Application of polypropylene nanosilica as additives in water based mud to improve rheological properties and shale stability

Abstract

Drilling in swelling clay formation is rather challenging owing to the delicate formation of the wellbore. This is mostly because of the propensity of clay to swell when in contact with water. The high reactivity of swelling clays with water causes their constituents to swell and these can cause severe drilling problems, such as damage to the production zone. Potassium chloride (KCl) has been the most typical shale swelling control additive used to formulate WBM. However, at higher concentrations of KCl in WBM, the mud separates into two phases, which are liquid and sediments, and the swelling-control activity of the KCl is short-lived in WBM. A better efficient clay swelling-control additive, such as composite of polymer and nanoparticle, might be more effective. Therefore, in this study, the efficiency of synthesized polypropylene based nanosilica composite (PP-SiO2 NC) on clay swelling was carried out and its performance was compared to KCl mud and other types of water based mud. Samples of shale from Simpang Renggam shale formation were selected and tested for swelling behaviour over five different types of WBMs, which are (i) Basic mud (ii) KCl mud (iii) PP-SiO2 NC mud, (iv) Commercial SiO2 NP mud, and (v) Mixture of KCl and PP-SiO2 NC mud. At normal temperature 80°F and elevated temperature 250 °F, PP- SiO2 NC mud gave better results in the rheological properties such as gel strength, plastic viscosity, and yield point compared to other type of WBM. Improved shale swelling inhibition were achieved at a lower concentration (0.3 -1.0 g) of synthesized PP-SiO2 NC compared to 30g conventional KCl mud, which is required to attain its optimum inhibition level. 0.6g of PP-SiO2 NC based mud alone prove to be the best formulation as it only cause shale to swell up to 7.11% compared to KCl mud at 15.3%, mixture of KCl and PPSiO2 NC mud at 9.2%, and commercial SiO2 NP mud at 10%. Indubitably, the synthesized PP-SiO2 NC mud provide better in rheological properties at normal and elevated temperature and more efficient in minimizing clay swelling behaviour compared to other type of WBM and it has a higher propensity to prevent loss of filtrates into the formation.