Sedimentology and depositional environment of the Kazhdumi Formation Sandstones in the northwestern area of the Persian Gulf

Bijan Noori,Bahram Movahed,Nader Kohansal Ghadimvand,Mohammadreza Yousefpour

doi:10.4236/ojg.2016.611100

Abstract

Kazhdumi is one of the Bangestan Group formations aging late early Cretaceous (Albian). Three subsurface sections of the sandstone bearing part of Kazhdumi in the studied area located at northwest of the Persian Gulf are assessed for determining sedimentary facies and depositional environment. Based on the recognized facies, the sandstone bearing zones of Kazhdumi and their relevant paleoenvironments can be addressed as: first one is the B sandstone zone containing thick sandstone layers alternating with shale and siltstone thin layers which are deposited by river influenced conditions because of the characteristics like: cross bedding, oxidized constituents and palesol. The second one, the A sandstone zone which is deposited under a key limestone layer, is composed of sand/sandstone layers with marine features and presents the interaction of marine-river condition in deltaic channels. This zone, is a transition interval showing the changes of river-dominated condition to marine one. The third one is the A sandstone zone deposited above the key limestone layer containing fine grained laminated siliciclastic and chemical sediments. Alternation of distal channel facies and green marine shale of delta containing glauconite, pyrite and organic matter residuals, all confirm the reduction condition in estuarine environment. Applying facies analyses results, isopach maps, porosity distribution maps and sandstone grain size study, the paleocurrent pattern is determined from the southwest to northeast.

Highlights

The sandstone bearing part of the Kazhdumi Formation with a sandstone-shale lithology in type-section in Kuwait is recognized as a gigantic reservoir and reservoir sandy layers of Kazhdumi Formation are formed in some Iranian offshore oil fields [1] (Figure 1)
Facies determination and depositional environment interpretation of Kazhdumi Formation sandstone deposits in studies wells, S, N and H is carried out based on sieve analysis of 51 loose sandstone samples, core in some intervals, thickness maps of Kazhdumi Formation and its zones at well location, extracted porosity distribution map of Kazhdumi sand in the northwest of the Persian Gulf and analyzing 670 thin section samples including 470 thin sections from a core interval (150 meters) of Well S, 105 thin sections from a core interval (28 meters) of Well N and 95 thin sections delivered from 6 meters cored interval and drilling cuttings in Well H
The “A” sandstone zone, below the key limestone layer, was deposited in river dominated to marine dominated conditions in delta channels

Summary

Introduction

The sandstone bearing part of the Kazhdumi Formation with a sandstone-shale lithology in type-section in Kuwait is recognized as a gigantic reservoir (the Great Burgan, the second gigantic hydrocarbon reservoir in the world) and reservoir sandy layers of Kazhdumi Formation are formed in some Iranian offshore oil fields [1] (Figure 1). The Burgan Formation was introduced and described by Owen and Nasr [2] in the Burgan Field (well No 113) and mostly composed of sandstone which was enriched. Detailed petrographic studies, depositional environment analyses and paleoclimate descriptions have been used to understand the processes of the sandstone unit deposition

Methods

Results

Conclusion