AN APPROACH TO THE COMPREHENSIVE GRADING OF UVCONVENTIONAL RESERVOIR OF QIAN FOYAN FORMATION IN WESTERN PART OF NORTH SICHUAN

The sandstone of Qianfoyan Formation is tight and poor in micropore-geometry, but commercial oil were found in coarse calcareous shelly quart-zose siltstone. The reason for the storing of oil in Qianfoyan Formation is that the tight sandstone contains multiple layer of unhomogeneous resevoir interlinked by high angular fissures, which control the accumulation and production of oil and gas. Based on the features of the comprehensive logging curves, qualitative discrimination and grading are made.