First Implementation of In-House Developed Base Oil in UAE Offshore Drilling Operation
Authors: Haddad Mohamed , O. Alhameli Falah , Khan Riad Nesheer , Zaheer Babar Muhammad , Saleh Ahmed , De Barros Adelson Jose Calleia , Sonawane Mukund Jibhau , Kulkarni Neeraj Mukund , Goncalves Fabio Barros Fernandez 
Published: October 2022

Abstract
This paper presents multidisciplinary technical collaboration that enabled a major operator in ABU DHABI developing, in-house, Ultra Low Toxicity Base oil (ULTBO) for drilling fluid applications in Offshore UAE. The ULTBO was carefully designed to meet the drilling fluids, safety, and environmental requirements and regulations for drilling operation in Offshore Abu Dhabi.
From one side, the ULTBO consists of n-alkane linear hydrocarbons with an ultra-low aromatic content (&lt; 0.1%) and exhibiting high flash point (86 °C) that promote people safety, environment sustainability and provide much less compatibility issues for rig equipment elastomers and gaskets.
From the other side, the ULTBO has low kinematic viscosity of 1.99 mm2/s at 40° C that surround the groundwork for efficient pressure management. It has high performance properties and relatively narrow boiling range which can, also, offer much less viscosity creeps related to evaporation and deliver more stable rheological profile under downhole high temperature and pressure conditions. This is turning drilling of extreme extended reach wells feasible by controlling the risk of losses and well control situations related to high equivalent circulation densities (ECD) and induced fractures (Nasrallah et al. 2017 and Hanson et al. 2019).
A Comprehensive testing was performed to qualify the in-house ULTBO. This includes property measurement, performance, compatibility, and stress tests. Besides, the performance of the ULTBO fluid was assessed under simulated downhole conditions and compared head-to-head against the standard ULTBOs being used in the field. It is well known that fluids with the same viscosity at the surface conditions can have completely different rheological profile under increased pressures and temperatures (Rommetveit et al. 1997). Testing the fluids under replicated downhole conditions would help spotting any excessive thinning effect that would lead to poor hole cleaning and high erosion, or any excessive thickening that would lead to extreme pressures, high ECD and induced losses.
Moreover, this work includes compatibility assessment of the ULTBO NAF blended with the standard base oil NAF used in the field, at different ratios. Confirming no compatibility issues would relax the boundaries for these fluids recycling, transfers, and handling at the operator storage facilities and supply boats.
In the field, the performance of the ULTBO was assessed, initially, in 12 ¼’’ troublesome shale section in one of the challenging conductor-sharing well, and then, in 8 ½’’ reservoir section within the same field.
The deployment and validation of the in-house ULTBO would result in increased drilling efficiency, while securing business continuity. It would generate significant savings, increased profitability, and provide an alternative base fluid for local and global drilling fluid market.