First Nitrified Managed Pressure Drilling Application in United Arab Emirates

Abstract

Drilling fluid losses while drilling a mature cretaceous limestone reservoir unit (Formation A) has been worsening over years with reservoir depletion and lack of pressure support. New drilling methods were needed to eliminate or reduce total losses and the associated non-productive time with them. Nitrified Managed Pressure Drilling proposed to help in mitigating losses and reducing non-productive-time. This paper explains the challenge, details the solution that was proposed to tackle, and discusses the results of the application.

Nitrified Managed Pressure Drilling (MPD) decreases the Equivalent Circulation Density (ECD) below the lowest possible static mud weight (water) and at the same time deals safely with any unintended hydrocarbon influxes while drilling the reservoir 6″ hole section. The well data was analysed and modelled with different Nitrogen pumping rates and Surface Back Pressure (SBP) to determine the best rates that a mitigates losses but at the same time prevent hydrocarbon influxes. A closed-Loop drilling system proposed utilizing rotating control device, a separation package, and locally produced membrane Nitrogen allowed to manage the annular hydraulic pressure profile accordingly and mitigate the total losses scenario eliminating the wait on water time

Rigorous planning and disciplined execution have led to safe and successful conclusion with no QHSE issues encountered. The designed Nitrified Managed Pressure Drilling solution succeeded in preventing the drilling fluid losses in the reservoir section by reducing the overbalance pressure of the drilling mud from 700 psi to 250 psi, which resulted in the elimination of 3 days of the rig's non-productive-time related to waiting on water. The closed-loop system coupled with a precise data acquisition and monitoring system has helped in maintaining a slight overbalance condition over the reservoir preventing any unintended hydrocarbon influxes to the surface. The lessons learned captured from this operation have contributed to the optimization of the Nitrified MPD in (Formation A) and to the overall MPD implementation in ADNOC fields.

This paper displays the first application of nitrified managed pressure drilling in the United Arab Emirates. The equipment design and planning have accounted for many different scenarios, as this type of drilling technology enables more precise wellbore pressure management with less interruptions to drilling ahead.