This research work presents the experimental results of the effect of polypropylene beads' concentrations in water-

An underbalanced drilling using foam drilling fluid is one of the most effective solutions which are capable of preventing formation damage, differential sticking, or circulation lost. Nevertheless, the limitation of using foam drilling fluid is the stability of its rheological properties which would affect its lubricity characteristics. Therefore, a research study was carried out to determine the stability and effectiveness of water soluble polymers as an additive in foam drilling fluid. To produce the required and most stable foam, four types of surfactants had been tested, namely sodium dodecyl sulfate (anionic), cetyltrimethylammonium bromide (cationic), T×100 (non ionic), and n-alkyl betaines (amphoteric). Then, the water soluble polymers, namely xanthan gum, hydroxyethyl cellulose, guar gum, and carboxymethyl cellulose, were evaluated as a stabilizer in the said foam drilling fluid. The laboratory works involved lubricity and rheological properties tests, which were conducted at ambient condition. The experimental results showed that the use of xanthan gum with anionic surfactant produced the most stable foam drilling fluid compared to other polymers. Rheological properties of the polymer foam drilling fluid were compared with water-based mud, and it was revealed that polymer foam drilling fluid could perform as effective as the latter. The significant advantage of using polymer foam drilling fluid was its coefficient of friction which was found to be lower than the water-based mud.

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The major concern in multilateral drilling is the torque and drag that arises as we drill deeper coupled with the escalation of bottomhole temperature, which can be overcome through the use of a lubricant: a solid or liquid form. Solid lubricants have been proved to be able to reduce the coefficient of friction substantially. In this research work, polymer beads were used as a lubricating agent in a high-temperature condition. The polymer beads which possessed improved physical properties were constructed using polymerization of styrene monomer added with divinylbenzene. The molecular structure and thermal properties of the polymer beads were evaluated using Fourier transform infrared analysis (FTIR) and thermogravimetric analysis (TGA), respectively. The lubricity test was conducted on four different types of sample, namely oil-based mud, water-based mud, and water-based mud with polymer and glass beads, at temperatures ranging from 60 to 180°C. The experimental results were found to give an average reduction of 27.5 % of coefficient of friction at elevated temperature and the rheological properties experienced slight changes above 100°C as compared to water-based mud. In a nutshell, the polymer beads show the potential to be used as a lubricating agent in hightemperature conditions.

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