不同水泥石声学和力学参数的实验测量和对比分析OA

To perfect the quantitative acoustic logging evaluation system for low-density and ultra-low density cement sheaths and solve the technical problem that existing standards cannot adapt to low-density cement with various lightweight additives and cannot accurately judge the hydraulic isolation capacity of cement sheaths only by acoustic impedance,a full set of technical methods are adopted.It includes establishing a numerical calculation model for borehole acoustic field of cased wells,carrying out indoor tests on acoustic and mechanical parameters of 23 types of set cements under multiple curing cycles,simulating cement bond log(CBL)full-wave waveforms and flexural Lamb wave attenuation characteristics of imaging logging,and establishing a complete experimental system including comparative tests on hydraulic isolation of cement sheaths.The research results show that:①A total of 151 groups of 604 set cement samples are tested.After 72 hours of curing,the longitudinal wave velocity of set cement has the optimal linear correlation with compressive strength,while the transverse wave velocity,acoustic impedance and density have weak correlations with compressive strength,and the compressive strength difference of set cements with the same density or impedance can reach up to 20 MPa.②High-pressure curing environment will crush lightweight materials inside low-density cement,and simultaneously increase the acoustic wave velocity,acoustic impedance and compressive strength of set cement,with the increase range determined by the pressure resistance of lightweight materials.③The hydraulic isolation strength of three types of low-density cement with a density of 1.3 g/cm3 varies greatly,the isolation strength of composite glass bead cement is 12.50 MPa,that of floating bead cement is 7.85 MPa,and that of composite perlite A is only 3.40 MPa,and the isolation strength is positively correlated with the compressive strength of set cement.④The amplitude of CBL casing wave increases monotonously with the decrease of set cement acoustic impedance,and the attenuation of flexural Lamb wave increases first and then decreases with the increase of cement impedance,reaching a peak at 3.9 MRayl,and Lamb wave has higher sensitivity for distinguishing the cementation state of low-density cement than traditional CBL logging.It is concluded that single parameters such as density and acoustic impedance cannot characterize the isolation performance of low-density cement sheaths,flexural Lamb wave imaging logging can improve the identification accuracy of low-density cement cementation,and special evaluation charts matching compressive strength-logging response need to be established for cement with different lightweight additives,which provides theoretical support for fine interpretation of low-density cement cementing quality on site.