The Influences Of Tectonic And Sedimentary On The Petroleum Accumulation In Aqituwula Sag In Erlian Basin

Currently,the Late Yanshanian Creaceous Strata is the key of hydrocarbon target in Erlian Basin.The main oil layers of the eight sags from which the proved reservoir comes are all located in Creaceous Strata.Over the years,the limitation of the single oil-bearing strata tends to be more distinctive along with gradually severe exploration situations.During the exploration of Creaceous Strata,Jurassic Strata located under the original Creaceous Strata in Erlian basin was found,extending widely within the basin.The oil-gas show is active.The less attention to Jurassic Strata causes the ambiguous knowledge about its structure and sedimentary system.Further study based on the successful exploration of Creaceous Strata should be carried for Jurassic Strata,which could work alternatively to offer more productions in Erlian basin.Aqiwula sag is seen as classical Jurassic and Cretaceous superimposed sag in Erlian basin.The synthetic study on the superimposed sag will guide efficiently the future exploration of the similar sags,which acts on improving potentially Jurassic hydrocarbon explorations in Erlian basin.Combining the multi-techniques such as seismic interpretation,sedimentary facies evaluation and source rock evaluation,the structure,sedimentary and reservoir characteristics of Aqituwula sag and geochemical characteristics of hydrocarbon source rocks were studied.The features of Jurassic and Cretaceous superimposed sags were analyzed.The reservoir control factors and oil distribution were revealed.The results show that Aqituwula sag is regarded as Jurassic and Cretaceous reformed superimposed sag.The reservoir control factors mainly include favorable structures,effective sand bodies,control on the expanded form of hydrocarbon source rocks and four positive tectonics developed from oil-generating sags,which is of benefit to accumulate oil.To develop the effective sand bodies in the fan delta with two main provenances originating respectively from the south and the north creates strong reservoir conditions.The growth of effective source rocks in the first member of Teng formation and two more Jurassic formations leads to 60 million ton resource scale.The oil distribution is highlighted as ‘west Cretaceous,east Jurassic,longitudinally superimposed oil accumulation in the cross zone'.Namely,the Cretaceous reservoir is distributed within Ulan tectonic,Shaer tectonic and Xiretao tectonic located in the west of the sag.The Jurassic reservoir is located in Zhamuha tectonic in the east of the sag.The Cretaceous and Jurassic superimposed reservoir is developed in the cross zone.