Technology for Prediction of Underwater Distributary Channel Reservoir and Application in B Structure,Xihu Sag

The sandstone reservoirs in B Structure are characterized by low porosity and low permeability,deposited under shallow water depositional system,with underwater distributary channels well developed,and the sand bodies change quickly in lateral direction.For delineating the lateral change of sand bodies correctly and finding the favorable reservoirs with good physical properties and high hydrocarbon saturation from low porosity and low permeability reservoirs,pre-stack inversion technology for prediction of underwater distributary channel reservoir has been used.Based on petrophysic analysis,the elastic parameters and their combination that can be used to identify sand bodies and favorable reservoir are established.It has been confirmed through analysis of seismic characteristics of low porosity and low permeability sandstone reservoirs that it is feasible to identify favorable reservoir using prestack inversion.Then the process and key techniques for pre-stack inversion are optimized for the study area.The pre-stack inversion results have been used to delineate the geometry and distribution range of underwater distributary channels in S1 layer in Structure B,and also used to predict favorable reservoirs and guide the drilling location design of an appraisal well in B Structure.It has been confirmed by the actual drilling results that this reservoir predication technique is effective.