A AVO Analysis Technique Applied To North Kendong Area

The northern part of Kendong area belong to the sourth of Chengdao,Kendong, Changdi,Gudong,Kendongburied-hill drape structural belt which is nnw-directed, neogene Guantao formation drapeing above Gudong-Kendong buried-hill is the fluvial facies strata.The upper member of Guantao formation is meander sediment system.And 4,5sand sets are main oil-gas reservoirs.The oil-gas exploration of the northeast of Kendong area is divided into three stages according to time and purpose of explorationsince 1987.Now we are on the third stage of the finding structure background of lithology reservoir for the objective . As the impedance difference between the beraing oil-gas reservoir rock and country rocks increase, the oil and gas drilling are based on the amplitude of reflection characteristics . Most of the wells used this method are successed, such as Kendong 34, Kendong 47, Kendong 481 wells. But some drilling wells are failed, such as Kendong 346, 482 Kendong , 82, and so on.In the purpose layers of drilling wells are water layers. The failed wells performance strongly on the post-stack seismic profiles in the same as the seismic reflection characteristics of the bearing oli-gas reservoir.This indicate the strong amplitude information on post-stack seismic data may be related to oil and gas, but also may be related to changes in lithology .This method cannot be uesed to determine oil and gas directly. So the key of increasing the successfull rate in oil - gas exploration is to detect the bearing oil-gas with strongly amplitude sand.Guided by the petrophysical theory, combining comprehensive analysis on reservoir characteristics with logging petrophysical attributes, the paper points out that pre-stack seismic data is adapted to hydrocarbon detection in the upper Guantao formation in this area. In view of the low signal-to-noise ratio for pre-stack angle gathering presently, a method is proposed that partial stack gathering is applied to AVO inversion. Through AVO attributes processing, the IV and V sand groups in upper Guantao formation is analyzed.Results show S-wave impedance andμρare of prominent effect in lithological identification while Poisson ratio and large angle stack seismic data are good for hydrocarbon detection. The hydrocarbon detection results and the drilling results have a high coincidence rate up to 93%. The method of hydrocarbon detection based on the large angle stack seismic data has the advantage such as simplicity, rapidity and effectiveness, so it can be popularized and applied to the shallow fluvial facies formation in jiyang depression, the work flow of comprehensive application technique of pre-stack attributes is of positive effect in increasing the success ratio of exploration , developing and improving subtle reservoir description.