Reinjection Effect Study of Different Geothermal Well Completion in Porous Sandstone Reservoir in Tianjin, China

Abstract

Since the 1970’s, Tianjin has exploited sandstone aquifer geothermal water. The amount produced has increased with time. By the end of the 1980s, reinjection tests had been carried out in sandstone reservoir in Tianjin. During these tests, about 30-50m3/h of waste water were injected into the reservoir. However, the injectivity decreased quickly during reinjection. Tests of sandstone reinjection were carried out again in the winter of 2004-2005, and the results were similar to that of the previous tests. Through many years of research, many studies and analyses have been performed on ground filter systems for reinjection, service regulations, and other aspect. The problems of reinjection in Porous Sandstone Reservoir have not been solved. Reinjection problems in sandstone reservoirs still occur at low reinjection rates and short duration times. Poor injection effect becomes bottleneck problem of sandstone of sustainable development of geothermal resources. The completion technology of reinjection wells were focused on in porous sandstone reservoirs in the latest five years and have made some achievements. The article describes two successful geothermal reinjection examples in sandstone aquifer reinjection in two different places. Different well completion which is filter and perforation are applied in the two projects. The reinjection test data indicate that the well completion is the key reinjection effects through the research of reinjection. Perforation can increase the effect of reinjection by combination of two well completions in same place. The reinjections rate of wells perforated are 100-130 m3/h, which is triple to fivefold more than the well which is installed the filter. Now the well completion of perforation is widely used in Tanggu and Wuqing district which is concentrated production area of sandstone reservoir in Tianjin