| Title | Large Karstic Hot Water Reservoirs in Sedimentary Basins in China: Genesis, Energy Potential and Optimal Exploitation |
|---|---|
| Authors | Zhonghe PANG, Yanlong KONG, Lu LUO, Jumei PANG, Fengtian YANG |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | karstic reservior, hot water, sedimentary basins, optimal expoitation, China |
| Abstract | Carbonaferous rock formations are widely found in sedimentary basins in China. Hot water reservoirs have formed in these rock formations. A major part of the hot water used for space heating in north China is abstracted from these formations. In order to properly assess the energy potential of these reservoirs and to work out a rational mode of exploitation, systematic research has been carried out in the last a few years, taking several fields in the Bohaibay Basin as an example. Based on heat flow measurements, geotemperature field modeling and groundwater circulation studies, it has been found out that the heat accumulation in the shallow crust has been realized by a two processes: one is the heat re-distribution by differentiated heat flux due to difference in thermal conductivity of the formation rocks, the other is the heat swipt effect of regional groundwater circulation. Hot water temperature is the highest if the two processes are both enhanced by tectonic conditions. Injection tests of waste water have been performed to define an optimal mode of exploitation. Karstic reservoirs are fund to be favorable in injection, where gravity injection in one injection well can accommodate waste water from two production wells, a major advantage over sandstone reservoirs in the same region. Actual injection can be optimized based on tracer tests. Numerical experiments have shown that, life time of a field can be further elongated if injection is placed outside of the field with reasonable distances from the main production zones. Hot water in the karstic reservoirs in Xiongxian County of Hebei Province has been efficiently utilized to a large scale for space heating. Similar practice can be reproduced in other regions of the country. Similar kasrtic reservoirs are found to exist in several big sedimentary basins in China, so the energy potential is huge if developed. |