Facies and Isotopic Studies of Kangan Formation, LowerTriassic in Persian Gulf
The Lower Triassic Kangan Formation with a thickness of 190m is one of the major gas bearing carbonate sequences. In the upper part, it consists of an alternative sequence of shale and anhydrite.
This sequence along with Aghar shale acts as a good cap rock. In the lower part, it consists of dolomite and limestone alternation that act as a gas reservoirs. Dolograinstone and grainstone show high porosity and thus has increased permeability of the formation. Based on microfacies studies, Kangan Formation deposited in tidal flat (supratidal ? intertidal), and lagoon and shoal environments. Oxygen and carbon isotope values range from ?3.6? to -5.8?. (Mean ?4.7?) and from +0.3? to +2.8? (mean +1.55?) respectively.
Paleotemperature calculation based on heaviest and highest oxygen isotope values of dolomites shows that depositional and diagenetic temperatures are and respectively.
In this calculation, of ?0.5? (SMOW) for Triassic seawater (Al ? Aasem et al., 1995) and values of +2? to +8? for basal fluids (Srinivasan et al., 1994) was assumed to estimate depositional and diagenetic temperature respectively