This paper discusses the factors to be taken into account when designing cement jobs using fluids in turbulent flow and some of the overlooked benefits of using turbulent-flow design for mud removal. It will be demonstrated that, when designed and executed properly, the use of turbulent-flow mud removal with Newtonian fluids can be beneficial in deepwater (DW) cementing operations.

Introduction

When one considers the risks associated with poor zonal isolation in DW wells, such as release of well fluids to the environment, gas migration to the surface, underground blowouts, and well-killing operations, the importance of proper cementation and sufficient zonal isolation becomes clear. These issues are often difficult and time-consuming to address, a situation further complicated by the daily cost of DW-well operations.

One of the complexities in DW wells is that of drilling with oil-based or synthetic-based muds, commonly referred to as nonaqueous fluids (NAFs). NAFs are compressible fluids that dynamically change density and rheological properties as temperature and pressure increase or decrease. This makes modeling flow regimes for proper mud removal very difficult. These types of drilling fluids also oil-wet the surfaces to be cemented, making cement bonding more troublesome. When cement slurries are contaminated with NAF, it can extend thickening times, cause undesirable gel-strength development, and ruin compressive-strength development.