Enhanced cuttings transportation in deviated and horizontal wells using polypropylene–nanosilica composite

Abstract

Field cases revealed that cuttings transport optimization from the bit towards the surface eventuates in the cutback of drilling costs. In deviated and horizontal wells, cuttings transport is more complicated and has unremittingly been investigated due to complex fluid profile and the limitation of precise data on pipe rotation, hole angles, annular velocities, and cuttings sizes, which have to be considered concomitantly. Partially hydrolyzed polyacrylamide (PHPA), an extensively used polymer for cuttings transport due to its sterling drag-reducing feature, good viscosifying properties, and ease of solubility in water–based mud (WBM), has the problem of flocculation and viscosity at high temperature, which hinders the cuttings transport efficiency. Recently, polymer nanocomposite (PNC), a novel material formed from the hybrid of polymer and nanoparticle has received growing interest and is propounded for drilling operations because of its exceptional and intriguing properties. However, the behaviour of this material for drilling mud in a typical cuttings transport process is lacking in open literature. Herein, polypropylene–nanosilica composite (PP–SiO2 NC) was synthesized by hot emulsion sol–gel method, and its surface charge was modified using (3–Aminopropyl) triethoxysilane. The modified (PP-SiO2 NC-NH2) and unmodified (PP–SiO2 NC) were characterized by different investigative techniques to study their dispersion, micromorphology, bonding, and thermal stability. The PP–SiO2 NC–NH2 drilling muds were compared with those of the PHPA to investigate their effects on cuttings transport efficiency (CTE). The effect of annular velocities (between 66.1 and 234.1 ft/min), hole inclinations (from 45 to 90°), cuttings sizes (between 0.50 and 4.00 mm), and concentrations (between 0.4 and 1.2 g) of PP–SiO2 NC–NH2 and PHPA on CTE in a field-oriented cuttings transport flow loop with dimensions of 2.4–in.×1.2–in., 16–ft. long annulus were exclusively examined. Characterization data showed that amine layers were effectively deposited on the surface of the PP–SiO2 NC–NH2 particles and these particles were distributed between 80 and 390 nm, which signifies long term stability of drilling muds, especially at high temperature applications. All the mud samples of PP-SiO2 NC-NH2 were within the recommended operating limits, unlike 0.8 and 1.2 g of PHPA - their properties were greatly flocculated due to the PHPA’s anionic character. The properties of WBM enhanced when PP-SiO2 NC-NH2 and PHPA were added, but higher CTEs occurred with the PP-SiO2 NC-NH2 drilling muds due to their uniform distribution and increased colloidal interactions with drilled cuttings. Concentrations of 1.2 g PP-SiO2 NC-NH2 and 0.4 g PHPA demonstrated the optimum concentrations for enhancement of rheological properties and were the most suitable choices for enhanced cuttings transport. With the highest annular velocity of 234.1 ft/min at the horizontal annulus (90°), the CTE of the WBM related to the largest cuttings size (2.80–4.00 mm) was enhanced from 82.4 to 96.2% by 1.2 g concentration of PP-SiO2 NC-NH2 with pipe rotation. Similarly, 0.4 g optimum PHPA concentration increased the CTE of the WBM from 82.4 to 94.6%. The transport of larger cuttings depends more on annular velocity, unlike that of the smaller cuttings, which was more influenced by mud viscosity. Furthermore, rotation of inner drill pipe and increase in annular velocity effectively increased the drag effects leading to higher cuttings transport. This study is advantageous for expanding the frontiers of knowledge in PNC application for drilling operations, especially for cuttings transport.