Differences between mud pressure in a wellbore and pore pressure in high permeability rocks can lead to differential sticking, particularly when drilling deviated wells and encountering mud losses. Several solutions, all challenging, can be used to address this problem, where the conventional mitigation method of managing the mud weight (MW) is often used. However, managed pressure drilling (MPD) offers a promising solution with a positive risk-adjusted cost and other benefits.

Wells in the E oilfield in southern Iraq are typically drilled overbalanced and therefore often experience a high percentage of non-productive time (NPT) due to differential sticking. This study evaluates the feasibility of using MPD to optimize the drilling process by decreasing the mud weight while applying the required surface pressure to achieve the target bottom hole pressure (BHP). A simulation software, which uses different mud weights to determine the required choke surface backpressure (SBP) to achieve the targeted equivalent circulation density (ECD).

Historically, differential sticking has not been a primary driver to justify MPD. However, MPD offers more dynamic and rapid wellbore pressure control by adjusting SBP applied to the annulus for a given MW, and can actually decrease the risk of differential sticking. Instead of shifting MW or changing other drilling parameters, MPD adjusts the required ECD and/or equivalent static density (ESD) based on the formation pore pressure gradient. Additionally, MPD directly lowers SBP in the event of mud losses due to high ECD/ESD to decrease the BHP without the need to reduce MW.

This paper discusses the application of using a hydraulic simulation software to model the drilling development plan. The software optimizes MW and SBP while drilling, making pipe connections, and completing the well. Furthermore, it discusses the sensitivity effects of each parameter on wellbore pressure and provides guidelines for managing pressure by adjusting these variables.

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