The Mesopotamian Stratigraphy researches..

Sequence Stratigraphy and Sedimentary Systems of (Late Touronian- Early Campanian) Cycles ( Khasib, TAnuma, and Sa’di) Formations in West Qurna Oilfeild Southern Iraq

Mazin Adbdul-Monim Mohammed Al-Shaoosh

(mazin_shaoosh@yahoo.com)

Abstract

This study is dealt with sequence stratigraphic concepts during the cretaceous period, precisely  (Late Touronian - EarlyCampanian) cycle that includes  (Khasib, Tanuma &  Sa`di )  formations  at West Qurna oilfield , southern Iraq.

The study depended on microfacies analysis that shows there are four main microfacies and fifteen submicrofacies. That are distributed vertically and laterally along the extension of the field also the diagenetic processes have been studies.           Depending on this microfacies analysis , the depositional environments has been determined as follows :  sub-basinal ,slope , lagoon, shoal, open sea shelf, and the basinal environment .            

The sequence stratigrphic concepts have been used that depends on well  logs in addition to the petrographic description of microfacies , these concepts are as follows : 

1-Base level transiet cycles.

2-Stacking pattern of parasequence.

3-Shallowing upward cycles.

The Sequence boundaries  of the depositional systems have been detected . The transgressive systems tract reflects the deposition of khasib formation and the upper part of sa’di formation , in addition, the highstand systems tract reflects the deposition of tanuma formation and the lower part of sa’di formation that is representing the highstand systems tract at its late stage . The lower sequence boundary is of type-1 , while upper boundary is of type-3 , whereas the   maximum flooding surface within the  deep  Khasib formation that is representing by   (oligostiginal lime Packstone microfacies)  .

The depositional model of the studied succession is well represent the shelf setting . Depending on (mazzullo, 1994) model  for porosity prediction which depends on stratigraphic sequence concepts that indicate the increase and decrease due to sea level fluctuation, the increase of porosity near sequence boundaries and parasequence due to sea level decrease .

The interrelation between the sequence stratigraphic analysis and reservoir characterization stows that the sa’di reservoir is representing the late highstand systems tract. 

 Unpublished M.Sc. Thesis, University of Basrah, College of Science, 2003