The effects of borehole enlargement length on the slowness response of a dual transmitter and receiver acoustic logging system
扩径段厚度对双发双收声系时差响应的影响

The precision of acoustic logs directly affects the quality of oil and gas formation evaluation,the oil and gas reserve computation and the synthetic seismic records.The characteristics of the responses of a logging system with two transmitters and two receivers at a borehole collapse interval were first simulated by numerical method.It has been found that when the length of hole collapse interval is equal to a specific value,the difference between the recorded values and the true values reaches maximum,while the hole collapse interval is longer or shorter than this value,the differences become smaller,proportionally to the deviation from the value.If the borehole diameter is equal to or large than the critical diameter,mud wave will first arrive to receiver through the hole collapse interval.In a bed with a constant slowness,the critical diameter reaches maximum when the length of borehole collapse interval is equal to the specific value.The critical diameter becomes smaller for any other lengths of the borehole collapse intervals.A chart for determining the critical diameter is developed to identify the borehole conditions of the mud wave being the first arrival in the received signals.