Research And Application Of RVSP Exploration Technology In Carbonate Exposed Coalfield

There are relatively abundant coal resources in the carbonate area of southern China,but the exploration effect is obviously poor with the current seismic exploration technology.The difficulties of seismic exploration in such area are as follows: poor excitation conditions,the static correction is difficult and the current RVSP seismic data processing and imaging methods are not mature.In this paper,the following aspects are studied:(1)Derived the theoretical expression of the near-source and the far-source wave field,and the influences to the wavelet related to cavity radius,linear strength of rock and dynamic modulus are analized through numerical simulation.(2)Simulated the lighting effect of single-shot excitation,delay excitation,combination excitation and phase control excitation in order to seek a better way to stimulate.(3)Carried out physical experiments of transmission and reflection to sandstone and limestone alone or in combination,and analyzed the changes of energy and frequency of waves(transmitted or reflected waves)under different conditions,and studied the seismic signal excited in carbonate rocks.(4)Established geological models of bedrock exposed,surface fluctuated gently and severely of different surface conditions to study the applicability of the first break CT static method to reconstruct the velocity model in RVSP exploration.(5)Studied the equivalent surface treatment technology of RVSP under different assumptions such as single-target homogeneous medium,fully equivalent homogeneous medium,single-target layered medium,multi-target layered media and fully equivalent layered medium.The equivalent effect of different depth target is studied in the case of single-target layered media.(6)Through theoretical research and numerical model test,the seismic attenuation estimation and compensation method based on matching persuit are studied.Through the above research,this paper has got the following results:(1)Through numerical simulation and physical experiment,it is concluded that limestone excitation is an important reason for the bad signal-to-noise ratio in seismic exploration of carbonate rock.(2)The RVSP equivalent ground transformation methods under different geological conditions are studied.(3)In order to improve the effect of amplitude attenuation method,zero phase and centroid frequency conversion is proposed.(4)For the first time,the 3D RVSP method is applied to the reflection wave exploration of coal seam in Guizhou Wulunshan coal mine,and an ideal result has been obtained.In summary,the research results of this paper have important significance to improve the seismic exploration precision in carbonate rock area.