The effects of diagenesis on the petrophysical and geochemical attributes of the Asmari Formation, Marun oil field, southwest Iran

Abstract

The distribution of good reservoir quality and its causes is the main challenges in carbonate reservoir characterization. This study investigates the effects of diagenetic processes on the reservoir quality of the carbonate successions of the Asmari Formation, in the Marun oil field, southwest Iran. The study applies an integrated approach including core petrography, petrophysical rock typing, stable carbon and oxygen isotopes as well as major and trace elements analyses. Petrographic studies and geochemical analyses express that the Asmari limestones have been affected mainly by compaction, dissolution, recrystallization, calcite and anhydrite cementation and dolomitization. Among those diagenetic overprints, dolomitization and dissolution played an important role to enhance the reservoir quality of the formation. Moreover, four types of dolomites were recognized and the rate of dolomitization increases toward the top of the Asmari carbonate successions. Possible models for dolomitization include mixing zone, brine reflux, seepage reflux and tidal pumping of seawater. Employing Flow Zone Index and Discrete Rock Type concepts led to classification of the Asmari reservoir into seven reservoir rock types. Integrating reservoir rock typing with petrographic studies and geochemical analyses also confirms that reservoir quality of the Asmari Fm. would have been mainly controlled by diagenetic processes. Moreover, stable isotopes, trace elements and facies analyses support the idea that carbonate intervals of the Asmari Formation were deposited in a warm, shallow-water environment under a saline condition.

Petroleum Geology of the Cenozoic Succession in the Zagros of Sw Iran: A Sequence Stratigraphic Approach

“…(iii) Researchers have identified both original calcium carbonate mineralogies and several generations of dolomite in the platform carbonates, notably in the Asmari Formation (e.g. Jafari et al, 2020;. The earliest generation of dolomitization is syndepositional, generally being interpreted as driven by sabkha-associated evaporation, and is therefore of environmental significance.…”

Morphoevolution of the Seymareh landslide-dam lake system (Zagros Mountains, Iran): Implications for Holocene climate and environmental changes

“…In this regard, we compare the δ 18 O vs δ 13 C results with oxygen and carbon isotope data of the lacustrine carbonates deposited in the Seymareh River basin (Al-Aasm et al, 2009;Navidtalab et al, 2016;Kalanat and Vaziri-Moghaddam, 2019;Jafari et al, 2020;Razmjooei et al, 2020aRazmjooei et al, ,b, 2021 (Fig. 11), and the δ 18 O concentrations with the grain classes (sand, and clay) (Fig.…”