Spatial distribution characteristics of strata and main thermal reservoirs and geothermal water resource potential in Xiong'an New Area

Abstract

It is rich in geothermal resources in mid-deep dolomite thermal reservoir in Xiong’an New Area. In order to improve the understanding of dolomite thermal reservoir characteristics and geothermal water resource potential, and guide the large-scale development of mid-deep dolomite thermal reservoir geothermal resources in Xiong’an, based on drilling, seismic, geological and other data, the strata spatial distribution characteristics, reservoir characteristics of dolomite thermal reservoir in this area and the geothermal water resource potential of dolomite thermal reservoir in the main construction area of Xiong’an are studied. The research shows that: the main thermal reservoirs in Xiong’an New Area are Wumishan Formation and Gaoyuzhuang Formation, which are distributed in the whole area except in some faults surface areas. Buried depth of Wumishan Formation is relatively shallow in Rongcheng Rise and Niutuozhen Rise, and relatively deep in Gaoyang low rise. Gaoyuzhuang Formation has similar distribution characteristics, with deeper burial depth and higher temperature. The distribution of other strata are limited except the Minghuazhen Formation of Neogene and Quaternary. Many normal faults mainly in NNE extension direction are developed in the area, which intersect with a few faults in other directions, communicating groundwater flow and heat flow, creating a large number of fractures on both sides of the faults, controlling the direction and scale of karst development, and forming a large number of dissolution holes. At the same time, the highlands of paleogeomorphology of the Wumishan Formation in the tectonic evolution, was mostly denuded in the Himalayanian, forming an unconformity with the Cenozoic, which together constitute an important transport channel and reservoir space in the area. The compound space of karst pores and fractures is the main thermal reservoir space of Wumishan Formation in this area, and the separate fractures and pores are the secondary thermal reservoir space. Once large karst caves are developed, they are often the main water producing layer. Geothermal water resources in dolomite reservoir with roof buried no more than 5 000 m (the bottom depth can reach 6 000 m) in the main construction area in Xiong’an New Area. Considering using 50% of the total hot water reserves in 100 years and the single well output of 110 m3/h based on the principle of "three production and two injection", the most suitable number of production wells is 233. At present, the main construction area can meet the annual demand of 4 787×104 m2 of heating area, accounting for 30.1% of the actual demand. It is concluded that the Wumishan Formation is shallowly buried, which is currently the main thermal reservoir under the current economic and technological conditions. Gaoyuzhuang Formation with the deeper burial depth is the most important backup thermal reservoir, which will be developed and utilized on a large scale in the next 20 years. However, even if they are developed at the same time now, they could not meet the clean energy demand of the main construction area of Xiong’an New Area, and it is necessary to develop a“multi energy complementary”system. Whether the excess geothermal resources outside the region can be gathered and transmitted to the target areas within the region is subject to economic cost and environmental risks. At present and in the future, it is both important and necessary to develop and apply energy-saving and thermal insulation technology.