Adverse conditions are often encountered during managed-pressure drilling (MPD). These conditions can include wellbore instability, kicks, and losses that create challenging scenarios for cementing operations, such as a narrow operational window between the pore pressure and the fracture pressure, which can compromise the necessary barrier and require unconventional solutions in deep water. This paper reviews a successful managed-pressure-cementing (MPC) operation and presents findings and lessons learned.

Introduction

The case in this paper is an exploratory well drilled at a water depth of 1700 m in the Caribbean Sea. Well 1 was designed to drill through a potential shallow gas interval directly below a 22‑in. shoe using MPD. A total length of 350 m of 22‑in. open hole was drilled to the 18‑in.-­casing point. An unexpected high-pressure water/gas sand was encountered below the 22-in. shoe with a pore pressure of approximately 9.85 lbm/gal.

The fracture pressure at the 22‑in. shoe was measured to be 9.9 lbm/gal, which leaves a narrow operational window of 0.05 lbm/gal. The strength of the 22‑in. shoe was confirmed by a dynamic ­formation-integrity test.

A conventional cement operation was not feasible because of the required mud-weight (MW) increment and the resulting equivalent circulating density (ECD) with the 18-in. liner at the bottom, which limited the likelihood of success. The use of a high-strength, low-density slurry weighted to 11.5 lbm/gal was considered but was rejected because of the additional time and logistics required for a special cement-slurry dry blend. This resulted in the decision to implement MPC to increase the probability of achieving a barrier in place through the 18-in.-liner shoe and overlap the previous casing shoe.