Foam cementing has been widely used for offshore applications where the formation has low fracture gradients, and shallow water flow may occur. One challenge of foam cementing is to ensure that the foamed slurry is stable at the desired foam qualities with low permeability. Therefore, stabilizers are commonly applied along with the foaming agent. This paper describes the comparison testing and several offshore applications of a new liquid foam stabilizer that improves logistics and flexibility on the rig, and prevents excessive viscosity and foaming during mixing.
The new liquid foam stabilizer was tested in the laboratory to compare its performance with that of a dry stabilizer used previously in the field. The stabilizer was then used in several offshore wells to assess its performance in real-world operations. In particular, one problem with dry foam stabilizers is that they can promote excessive foaming during mixing, which leads to pump cavitation if not controlled with a defoaming agent. The field operations were arranged to test a new operational procedure for use with the liquid foam stabilizer to avoid cavitation without a defoamer.
The laboratory testing determined that the new solids-free liquid foam stabilizer disperses easily in the cement slurry. The new stabilizer was also found to improve the stability of the foam and the density distribution of the set foam cement compared with no stabilizer. Furthermore, several case histories will demonstrate that the combination of the liquid additive and the new operational procedure improved the slurry mixability without any pump cavitation issues.
The new liquid foam stabilizer has more predictable and reliable response than conventional dry stabilizers, and the case histories will demonstrate how its use improves cementing flexibility and logistics.