银额盆地拐子湖凹陷构造特征及其对古地貌演化的控制

Structural characteristics and their controlling effects over the paleogeomorphic evolution for Guaizihu Sag in Yin’e Basin

银额盆地拐子湖凹陷勘探程度低,近年钻井显示的良好含油气性揭示了该区良好的勘探前景。综合分析盆地构造和古地貌特征是研究盆地沉积充填与储层发育特征的前提。结合区域构造背景,综合钻测井与地震资料,对研究区构造特征进行分析,再利用层序地层学法和地震地层学厚度趋势法恢复剥蚀地层厚度,明确不同演化时期古地貌演变特征。结果表明:拐子湖中凹表现为北北东走向、东断西超的箕状断陷样式,具有明显的断、坳双重结构,经历断陷期、断坳转换期、坳陷期3个构造演化阶段,其中断陷期边界断裂的活动具有弱—强—弱的变化趋势;断陷早期呈现多个半地堑并存的地貌格局,断陷晚期逐渐演变成一个典型的箕状断陷湖盆,地貌逐渐变平缓;断坳转换期和坳陷期断裂的活动性减弱,地貌进一步变平缓;受构造控制的盆地结构、同沉积断裂、构造调节带和剥蚀作用4个方面对古地貌具有明显控制作用。研究结果为拐子湖凹陷沉积充填及油气储层发育分析提供地质依据。

The exploration degree of Guaizihu Sag in Yin’e Basin is low,while in recent years,the drilling in this area has revealed a good exploration prospect.Comprehensive analysis of the structures and paleogeomorphic characteristics of the basin is the prerequisite for studying the sedimentary filling and reservoir development characteristics of the basin.Integrated with the regional tectonic background,and moreover the drilling,logging and seismic data,the structural characteristics of the study area were analyzed,and then with the help of the methods of sequence stratigraphy and seismic-stratigraphic thickness trend,the thickness of the denuded strata was recovered,thus the paleogeomorphic evolution characteristics in different evolutionary periods were finally identified.The results show that the central Guaizihu Sag is a NNE-strike half-graben fault depression with faulting in the east and overlapping in the west.The sag has obvious dual structures of the fault depression and depression,which has gone through three stages of the structural evolution:faulted period,fault-depressed transition period and depression period.The tectonic activity of the boundary faults in the faulted period has a weak-strong-weak trend.In the early stage of the faulted period,there were many half-graben existing together,while in the late faulted period,the basin gradually evolved into a typical haft-graben fault basin,and the landform gradually became gentle.The activities of the faults in the transition and depression periods were weakened and the landform became more gentle.The basin structure,syn-sedimentary faults,structural transform zone and denudation controlled by the structure play an important role in controlling the paleogeomorphic landform.The study results provide the geological evidences for the sedimentary filling and oil-gas reservoir development in Guaizihu Sag.