3.5 Cementing Quality Evaluation

The basic requirements of China's cementing quality regulations: ① Based on geological and engineering design, casing depth, magnetic positioning, and cement slurry return height meet the specified requirements; ② Qualified casing string strength, specified minimum inner diameter of casing and sealing pressure test requirements, wellhead installation requirements of qualified quality; ③ Good cement ring sealing quality to prevent oil, gas and water layers from channeling and leaking. For the cement injection process, the above three requirements are the main aspects of cement sheath quality appraisal and evaluation.

Inspection methods for cement sheath quality include:

Well temperature logging is mainly used to determine the return height of cement slurry outside the pipe, and is also used as a supplementary explanation for the filling degree of cement slurry. The heat generated by cement solidification will cause the temperature to rise several degrees above the normal temperature. This factor is used to complete well temperature logging. By more clearly measuring the position where the cement slurry returns to high, the filling efficiency can be calculated. The annulus volume divided by the cement slurry volume is the filling efficiency, and is also used as an indicator parameter for whether cement channeling occurs.

Acoustic logging, also known as cement consolidation logging, is a method that emits sound waves or vibration signals to the formation based on the principle of acoustics, and then receives and records the round-trip time of the signals. According to the acoustic signal measured in the test well, the cement surface and cementation condition can be judged.

Variable density logging is generally called cement cement logging. The transmitter sends out a vibration pulse and the receiver receives it. And record the cement bonding logging curve to judge the quality of cementing.