Research On Numerical Simulation Of The Response Characteristic Of Multipole Acoustic Log In Natural Gas Reservoirs

The accurate identification and evaluation of natural gas reservoir is the key to the exploration and development of gas bearing reservoir. By establish two-phase porous formation's multipole borehole acoustic field numerical model, Systematic study of the logging response characteristics on the multipole array acoustic in the gas reservoir. Extract the sensitive parameters to identify and evaluate the gas bearing reservoir. Accordingly, form a rapid and accurate multipole array acoustic method to identify the natural gas reservoir.Based on the theory of borehole acoustic field,we build the two-phase porous formation's multipole acoustic field numerical model. To simulate the array acoustic wave in different geological conditions which are stimulated by multipole source. Analysis compressional wave, shear wave and mode wave that different component waveform of full wave's logging response characteristics of the gas. Using time-frequency analysis technology to extract information from acoustic full wave, and it makes time domain and frequency domain to effectively integrate. Opening a window to the signal by time-frequency analysis technology, we can get the time local domain information from various spectrum components. By using time-frequency spectrum figure, we can clearly and directly observe the energy of full wave's various components change with different gas saturation. Find out the special response of the gas layer.The velocity information of acoustic is an effective mean to identify gas layer. Ratio of compressional and shear wave velocity presence some applicable scope. Simulate the array acoustic logging response in different porosity, permeability and gas saturation. Extracting characteristics response of ratio of compressional and shear wave velocity. And decide its application in different environment. By comparing with the oil layer, determine its special response in gas layer, and lay the foundation for fast and intuitive multipole array acoustic identification and quantitative calculation. Spectrum information of dipole flexural wave can also be used to identify gas layer. By extracting the spectrum of dipole flexural wave from array acoustic, analysis the various sets of parameters of dipole flexural wave's response characteristic for gas layer in different porosity, permeability and gas saturation. And find out the sensitive parameters from them that have the special response for gas layer. Determine the different parameters'application in different environment, and to be as a standard of qualitative identification of gas reservoir.All these researches provide a completely new method for fully using well logging information to identify gas reservoir.