# Extended-Reach Drilling (ERD)--The Main Problems and Current Achievements
## 3 Drilling Fluids for Extended-Reach Wells
### Drilling Fluid Selection
A synthetic-based mud was shown to technically be the strongest, followed by a high-performance amine-modified water-based system that can be combined with techno-economically feasible treatment and disposal options that minimize the environmental impact [76]. To maximize the cuttings removal from the hole, new formulations of water-based muds were developed with the addition of different additives, such as: polymer beads (polyethylene, polypropylene), fibers (monofilament synthetic, polypropylene monofilament, cellulose nanofibers and natural hydrated basil seeds), nanoparticles, bio-based additives and a fuzzy ball [74]. The polymer beads improve the hydrodynamic resistance within the drilling fluid, leading to an increase in the drag coefficient. The fibers are dispersed in sweep fluids to form a stable network structure due to their entanglement. The fiber network prevents cuttings settling by mechanical contact and hydrodynamic interference between cuttings and fibers, and thus improves the drilling fluid carrying capacity. Bio-based additives and organic oils have been proposed to reduce the environmental impact of water-based muds and oil-based muds. So far, both oil-based mud (OBM) and water-based muds (WBMs) have been used in practice, which can be seen in Tables 1 and 2, as well as the depth and assembly used to drill each of the wells. Tables 2 and 3 summarize available data for 30 extended-reach wells drilled worldwide on 18 production fields. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Source** & **Well** & **Field** & **Location** & **KOF (m)** & **Measured Depth** & **True Vertical** & **MD/TVD** & **Delling** & **Mud Type** \\ \hline
[75] & N/A & Samburgburg &
\begin{tabular}{c} Western Siberia, \\ Russia \\ \end{tabular} & approx 2120 & 471 & approx. 3250 & 1.34 & RSS & oil-based \\ \cline{2-9}  & \multicolumn{2}{c}{Control} & \multicolumn{1}{c}{2118} & 5825 & N/A & - & RSS & oil-based \\ \cline{2-9} Ahn, 2015. [86] & A & N/A & N/A & 3012 & 6096 & N/A & - & - & - \\ \cline{2-9}  & \multicolumn{2}{c}{B} & \multicolumn{2}{c}{1993} & 4434 & N/A & - & - & - \\ \cline{2-9}  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & 1993 & 4434 & N/A & - & - & - \\ \cline{2-9}  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & 1993 & 4434 & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ \hline
2016. [69] & Typical & Eagle Feed & USA & 1829-3048 & 4877-6096 & 1829-3048 & 2-2-67 & - & - \\ \hline
2017. [87] & Perls-9 & Perls & Venezuela & 207 & 4660 & 2867 & 1.61 & - & oil-based \\ \cline{2-9}  & \multicolumn{2}{c}{} & 12 & N/A & 6061 & 1571 & 3.86 & - & - \\ \cline{2-9}  & \multicolumn{2}{c}{} & 13 & Vury Kerdugian & Caspin Sca & N/A & 6900 & 1573 & 4.06 & - & - \\ \cline{2-9}  & \multicolumn{2}{c}{} & 15 & N/A & 4684 & 1572 & 2.98 & - & - \\ \hline Vasquez Rosutta & \multicolumn{2}{c}{} & N/A & G & Oman & N/A & approx. 3600 & 1078 & 3.34 & - & - \\ \cline{2-9}  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & approx. 350 & 8800 & 2210 & 3.98 & RSS & water-based \\ \cline{2-9}  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & approx. 350 & 9000 & 2079 & 4.33 & RSS & water-based \\ \cline{2-9}  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & approx. 350 & 9000 & 2079 & 4.33 & RSS & water-based \\ \cline{2-9}  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ \end{tabular}
\end{table} 
Table 2: _Cont._