The Research Of The Application Effect Of The Magnetotelluric Method In The Evaluation Of The Regional Oil And Gas

The topic of the paper is from the project of geological survey which is fromChina Geological Survey Bureau---“the comprehensive research of the marine oiland gas and the evaluation of the district in the upper and middle key area ofYangtze”.In the west side of Xuefeng mountain, there are many excellent primary oiland gas geological conditions and multiple high-quality oil and gas combination ofreservoir and cap strata, and there is a good exploration prospect. But because of itsunique rugged topography and complex geographical conditions, it seriously affectsthe efficiency and effect of seismic exploration and greatly increases the explorationcost. The magnetotelluric(MT) method with natural alternating electromagnetic fieldas source, without the artificial source, therefore, there are many advantages such asequipped with lightweight, simple operation, low construction cost, etc; Meanwhile,the MT method is based on the different frequency to detect the alternatingelectromagnetic signal, so the frequency of the electromagnetic field is the only factorto affect the detection depth, as a result, there are many other advantages such asstrong penetrating power, little effect of the impedance shield, great exploration depth,etc. So the MT method can be applied to the area where with complex geographicalconditions and the seismic exploration is not affective, through the analysis of MTdata, it can be speculated the fault, and get the information of structural trap、formation interface、sedimentary facies belts,etc. Therefore, it provide importantbasis for evaluating exploration prospect area of oil and gas and it is very important inthe study of the application of geological exploration for oil and gas.At first, the paper starts from the basic theory of MT, introduces the electricalproperties of the earth, including the general characteristics of the electricaldistribution of the earth, the resistivity of rocks in the superficial earth and deep earth,analyzes the theory of MT, indicates the theoretical basis of the application of MT.Then, introduces the work methods and techniques of the MT, including field work,data processing and data interpretation, analyzes the problems which need to benoticed in the work. Meanwhile, combined with practical application, the paperexpounds the geological survey of west of the Xuefeng mountain, briefly introduces the field work and data processing of the application instance, and made a detailedexplanation and evaluation of oil and gas, finally come to the conclusion andsuggestion.This paper focuses on the application of MT in a prospective area of oil and gas:firstly, according to the geological data of the area, analyzes the tectonic units andgeological characteristics of the line preliminarily; Then, processes the original dataof the MT in the area qualitatively and quantitatively, including data editing,polarization mode discrimination, curve type and distortion analysis and correction,and compiles the MT curve type map and frequency-apparent resistivity map forqualitative analysis on the basis. And calculate the data for quantitative inversion toget the MT inversion map of the continuous media. Then combined the qualitativeanalysis and quantitative interpretation of the results with the geology, physicalproperties and other oil and gas geological data of the area for geologicalinterpretation, and compiling geological interpretation section; Finally, takes thegeological interpretation section as the forward model to get inversion data, thencompared the inversion figure with the original inversion figure to confirm theaccuracy of the geological interpretation section and deduce the tectonic belt of thefavorable oil and gas structural belt.In the end, the paper puts forward some relevant suggestions, in the futureresearch of the application effect of the MT method in geological exploration of oiland gas, it should strengthen the study of construction of more practical forwardmodeling and extract the electromagnetic characteristics of the structure, and only inthis way can further improve the interpretation precision and provide theoreticalreference basis for future oil and gas exploration work.