DEVELOPMENT GEOLOGICAL CHARACTERISTICS OF THE LOWER PERMIAN OVERLAPPING GAS RESERVOIRS IN DANIUDI GAS FIELD

The Lower Permian overlapping gas reservoirs in Daniudi Gas Field consist of P₁s¹,P₁s²,P₁x¹,P₁x² and P₁x³.The gas reservoirs are overlapped each other vertically and intersected horizontally.The gas reservoir type is low permeable and dense sandstone lithologic gas reservoir,which has the constant volume and elastic drive.P₁s¹ and P₁s² gas reservoirs are mainly delta plain subfacies distributary channel sand body deposition and P₁x¹,P₁x² and P₁x³ gas reservoirs are mainly fluvial braided channel sand body deposition.The natural gas from P₁x² and P₁x³ gas reservoirs are dry gas and the rest are wet.The Lower Permian overlapping gas reservoirs are large gas reservoirs with lower abundance,mid-deep and medium-low yielding.Adoptting natural depletion development mode,it showed that single-well production of P₁x³ and P₁s¹ gas reservoirs is relatively high with fairly stable production,P₁x² gas reservoir takes second place and the single-well production of P₁x¹ and P₁x² gas reservoirs is relatively low.Multi-layer producing may increase production of single-well and intermission production is favorable for stable yielding and enhancing recovery of gas reservoir.Recognition to the geological characteristics of Lower Permian overlapping gas reservoirs is the basis of making gas field producing programs and developping gas reservoir scientifically,reasionablly and efficiently.