Experiments and Applications of Water Phase Trapping in Tight Gas Sand reservoirs.

Water trap constitutes a hampering barrier and an urgent research topic for effective exploration and exploitation of tight gas sand reservoirs.A series of scientific experiments and field applications were conducted taking Ordos Northern Basin as the entry example for resolving this problem.Ordos Northern Basin reservoir is mainly composed of fracture-developed sandstone with abundant different clay components and is characterized by its low porosity and permeability,low pressure,high capillary pressure,low initial water saturation.The mechanism and characteristics of water trapping in this reservoir was examined with typical sandstone core samples in details by lab experiments on spontaneous water imbibition andby calculations of water trapping index.The results of the experiments showed that the better physical properties and lower initial water saturation may easily result in imbibition-induced damage.Based on the knowledge obtained from these experiments,the reason of the quick and instant discovery of P1x2+3 gas-rich reservoir in Tabamiao region by using bridging techniques was successfully realized.