Research On Borehole Acoustic Field Simulation And Cementing Quality Evaluation Of Adhering Sand Casing Well

Nowadays, Daqing Oilfield has got into the adjustment and development phase of tertiary infill drilling, so the thin and poor reservoir that has the characteristics of small thickness, poor physical property, low permeability, big differences of pore pressure among layers is regarded as development object, which has put forward more rigorous demand to cementing quality. Adhering sand casing is regarded as infrastructure to improve the cementing quality of oilfield, which has been applied to cementing operation of oil layer.From the point of acoustic analysis, two layers of medium cementing agent and sand locates in the position between adhering sand casing and cement sheath, which changes the propagation path of logging acoustic wave and component of casing wave, influences the full waveform that has been received by receptor and leads to incorrect explanation results of cementing quality. In this paper, by taking solving wave equation that has been satisfied by borehole medium of adhering sand casing well as breakthrough point, research on borehole acoustic field simulation and cementing quality evaluation of adhering sand casing well have been studied. The specific research contents include the following aspects:First of all, based on basic assumptions of elastic mechanics, cubic volume element has been chosen to conduct force analysis and moment equilibrium equation, construct mechanical equilibrium equation and motion equation to deduce the wave equation of infinite homogeneous medium, isotropic medium and perfect elastic medium. Solve the wave equations in arithmetic coordinate system, cylindrical coordinate system and spherical coordinate system, which provides the theoretical basis for numerical simulation of borehole acoustic field.Furthermore, based on the physical models of wells under different bond conditions has been conducted. According to the continuity conditions of stress and displace of layers medium boundary, acoustic wave equation could be solved by using separation variable method. By introducing Tsang sound source function, the borehole acoustic field of casing well could be calculated by real axis integral method and FFT technology and analyzed the characteristic of the full waveform.Thirdly, according to the physical model of adhering sand casing well, studying the propagation path of sound waves in the hole medium, analyzing the composition of casing wave, applying the transfer matrix method to simplifying undetermined coefficient equations of sound field potential function, the borehole acoustic field of adhering sand casing well under different bond conditions have been solved. Based on the former research, taking the fine cementing of adhering sand casing well for example, the influences of sand size, sanddensity, cementing agent thickness and cementing agent components on the full waveform of adhering sand casing well have been analyzed.Finally, acoustic logging simulation experiment was designed based on the similarity criteria. By analyzing the relative amplitude correction coefficient of adhering sand casing well under different bond conditions, the cementing quality evaluation standard of adhering sand casing well was established, and then the influences of casing diameter, casing wall thickness, cement density, and cement quality impact on the casing wave arrival time and amplitude have been analyzed.It has very significant theoretical and actual meanings to conduct research on borehole acoustic field simulation and cementing quality evaluation of adhering sand casing well.Theoretically, it could enrich the theoretical study of acoustic field, which provides theoretical basis for cementing quality evaluation on acoustic logging of adhering sand casing well.Actually, it could be used to guide the cementing quality evaluation of adhering sand casing well and improve the accuracy of cementing quality interpretation.