超低密度水泥固井质量评价方法

为了准确评价超低密度水泥浆固井质量，采用室内试验方法，研究了养护时间、温度和密度等参数对超低密度水泥石强度和声学特性的影响规律，拟合得到不同密度水泥石抗压强度与纵波、横波声速之间的关系方程；结合套管井井下声场分析结果，构建了基于抗压强度的超低密度水泥测井评价相对声幅改进算法，并建立了基于抗压强度的相对声幅校核图版。验证结果表明，漂珠类超低密度水泥石的相对声幅与抗压强度之间的对应关系较好，随着抗压强度增加，相对声幅减小；在相同抗压强度条件下，相对声幅随着水泥浆密度升高而减小。研究表明，应用超低密度水泥浆固井质量评价相对声幅校核图版，可以显著地提高固井质量评价的准确性和针对性。 

Evaluation Method for Cementing Quality of Ultra-Low-Density Cement

For an accurate cementing quality evaluation of ultra-low-density cement slurry, an indoor experiment was carried out to study the influence of parameters such as curing time, temperature, and density on the strength and acoustic properties of ultra-low-density cement stone. The relationship equation between the compressive strength of cement stone with different density and the acoustic velocities of P-waves and S-waves was obtained by mathematical fitting. In combination with the downhole acoustic field analysis of cased wells, an improved algorithm of relative acoustic amplitude was developed for the evaluation of ultra-low-density cement slurry logging based on compressive strength, and a correction type-curve of relative acoustic amplitude was built on that basis. The verification results showed that for the cement slurry of cenospheres, the relative acoustic amplitude corresponded well to compressive strength, and with the increase in compressive strength, the relative acoustic amplitude decreased. Under the same compressive strength, the relative acoustic amplitude was reduced with the growth of cement slurry density. The research demonstrates that the application of the correction type-curve of relative acoustic amplitude for the cementing quality evaluation of ultra-low-density cement slurry can significantly improve the accuracy and pertinence of cemen-ting quality evaluation.