# Green Approach in Water-Based Drilling Mud Design to Increase Wellbore Stability
## 3 Results  
Table 3 shows the results of API filtration measurements for the nine tested mud samples. From the presented results, it can be concluded that API filtration decreased with the increasing concentration of MPP. A significant reduction in filtration (from 18 to 13.5 mL) was observed by adding MPP particles less than 0.10 mm at the smallest tested concentration of 0.5% by volume of water (A1), while a significant reduction was achieved at a concentration of 1% by volume of water (B2) by adding larger particles from 0.1 to 0.16 mm (from 18 to 13 mL). The largest decrease in API filtration was gained for larger MPP particles ranging in size from 0.1 to 0.16 mm, added at a concentration of 2% by volume of water (B4), and was 10 mL compared to the measured API filtration of the base mud (18 mL). The thickness of the mud cake, regardless of the concentration of MPP, was slightly decreased by the addition of MPP in comparison with the thickness of the mud cake measured with BM (1.5 mm). A certain amount of mandarin powder obtained from mandarin peel dissolved in water [47], which led to an increase in the viscosity of the filtrate, contributing to a decrease in filtration value. In addition, the MPP was assumed to plug the pores in the mud cake, further reducing filtration. Figure 6 shows SEM images of the mud cakes obtained after API filtration of base mud (BM), and two mud samples containing different sizes of MPP at a concentration of 2% by volume of water (A4 and B4 mud samples). Figure 6 shows the relief surfaces of the mud cake without the indicated pores. It can be seen that for BM the surface is quite uniform with no significant change in texture, while for muds containing MPP, larger accumulations are observed over the entire surface, which are presumably mandarin particles filling small pores in the created mud cake, resulting in a significant decrease in API filtration values. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & & & & & & & \\ \hline
**BM** & **A1** & **A2** & **A3** & **A4** & **B1** & **B2** & **B3** & **B4** \\ \hline \multicolumn{8}{c}{**Mandarin peel powder concentration (\%) by volume of water**} \\ \hline
**0** & **0.5** & **1** & **1.5** & **2** & **0.5** & **1** & **1.5** & **2** \\ \hline \multicolumn{8}{c}{**API filtration (mL)**} \\ \hline
18 & 13.5 & 13.5 & 11.5 & 11.5 & 16 & 13 & 10.5 & 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Influence of adding MPP on API filtration [46]. The results for filtration through a 0.4 \(\upmu\)m\({}^{2}\) (400 mD) ceramic disc showed a significant decrease in PPT filtrate volume after 30 min for mud A2 (30 mL) containing MPP with a size less than 0.10 mm at a concentration of 1% by volume of water related to the results obtained for BM (52 mL), while twice the concentration of MPP (2% by volume of water) does not result in a significantly greater reduction in PPT filtrate volume (mud A4, 26 mL). For mud containing MPP with particles size from 0.10 to 0.16 mm, the PPT filtration volume after 30 min for mud containing MPP at a concentration of 1% by volume of water (B2) was similar (32 mL) to mud containing particles less than 0.10  
than 0.10 mm (A2 and A4). At a concentration of 2% by volume of water (B2), spurt loss was considerably lower (4 mL) in comparison to values measured with BM (8 mL). Filtration through a 0.75 \(\upmu\)m\({}^{2}\) (750 mD) ceramic disc showed a significant decrease in filtration volume after 30 min for mud containing MPP less than 0.10 mm at a concentration of 1% by volume of water (A2) (37 mL), related to values measured with BM (52 mL). In contrast to the measurement through a 0.4 \(\upmu\)m\({}^{2}\) (400 mD) ceramic disc, increasing the concentration to 2% by volume of water significantly reduced PPT filtration (22 mL with A4).