定量评价固井Ⅱ界面胶结质量的方法研究

声幅-变密度测井技术可以有效地评价固井I界面(套管和水泥环)的胶结质量,但对固井Ⅱ界面(水泥环和地层)胶结质量的评价方法研究还不够完善.结合现场固井资料对比分析了前人评价Ⅱ界面胶结质量的方法,在此基础上提出一种简单、有效的方法定量评价固井Ⅱ界面胶结质量.该方法利用裸眼井声波时差和井径资料估计变密度波列中的地层波到达时间,并以该时刻为起点开窗;然后对时窗内的波形作快速傅立叶变换,在频域内求地层波能量.这样消除了高频的套管波和噪声的影响,获得了准确的地层波能量.考虑到地层声衰减的影响,定义了更合理的Ⅱ界面胶结指数.给出了用该方法处理现场固井资料的例子.

On Quantitative Evaluation of Second Interface Cementing Quality

The conventional CBL-VDL logging technique, which is applied to evaluate cementing quality in a cased hole, is efficient for first interface (case and cement annulus) but not second (cement annulus and formation). Based on field data and analysis of methods adopted by others, this paper presents a simple but effective method to evaluate cementing quality of second interface. The arrival time of the formation wave of VDL is derived from the open-hole acoustic and caliper data, which is regarded as the starting point to take time window. Then the waveforms in the window are performed with FFT and the formation wave energy is calculated in frequency domain. Thus the interference of high frequency casing wave and noise can be eliminated and the accurate formation wave energy obtained. Considering the influence of formation wave attenuation, the bond index of second interface is defined in this paper more reasonably. At last, the method is used to process field cementing data.