## 5 Conclusions  
In this research, a multi-objective optimization was performed, based on pre-operational drilling tests linked to a new recent methodology aimed at improving the drilling process using a possible ideal combination of the ROP and MSE. This methodology was mainly based in a recreation (play-back methodology) of the usual DRT from a field dataset, from a real pre-salt drilling operation. The main conclusions drawn from this research are as follows:  
* The new concept of pre-operational testing based on the MSE showed promise through effective improvements in the drilling processes.
* The combination of the highest ROP and the lowest MSE allows us to perform an efficient drilling operation, preventing machinery and equipment overload, and consequently showing possible ways to improve the operational efficiency.
* The desirability method, as per [PERSON] (1980), allowed rooms to optimize drilling process satisfactorily, which may be extended to other operations and scenarios.
* For the WOB intervals of 3, 5, and 7 [klb], a good fit of the parameters was obtained, and as an interesting outcome for the industry, it was determined that a DRT using 5 and 7 [klb] may be sufficient to be applied in a real-time field operation.
* Through the parameters obtained from pre-operational tests, specifically for the data analyzed, it was possible to obtain eventual cost-saving and time-saving values ranging from USD 1,056,180 to 1,151,898 and 19.50 to 21.27 [h], respectively.
* The results of this research can be applied to the exploration of other natural resources, such as natural hydrogen and geothermal sources.  
Conceptualization, D.Z.M.; methodology, D.Z.M. and A.N.; formal analysis, D.Z.M. and A.N.; writing--original draft preparation, D.Z.M.; writing--review and editing, A.N., V.F.D. and M.H.M.; supervision, A.N. All authors have read and agreed to the published version of the manuscript.  
This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior--Brasil (CAPES)--Finance Code 001, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Financiadora de Estudos e Projetos (FINEP), and Ministerio da Ciencia, Tecnologia e Inovacao (MCTI), through the PRH 34.1 FEG/UNESP program, process number 0444/19.  
Not applicable.  
Data Availability Statement: Data are contained within the article.  
Acknowledgments: The authors would like to thank the Editor-in-Chief, Editor, and anonymous Reviewers for their valuable reviews.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**110 [rev/min]**} & \multicolumn{4}{c}{**120 [rev/min]**} \\ \hline  & **Time** & **Cost** & **Time Savings** & **Cost Savings** & **Time** & **Cost** & **Time Savings** & **Cost Savings** \\  & **[h]** & **[USD]** & **[h]** & **[USD]** & **[h]** & **[USD]** & **[h]** & **[USD]** \\ \hline
01 & 4.76 & 257,756 & 20.69 & 1,120,578 & 4.18 & 226,437 & 21.27 & 1,151,898 \\
02 & 4.76 & 257,958 & 20.68 & 1,120,376 & 4.18 & 226,521 & 21.26 & 1,151,813 \\
03 & 4.77 & 258,645 & 20.67 & 1,119,690 & 4.19 & 226,797 & 21.26 & 1,151,537 \\
04 & 4.80 & 259,977 & 20.65 & 1,118,358 & 4.20 & 227,306 & 21.25 & 1,151,028 \\
05 & 4.84 & 262,196 & 20.61 & 1,116,138 & 4.21 & 228,104 & 21.24 & 1,150,230 \\
06 & 4.91 & 265,692 & 20.54 & 1,112,643 & 4.23 & 229,270 & 21.21 & 1,149,065 \\
07 & 5.01 & 271,132 & 20.44 & 1,107,202 & 4.26 & 230,915 & 21.18 & 1,147,419 \\
08 & 5.17 & 279,802 & 20.28 & 1,098,532 & 4.31 & 233,213 & 21.14 & 1,145,122 \\
09 & 5.44 & 294,609 & 20.01 & 1,083,725 & 4.37 & 236,438 & 21.08 & 1,141,897 \\
10 & 5.95 & 322,154 & 19.50 & 1,056,180 & 4.45 & 241,080 & 21.00 & 1,137,255 \\
11 & 5.95 & 322,154 & 19.50 & 1,056,180 & 4.58 & 248,122 & 20.87 & 1,130,213 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Cost and time analysis related to the parameters and values presented in Table 3.