## 3 Results and Discussion
### Characterization of the Salled Water-Based Fluid Formulations
Since the readings at higher speeds were not obtained for some formulations, as shown in Table 7, the statistical regression of these data was not possible. However, it is possible to infer that the increase in the PAC LV content acts predominantly on the rheological behavior of the formulations, since very high readings, which exceeded the capacity of the equipment, were verified for all formulations with the maximum content of this additive, including formulation F0, which was prepared without the addition of palygorskite. A similar behavior was described by [PERSON] et al. [42] with a fluid containing bentonite. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Formulation** & **L600** & **L300** & **L200** & **L100** & **L6** & **L3** & \(\upmu_{\text{a}}\) **(cP)** & \(\upmu_{\text{p}}\) **(cP)** & **YP (lb/100 ft2)** \\ \hline
0 & * & 239 & 195 & 134 & 23 & 15 & * & * & * \\ \hline
1 & 96 & 63 & 48 & 30 & 3 & 2 & 48 & 33 & 30 \\
2 & 115 & 78 & 60 & 37 & 5 & 3 & 58 & 37 & 41 \\
3 & * & * & 254 & 180 & 35 & 22 & * & * & * \\
4 & * & * & * & 230 & 50 & 34 & * & * & * \\
5 & 237 & 168 & 136 & 90 & 14 & 8 & 119 & 69 & 99 \\
6 & 233 & 167 & 134 & 90 & 14 & 8 & 117 & 66 & 101 \\
7 & 227 & 161 & 129 & 86 & 13 & 8 & 114 & 66 & 95 \\ \hline \hline \end{tabular}
* Values not determined as the equipment’s reading capacity was exceeded.  
\end{table} 
Table 7: Readings obtained from the Fann 35A viscometer for the salted water-based fluid with palygorskite. Figure 4: Appearance of the fluid F4 (in triplicate) after resting at room temperature for 10 days. The authors observed substantial increases in the viscosity and yield point of the fluids as the PAC LV content increased, with the highest concentration of the polymer (4% \(w\)/\(w\)) resulting in values higher than the reading capacity of the equipment used. On the other hand, when comparing formulations F1 and F2 with the same content of PAC LV (4 g) and 10 and 20 g of palygorskite, respectively, it is noted that the addition of a higher clay content results in increases in the value of all the rheological parameters analyzed. This behavior is due to the mechanism by which palygorskite acts as a viscosity-ing agent, since the length of the fibers and the number of silanol groups on the surface of the particles help to aggregate the fibers and form a random network that traps water, increasing the viscosity of the suspensions [43]. The increase observed in the rheological parameters, attributed to the interaction between the PAC LV and palygorskite particles and, above all, to the increase in PAC LV content, demonstrated, preliminarily, a positive aspect of these formulations, since this behavior minimizes the solid sedimentation of the fluids. This was confirmed by the homogeneous appearance of the fluid F4 (Figure 4), which was prepared with the maximum content of PAC LV and palygorskite, after resting at room temperature for 10 days, with no apparent solid sedimentation. It is also worth highlighting that the substantial increases in the values of rheological parameters observed for this formulation (F4) do not represent a limitation regarding its use in well abandonment operations when considering a possible overload during its pumping, since in this type of operation, the fluid is not continuously recirculated in the well, as it happens during drilling operations. Therefore, based on the analysis of filtrate volume results and rheological behavior, as well as considering the implications of these parameters on the operational requirements of the abandonment operation, the fluid prepared with a higher content of PAC LV and palygorskite (F4) showed the most promising behavior for application as a barrier element, presenting a smaller filtrate volume and capacity to maintain solids in suspension for 10 days, which guarantees the maintenance of the hydrostatic pressure of the fluid column for temporary abandonment operations.