Mitigating Drilling Hazards in a High Differential Pressure Well Using Managed Pressure Drilling and Cementing Techniques

Abstract

Formation pressure heterogeneity in a reservoir can represent a significant challenge when a high overbalance condition is created in a zone with low pore pressure; leading to total losses, and potential stuck pipe events which subsequently increase well costs and non-productive time. This paper describes a case involving high differential pressure between the heel of the reservoir, and toe of the lateral, and where drilling in an up dip direction increased the complexity of the operation. The original well design considered drilling the entire reservoir section in one 6 1/8–in. section. However, to mitigate identified operational challenges, the 7-in. liner depth was adjusted to cover the high pressure section of the reservoir, thus isolating the weaker reservoir zones at well total depth. Managed pressure drilling (MPD) was deployed to drill both sections to reduce the overall overbalance condition and to provide an additional method to determine the pore pressure. Furthermore, the 7-in. liner was run in MPD mode to minimize the chances of differential sticking; and cemented in place using Managed Pressure Cementing (MPC) technique to mitigate against inducing downhole losses during the cementing operation which would have impacted zonal isolation efficiency, and the long term well integrity leading to possible sustained casing pressures (SCP). Managed Pressure Drilling (MPD) is an adaptive drilling technique that is used to precisely assess the formation pressure and manage the bottomhole pressure accordingly. MPD allows the use of a lighter mud density to reduce the overbalance condition and by manipulating the annular surface pressure a condition of constant bottom-hole pressure can be maintained. MPD was implemented to determine the formation pressure and define the optimal mud density for the operation during drilling, and while running and cementing the liner, thus mitigating the risk of potential losses and differential stuck pipe.