MT Sounding And Geothermal Resource Assessment In Xianxian Convex Of Bohai Bay Basin

Magnetotelluric sounding is a passive source exploration methods,using natural alternating electromagnetic field.Since it would not be shielded by high resistance layer and has a good reaction to low resistivity layer,now we use it more and more often in the exploration of geothermal resources.Existing data has confirmed the exploration area is rich in geothermal resources,and it is one of the rarest geothermal anomaly areas.It is shallow,good-water-quality and has high warming rate.To the rational utilization of geothermal resources,we laid nine MT sections(119 sites).By pre-processing the collected data we obtained a quality signal.We obtained electric model by one,two,three-dimensional inversion with the signal,to distinguish important geological interface and determine the base downs.As can be seen from the electric model,the resistivity contours in the longitudinal performance of a alternant layered structure of high and low.It is closely related with stratigraphic distribution and illustrates the higher resistance basement with depth.Among them,the Minghuazhen of Tertiary strata is more concerned for the potential geothermal resource.We determined the average depth of 1560m,the overall depth decreases from north to south,and resistivity is in the range of 2?20?· m.In the transverse direction,resistivity features high and low blocks,signifying the recessed areas and raised areas,which is distributed by faults.To figure out the faults distribution is of particular importance since the mostly known geothermal fields of the area is caused by them.We analyzed the two-dimensional characterization,and concluded the faults by the results and other electric characterization.The major fault,XianXian fault,is basically consistent with the known results and we figured out a more precise location.We analyzed the distribution of water-rich strata and concluded geothermal anomaly areas to provide a reference for geothermal development.Meanwhile,we recommend two-dimensional MT inversion for the use of geothermy exploration.