| Author's Name: WANG Nai, WANG Xiujiao, LI Nan, LIU Yumei, LIN Tengfei, WANG Weijun, DONG Junchang, YANG Shuang, LUO Beiwei |
| The Iran A Oilfield of the Upper Cretaceous Sarvak Formation is a massive bottom-water bioclastic limestone reservoir with strong heterogeneity. Production preformation of oilfield indicated that barriers and baffles(BB) in the reservoir severely restricted the development of the oilfield. The type, porosity-permeability relationship, log response characteristics and identification criteria of BB in the carbonate rocks of the Cretaceous Sarvak Formation in the A Oilfield were analyzed through comprehensive study of cores, thin section and well logs, and the genesis and distribution
characteristics of BB were systematically studied to evaluate the scale of BB developed in the oilfield. It is shown that two different types of BB mainly developed in Sarvak Formation, including wackestone BB and packstone BB, and according to the main controlling factors of BB development, they can be divided into sedimentary genesis, diagenetic genesis and
sedimentary-diagenetic composite genesis which means that BB are affected by sedimentary environment in the early
period and then porosity space further reduced by diagenesis later. The wackstone BB, with average thickness of 15 m developed in Member 2 and with average thickness of 5m developed in Member 7 of Sarvak Formation, were controlled by the sedimentary facies including lagoon and restrict platform. The packstone BB, controlled by diagenetic genesis, is developed locally in Member 3 and Member 8 of Sarvak Formation with thickness about 3.25m to 4.5m.Penecontemporaneous cementation, burial compaction, burial ementation and dolomitization are the main diagenesis which caused the decrease of the porosity. In addition, a large number of thin BB is developed with variable thickness( about 4.8m to 7.1m) in Member 6-Member 4 of Sarvak Formation, which were controlled by both of sedimentary and diagenesis including compaction, cementation and dolomitization. It is concluded that the distribution of BB in Sarvak Formation have obvious rules in A Oilfield. The thick and stable BB developed in Member 2 of Sarvak Formation distribute in the whole research area, and the thin and local BB of Member 7 and Member 4 of Sarvak Formation is mainly developed in the west of research area. |
