Improving Drill-String Extended Reach Efficiency in High-Temperature and High-Pressure Conditions: An Experimental Investigation

Abstract

Drill string buckling behavior is of interest to the oil and gas industries. Buckling severity increases as drilling continues and causes a lock-up condition beyond which drilling cannot commence. The friction force between the drill string and the wellbore is key in influencing drill string buckling initiation and progression. Herein, the effects of adding nano-sepiolite (NSP) as an additive to water-based drilling fluids on the friction between the drill string and wellbore wall were investigated. Various samples with different sizes and compositions of NSP were tested for their ability to reduce the coefficient of friction (COF) that delays the onset of buckling to facilitate deep drilling by providing improved lubrication characteristics. The drill string sinusoidal and helical buckling and lock-up condition and the axial force transfer (AFT) were experimentally investigated. The water-based drilling fluids’ lubricity, COF between the drill string and the wellbore wall, and the stability of the rheological properties of the NSP-modified water-based drilling fluids containing 1–6 wt% NSP were tested in a high-temperature and high-pressure (HTHP) environment utilizing an in-house experimental setup. Sepiolite in nano-form at 4 wt% and with a size distribution of 30–60 nm improved the stability of the water-based drilling fluids rheology, significantly decreased the COF of the water-based drilling fluids, and improved the drill string axial force transfer. NSP additives significantly improved the COF and the drill string AFT in the HTHP environment compared with that of other commercial drilling fluids.