Thermal modelling of gas generation and retention in the Jurassic organic-rich intervals in the Darquain field, Abadan Plain, SW Iran

Arsalan Zeinalzadeh,Mohammad Kassaie-Najafi,Reza Rezaee,Asadollah Mahboubi,Reza Moussavi-Harami

doi:10.1007/s13202-018-0573-x

Arsalan Zeinalzadeh, Mohammad Kassaie-Najafi + Show 3 more

Open Access

https://doi.org/10.1007/s13202-018-0573-x

Copy DOI

Abstract

The petroleum system with Jurassic source rocks is an important part of the hydrocarbons discovered in the Middle East. Limited studies have been done on the Jurassic intervals in the 26,500 km2 Abadan Plain in south-west Iran, mainly due to the deep burial and a limited number of wells that reach the basal Jurassic successions. The goal of this study was to evaluate the Jurassic organic-rich intervals and shale gas play in the Darquain field using organic geochemistry, organic petrography, biomarker analysis, and basin modelling methods. This study showed that organic-rich zones present in the Jurassic intervals of Darquain field could be sources of conventional and unconventional gas reserves. The organic matter content of samples from the organic-rich zones corresponds to medium-to-high-sulphur kerogen Type II-S marine origin. The biomarker characteristics of organic-rich zones indicate carbonate source rocks that contain marine organic matter. The biomarker results also suggest a marine environment with reducing conditions for the source rocks. The constructed thermal model for four pseudo-wells indicates that, in the kitchen area of the Jurassic gas reserve, methane has been generated in the Sargelu and Neyriz source rocks from Early Cretaceous to recent times and the transformation ratio of organic matter is more than 97%. These organic-rich zones with high initial total organic carbon (TOC) are in the gas maturity stage [1.5–2.2% vitrinite reflectance in oil (Ro)] and could be good unconventional gas reserves and gas source rocks. The model also indicates that there is a huge quantity of retained gas within the Jurassic organic-rich intervals.

Highlights

The Late Jurassic intervals are source rocks of 14 petroleum systems in the world
The elemental analysis results (Table 1) show that the sulphur/carbon ratio (S/C) in the Lower Sargelu zone is above 0.04% allows the classification of these kerogens as highsulphur (Lewan and Ruble 2002; Orr 1986)
The C27, C28, and C29 steranes indicate that the organic matters in the Jurassic source zones mainly originated from marine organisms

Summary

Introduction

The Late Jurassic intervals are source rocks of 14 petroleum systems in the world. These contain a fourth of the discovered hydrocarbon. The Jurassic source rocks are sources of hydrocarbon for the Jurassic–Tertiary reservoirs in the Mesopotamian Basin (Abdula 2015; Abeed et al 2011; Alsharhan et al 2014; Pitman et al 2004). They may have unconventional shale oil and shale gas in areas. Australia which are within oil and gas windows, respectively (Aqrawi and Badics 2015) These source rocks include the Bajocian–Bathonian Sargelu and Callovian–Oxfordian Najmeh Formations, which extend in the Zagros Fold Belt and Mesopotamian Basin (Al-Ameri et al 2009; Aqrawi and Badics 2015; Bordenave and Hegre 2010; English et al 2015; Sachsenhofer et al 2015)

Objectives

Results

Conclusion