بایواستراتیگرافی سازند های آسماری تا سروک در چاه

_Abstract :

The Palangan well # ۱ was drilled in ۱۹۸۱ by the National Iranian Oil Company. A detailed paleontological study was carried out on the cutting samples of drilled sequence of this well. The study was undertaken in order to establish the well-known biozones of the Zagros basin throughout the drilled sequence of Palangan well # ۱. A total of ۸۷۱ thin-sections were prepared from the drilled sequence of this well and they were studied under microscope . Likewise , the Qaleh- Nar # ۲ (۱۴۰۰ thin –sections at ۴۰ km northern Andimeshk city) and Lab-e- Sefid # ۱(۶۰ km northeastern Dezful city) were investigated again in order to correlate with the Plangan # ۱. As a result, ۷۹ microfauna and microflora were identified and they were arranged in fifteen biozones as the followings:

۱- Neoalveolina melo crdica zone # ۶۱

۲- Austrotrillina howchini-Peneroplis evolutus assemblage zone # ۵۹

۳- Lepidocyclina-operculina-Ditrupa assemblage zone # ۵۶

۴- Globigeina spp. assemblage zone # ۵۵

۵- Globorotalia cerro-azulensis/Hantkenina assemblage zone # ۵۲

۶- Turuncorotaloides-Porticulasphaera-Globorotalia spinulosa assemblage zone # ۴۷

۷- Globorotalia rex/Globorotalia aragonensis, Globorotalia formosa assemb;age zone # ۴۵

۸- Globorotalia velascoensis-Globorotalia pseudomenardii assemblage zone # ۴۲

۹- Globorotalia Globigerina-Globigerina daujergensis assemblage zone # ۴۱

۱۰- Globotruncana stuarti, Pseudotextularia varians assemblage zone # ۳۹

۱۱- Globotruncana elevata elevata zone # ۳۳

۱۲- Globotruncana ventricosa concavata/carinata assemblage zone # ۳۲

۱۳- Valvulammina-Dicyclina assemblage zone # ۲۹

۱۴- Nezzazata-Alveolonid assemblage zone # ۲۵

۱۵- Oligostegina facies zone # ۲۶ facies

Based on the above-mentioned biozones, the drilled sequence of Palangan well # ۱, in dencending stratigraphical order can be divided into the Asmari , Pabdeh , Gurpi , Ilam and Sarvak formations.

Beside of the biozones, the electrical logs (gamma & sonic logs) were also used for differenciation of the above-mentioned rock units, in order to determine the true thickness each rock unit and to estimate the real amount of hydrocarbon in reservoir rocks.

Likewise, the lithological and paleontological data of Palangan well # ۱ were correlated with those of Qaleh - Nar well # ۲ and Lab-e-Sefid well # ۱, resulting in trend of lithological and paleontological changes. Based on the above-mentioned biozones, there are two hiata throughout the drilled sequence of Palangan well # ۱ , Qaleh - Nar well # ۲ and Lab-e-Sefid well # ۱. The first hiatus occurs in Gurpi formation , encompassing the Late Maestrichtian.The second hiatus is present between the Ilam and Sarvak formations , including the Coniacian strata.