Experimental investigation of the shear bond strength between HGM cement and shallow formation in deepwater environments

Abstract

Due to its low density and high strength, hollow glass micro-sphere (HGM) has become a popular additive to cement slurry in deepwater cementing. The shear bond strength (SBS) between the well cement and formation ensures the safety and integrity of oil and gas wells. We designed a simulation experiment to measure the SBS between HGM cement and shallow formations in deepwater environments. We studied the evolution of the tensile force when pulling a simulated pipe string and cement ring out of the soil layer with a constant force. The results suggest that the HGM content and size of the cement ring have no effect on the change in the tensile force over time. At the peak of the tension curve, the cement ring and soil begin to slip, causing the tensile force to decrease with time. We divided this curve into two sections, with the peak value as the dividing point. The first section is the accumulating section where the tension increases without displacement of the cement ring and the soil. The second section is the dynamic slip section. Additionally, we proposed the concepts of static SBS and dynamic shear bond coefficient. The static SBS is the strength at the pull-off position, and the dynamic shear bond coefficient is the cementation coefficient of the cement ring in the dynamic slip stage. We divided the cement ring into segments along its length, calculated the shear bond coefficient of the cement ring at different depths, and studied the variation in the dynamic shear bond coefficient with depth. The static SBS increases with decreasing HGM content and casing size, and the static SBS of the small casing is significantly greater than those of the middle casing and the large casing. The dynamic shear bond coefficient decreases after the occurrence of dynamic slip. This study provides important insights into the evolution of the cement-formation SBS, and the results can provide guidance for future cementing design.