Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
A Study of Volcanic Rocks Identification by Seismic Methods in Subei Basin
(1) Ocean Research Department, Petrochina Hangzhou Research Institute of Geology, Hangzhou, China.
In recent years, volcanic rocks exploration enjoys growing popularity globally, and scores remarkable achievements. The reserves and output of volcanic rocks are increasing yearly.
The volcanic rocks, however, are difficult to identify, which is mainly attributed to their complex structural features and drastic lateral variations.
The aim of the study of volcanic rocks identification methods in Subei Basin (Jiangsu Province, China) is to identify volcanic rocks accurately and efficiently. According to the positions where the volcanic rocks were formed, three kinds of volcanic rocks are available in the area under study: volcanic crater rock, volcanic conduit rock and volcanic intrusion rock. Different kinds of volcanic rocks show various seismic reflection characteristics and attributive characteristics. According to those features and well-logging information, five methods can be used to identify volcanic rocks: seismic profile, amplitude time slice, coherence time slice, seismic amplitude attribute and seismic inversion. Volcanic crater rock can be identified through seismic profile, amplitude time slice, coherence time slice and seismic amplitude attribute. This kind of volcanic rock is characterized by down cut and high amplitude and the image on its amplitude time slice, coherence time slice and seismic amplitude attribute diagrams is ellipsoidal. Volcanic conduit rock also can be identified through its seismic profile, amplitude time slice, coherence time slice and seismic amplitude attribute. It has cylindrical irregular reflection and ellipsoidal images on its amplitude time slice, coherence time slice and seismic amplitude attribute diagrams. The difference between volcanic crater rock and volcanic conduit rock is that the latter has lower amplitude and lower coherence value than the former. Volcanic intrusion rock can be identified through seismic profile, seismic amplitude attribute and seismic inversion. It is featured by continuous high seismic reflection and high acoustic impedance.
Thanks to this study, many volcanic rocks have been identified accurately and quickly. Some of them have been proved by wells. Therefore, it can be concluded that those methods have achieved remarkable effect of identifying volcanic rocks in the area under study.