Riserless cementing in deep water typically presents shallow-flow zones in unconsolidated formations. This can result in excessive washouts creating difficulties with mud conditioning and requiring large volumes for full cement coverage back to the sea floor. Additionally, there can be narrow pressure margins and drastic temperature differentials from surface to mudline to bottomhole. All of these challenges require not only reliable equipment and experienced personnel, but specialized fluid systems for competent cement placement to maximize casing support and isolation for drilling operations. Thus optimizing the slurry design and having a robust execution plan are important.
In order to minimize material costs and the expense of repeated trips to shore, use of the same cement for multiple sections is preferred. This is often accomplished with the use of additive technology, like liquid additives and automated metering systems, to appropriately adjust the mechanical and chemical properties of the cement system on the spot. This is economical for the operator and environmentally wise by minimizing discarding of un-used materials and supply transport to the vessel.