| UAE,short for The United Arab Emirates,is mainly situated in the East Sub-basin and South Gulf Salt Sub-basin of the Rub'Al Khali Basin,which is a Phanerozoic passive continental margin basin above the basement of(Pre-)Cambrian salt.This region experienced 5-stage tectonic evolution,which greatly influenced the oil and gas accumulation system in Rub'Al Khali Basin.In order to systematically analyze the controlling factors and oil and gas enrichment pattern in this area,this paper has applied tectonic,sedimentary and accumulation theories and methods to study the tectonic evolution of the Jurassic petroleum system in UAE and its control on hydrocarbon accumulation,basic petroleum geological conditions and accumulation characteristics.This paper summarized the characteristics of Jurassic Petroleum System of UAE:Rub'Al Khali Basin has very favorable petroleum geological conditions.Jurassic Petroleum System develops two major plays.Combing research on characteristics of reservoir-cap rocks and hydrocarbon generation/migration of main source rocks,this paper initially proposes that Jurassic Petroleum System is the best accumulation system in UAE.The advantages of accumulation elements of Jurassic Petroleum System are source rocks,plays and traps.First,this paper initially classifies and predicts the main source rocks of Jurassic Petroleum System in UAE.Source rocks are widely spread and of various qualities,and high-quality source rocks in the western UAE.Second,two major plays are of good reservoir-seal conditions,with relatively limited distribution of Upper Jurassic Play when compared to the wide distribution of Lower Cretaceous Play.Third,superimposition of multi-stage tectonic movement provides good conditions in forming favorable traps,which are mainly anticlines in the discovered reservoirs.These traps have three formation mechanisms: salt-arch movement,activated palaeo-basement uplift,and thrust faults.The best trap type in UAE is salt-arch anticline.Combining research on formation mechanism of carbonate platform,reservoir characteristics of rudist build,sedimentary environment and typical wells,this paper innovatively establishes a carbonate sedimentary model,named "Rudist Rimmed Platform on Gentle Slope," for the study area(Fig.3-26,3-27).This paper firstly defines that the distribution of good reservoir rocks was controlled by high-energy facies,such as reef and shoal.Favorable reservoirs developed in reef-core and pre-reef environment(Fig.3-28).This paper concludes that the shallow carbonate shelf-basin slope facies of this sedimentary model are most favorable area for rudist reef development,with best reservoir properties.This facies develop the most important enrichment region of oil and gas in UAE.Pre-reef facies of rudist reef mainly develops in deep-water carbonate shelf with low energy,which area is flat.The research region is characterized by broad slope of deep-water shelf,and develops a few patch reefs and tower reefs,which is also the enrichment region of oil and gas in UAE.Based on analysis of oil and gas accumulation characteristics and discovered reservoirs,this paper innovatively proposes the hydrocarbon accumulation pattern in Jurassic Petroleum System of UAE and defines the development of anhydrite cap rocks as the main controlling factors for accumulations.Oil and gas accumulated in Upper Jurassic Arab-Hith Play mainly develops in the west of South Gulf Salt Sub-basin and East Sub-basin of the Rub'Al Khali Basin;while oil and gas accumulated in Lower Cretaceous Play mainly develops in the mid-west of South Gulf Salt Sub-basin and East Sub-basin.Horizontal distribution of oil and gas is controlled by developing Range of high-quality source rocks,and pattern of oil and gas horizontal distribution is controlled by tectonic structures.Anhydrite cap rock is the main controlling factors in this region.The distribution and sealing capacity of Hith anhydrite cap rock controls the vertical distribution of oil and gas in Upper Jurassic and Lower Cretaceous. |
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