Swart ve diğer tüm çalışmacılara sonsuz teşekkürlerini sunmaktadır. Sorumlu yazar ayrıca çalışmasının 2214A programı (1059B141700284) kapsamında desteklenmesinden dolayı TÜBİTAK’a müteşekkirdir. Yazarlar makalenin değerlendirilme aşamasındaki değerli katkılarından dolayı hakemlere ve editörlere şükranlarını sunmaktadır.

Clumped Isotope Signatures of Dolomites as Reservoir Rocks, Southeast Anatolia

Abstract

Clumped isotope technique is a new generation of geothermometry that possesses a great ability to understand diaganetic processes in deeply-buried ancient rocks well. A total of 28 dolostone samples from Cambrian to Eocene aged dolomitized rocks across burial depth range of ~1-3.2 km were measured using this method. In this study, the paleotemperature of dolostones and δ18O of the dolomitizing water values have been determined in a regional selection of cores and drilling cuttings obtained from dolomite reservoirs of SE Anatolia. The clumped isotopes found a temperature range of 37.2-161.9 oC and δ18Ofluid of +0.9‰ to 9‰. Our study revealed evidences supported by petrographic evaluation for four distinct patterns in the paleotemperatures and δ18Ofluid. The first group reflects early dolomitization temperature of 43±7 oC for Hoya Formation and partial recrystalization temperature of 53oC for Mardin Group-ED, linking to intensive evaporation effect at the surface and/or shallow burial event. The second group consisting of Cudi Group dolostones provided temperature values between 64.3 oC and 93.8 oC, calculating δ18Ofluid values until 9‰. It is considered to represent recrytallization temperature occured by highly evaporative marine waters. Clumped isotope signatures consisting of Mardin Group-GD ve Koruk Formation dolomites from the third group were converted into temperature and δ18Ofluid values up to 134.5 oC and 8‰. These values are characterized with punctuated recrystalization event under deep burial conditions. Last group having highest T (oC) and δ18Ofluid values exceed 140 oC and +6.5‰. These results are interpreted to display existence of hydrothermal fluids responsible for thick dolomite depositions. Therefore, this research unveils huge potential of clumped isotope method to help decode dolomitization events that produced oil reservoirs.

Keywords

Cudi group, Dolomite, Dolomitization, Clumped ısotopes, Mardin group, Paleotermometry

Project Number

2214A PROGRAMI PROJE NO: 1059B141700284

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