渤海古近系扇三角洲精细研究及有利储层预测

研究区位于渤中凹陷与黄河口凹陷之间，其沙三段为扇三角洲沉积，而由于埋藏深、储层致密、砂体分布规律认识不清等因素，严重制约了油田的开发，因此，确定沙三段扇三角洲砂体展布规律、识别有利储层成为开发地质重点研究内容。沙三段沉积时期处于渤海湾盆地第2次裂陷作用时期，为典型的断陷湖盆，研究区沙三段层序处于湖扩体系域，靠近盆缘断裂，扇三角洲向湖盆方向发育，并随湖平面上升呈退积型沉积。本次研究参考退积型扇三角洲野外露头特征，通过井震结合，利用井位电性特征与地震同相轴对应关系及地震时频分析对扇三角洲期次进行划分；通过统计地震资料沟谷分布，对扇三角洲水下分流河道分布及走向进行刻画，进一步根据井位砂体厚度与井距间关系式对砂体尖灭位置进行定量表征，利用以上方法将各期砂体展布情况进行描述；通过对低渗储层形成影响因素进行分析，对油田沙三段有利储层进行预测，为油田下步调整提供依据。

A DETAILED STUDY OF PALEOGENE FAN DELTA IN BOHAI SEA FOR PREDICTION OF FAVORABLE RESERVOIRS

The study area is located in the overlapping area of the Bozhong sag and Huanghekou sag. The reservoirs of the 3d Member of the Shahejie Formation is a kind of deeply buried and compact fan deltaic sand body distributed in an unclear pattern, by which the development of oil fields is severely restricted. Therefore, to identify the favorable reservoirs and to define the fan delta sand body distribution pattern of the 3rd Member of the Shahejie Formation have become the major concern of the development geologists. The 3rd Member of the Shahejie Formation is the product of the second stage of rifting of the Bohai Bay Basin, and therefore, the study area is a typical fault basin. Sequence stratigraphic study suggests that the 3rd Member was the deposits of transgressive system tract near the basin edge fault. Fan deltas were well developed in the direction towards the lake center. With the rise in lake level, fan deltas retrograded. Taking the retrograded fan-delta outcrops and their characteristics as references to carry out well seismic correlation, using the corresponding relationship between well electrical characteristics and seismic events, conducting seismic time-frequency analysis for division of development stages of fan deltas, and making the statistical distribution of seismic data in valleys, we described the underwater distributary channels of the fan deltas and their trend. Further, according to the relation between sand body thickness and well distance quantitatively to define the position of the pinchout line. Using the above method to describe the distribution of sand bodies and the controlling factors of low permeability reservoir. Upon the basis, prediction of favorable reservoir is carried out as a clue for adjustment of oil production.