Foaming a cement slurry is known to reduce the fluid loss compared to that of the unfoamed base slurry (McElfresh, P. M. and Boncan, G, 1982). This study looks to quantify the effect other parameters such as fluid loss additive concentration, fluid loss additive type (ie: film former, particle bridging or water viscosifier), foam quality and temperature have on the foamed fluid loss performance.

Base foam cement slurries were designed with in the density range of 16.6-16.8 ppg. Static fluid loss testing was conducted on all slurry designs without foaming. The slurries were conditioned in an HPHT consistometer at either 50, 66 or 90 °F and 6250 psi prior to conducting static fluid loss testing. Two fluid loss values for the base slurry designs were targeted (approx. 100 and 200 mL API) to quantify the effect fluid loss additive concentration has on foamed fluid loss performance. The designs were then foamed to foam qualities of 10% and 40% in a Multiple Analysis Cement System (MACS) analyzer and conditioned for 30 minutes before being transferred to a foamed fluid loss cell and tested.

The control slurry with no fluid loss additive was tested at 66 °F and foamed to a 10% and 40% foam quality. There was a significant decrease in fluid loss after foaming with an almost 86% reduction in fluid loss versus the uncontrolled blowout value obtained by the base design. In the absence of fluid loss additive in the slurry, the fluid loss values showed improvement with increasing foam quality. The slurries containing a fluid loss additive showed the same reduction in fluid loss once foamed but didn’t show a significant change in fluid loss between the 10% foam quality to the 40% foam quality. The trend was the same for the slurries that started with an approximately 200 mL and 100 mL fluid loss. Both saw reductions when foaming but no significant change between foam quality values. An increase in slurry temperature generally produced lower fluid loss values once foamed.

Foamed fluid loss was performed and compared between slurries with and without a fluid loss additive present. Some of the slurries with fluid loss additives didn’t have fluid loss performance that correlated to foam quality. Two of the tested fluid loss additives showed a strong synergy with foaming to reduce the fluid loss. In comparison, the slurry without any fluid loss additives had fluid loss performance directly correlated to foam quality presenting some operational complexity.

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