Geophysical Exploration Of The Hot Dry Rock Resources In The Southeast Of Guangxi

At present,traditional fossil energy resources become more and more scarce with the development of economy.Therefore,people need to devote great effort to developing alternative energy sources as human being advance constantly.As a consequence,researchers have emphasized the importance of geothermal energy which is relatively widespread,among which the hot dry rock geothermal energy is regarded as an essential part and is paid more attention to.Many countries have been in the progress of conducting multiple practices on developing hot dry rock resources in recent decades,thereby accumulating abundant relevant research results,including exploration and development technology.China has also made significant accomplishments in the exploration,construction,and application of hot dry rock geothermal resources in the past decade.The tectonic activity in Guangxi,China has long been active,including the Caledonian Movement,Indosinian Movement,and Himalayan Movement that ultimately led to complex structures and substantial tectonic events in this region.Guangxi has multiple Meso-Cenozoic,mostly rift basins conducive to accumulate heat at a low level.The southeastern part of Guangxi has a basement consisting of Paleozoic or Mesozoic granite so that most of the hot dry rock came from these granite bodies with high temperature.Multiple low and medium temperature hot springs are distributed on the surface of the region,indicating the potential ample geothermal resources in the Guangxi area yet to be discovered.The local geological and geophysical conditions in Guangxi demonstrate a plentiful supply of hot dry rock.It is significant to explore hot dry rock resources and determine its location by conducting geophysical analysis in the Guangxi area.This thesis analyzed and summarized the regional geological conditions,stratigraphic distribution,major distribution of rocks,tectonic activities and its formed areas,new tectonic activities and its formed breaks and inactive and active basins in Guangxi Province,which provided foundational research materials for dividing the region into prospective areas based on hot dry rocks resources.In this paper,the researcher processed and analyzed the gravity and magnetic peculiarity in Guangxi.The first step was to perform regular processing on abnormal gravity and magnetic data in the region,including manipulating magnetic pole(for abnormal magnetic data)and performing logical extension,derivation,and Euler deconvolution.The researcher thus obtained numerous vital figures,including the general distribution of underground gravity and magnetic field,underground structure,and geological body boundary in the Guangxi area.The result revealed the concaves or convexes in the underground basement as well as the geological structure division.The researcher then used the Parker-Oldenburg method to calculate the abnormal gravity and magnetic data separately and obtained the characteristics of Moho depth and Curie depth.Besides,the researcher used the ICA method to analyze and calculate the abnormal gravity and magnetic data to comprehend the distribution characteristics of the basement lithology in Guangxi,especially for the acid rocks from all the granites.Then,the abnormal gravity and magnetic data were heightened,and the continuity and amplitude of the peculiarity have been strengthened.In contrast,the background peculiarity has been suppressed,and local peculiarity has been emphasized,particularly in the abnormal geological area where the basins have flat inner terrain.Thus,the structural traces have been highlighted.The researcher then calculated the geothermal flux density from the abnormal magnetic data in Guangxi and the underground temperature from the temperature measurement data from the local wells in Guangxi.The temperature distribution and thermal lithospheric depth at multiple locations were also obtained.Based on the distributions and characteristics of hot springs in Guangxi,the researcher has located a promising possibility of developing hot dry rock resources in the southeastern region.In the end of the thesis,the researchers analyzed the distribution of breaks and the basin structure based on the geological formation mentioned above.Besides,the gravity field and magnetic field trend distribution were analyzed through the abnormal data of gravity and magnetism to calculate the Moho and Curie depths.By measuring precipitation data,the researchers also calculated the heat flux density of the earth,the underground temperature distribution,and the thermal lithosphere's thickness-from the abnormal temperature at two locations in the hot spring and well.Integrating the analysis of basement rock masses and the distribution of granite bodies,the researchers summarized four most prospective areas for hot dry rocks in eastern Guangxi,including Hepu Basin-Nankang Basin,Shiwandashan-Nanning Basin,Qiaowei Basin,and Bobai Basin.This paper laid a solid foundation for future investigation in hot dry rock resources in Guangxi.