Abstract:

Ordos Basin dominantly developed tight sandstone gas reservoirs in the Upper Paleozoic, with great exploration potential as large geological reserve, more than 5 trillion m3. By analyzing the tectonic evolution history of the basin, combined with inclusion thermometry, zircon UPb dating and authigenic illite KAr dating etc., it is defined that the controlling role on Upper Paleozoic tight sandstone gas reservoir is the tectonic evolution since the Late Paleozoic. Studies have shown that sedimentary palaeotopography was gentle and tectonic subsidence was slow during the CarboniferousPermian, which formed source rocks and sandstone reservoir with great extent. During the TriassicMiddle Jurassic, sedimentation became rapid with significant compaction and siliceous cementation. Along with strong waterrock interaction, tight sandstone reservoir began to occur. Intensive tectonic activities with the occurrence of thermal tectonic events made a large number of natural gas generated and migrated to accumulate during the Late JurassicEarly Cretaceous, which resulted in forming tight gas reservoir. From the Early Cretaceous to present, some natural gas was lost, and lots of lowpressure gas reservoirs have formed due to stratum uplift and denudation.

Key words: Ordos Basin, Upper Paleozoic, tectonic evolution, tight gas reservoirs, lowpressure gas reservoir