孤北洼陷长堤断裂带扇三角洲砂砾岩体沉积特征及空间展布规律

受多种地质作用的联合控制，断陷湖盆陡坡带内的扇三角洲型砂砾岩体在空间展布上具有较大的差异。综合利用岩心、测井和地震等资料，系统研究了孤北洼陷长堤断裂带周缘砂砾岩体的空间分布特征，分析了砂砾岩体形成的主控因素。研究表明砂砾岩体的形成主要受断层活动强度、湖平面变化和物源供给等因素控制，不同地区影响因素作用的强弱导致砂砾岩体分布的差异性。长堤断裂带北部地区断裂活动强，物源供给充足，扇体发育的规模较大，在剖面上多表现为多期垂向加积的特点，扇体前部往往发育大规模的滑塌浊积扇；南部地区断裂活动较弱，且物源供给弱，扇体发育的规模小，在剖面上表现为先退积后进积的叠加样式。受次级断层交替活动的影响，扇体在垂直物源方向上表现为多期的楔形叠加。总体上有利的相带，扇体的侧向尖灭和顶部泥岩的封堵联合控制了研究区油气的分布。

Sedimentary characteristics and spatial distribution of coarse clastic rocks of fan delta in Changdi fault zone in Gubei sub-sag,Jiyang Depression

Fan delta coarse clastic rocks on steep slopes of faulted lacustrine basins have large variability in spatial distribution due to the joint control of various geological factors.Various data including core, log and seismic data are integra-ted to investigate the spatial distribution characteristics and the main controlling factors on formation of the fan delta coarse clastic rocks in the 2^nd to the Upper 4^th Member of the Eocene Shahejie Formation on the periphery of Changdi fault zone in Gubei sub-sag.The study results show that the development of fan delta coarse clastic rocks are controlled by the intensity of fault activity, change of lake level and sediment supply.The contributions of each influential factor are different in different areas, resulting in the differences of distribution of these fan delta coarse clastic rocks.In the northern part of Changdi fault zone, fault activities are strong and sediment supply is sufficient, thus the fan delta deposits are large in scale and are characterized by vertical aggradation of multiple stages on sectional view.In addition, large slump turbidite fans are common in fan front.On the contrary, in the southern part of the fault zone, faulting is relatively weak and sediment supply is insufficient, thus the fans are small in scale and show a superimposition pattern of early retrogradation and late progradation.Owing to the alternative activity of secondary faults, the fan delta coarse clastic rocks are characterized by wedge-shaped superimposition of multiple stages in the direction of perpendicular to provenance.In general, the distribution of oil and gas in the study area are controlled by favorable sedimentary facies zones, lateral pinch out of the fans and sealing of top mudstone.