Managed-Pressure Cementing Provides Zonal Isolation in Deepwater Gulf of Mexico
Authors: Feder Judy 
Published: September 2019

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 194536, “Managed Pressure Cementing (MPC) Within a Narrow Pressure Window, Deepwater Gulf of Mexico Application,” by Michael Teoh, Sharief Moghazy, SPE, Keith Smelker, and Roger Van Noort, SPE, Shell, and Juan C. Valecillos, Julian Hernandez, and Maurizio Arnone, Weatherford, prepared for the 2019 IADC/SPE Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition, Amsterdam, 9–10 April. The paper has not been peer reviewed.

Managed-pressure cementing (MPC) is an important technique for primary cementing operations in wells with narrow pressure margins between the pore and fracture gradients. This paper presents the design considerations, methodology, and results of two deepwater MPC operations conducted to cement production casing strings within a target operating window of approximately three-tenths of a pound.•Modern transient hydraulic modeling software permits the calculation of adequate surface pressure levels to control the annular pressure profile during the different stages of a cementing operation. On the basis of a•predetermined annular pressure target, different variables can•be designed to produce surface and•downhole pressures within existing limits of a particular operation. This capability, combined with modern managed-pressure-drilling (MPD) systems, enables accurate control of the annular pressure profile during cementing and makes it possible to obtain near-constant bottomhole pressure (BHP) throughout the cement•placement operation while using statically underbalanced mud columns.

Introduction

Preventing fluid losses during slurry placement generally is necessary in achieving the goals of a cementing operation. Effective zonal isolation behind the casing or liner wall is related intimately to preventing losses toward, and flow from, the formation during and after the cement circulation. When cementing a casing or liner string within limited openhole pressure margins, maintaining the bottomhole circulating pressure below the fracture gradient is not feasible in most cases when using conventional methods.

Cementing fluid dynamics are generally more complex than the fluid dynamics observed during the drilling phase. Additionally, multiple fluids with diverse properties and with generally higher viscosities are pumped at different rates. All of these factors, combined with high cement-slurry densities, contribute to equivalent circulating density (ECD) levels at the well bottom during cementing that are not observed while drilling. In many cases, these ECD levels lead to losses or even fracturing of the formation. The inability to measure downhole pressures during the operation adds to the complexity of the cementing job.

In recent years, MPD systems, with their ability to control precisely the well pressure profile, have emerged as an alternative solution to the problem of cementing efficiently within tight margins in deepwater wells. Used together with advanced hydraulic modeling software that can predict fluid properties accurately downhole under dynamic and static conditions, the latest MPD systems are enabling drilling engineers to manipulate variables that in the past were out of reach during the drilling and cementing-job planning.

The two wells discussed in the complete paper were drilled in the Gulf of Mexico (GOM) in approximately 8,500 ft of water from rig kelly bushing to mudline. The paper provides definitions related to the MPC subject, an overview of the applications, a summary of the engineering approach and calculations, and the results obtained during these cementing operations.