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The measurement of underground medium variation using a repeated artificial source has gradually become an important goal to pursue. In recent years,we have developed and improved a technology system with large capacity airguns excited in land reservoirs by transplanting marine seismic exploration technology. The excitation effect has a close relationship to airgun capacity,water environment,and excitation conditions. In view that large capacity airgun must be excited without a water environment,we expand the system to use in downhole. Based on the BHS-2200 LL downhole airgun with a capacity of250in3,this paper carries out a comparative analysis on the characteristics of an airgun source excited in 0. 2m- and 5. 0m-diameter wells,and the results show that:( 1) The dominant frequency of the airgun signal excited in a 5. 0m well is mainly from 10 Hz to40Hz,lower than that in a 0. 2m well,and the larger body of water is good for bubble oscillation.( 2) In terms of exciting energy,the signal excited in a 5. 0m well has stronger energy than in a 0. 2m well,with a difference of 1 order in magnitude,and the signal can be detected up to 9km excited in a 5. 0m well with a single shot.( 3) The airgun signal has good repeatability in both excitation wells. The downhole airgun excitation technology system has potential application in dynamic monitoring near a fault zone with a small scale range, exploration of oil and mineral resources, and modern urban geophysical environment.
The measurement of underground medium variation using a repeated artificial source has gradually become an important goal to pursue. The excitation effect has been enhanced an technology system with large capacity airguns excited in land reservoirs by transplanting marine seismic exploration technology. In view that large capacity airgun must be excited without a water environment, we expand the system to use in downhole. Based on the BHS-2200 LL downhole airgun with a capacity of250in3, this paper carries out a comparative analysis on the characteristics of an airgun source excited in 0. 2m- and 5. 0m-diameter wells, and the results show that: (1) The dominant frequency of the airgun signal excited in a 5 0m well is mainly from 10 Hz to 40Hz, lower than that in a 0. 2m well, and the larger body of water is good for bubble oscillation. (2) In terms of exciting energy, the sign 0m well has stronger energy than in a 0. 2m well, with a difference of 1 order in magnitude, and the signal can be detected up to 9km excited in a 5. 0m well with a single shot. ( The downhole airgun excitation technology system has potential application in dynamic monitoring near a fault zone with a small scale range, exploration of oil and mineral resources, and modern urban geophysical environment.