Seismic Prediction Of Overflow Facies Volcanic Reservoir In Yingcheng Group In Xuxi Area

This issue derives from the National Basic Research Program of C hina(973 Program)The identification and evaluation technology of volcanic hydrocarbon reservoir.The volcanic reservoir with great exploration potential has become an essential growth point in Daqing oilfield.During the past ten years,the explorationists have mainly sought the volcan ic high positon in structure in Xujiaweizi fault depression.However,with the verification of obvious explosive facies volcanic reservoirs and the increasing exploration requirement,the overflow facies volcanic reservoirs are raising more concerns of the researchers.While,how to identify and verify this type of reservoirs and find out the favorable areas becomes a vital problem.Comparing with the sedimentary stratum,volcanic strata are more complex.Different geological origins and volcanic rock lateral movement lead to the anisotropic feature and disordered reflections in seismic profiles.According to this problem,we interpret the volcanic reservoir in stages.Combined with seismic,drilling and logging data,we make the plan of identifying volcanic eruption periods within volcano strata and interpreting eruptive rock masses within periods.Division of volcanic facies is a significant part of volcanic reservoir research.We establish standard of volcanic facies division and determine main facies of single wells.Based on this,We use seismic profiles,horizontal time slices and preferred seismic properties to comprehensive analysis and generally identify volcanic channel facies,explosive facies and overflow facies.With the constraint of volcano eruption mode and volcanic rock masses horizon data,the initial model is built to accord with volcanic geological feature.Based on this model,we use poststack inversion to predict the volcanic reservoir.The lithology of volcanic stratum is very complex,including neutral,medium and acidic volcanic rocks.By using the mind of lithology classification,we analysis the rock physics parameters.After screening the mudstone,we classified the rest into basalt,andesite group and rhyolite group.Meanwhile,determine the threshold value of all kinds of rock reservoirs.According to this conclusion,we identify volcanic lithology and predict volcanic reservoirs with elastic parameter data calculated by prestack inversion.We also use several error analysis methods to verify the credibility of the prediction result.Then,we comprehensively analysis prediction result with the reservoir forming conditions,prestack prediction and facies results to select the overflow facies favorable reservoirs.Although overflow facies volcanic reservoirs prediction has only just began with a large number of difficulties,this research will play a significant role to promote further study and improve exploration precision of volcanic reservoir prediction.