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Integrated Rock Typing of the Grainstone Facies in a Sequence Framework: a Case from the Jurassic Arab Formation in the Persian Gulf
Author(s) -
ASSADI Ali,
RAHIMPOURBONAB Hossain,
KADKHODAIEILKHCHI Rahim
Publication year - 2018
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.13636
Subject(s) - grainstone , geology , anhydrite , dolomitization , evaporite , diagenesis , facies , dolomite , sedimentary depositional environment , geochemistry , carbonate rock , carbonate , petrography , wackestone , calcite , petroleum reservoir , reservoir modeling , petrology , sedimentary rock , paleontology , gypsum , structural basin , geotechnical engineering , materials science , metallurgy
The late Jurassic Arab Formation, a significant carbonate‐evaporite reservoir rock in the Persian Gulf, is characterized by frequent grainstone facies. For rock type identification and reservoir characterization, core description, petrographic studies and pore system evaluation are integrated for Balal oil field in the Persian Gulf. The grainstone facies are developed into three shoal subenvironments on a carbonate ramp platform: leeward, central and seaward. Compaction, dissolution, cementation, anhydrite mineralization and dolomitization are the main diagenetic processes affecting the depositional pore system. Considering depositional and diagenetic features and pore types, the grainstones are classified into six rock types (RT 1 to RT6). Rock types 1, 2 and 5 have large pore throat sizes with intergranular and touching vug pore types. In rock type 3, moldic pores lead to high porosity and low permeability. Rock types 4 and 6 are cemented by anhydrite, calcite and dolomite. Generally, RTs 1, 2, 3 and 5 are related to late Transgressive systems tract (TST) and early Highstand systems tracts (HST) and show fair to good reservoir quality. In contrast, RTs 4 and 6 of late HST system tract show lower poroperm values, due to evaporite mineralization. Characterization of the grainstone facies provides a comprehensive understanding of the reservoir zones of the Arab Formation.