Acoustic logging on ultralow density cement bonded quality evaluation in cased hole

Cementing operation after drilling boreholes ensures oil and gas to be extracted effectively and avoids oil spill events such as BP Mexico oil leakage events. However, the loss of cement in deep formation due to its high density happens and raises issues. In order to overcome this problem, ultralow density cement or gas-based cements are used more and more commonly in recent years. Current acoustic evaluation tools, used to determine the cement bond quality, are designed for conventional high density cement. Therefore, they are not capable to image the ultralow density cement, whose acoustic properties are similar to borehole drilling mud. In this paper, a new acoustic technique is developed to image the ultralow density cement behind case. Finite difference method and analytical methods are used to simulate the wave-field of cased borehole which ultralow density cement bonded on. Based on the simulations, the optimal parameters of the evaluation tool design are proposed including spacing (from source to the nearest receiver and between the two neighboring receiver), frequency of source.