The Kimmeridgian-Tithonian aged Arab Formation, as the main reservoir of the Jurassic succession in the Balal oilfield, located in the offshore region of the Iranian sector of the Persian Gulf, is investigated in this...The Kimmeridgian-Tithonian aged Arab Formation, as the main reservoir of the Jurassic succession in the Balal oilfield, located in the offshore region of the Iranian sector of the Persian Gulf, is investigated in this study. The formation is composed of dolomites and limestones with anhydrite interbeds. Based on detailed petrographic studies, six microfacies are recognized, which are classified in four sub-environments including supratidal, intertidal, lagoonal and the high energy shoal of a homoclinal carbonate ramp. The main diagenetic features of the studied succession include dolomitization, anhydritization, cementation, micritization, fracturing and compaction. Based on stable isotope data, dolomitization of the upper Arab carbonates is related to sabkha settings (i.e. evaporative type). In terms of sequence stratigraphy, three shallowing-upward sequences are recognized, based on core and wireline log data from four wells of the studied field. Considering depositional and diagenetic effects on the reservoir quality, the studied facies are classified into eight reservoir rock types (RRT) with distinct reservoir qualities. Dolomitization has played a major role in reservoir quality enhancement, whereas anhydritization, carbonate cementation, and compaction have damaged the pore throat network. Distribution of the recognized RRTs in time and space are discussed within the context of a sequence stratigraphic framework.展开更多
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...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 inter- granular 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.展开更多
文摘The Kimmeridgian-Tithonian aged Arab Formation, as the main reservoir of the Jurassic succession in the Balal oilfield, located in the offshore region of the Iranian sector of the Persian Gulf, is investigated in this study. The formation is composed of dolomites and limestones with anhydrite interbeds. Based on detailed petrographic studies, six microfacies are recognized, which are classified in four sub-environments including supratidal, intertidal, lagoonal and the high energy shoal of a homoclinal carbonate ramp. The main diagenetic features of the studied succession include dolomitization, anhydritization, cementation, micritization, fracturing and compaction. Based on stable isotope data, dolomitization of the upper Arab carbonates is related to sabkha settings (i.e. evaporative type). In terms of sequence stratigraphy, three shallowing-upward sequences are recognized, based on core and wireline log data from four wells of the studied field. Considering depositional and diagenetic effects on the reservoir quality, the studied facies are classified into eight reservoir rock types (RRT) with distinct reservoir qualities. Dolomitization has played a major role in reservoir quality enhancement, whereas anhydritization, carbonate cementation, and compaction have damaged the pore throat network. Distribution of the recognized RRTs in time and space are discussed within the context of a sequence stratigraphic framework.
基金the Research Institute of Petroleum Industry (RIPI),Tehran,for sponsorship
文摘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 inter- granular 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.