Research and Application on Measuring Casing Thickness and the Density of Cement Sheath by Using Three-Detector Density Logging Tool

Hudson Oilfield is the largest integrated ultra-deep facies sandstone reservoir in Tarim Oilfield, and more than 90% production Wells have been in operation for more than 5 years. Affected by geological, engineering, development and other factors, 119 casing losses have occurred in 71 oil and water Wells by the end of 2022, which seriously restricts the stable production of Hudson Oilfield. Casing quality monitoring and cementing quality reevaluation have become important supporting technologies for casing damage management. It is difficult for density logging to be measured in casing due to the influence of fouling on the wall and poor compensation effect of traditional dual source spacing density logging tool. Therefore, a backscatter detector is placed in the range of negative source distance to form a three-detector array density log, which can quantitatively compensate the wellbore size and better reflect the wellbore information. The MCNP numerical simulation software was used to study the density logging response of different source distances, optimize the design of short, medium and long detector source distances, improve the measurement sensitivity of casing thickness and cement ring density, and improve the resolution of density curves by frequency matching method. Compared with the traditional two-source distance casing-cement ring density tool, the error of casing thickness and cement ring density obtained by three-detector density tool is smaller, and the measurement results are less affected by well fluid. The application of this technology in Hudson oilfield has achieved good results and provides strong technical support for the treatment of casing damage in old Wells.