Study on Tianjin Tertiary Sandstone Aquifer Reinjection Plugging Mechanics

Abstract

Since the 1970’s, Tianjin has exploited Tertiary geothermal water. The amount produced has increased with time. Up until now, the amount exploited from the tertiary sandstone aquifer has been larger than the amount of from basement aquifer. However, long term reinjection to Tertiary sandstone is not possible. This paper discusses the mechanics of reinjection plugging based on reinjection testing carried out in Tianjin sandstone aquifer in 2004 and in 2005. Rock porosity, water quality analysis, water graininess and bacteria analyses have been performed. The Phreeqc software is used for water/rock interaction calculations (Spycher and Reed, 1976). It’s considered that the strata characteristics of loose, clay-cemented, fines and tight fissures in the Tertiary sandstone aquifer are the major internal reason for plugging. The combined action of deposition of suspended sediments, precipitation of secondary minerals, and bacteria growth in reinjection fluid are external causes. Suspended sediments deposition is the main reason for Tianjin Tertiary sandstone aquifer reinjection plugging. Reinjection temperature and volume are also influences on the reinjection. Prevention and cure measurements to reinjection plugging have been raised accordingly.