Cesium Formate Brines

Decrease well construction time and cost

HPHT well construction operations using cesium formate brine are faster and more effective than those using traditional fluids. In over 30 North Sea deep-gas well constructions carried out in overbalance with cesium formate brine since 1999, there were no differential sticking or well control incidents while drilling, logging or completing. Studies show that average completion time in North Sea wells between 1999 and 2010 is 21 days against an average of 46 days¹ for wells drilled with oil-based muds (OBMs) with a corresponding reduction in costs.

¹SPE 145562

Maximize production rates and deliver recoverable reserves faster

Cesium formate brine is non-damaging and helps deliver HPHT wells that routinely meet or exceed production performance expectations. Experience shows that this is particularly true in deep-gas wells drilled and completed in open hole entirely with cesium formate brine.

Facilitate better reservoir definition

Solids-free or low-solids cesium formate brines make very conductive drilling fluids, which create the ideal medium for all acoustic measurements and high-resolution resistivity image logging. The high-quality image logs obtainable in cesium formate brine reveal sedimentary features on a centimeter scale, providing geo-modelers with important information on structural dip, depositional environment and orientation of sand bodies. This detailed information allows creation of superior reservoir models.

Cesium formate brine is unique among HPHT drilling fluids by having a very dense filtrate (up to 2.30 g/cm3/19.2 lb/gal) with a stunningly high photoelectric cross section (Pe) of up to 259 barns/elec. Any invasion of this mud filtrate into the formation around the well bore becomes highly visible to nuclear logging tools. The logged photoelectric effect provided by invasion of cesium formate filtrate is extremely useful for correcting density curves for mud/borehole effects and mud filtrate invasion, and for estimating filtrate saturation. It is also ideal for defining permeable sands. Combining the photoelectric effect and its high vertical resolution with resistivity measurements from both the drill pass and ream pass of a logging while drilling (LWD) produces a very reliable and accurate net reservoir definition.

Eliminate expensive well interventions

Cesium formate brine reduces the risk of well interventions and maximizes the production life and durability of the well. Cesium formate brine can be formulated with acid-soluble calcium carbonate particles and formation-friendly polymers to make low-solids drilling fluids, which are also used as lower completion and screen-running fluids. In these cases, upper completions using clear cesium formate brine usually follow. On conclusion of a well-construction operation, the well can be safely suspended for long periods with the same cesium formate fluid. Whichever scenario is chosen, the reservoir is only exposed to one filtrate – cesium formate brine – if the well is open hole and the likelihood of an intervention vastly reduced.

Reduce operational risk

There have been no well control incidents in any HPHT deep-gas well drilled and completed with cesium formate brine, including 14 wells drilled and completed over 432 days in Statoil’s Huldra and Kvitebjørn fields. This remarkable ‘zero incidents’ record set since the first HPHT drilling and completion with cesium formate in 2001 is ample proof of the improved HPHT well control environment provided by cesium formate drilling, completion, intervention and suspension fluids.

Cut safety, health and environmental risk

Cesium formate is non-hazardous to the environment with the formate ion biodegrading entirely when diluted with water. Cesium formate meets the demanding environmental standards set by the Centre for Environment, Fisheries and Aquaculture Science (CEFAS) in the UK, the Norwegian Pollution Control Authority (SFT) and other environmental authorities across the world. Used in highly sensitive environments from the Barents and North Seas to onshore use in Hungary and Alaska, formate brines reduce the environmental effect of hydrocarbon exploration.

Cesium formate is not only kind on the environment, but kind to your people as well. It's non-hazardous, with excellent test results against conventional fluids for dermal toxicity.