歧口凹陷歧南断阶带沙二段浊积扇沉积特征

Characteristics of Turbidite Fan Deposits in the Second Member of Shahejie Formation in Qinan Faulted Zone of Qikou Sag

歧口凹陷歧南断阶带的主要含油层系为沙河街组沙二段,浊积扇是其最发育的沉积相,也是最有利的储层。根据岩心、录井、测井及地震资料,对歧南断阶带沙二段储层的沉积特征进行了综合分析。结果表明,研究区浊积扇岩石类型为岩屑长石砂岩、长石砂岩,粒度概率曲线以弧形为主,沉积构造可见浊流构造和典型鲍马序列,浊积扇主要是受同沉积断层海四断层控制。根据其沉积背景和沉积特征,建立了该区浊积扇的沉积模式,其中位于中扇的辫状水道微相砂体物性好,是有利的储集相带,深湖暗色泥岩为主要的烃源岩和盖层,因此歧南断阶带沙二段具有优越的隐蔽油气藏形成条件,是油气进一步勘探开发的有利目标。

The second member of the Shahejie Formation was the main petroliferous stratum in the Qinan Faulted Zone of Qikou Sag,where turbidite fans were widely developed sedimentary facies and the best reservoirs.In combination with core,mud logging,logging and seismic data,the characteristics of sedimentary facies were comprehensively analyzed.The result indicates that the turbiditie rock types are lithic arkose and arkose,grain size probability curve is mainly the arc-like type,the most of the sedimentary structures are gravity flow structures and the typical Bouma sequence,and the turbidities are controlled by synsedimentary fault of Haisi Fault.According to the sedimentary setting and characteristics,the depositional modes of turbidite fans are summarized.The sand of braided channel in middle fan is the high quality reservoir and the favorable sedimentary microfacies.Dark mudstone of lake facies is the major source rock and caprock.Therefore,the second member of the Shahejie Formation in Qinan Faulted Zone has the best forming conditions of subtle reservoirs,it is the favorable target for further oil and gas exploration.