Wireless wells 

John Sheehan

December 1, 2016

For the first time, wireless technology has been used downhole on a subsea well. John Sheehan speaks with FMC Technologies to learn more.

Communicating beneath the waves.
 Images from FMC Technologies.

An annulus monitoring system (AMS), which has been installed and tested in a Petronas-operated offshore exploration well in Malaysia, will save time and drive down operator costs, according to developer FMC Technologies.

The AMS is a wireless communication system that provides crucial, independent condition-monitoring within a subsea wellhead to operators for the first time, from the onset of drilling and throughout the life of the well.

The technology, a winner of the 2015 OTC Spotlight on New Technology award, delivers real-time information to the operator about annular fluid and components during critical phases of well installation and startup, when well conditions are most unpredictable.

Up until now there has been no annulus measuring capability subsea because valve penetration into the annulus is not allowed, unlike for surface operations.

Bernard McCoy, Jr., director of subsea drilling services, FMC Technologies, explains that the technology provides the same data that would be available for surface type wellhead applications, but subsea – for the first time.

Explaining how it works, he says: “We measure the annulus pressure under the casing hanger with a standard pressure/temperature sensor so it can detect the pressure and temperature of the fluid beneath the hanger.

“The real value of the technology is the ability to transmit that data – the reading of that pressure/temperature sensor through the casing annulus and the wellhead housing itself wirelessly to a receiver that is on the outside of the conductor housing. There are no wires and no required intermittent communication between each of the casing strings.”

He says the proprietary technology allows for direct communication from the annulus through metal, cement and brine into the receiver on the conductor housing.

EM and acoustics

A wireless well.

The technology, first developed for submarines and which has been adapted by FMC over the last five years, uses a combination of electromagnetic waves and acoustic data.

“We install this at the time of initial casing hanger installation, so it is there from moment one, when the casing hanger is landed in the wellhead housing,” he adds. “From that moment on it is able to transmit the data passively, so, actually, the receiver on the outside of the conductor is really doing almost all the work to detect the pressure/temperature underneath the casing hanger.”

The sensor is designed as a modular sleeve that goes around the casing on the casing hanger, so it is able to work on various casing sizes and thicknesses across the whole range of casing types.

“It is designed to work through the known casing programs that are out there for our wellhead systems, so it is uniquely honed to be able to ping right through the casing strings as well as the wellhead housing,” he says. “To detect that signal it is approximately 25in away from the sensor itself and then once it gets to the conductor housing its able to be transmitted using various techniques that are already out there in the industry.”

A remotely operated vehicle can drive by and pick up the signal or it can be linked to the transponder and pinged back to a vessel on the surface. It can also be pinged to the blowout preventer communication system and sent back up to the surface.

Aiding abandonment

“The really interesting thing about this technology is you’re able to measure the pressure and temperature in that annulus over a longer period of time as the formation is sealed in, as it is potentially abandoned or as you continue into production you can monitor the characteristics of that annulus,” McCoy says. “This is much like you would on a surface wellhead where you can open a valve and measure the pressure that is there in the annulus.”

He says the data that is collected can be used to help design production casing programs more efficiently. “Today, when you perforate the casing to pull it back and you cut the casing, you have no idea if there is pressure behind that casing hanger. It is a limitation of our industry at the moment for subsea applications. This would be able to help you determine if you had pressure and then you could go through changing your mud or changing the way you are going to do that cutting and perforating operation versus going in blind, where you don’t know what the pressure is back there.”

McCoy says that the Petronas exploration well on which the AMS was tested went directly into abandonment, and the technology helped them save rig time. Petronas isn’t the only operator that has shown interest in the system, McCoy says a number of other FMC customers are in the finishing stages of preparing to run the equipment.

Going further

McCoy says that in addition to temperature and pressure, FMC wants to measure other things in the same space. “Fluid density may be one thing that we add to determine if that annulus fluid can change over time if it breaks down or becomes mixed with other types of annulus fluid.”

He says after that, the next logical thing would be to perform measurements deeper in the well, and make sure pressure, temperature, and density of the fluid across both of these measurements are consistent or changing.

“Right now in the industry, because we don’t know what those pressures are, we typically grossly over-design our casing programs for this annulus pressure,” he says. “You can’t really determine what you need, so when in doubt make it stout. That ends up providing a lot of extra casing weight, a lot of extra pipe, wall thicknesses, etc. This will allow you to design exactly to what the well is, providing some degree of savings in the future.”

He says that as well as in Asia Pacific, there is a lot of interest in Brazil and South America.

“Most of the interest is around frontier space where exploration hasn’t really been done before, so you have no idea what you may find or what the well may look like or what the pressures are going to be,” McCoy says.