The Research Of Sedimentary Microfacies And Reservoir Characteristics Of Shanxi Formation In Y131- Y319 Area Of Yan Chang Oil

According to the stratigraphic division and correlation, the types of sedimentary facies,evolution regulations, reservoir beds characteristics and gas reservoir characteristicsdescription research in the Y131- Y319 Area, some knowledges were acquired as follows: 1. The stratum of Lower Permianwas divided into four segments, including He5, He6, He7,and He8, and Shanxi Formation was divided into the Shan 1and Shan 2 He 8, Shan 1 and Shan 2 are the main gas-bearing zones in this area. 2. According to the tectonic study in this area, a gentle slope developed in He 8, Shan 1 and Shan 2 and Benxi Formation,which dip angle is about 1 °. The nose structure was few found in this area. 3. The underwater distributary channel and mouth bar of the delta front were developed during He 8, Shan 1 and Shan 2 times, sedimentary microfacies mainly include underwater distributary channel sandstone and interdistributary bay mudstone; Barrier island and tidal flat facies developed during Benxi times. 4. Based on the analysis of core data in the Upper Palaeozoic, the results show that the reservoir porosity is mainly between 0.1% ~ 20.0%, the permeability is between 0.01 ~ 10.0 mD.Permeability change is mainly controlled by porosity, permeability and porosity have the positive correlation. The permeability is also controlled by the difference of pore structure in main bearing reservoir beds. The porosity and permeability are lower than other area in Ordos Basin, the average porosity is less than 4.98%, the average permeability is less than 1.1 mD, belongs to tight reservoir. 5. The reservoirs are the dry gas reservoirs without sulfur,because their dry coefficient is 0.99, and they also do not contain H2 S. The water in four bearing layers is weak acidity(PH average 5.36), water type for CaCl2 type(surin classification).The total salinity is 12.94 to 210.09 g/l, the average salinityis 69.86 g/l. 6. According to the studies on the reservoir beds distribution and the heterogeneity of gas distribution, the shape of reservoirs are sweet pots. Combined with reservoir bedscharacteristics, the type of gas reservoir in this area is belong to the "quasi continuous tight sandstone gas reservoir ".