Research And Application Of Magnetotelluric Data Based On Layer Stripping On Dry Hot Rock Monitoring

In today's society,traditional energy sources have been developed and utilized on a large scale,which cannot meet the needs of rapid economic development.The development of new energy is the trend of social development.Dry hot rock is defined as a thermal storage rock mass with a small fluid content in the deep earth and a temperature higher than 180 °C.With large reserves,renewable,clean and environmentally friendly,it is a strategic replacement energy source with great research prospects.The integrated geophysical method plays an important role in the exploration of dry hot rock.At present,the main exploration methods include gravity,magnetic and electromagnetic exploration.By measuring the physical properties of deep rocks,the underground temperature structure is indirectly obtained,and the dry hot rock development target is determined.Area.In addition,geophysical exploration methods can also monitor the development status of dry hot rock.During the development of dry hot rock,the reservoir resistivity will change due to water injection.The reservoir can be monitored by the Magnetotelluric sounding method.The method is economical,environmentally friendly,easy to lay,mature in theory,and has a large depth of detection.However,due to the absorption of the signal by the covered shallow formation,the amplitude of the signal transmitted to the deep is weakened,so that the Magnetotelluric sounding data collected on the ground cannot observe the resistivity change at a specific depth well.Therefore,it is necessary to find a suitable method to improve the Magnetotelluric data in order to improve the deep resolution of the Magnetotelluric sounding data.In view of the problem of reservoir monitoring and low depth resolution of Magnetotelluric sounding data,this paper proposes an IV effective scheme.The research contents are as follows:Firstly,based on the dry hot rock reservoirs and developable conditions,a reasonable geothermal reservoir model is established to provide a factual basis for the subsequent thermal storage monitoring simulation.Then the resolution of the Magnetotelluric data collected for the ground is low enough to detect the change of the smaller resistivity caused by the structural anomaly at a given depth in the underground in the monitoring investigation,and the layer stripping method is adopted according to the one-dimensional Magnetotelluric measurement.The deep theoretical analytical solution formula,the reverse derivation of the layer stripping method formula.The layer stripping method relies on the known structure of the upper layer to observe reservoir changes at specific depths.This method enhances the resolution of a specific depth signal,so a small resistivity change can be seen by directly observing the resistivity curve at a specific frequency(corresponding to a specific depth),and further inversion interpretation can be obtained closer to the actual target reservoir.The result of resistivity.The layer stripping inversion of the simulated 1D and 2D Magnetotelluric sounding data is carried out,and the following conclusions are drawn: in the one-dimensional case,the resistivity of the reservoir depth obtained by the layer stripping method is very accurate;Although the layer stripping method cannot obtain the accurate resistivity of the reservoir,it improves the resolution,and the inversion result is closer to the actual resistivity,and the boundary and depth inversion of the two-dimensional reservoir model are more accurate.Under certain conditions,this method overcomes the shortcomings of Magnetotelluric to observe the shortcomings of small resistivity changes,and also uses the economic and environmentally friendly Magnetotelluric method to monitor dry hot rock reservoirs.Finally,the paper applies the layer stripping inversion method to the measured Magnetotelluric data in the Gonghe region.The obtained inversion results are higher than the conventional inversion method and are closer to the actual underground electrical structure.More accurate geoelectric information,especially in the vicinity of the 35-37 measuring point,is more in line with the known geological structure of granite in the Qinghai Republic,providing guidance for the research and development of dry hot rock in the region.In addition,the Magnetotelluric method based layer stripping is not only used to monitor dry hot rock reservoirs,but can also be referred to in other reservoirs with electrical changes.