Analysis on seismic response characteristics of channel sands and its influence factors: Case study of Upper Guantao Formation in KD1 area

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 condition 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 68%.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."