An Assessment of the Dynamic Moduli of Atmospherically Generated Foam Cements

Abstract

The objective of this paper is to evaluate the dynamic moduli of atmospheric generated foamed cements at varying foam qualities routinely used for zonal isolation during well construction. Mechanical properties of the hardened foamed cement samples, such as Young's modulus (YM) and Poisson's ratio (PR) will be discussed, as well as permeability. All of these properties were obtained as a function of cyclic confining pressure ranging from 12 - 52 MPa (1,740 – 7,540-psi). The dynamic parameters were derived from ultrasonic velocity measurements, while permeability was measured using the transient method. Stepwise loading and unloading schedules were conducted to test the permeability and mechanical properties of the foamed cement at simulated wellbore conditions. Applied pressures varied between 6.5 MPa (943 psi) to 46.5 Ma (6,744 psi) in 4 MPa (580 psi) increments in two full up/down cycles. At every increment during these cycles, ultrasonic compressional (P), fast shear (S1), and slow shear (S2) wave velocities were measured, as well as the samples’ response to the upstream sine pressure wave of approximately 0.5 MPa amplitude. From the sonic velocity data the dynamic moduli including YM and PR were calculated, while the sample's response to the pressure wave was used for permeability calculations. Observations of both neat and foamed samples reveal variations in YM as well as changes in the other properties and characteristics. Differences were observed between the foam qualities, depending on the parameter being assessed. This information should enable design contingencies and allow for more resilient designs of foamed cements when used during well construction. In addition, industry can use these results as a baseline for comparison with previous, current, or future work including recently acquired field-generated foamed cement samples (Kutchko et al., 2014).