277 / 2019-07-09 16:45:45

歧口凹陷歧南断阶带明下段沉积相识别及沉积模式分析 Sedimentary facies recognition and sedimentary model analysis in Lower Minghuazhen Formation of Qinan fault step belt, Qikou sag

河湖交替相； 明下段； 歧南断阶带；歧口凹陷； 渤海海域,fluvial-lacustrine facies; Lower Minghuazhen formation; Qinan fault step belt; Qikou sag; Bohai Bay

现有的单一曲流河相认识无法准确全面地概括歧南断阶带范围内储层展布特征，为了有效地指导断阶带范围内明下段储层预测及油田勘探，综合利用岩心、古生物、测井、地震等资料，在沉积特征及古地貌重新分析的基础上，对研究区沉积相类型进行了重新认识。研究结果表明：明下段沉积时期歧南断阶带范围内存在湖相沉积，但由于其位于凹陷边部，平缓的古地貌及湖平面的频繁升降导致断阶带位置处周期性的暴露与淹没，从而发育河湖交替相，纵向上湖平面下降期形成的条带状的曲流河相砂体与湖平面上升期形成的席状的湖泊浅水三角洲砂体交替出现。浅水三角洲砂体受湖浪作用改造，储层展布稳定，储层连通性较好，多发育构造层状油藏，天然能量较为充足；同时洪泛期发育的厚层泥岩可在纵向上对砂体形成封堵，从而形成有利的储、盖组合，具有较高的勘探潜力，为今后研究区勘探开发挖潜的主要目标。该认识的发现，有效地提高及指导了后期调整井的实施及剩余油的挖潜。
The reservoir distribution characteristics in the Qinan fault step belt can’t be fully and accurately summarized by the existing single meandering river facies model. In order to guide the reservoir prediction and oilfields development, the sedimentary characteristics and paleo-topography are analyzed by means of multi-parameter analysis, such as core data, paleontology, well logging and seismic data. The sedimentary facies type in the study area is finally reinvestigated. The result shows that lacustrine deposition exists in the lower Minghuazhen Formation (Nm) of the Qinan fault step belt. However, the study area is located at the edge of the sedimentary center, and the gentle palaeogeomorphology and periodic fluctuation of the lake level makes large area in the fault belt zone expose and flood periodically, thus the fluvial-lacustrine facies develops in the study area. Longitudinally, the banded meandering river sand bodies formed during the downward stage of lake level alternate with the sheeted shallow lake delta sand bodies formed during the upward stage of Lake level. Transformed by lake waves, Shallow water delta sandbodies are stable in distribution, reservoir connectivity is good, structural layered reservoirs develops, and natural energy is relatively abundant. Meanwhile, thick mudstones developed during flooding period can form vertical blockage to sand bodies, thus forming favorable reservoirs. The combination of caprock and reservoir has high exploration potential, which is the main target of exploration and development in the future. Thus, the fluvial-lacustrine facies mainly develop in the fault-step belt. The sheet lake sand and belt fluvial deposits alternate vertically. Guided by the new facies type theory, the adjusting wells drilling and the remaining oil exploitation are efficiently improved and guided.