In pore pressure estimation, Bowers’ velocity effective-stress method has always been a kind of computing model can not be ignored, use it to estimate pore pressure with high accuracy. Bowers pointed out that rock properties change or overpressure could cause velocity reversal data to diverge from the main compaction trend, and overpressure results from undercompaction or fluid expansion mechanisms. In the process of continued increase in effective stress, velocity-effective stress relations define the original compaction curves. As the effective stress decreases, a sharp decline in sonic velocity, velocity-effective stress relations define the rebound curves.

According to this theory, Bowers set up loading and unloading two pressure models, but in the study, we found a shortcoming in the Bowers’ unloading model. After Improvement, we arrived at a more reasonable theoretical model. In the application of well Moshen-1, we have verified its validity, and have achieved remarkable results.

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