Water hammer fracture diagnostics has been widely used in recent years, which enables field engineers to understand the stimulation effect from hydraulic fracturing treatment and optimize the completion strategy in time. Based on the high frequency acquisition equipment installed at the wellhead, the sampled water hammer signal is processed to obtain the reflection time of the fracture and the water hammer celerity in the wellbore, which is utilized to locate the downhole stimulation location. However, only the reflection time identified from the water hammer signal is used in current application, which means the waste of the useful information contained in the sampled signal.

In addition, the uncertainty of the water hammer celerity may lead to misjudgment of the downhole fracture, which is still challenging in nowadays diagnosis. Thus, profound investigation of the water hammer reflection characteristics and the its utilization to accurately identify the information of downhole events is the key. Water hammer travels through the wellbore, carrying information about wellbore parameters, which are easy to obtain in the fracturing design or during the treatment. Studying the effect of wellbore parameters helps better understand the details of the water hammer, which helps accurately identify the fracture information. In this paper, the influence of the wellbore parameters on the water hammer reflection details is studied for the first time based on the numerical study, including the wellbore cementing and diameter change. Besides, water hammer signals from field cases are also studied, and the waveform characteristics related with wellbore parameters influence was analyzed, providing some useful guidelines for field application. The results of our study can improve the identification accuracy and provide useful insight for water hammer diagnostics.

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