Abstract:

The reservoirs of the 3^rd member of the Permian Lower Shihezi Formation(P₁h₃) in the Daniudi gas field in the Ordos Basin are typical fluvial deposits.As reservoir prediction with seismic attributes is constrained by seismic resolution,uncertainty occurs in the prediction of channel sandstone reservoirs.High-resolution sequence stratigraphy is applied in this paper to figure out the distribution pattern of sedimentary facies of the targets in P₁h₃.It has been made clear that the seismic reflector on the top of P₁h₃(T₉^f) has the geologic significance of an approximate isochronous surface in the whole study area.The relationship between the thickness of the upper sandstone interval in P₁h₃ and the average amplitude of T₉^f conforms to the principle of tuning amplitude.Thus,the amplitude attributes that are sensitive to the sandstone in the P₁h₃ are optimized.According to integrated analyses of seismic facies,logging facies and sedimentary microfacies,it is thought that the plan view of sensitive amplitude attribute of P₁h₃ is consistent with the distribution pattern of sedimentary facies.Favorable zones for sandstone development could be predicted through relevant analysis.Application in area near the D66 well shows that 90% of the prediction matches the real drilling results.Therefore,under the constraints of sedimentary microfacies and sedimentary characteristics,seismic attributions can be used to accurately predict and characterize complex reservoirs.

Key words: high-resolution sequence stratigraphy, channel sandstone, seismic attribution, facies-constrained reservoir prediction, Daniudi gasfield, Ordos Basin