Study On The Key Technology Of The3D Seismic Exploration In The Loess Plateau Area And Its Application

Carrying out geological exploration and identifying the general geology is the premiseof planning and design of mining area. It’s also the premise of safety and high efficiencyproduction. JiuLongChuan mining area belongs to typical loess plateau area, which is coveredby the huge thick loess and whose landscape is mainly composed of loess tableland, valleyterraces and low hills. In view of the typical region, it is of great significance to carry out theresearch on the key technical problems and application of3D seismic exploration in loessplateau area.Taking JiuLongChuan coal mine as engineering background, this paper combinestheoretical analysis and engineering practice to study the technology of the3D seismicexploration in loess plateau area. Through the research on characteristics of deep structure andseismic excitation parameter, a reasonable method of field seismic excitation is proposed andthe seismic conditions are analyzed in the surface, shallow and deep layer. Based oncomparing different excitation horizons and excitation frequency, the paper analyses theinfluence to the seismic exploration and obtains selection method of3D seismic excitationparameters in loess plateau area. Excitation is selected in hard layer whose well depth isbetween10m~16m on the plateau. The well depth is between3m~12m in the ditch.6wellscombinational was adopted to stimulate in the areas where loess is thick and water table is deep,3~5wells combinational was to stimulate adopted in the areas where loess is thin; each wellcontains1~3kg gunpowder, and total dose should not exceed12kg, good information can beobtained.Under the detail techniques analysis in3D seismic data process, include staticcorrection, energy compensation, comprehensive eliminating noises, surface-consistentdeconvolution and DMO, aimed at the seismic characteristic of loess plateau, seismic dataprocess and relative test have been done using those techniques accordingly.Though the wayof contrast and ayalysis of data and test results, the key process techniques and corresponding parameters that suitable to loess plateau have been given, datum select as1200m, replacementvelocity as3500m/s, and prediction step as12ms in surface-consistent deconvolution.The paper studies on the prediction method and theory about coal seam structure andthickness in the loess plateau area. It establishes a interpretation method about structure andgives structure distribution about the three blocks of JiuLongChuan mining area. It identifiesthe main coal seam structure and variations in thickness. There are10fold, including fiveanticlines and five synclines. Exploration of the first block find out2normal faults whosefalls are more than5m and which are broadly in NW direction. Coal seam thickness andvariation trend are forecasted by adopting tuning theory and wave impedance inversionmethod. Based on the tuning theory and wave impedance inversion method, the predictionmethod about coal seam thickness in the loess plateau area is established. It forecasts coalseam thickness and variation trend in the three blocks of JiuLongChuan mining area.Based on two phase medium theory and the neural network theory, it establishes theprediction method of coal bed gas in the loess plateau area. It predicts the gas enrichmentzones in the first and third block. The3D seismic exploration has obtained three gasenrichment zones. The no.1relative enrichment zone is located in the north-central detectionarea, it is near NZ512drill-hole and its area is about0.04km2.The no.2relative enrichmentzone is located in the middle-east detection area, it is near NZ702drill-hole and its area isabout0.78km2. The no.3relative enrichment zone is located in the east detection area, it isnear NZ814drill-hole and its area is about0.39km2. The polar change of gas content of eightcoal layer is0~7.5ml/g in the third block.Finally, by contrast results of3D seismic exploration with results of drill-holeexploration, in the basis of above-mentioned research results, the paper studies questions suchas planning of mining areas, mine development plan and coal seam mining suggestion inNingZhong coal field based on geological investigation results of JiuLongchuan coal field,and provides reliable technical guarantee of scientific planning of mining area green miningfor JiuLongchuan coal field.