Biomarker Indicators of Source and Depositional Environment for the Organic Matters within Barsarin Formation (Upper Jurassic) in Kirkuk and Taq Taq Oil Fields, Northern Iraq

Dler

doi:10.32894/kujss.2008.41950

Abstract

The GC, GC/MS analysis for twelve bitumen extracts from Barsarin Formation in the wells K-109 and Tq-1 (Kirkuk and Taq Taq oil fields respectively) and for two oil samples from K-156 and Tq-1 wells revealed a euxinic, carbonate marine to mix environment for the initial organic matters. Pr / Ph, Pr / nC17, and Ph / nC18 ratios indicated also a marine source organic matters deposited under reduced condition with a less effect of biodegradation and mature stage of occurrence. The diasteranes / steranes ratio showed generally low ratios (0.27 – 0.56) as in most marine carbonate sources, while Algal-bacterial organic matter contribution for the extracts and the oil samples suggested depending on the predominance of C23 tricyclic terpane relative over the C19 tricyclic terpane and the C23 tricyclic terpane greater than C24 tricyclic terpane. The gammacerane Index indicated a low salinity environment of deposition for the initial organic matters existed in the analyzed samples.

Highlights

The Barsarin Formation was first described by Wetzel (1950), in Bellen, (1959)
The biomarker data obtained from the saturate GC/MS analysis of the eight source rock extracts and the two oil samples show no affect of contamination from the oil base mud (Appendix)
The same source supposed for the two oil samples taken from K-156 and Tq-1 wells

Summary

Introduction

The Barsarin Formation was first described by Wetzel (1950), in Bellen, (1959). The type locality and type section of Barsarin Formation located in Barsarin, Rowanduz district, north east Iraq. The biomarker data obtained from the saturate GC/MS analysis of the eight source rock extracts (five from K-109 and three from Tq-1) and the two oil samples show no affect of contamination from the oil base mud (Appendix). Didyk et al (1978) in Peters et al (2005) interpreted the redox conditions of the source rock depositional environment for crude oil based on a model for the origin of pristane (Pr) and (Ph) phytane. An oil accumulation have pristane / phytane ratio more than 3.0, indicative of a predominantly non marine source from terrestrial organic matter. The ratios of the Pr / Ph for the four uncontaminated extracts mentioned above in this study were generally low and ranged between 0.34 and 0.61 (less than 0.8) (table 2) indicating anoxic, reduced marine carbonate depositional environment. 0.87 for Tq-1 oil) and those of the extracts may be interpreted as those two oils generated from additional marine sources of organic matters (generally of Jurassic age) and from Barsarine source rocks

C Biodegradation D

Terpanes

Conclusions