The Analysis Of Acoustic Fields In Cased Boreholes&Method Studies Of Well Cementation Evaluation

The main method to evaluate and carry out cement bond quality in cased borehole is CBL-VDL logging information, it can provide the quality and condition of cementation aboutI,Iinterfaces. Through extracting energy value of casing wave and formation wave from variable density logging waveform,calculating BI of I,II interfaces, furthermore, we can evaluate bond quality by using CBL-VDL logging data. At present, the best result was obtained through using VDL as the main method to carry out bond quality in domestic oil field, but there are still some problems need to be improved related logging data interpretation.According to the question in evaluate the cementation of the second interface, This artical firstly analyze the cased-hole borehole acoustic pressure field, aim to find tile characteristic wave which instmcts the cemented condition of the second interface. Therefore, first of all, through the theoretical calculation, we have simulated free casing, the first interface with slot, the secondary interface with slot and cementing well four different circumstances full’wave waveform and inspected influence while parameter variations, emphatically to seek the characteristic wave that instructs the second interface with slot.According to present situation of VDL logging, in this article, discussed the methods and standard of evaluating1,11interface. This article mainly using amplitude compare method and VDL We established cement bond index calculation model of evaluation of the first、second interface.We can evaluate the bond quality of I interface not only by using cement filling but using strength of cement or cement ratio method. At the same time, this article used formation wave and Complex-Mode Wave which picked-up from VDL data to discuss and carry out the attenuation correction and interference correction interference correction, furthermore find the energy parameter and calculate the BI of Ⅱ interface. We extract the casing wave and the formation wave in the acoustic full waveform, and making attenuation correction and disturbance correction to formation wave. In addition, using standardized processing method and cementation exponent method, we established cement bond index calculation method of evaluation method of the first、second interface.Finally, the twocementing bond method has been applied to the actual casing wells, has the desired effect.