Problem and countermeasure of reserve estimation and calculation of tight lithologic gas reservoir：A case study in Upper Paleozoic gas reservoir in Daniudi Gas Field of Ordos Basin

In the Daniudi Gas Field which locates in the north of the Ordos Basin,a set of complete marine tidal flat-inshore delta-terrestrial braided channel sediments has been found in the Upper Paleozoic.Influenced by severe diagenetic effects and sealed by regional cap rocks in the Upper Shihezi Formation,box-shaped gas reservoirs which were composed of multi-layered large-scale tight lithologic gas reserves were formed in the Upper Paleozoic.Production in multiple layers has enhanced single well productivity and improved economic benefit.In view of the geologic and productive features of the Upper Paleozoic gas reservoirs in the Daniudi Gas Field,an estimation method of longitudinal superposition and crosswise connection as well as an economic evaluation plan of longitudinal multiple zone production and crosswise flatten were proposed.The questions of low yielding rate and low economic benefit were solved,providing ways for the estimation and calculation of tight lithologic gas reserves.