Managed Pressure, Deep Water Drilling, and Logging Under Continuous Reservoir Cross Flow Conditions - A Case History

Abstract Managed Pressure Drilling (MPD) and wireline logging under pressure were both successfully employed while drilling a pre salt, exploration well offshore Angola. The well was drilled with a 6th generation drillship using an integrated, Below Tension Ring (BTR) MPD package with the drilling contractor's Riser Gas Handler (RGH). Drilling exploration wells in pre-salt formations presents a plethora of challenges, with severe drilling fluid losses, often due to the natural fractures and/or vugular porosity encountered. This paper discusses the challenges faced drilling the desired hole section, managing severe losses, a downhole cross flow regime and high surface gas levels. Concern for exiting the salt section and taking total losses in a possible vugular carbonate is addressed and the contingent plans developed are discussed. Fluid loss management was critical and discussion is provided on the remediation methods used to limit losses. The paper describes how considerable gas was detected, handled and eventually controlled using the available surface equipment and methodology for preventing continuous gas influx and prolonged, off bottom circulating for removing the gas from the wellbore. Extensive wireline logging was completed, both at an intermediate stage and at total depth (TD). Most of the wireline logging was performed under minimal pressure with a logging adaptor installed in the rotating control device (RCD), 9 5/8" casing shooting nipple back to surface and wireline pressure control equipment (WPCE). The paper concludes with a series of key lessons learned that can be taken from this experience and considered when planning similar deep water, pre-salt exploration wells with the use of MPD equipment.