A Study Of Geothermal Reinjection In The Guantao Reservoir In Tianjin

As renewable resources, geothermal energy has very important effects onimproving the social energy framework and protecting the environment. Geothermalresources in Tianjin exist in two parts: the Tertiary and base-rock reservoirs. TheGuantao formation becomes the main reservoir of good quality and low rigidity ofthe geothermal fluids. It has been utilized diffusely for space heating, bathing,swimming pool, green house, industry, physiotherapy spa etc. in Tianjin. With therapid economic development in Tianjin, the scope of geothermal utilizationincreased very quickly, due to there is little re-injection during the exploration, thewater level draw down deeper and deeper, and the rate decreasing from1.8to5.5m/a,up to2013, the water level is82-110m. Reinjection of the geothermal fluids after useis effective means for maintaining reservoir pressure which is the key to sustainableutilization of geothermal resources. Reinjection of the geothermal fluid is alsoimportant environmentally way preventing surface disposal and pollution of surfacewaters.In the Tianjin area, several tests and research regarding reinjection into sandstonereservoirs have been carried out during1980s to2008, all together four tests, eachlasting a couple of years. Due to chemical scaling in wells and formation, pluggingof aquifers and corrosion of casings, the reinjection rates into the sandstonereservoirs decreased dramatically with time. The biggest reinjection rate during thetests was44.6m3/h, causing the water level to increase very quickly in thereinjection well to the well head.In this report, the author collected the information and materials of reinjectionevaluation and research of the drilling techniques, filtering techniques andre-injection regulations, describing the reinjection experience during the past decadesin Tianjin. Made an deeper research in these techniques, made a great progress inre-injecting return geothermal water into sandstone reservoirs in two different areas.Three demonstration projects were set up and the re-injection rates acquired greatprogress, up to100-120m3/h into a single sandstone re-injection well.