Kick Tolerance - A Risk-Based Strategy to Enhance Well Control in Narrow Margin Wells

Abstract

Determination of appropriate kick tolerance to safely drill a narrow margin well can be challenging. A conventional approach using conservative assumptions and a single bubble model can lead to premature deployment of contingency casing strings or render some scenarios un-drillable. Uncertainties in pressures and depths in HPHT wells make a robust design that can handle all possible scenarios especially challenging. This paper will examine a strategy for challenging these assumptions and presents a robust methodology for safely managing ultra-low kick tolerance and large subsurface uncertainties by taking advantage of MPD influx management techniques and multi-phase modelling. The key elements defining the well control envelope include formation strength, resolution of influx detection, realistic shut-in times, safety margin and method of influx control (circulating response with MPD vs non-circulating response with BOP). This kick tolerance strategy will be implemented for a lengthy HPHT campaign in the UK North Sea. The strategy is designed to enable drilling the reservoir sections to TD and achieving all well objectives where applying a more conventional approach may require contingency casing to be deployed and key well evaluation objectives to be regretted. In addition, the well control strategy will take advantage of MPD influx management to control potential influxes within very small volumes while continuing to circulate.

Understanding the Well Control Procedures for optimizing the Well Control System during Drilling

“…2.2.10 If the kick is no longer in the hole, close the well and begin preparing the kill mud. This is usually assumed prior to the start of the second circulation (Graham et al, 2022).…”