The improvement of cementation quality rating method based on compressive strength for low density cement system

In order to prevent the occurrence of cementing fluid leakage in low leakiness formation and protecting reservoir effectively, low density cement system is widely used. As the use of lightening admixture to reduce the density in low density cement system, the cement acoustic impedance of low density cement system is different from conventional density, it can not reflect the real cementing quality when using the criteria of conventional density cement cementing quality evaluation to evaluate the cement job quality of low density cement. Targeted at this problem, this paper conducted a method to improve the criteria of evaluation of cementing for low density cement. Studies have shown that the compressive strength and the acoustic impedance has a good linear relationship in different types of low density cement conserved 24 h and 48 h, so we put forward a method to improve the evaluation of cementing quality of low density cement based on the compressive strength of low density cement.