There are various seismic reflection types formed by channel sands in Guantao formation of Neogene in KD1 area due to a transitional sedimentary period from braided stream to meandering river. It is usually inapplicable when tracking strong seismic events to predict channel sand. So it is necessary to know the reflection features before we track sands using seismic data. Firstly, we analyze the lithology combination, velocity difference and thickness distribution according to the compare between reservoir and surrounding rock via all practical wells in primary sand groups. Then we build forward models to get the various seismic reflection types in condi-tion of different lithology combination and thickness assemblage. At the same time, we analyze the influencing factors resulting in the variety of amplitude. It is pointed out that most channel sands could form laminated sand-pack reflection and the probability of sand corresponding to strong amplitude is approximately 58%. With the same sedimentary background, the thickness of mud interlayer and velocity difference between sand and mud are the main influencing factors. So we should not aim only at those "light-spot" while deploying wells. It is important to choose favorable sedimentary facies and hydrocarbon accumulating area by geological analysis. The sands which formed weak seismic reflection might still contain oil or gas. The exploration practice shows the analysis method has a certain guiding significance for tracking sand and selecting drilling-well target%垦东1地区新近系馆陶组沉积时期为辫状河一曲流河的过渡时期,河道砂体形成的地震反射类型多样,以往井位部署时单纯追踪强同相轴的方法仍然会有部分砂体漏失.因此,在利用常规地震资料描述砂体之前,有必要明确河道砂体能够形成的地震反射类型.从研究区主力砂层组实际井储层与围岩的岩性组合、速度差异、厚度分布特征入手,建立正演模型,得出不同岩性、厚度、速度组合条件下河道砂体能够形成的地震反射类型,分析了引起反射振幅强弱的影响因素.正演模拟研究和实际资料的统计分析表明,研究区目的层段内大部分河道砂体均形成叠合砂包反射,大约有68％的砂体在地震剖面上呈强振幅反射特征.在相同的沉积背景下,泥岩隔层厚度、砂泥岩间速度差异对砂体地震响应特征变化起主导作用.针对研究区河道砂体进行井位部署时,不能只瞄准反射振幅“亮点”,而依靠地质分析,选择有利沉积相带和油气运移指向区尤为重要.即使是弱反射砂体,同样可能成藏.勘探实践表明,该分析方法对砂体追踪解释和井位目标优选具有一定的指导意义.
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