Characteristics Of Reservoir In The Second Segment Of Xujiahe Formation In The Upper Triassic Of Hechuan Area In Central Sichuan Basin

The dissertation pays a main research on the second segment of xujiahe formation of hechuan area in central Sichuan basin.researches the sedimentary facies,petrology characteristic,diagenesis of reservoir,properties and electrical characteristics,controlling factors of reservoir,we studied the evaluation and forecasting of the reservoir.The main depositional system of the second segment of Xujiahe are delta facies clip lake facies,which belong to delta front slope sub_facies,the main sedimentary microfacies are underwater distributary channel and estuary sand dam.reservoir rocks in higher levels of lithic and feldspathic,the lithology is mainly fine-medium lithic feldspathic sandstone and feldspathic detritus sandstone.The pore types are mainly intergranular pore,intragranular pore,matrix-pore and fractures.The diagenesis,which influences the pore development of the second segment of xujiahe,is mainly compaction,pressure solution,cementation and dissolution.The reservoir of the second segment of xujiahe is typical hydrocarbon reservoir with low porosity,low permeablity and higher saturation.From the porosity and permeability relations display reservoirs is porous reservoir.fractures undeleloped in reservoir, but property of reservoir is better with fractures;The electrical characteristics mainly for natural gamma and deep lateral overall for low value,compensated sonic and compensated neuton log for high value.The property of reservoir vertical for lower-Xu2 is better than upper, high value of porosity,reservoir thinkness and storage coefficient are in north east-south west direction a ribbon distribution,reservoir mainly by diagenesis,sedimentary microfacies and types of rocks factors.Hechuan area reservoir optimization evaluation criteria:①According to reservoir division standard of the second segment of hechan area,development ofⅠclass reservoir andⅡclass reservoir is favorable reservoir development zone.②sand of underwater distributary channel and estuary sand dam is thick and high porosity,which is favorable reservoir development zone.③High porosity,reservoir thinkness,high storage coefficient areas is favorable reservoir development zone.According to the evaluation criteria,combined with the whole studies of reservoir,forecast the second segment of Xujiahe formation ofⅠclass advantageous area 1,Ⅱclass advantageous area 3,Ⅲclass advantageous area 1.