Geochemical, geological, and petrophysical evaluation of Garau Formation in Lurestan basin (west of Iran) as a shale gas
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ORIGINAL PAPER
Geochemical, geological, and petrophysical evaluation of Garau Formation in Lurestan basin (west of Iran) as a shale gas prospect Amine Lotfiyar 1 & Ali Chehrazi 2 & Rudy Swennen 3 & Majid Ghasemi Siani 4 Received: 19 October 2017 / Accepted: 28 September 2018 # Saudi Society for Geosciences 2018
Abstract The Garau Formation in western Iran is a potential shale gas play. To evaluate its gas potential, a geochemical, geological, and petrophysical study was conducted on samples from the Baba Ghir 1 well drilled in Lurestan District (W Iran). Organic matter analysis of Garau Formation shows that total organic carbon (TOC) ranges between 0.42 and 2.43 wt% and this formation possesses kerogen type III with a high degree of maturity, reflecting gas window conditions. Mineralogical analyses show that the lithology of Garau Formation in this well is carbonate-dominated and the clay mineral content is less than 4%, and displays several characteristics that are similar to the Eagle Ford shale. Based on the relationship among quartz, carbonate, and clay minerals, the brittleness index is about 25%, a value of importance to select the best stimulation fluid. Petrophysical evaluation shows a porosity of about 5–15%. Estimation of the amount of free gas reserves possesses a good correlation with the reserves that were estimated based on petrophysical interpretation. Because of absence of underground contour maps, calculation of adsorbed gas volumes was not possible but estimates of gas storage capacity (GC) shows an increase with depth. All data indicate that the Garau Formation can be considered as a promising gas shale play. Keywords Garau Formation . Baba Ghir 1 well . Mineralogy . Geochemistry . Rock-Eval pyrolysis . Petrophysics
Introduction Designation of a hydrocarbon reservoir as unconventional emphasizes the fact that the rock acts as a source, store/reservoir, and seal of the hydrocarbons it contains. In contrast, the conventional reservoir usually involves the accumulation of * Amine Lotfiyar [email protected] Ali Chehrazi [email protected] Rudy Swennen [email protected] Majid Ghasemi Siani [email protected] 1
Department of Petroleum Engineering, Faculty of Chemistry, Oil and Gas Engineering, Semnan University, Semnan, Iran
2
RIPI, Tehran, Iran
3
Department of Earth and Environmental Sciences, KU Leuven, B-3001 Leuven, Belgium
4
Department of Geochemistry, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran
hydrocarbons after their generation and migration from a different and often distant source rock, as well as being sealed by an impermeable cap rock belonging to another impermeable lithological formation. An unconventional hydrocarbon reservoir may, therefore, be regarded as being self-sourced and of a highly impermeable nature, usually requiring stimulation through induced hydraulic fracturing if it is to be commercially viable. Only a third of worldwide oil and gas reserves are conventional, the remainders are unconventional resources (Horsfield and Schulz 2012; Chen
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