The effects of cement density and casing dimension on casing waves in oil wells

The acoustic field in a cased hole is studied through numerical modeling by combining experiment measurement when the first and second interfaces are bonded well. The effects of the density of the cement, the diameter and thickness of the steel pipe on the amplitude of the casing arrival (ACA) are investigated, and a part of the numerical results are compared with the experimental results. The results show that the ACA decreases with the increasing density of the cement. There exists a large difference between the ACAs for the low- and normal-density cements. Therefore, the different standard should be taken in the bonding evaluation for cements with different density. As the thickness of the casing increases while it's diameter keeps as a constant, the arrival time of the casing wave remains unvaried while the ACA increases. But when the diameter of the casing with a constant thickness increases, the arrival time of the casing wave is delayed and the ACA decreases. As for the three kinds of the steel pipe commonly used in oilfields, the relative amplitude of the casing arrival is larger in the big pipes. In addition, the numerical results of the varying trend of the relative amplitude of the casing arrival with the density of cements, on the whole, are in agreement with the experimental results.