## 3 Results and Discussion of Conducted Laboratory Research  
According to the lubricity tester manual, the test is performed for 5 min and then the friction force value is recorded; so, for the steel block, the test was performed for both polymer fluids with and without weighting additives in which one of three lubricants, X, Y and Z, was added at a concentration of 2% vol. The results of friction force for the steel block after 5 min of testing are given in Table 2, and they will be used for comparing the results obtained with test blocks made from thermoplastic polymers. From the results shown in Table 2, it is shown that the recorded results of friction force depend on the solid particles as well as the type of lubricant used in the mud system. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Component** & **Function** & **Polymer Mud with** & **Polymer Mud with Weighting** \\  & & **Lubricant (PL)** & **Additives and Lubricant (PWL)** \\ \hline Water & Base fluid & + & + \\ \hline KCl & Inhibit clay muds & + & + \\ \hline Sodium carbonate (Na\({}_{2}\)CO\({}_{3}\)) & Increase the yield of clay and & + & + \\  & the deposition of calcium & + & + \\ \hline Potassium hydroxide (KOH) & Maintain and control pH in & + & + \\  & inhibited muds & + & + \\ \hline PAC R & Filtration control & + & + \\ \hline PAC L & + & + & + \\ \hline Filter check & Reduce mud filtration & + & + \\ \hline Barazan D & Increase viscosity & + & + \\ \hline Baracarb-5 & & & + \\ \hline Baracarb-25 & Plugging material, weighting & & + \\ \hline Baracarb-50 & additive & & + \\ \hline Avacarb-ME & & & + \\ \hline Lubricant at concentration of 2\% & + & + \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Composition of mud fluid used in laboratory tests. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & **X** & **Y** & **Z** \\ \hline Friction force (N) & PL2 & 192.16 & 160.14 & 65.83 \\  & PWL2 & 176.15 & 136.12 & 148.13 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Friction force value for steel block after 5 min of testing. In order to have a better understanding of the materials that were being tested, the way they would react with lubricants and whether there would be a significant wearing of the test blocks or not, it was decided to prolong the test time to 15 min, with recordings every 5 min. The first drilling fluid to be tested was a polymer fluid without weighting additives and without lubricants. The value of the friction force for each block was recorded after 5, 10 and 15 min and Figure 8 shows a diagram of the measured friction force for the tested blocks in polymer fluid without weighting additives and without lubricants. From the measurement data shown in Figure 8, the value of the friction force for the steel block increases as the test time progresses, for the test blocks made of PA6 it decreases as the test time progresses, while for the test blocks made of POM and Teflon the value of the friction force does not significantly change. After 15 min of testing, the highest value of friction force was recorded for the steel block, followed by the test blocks made of PA6 and POM, while the lowest value was recorded for the test block made of Teflon. The second drilling fluid to be tested was a polymer fluid without weighting additives in which lubricant X was added at a concentration of 2% vol. (PLX2%). Figure 8 shows a diagram of the measured friction force for the tested blocks in polymer fluid without weighting additives in which lubricant X is added at a concentration of 2% vol. From the measurement data shown in Figure 8, the value of the friction force for the blocks made of PA6 and POM decreases as the test time progresses, while for the test block made of Teflon, the value of the friction force changed slightly. After 15 min of testing, the highest value of the friction force was recorded for the block made from PA6, followed by the test blocks made from POM, while the lowest value was recorded for the test block made from Teflon.