Research On Solidification Quality Evaluation Technology Based On Acoustic Characteristics

In recent years,with the deepening of oil and gas exploration and development in China,most oilfield developments have entered the middle and late stages.Due to the limitations of evaluation techniques themselves and the complexity of influencing factors,conventional cementing quality evaluation methods often result in misjudgment of cementing quality and cannot meet the requirements of high-precision research accuracy.In addition,the widespread application of enhanced oil recovery techniques such as fluid injection,acidizing,and fracturing has led to an increasing number of wells experiencing issues such as poor cementing quality at the Ⅰ and Ⅱ interfaces,development of fractures,and annular space bands.Cementing quality evaluation work is facing even more severe challenges.In response to the above-mentioned problems,this dissertation focuses on the issue of cementing quality evaluation using acoustic wave evaluation.By analyzing various factors that affect the attenuation of acoustic energy during casing wave propagation using acoustic wave principles,theoretical support is provided for reducing errors in small-scale indoor cementing quality acoustic wave detection experiments in the future.By testing rock samples with different bonding conditions,full-wave waveforms under conditions such as free casing,interface Ⅰ slotting,interface Ⅱ slotting,and good bonding were obtained.The influence of various parameter changes on the initial arrival time and amplitude was examined.Based on experimental data processing and result analysis,an evaluation model and standard for interface Ⅰ and Ⅱ cementing quality were summarized,and the evaluation standard was used to verify actual engineering wells.The main achievements and insights obtained are as follows:(1)Through the analysis of the propagation and energy attenuation process of casing waves,a downhole acoustic field model of casing waves was established in this study.It was found that scattering of the wave beam,partial energy absorption by drilling fluid,redistribution of energy at interfaces,and leaky Lamb waves inside the casing were the main factors causing the attenuation of acoustic energy.(2)In the experimental testing,different source distances and frequencies reflected different experimental results.When the source distance is too small,the casing wave and formation wave overlap,and it is impossible to distinguish between these two waveforms on the density map.Therefore,in the testing,a larger source distance was selected by considering the instrument parameters comprehensively.The high-frequency transducer can reflect more dense data and has higher resolution on the VDL imaging map.(3)When the cement bond of the Ⅰ interface is good,the bond area of the Ⅱ interface changes from good to poor,and the amplitude of the formation wave decreases while the amplitude of the casing wave remains low and stable.It is concluded that the amplitude of the casing wave and the CBL value are only related to the cement bond area of the Ⅰ interface,and are not affected by the bond area of the Ⅱ interface.The amplitude of the formation wave decreases with the increase of void area in the cement bond.The amplitude of the casing wave weakens with the increase of well diameter,while the amplitude of the formation wave increases.(4)Two different methods were used to evaluate the quality of the bond at the I and II interfaces,and evaluation systems and thresholds for both interfaces were obtained.The validity of the standards was verified through testing on actual engineering wells.