Study On The Reservoir Characteristics Of The Ma5 Member Of Block T43-S470 Well Area In Sulige Middle Area

T43-S470 well area is located in the Northwest Ordos basin. It covers about 500km2. The Ma5 member of in this region is an important production layer. Detailed study of the geological characteristics of reservoirs in this area is significant to the further exploration and development. Sedimentary analysis shows that the depositional environrnent of Ma5 member is generally in the tidal flat environment. The porosity, permeability and gas saturation of the study area sub layers of Ma513 and Ma541 are good. While Ma511 and Ma522’s are not as good as others’, which belongs to typical low porosity low permeability carbonate reservoir.The main diagenesis of Ma5 section includes dolomitization, compaction,pressure solution,dissolution, degypsumization, and dedolomitization.Dissolution is advantage to the reservoir. Reservoir space types include three categories and more than a dozen types.Among them, intererystalline solution pore and dissolution pore are the main reservoir space. Semi filling and full filling cracks of the study area ma51 – ma54 sub section take more than 80%,and semi filling and full filling the horizontal joints, vertical joints and miter seam take more than 75%. The main filling material is calcite, which affects the study area ma1- ma4 sub section miter seam to improve the reservoir permeability and promote the positive role of the natural gas migration.The reservoir is divided into four classes: class I、classe II、class III and class IV based on Porosity、Permeability Reservoir roek effeetive thiekness,o Pen flow ca Paeity,Pore strueture Parameters. Class I distributed in the ma13, which contains 5 regional distribution and the area is small. Class II distributed in the ma513,ma522,ma512 and ma513 covers the biggest area, and then is ma522, and the last is ma12. So more attention should be paid in ma513 and ma522 in the further important exploration.