The reservoir space of the Ordovician carbonates in Tazhong area

Tarim Basin

is mainly composed of fractures and secondary dissolved pores and cavities

and its seismic responses are bead-like reflections.The fact that the reservoir is covered by surface dunes and buried in depth leads to a relatively low signal-to-noise ratio of seismic data and the poor imaging precision for the reservoir.The oil-water contact is complex in the reservoir

making it hard to effectively identify its features by using post-stack hydrocarbon detection method.These problems have seriously restricted the progress of exploration and development of carbonate reservoirs in this area.In order to address these problems

we conducted research based on high-density seismic data in Tazhong area.As the high-density seismic data have higher signal-to-noise ratio and reservoir imaging precision

they are beneficial to study pre-stack hydrocarbon detection method for fractured-vuggy reservoirs.Firstly

more accurate P and S wave velocity can be worked out by Rock Physics Model.Secondly

AVO forward modeling of oil/gas and water wells is conducted

showing discrepant responses from different wells as a result.Therefore

the AVO attributive analysis technique can be used to identify liquids in carbonate reservoirs.Finally

pre-stack simultaneous inversion technique is used to quantitatively identify fluid types in reservoirs in the research area; The predictions are in turn compared with the results of formation testing

revealing an accuracy of liquid predictionsof 83.3%

which manifests that this method provides effective technical support for improving the success rate of drilling and reducing risks of hydrocarbon exploration.