Kick Detection and Well Control in a Closed Wellbore

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 143099, ’Kick Detection and Well Control in a Closed Wellbore,’ by Steve Nas, SPE, Weatherford, prepared for the 2011 IADC/SPE Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition, Denver, 5-6 April. The paper has not been peer reviewed. Closing the wellbore at the top with a rotating control device (RCD) for some kind of managed-pressure-drilling (MPD) operations raises a number of issues with regard to well control and kick detection. The use of an RCD provides drillers with an additional level of comfort because it is a pressure-management device, but it does not eliminate the need to have well control as a primary objective. Early kick detection and annular-pressure control are essential parts of MPD operations, but there can be confusion as to where the responsibility for well control lies. Introduction The detection of inflow from a formation is one of the primary safety aspects of drilling operations. Even with a closed wellbore and with the use of MPD technology, kick detection and the subsequent well-control procedures must remain in place. The rig crew can get a false sense of security that with MPD, the well is controlled at all times and as such there is no further need for well control. The causes of kicks are not removed when MPD operations are being conducted. The procedures and risk assessments for MPD operations must include kick-detection and well-control methods and procedures. Primary Well Control Controlling the annular-pressure profile is one of the main reasons for MPD, but it may not avoid kicks in a well. If the pore pressures of the formations being drilled are unknown, then kicks can still be taken. This leads to the next challenge: To contain an influx safely, the influx first must be detected. If MPD is used to control the bottomhole pressure (BHP) in the well, then it can be stated that MPD is the primary well control because the pressure in the well is controlled to avoid an influx of formation fluids into the wellbore. The use of an RCD to close in the wellbore makes drilling operations safer. However, it must be noted that, often, the objectives of MPD are to reduce the hydrostatic pressure, avoid losses, and drill the well with a lower mud weight. Reducing the mud weight can introduce more well-control events.