Improved second interface cementing evaluation using open hole slowness and formation wave energy of variable density log

Key words:  bond index of second interface  slowness  variable density log  formation wave energy  ? cementing quality

Abstract:

As an important link for cementing quality measurement, the bond of second interface has direct effect on the connection between oil and water bearing zones in the producing well. The arrival time of the formation wave of variable density lc^ (VDL) waveform was derived from the open hole acoustic data and the formation wave energy was calculated accurately in frequency domain. By the method, field VDL data were processed. The results show that, when the cement of first and second interface bonds well, there exists exponential relationship between the formation wave energy and slowness. Considering the effects of formation slowness on formation wave energy, especially the effect of fast or slow formation on the evaluation of second interface, a new bond index of second interface that mainly reflects the cement bond quality was provided. The processed results show that the new bond index curve is relatively smooth and the value is close to one in the well-bonded second interface, which can basically eliminate the influence of the formation velocity on the bond quality of second interface and can improve the evaluation quality of second interface.