Features of waveforms of acoustic logging in the low permeability sandstone formation

For the low permeability sandstone oil production,the slowness of longitudinal wave and the transverse wave are needed in the high pressure process.The fissure to be made by the process or own in the sandstone is the passageway for oil from layer to borehole.Sonic logging is an effective tool to measure the slowness and test the fissure in the borehole.In this paper,some waveforms of the low permeability sandstone in the northwest are displayed,which are measured by a new dipole acoustic logging tool to be designed.In the new tool,the immanent frequency of borehole is used to designe the transducers.The impedance of transducer is coupled with the transmitting circuit.The sonic power is lager and 16 bits A/D are used in the sonic tool.The information recorded in the original waveforms is more.In addition to the normal longitudinal wave,the transverse wave and the Stoneley wave,there are reflected waves that begin from the first wave of waveform,and other waves which change their arrival time with the depth.The existence of these waves makes acoustic logging waveform complex,interfere with the extraction of the transverse wave slowness.Comparing with other logging curves,we find that these reflected waves relate to the expanded diameter of the well,it makes the value of the slowness larger.Moreover,in the low frequency waveforms measured by the dipole,the obvious reflected waves are obtained,which relates to the fracture of the formation.It is used to test the fissure.