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Gamma-clustering sequence stratigraphy, case study of the carbonate Sarvak Formation, Southwest Iran

Abstract : Comprehensive study of seismic, well-logs and core data is essential in sequence stratigraphic analysis. In the absenceof seismic and core data, gamma-ray logging is an important stratigraphic tool due to its sensitivity to shale content ofstrata. In this paper, gamma-ray log data are divided into two clusters. One cluster with higher average of gamma valueis interpreted as being due to deeper sedimentary environments. A second cluster with lower average is due to shallowersedimentary environments or shelf deposits. This kind of interpretation is based on two assumptions: (1) a deeperdepositional environment produces higher gamma emission, and (2) the gamma-ray log is not much affected fromdiagenetic processes. At each sampling depth, a positive label is assigned to the cluster with higher, and a negative labelto the cluster with lower average. A cumulative diagram of the cluster labels was compared to previously studied environmentalfacies. It was illustrated that the diagram recreates the relative water depth change, so it identifies sequencesurfaces (sequence boundary and maximum flooding surface). The identified sequence surfaces were compared tocore-based sequence stratigraphy of the carbonate Sarvak Formation, southwest Iran, in two oil wells. Sequence stratigraphyinterpretations are judgmental, i.e., based on expert opinion, and being judgmental is a source of uncertaintyfor further decision making. This work reveals that stacking patterns and system tracts of the third-order sequences inthe carbonate reservoirs could be identified in a systematic way using gamma-clustering algorithm. Nevertheless, thewell-log resolution is a limiting factor for identifying the fourth-order sequences.
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https://hal-insu.archives-ouvertes.fr/insu-02315232
Contributor : Isabelle Dubigeon <>
Submitted on : Monday, October 14, 2019 - 12:48:29 PM
Last modification on : Wednesday, January 29, 2020 - 5:14:03 PM

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Majid Moradi, Behzad Tokhmechi, Masoumeh Kordi, Masoudi Pedram. Gamma-clustering sequence stratigraphy, case study of the carbonate Sarvak Formation, Southwest Iran. SN Applied Sciences, Springer Verlag, 2019, 1 (11), pp.1369. ⟨10.1007/s42452-019-1407-2⟩. ⟨insu-02315232⟩

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