While mud pulse telemetry produced efficiencies in drilling by sending signals to the surface, the completions environment was a different story.  For a long time, no telemetry system could send signals in both directions — up to the surface and back down.

The application of acoustic technology in the completions environment makes it possible to decouple communication from fluids and the formation. Now, bi-directional acoustics communications using encoded sound waves has helped make completions more efficient.

With that capability, operators are finding more ways to take advantage of the wealth of downhole data being sent up to the surface. But acoustic technology holds even more promise, according to Duncan Groves, product line director for smart services at Baker Hughes, because acoustics can be used to enable downhole control in completions. The service company is also coming out with its first acoustic-actuated liner hanger.

Baker Hughes XACT
XACT tool being picked up – no change to rig equipment or drill sting. (Source: Baker Hughes)

For some time, the drilling side of operations has had the luxury of bi-directional communications through mud-pulse telemetry and other technologies. As a result of all the measurements available in the drilling environment, drilling operations have become so efficient that “drilling a mile a day is a common thing now,” Groves said.

The goal was to make the long-established improvements in the drilling and production environments possible in the completions and intervention environments, he said. Enter the bi-directional telemetry system.

Achieving completions efficiencies requires getting the right measurements from the right places— then transmitting measurements so that data can be analyzed and acted upon, he said.

At the same time, completions are “extremely challenging operations,” Groves said. “We think drilling is bad with equipment banging around the hole, but here we’re dealing with aggressive completion fluids, proppants and frac fluids, high compressional loads, high pressures.”

In the past, downhole communication was a one-way street.

That began to change as acoustic communications were experimented with in the U.S. land drilling environment as shale plays started gaining traction. But clients wanted to have access to the technology in other places, Groves said.

“Our clients said to us, ‘We have information in U.S. land drilling. Where we don’t have it is deepwater Gulf of Mexico completions,’” he said.

So Baker Hughes worked on the engineering necessary to enable acoustic telemetry to work in the offshore completion environment. In 2015, the service company started field testing the solution in the Gulf of Mexico (GoM).

The resulting acoustic telemetry system, XACT, has been fully commercial for years and is in use both in the GoM and the U.K. North Sea, allowing for bi-directional communication in the drilling, completions and interventions environments, he said.

Sound technology

Acoustic telemetry can measure downhole pressures, tension and torque with other sensors available for installation.

A tool within the acoustic transmission system creates sound waves and sends those signals up or down the line. The signal weakens the further away it gets from the source, so booster or repeater tools are placed along the drillstring to propagate the digitally-encoded signal further up or down the line. The signal is actually a packet of information complete with data redundancy checks to minimize the chance for single points of failure.

Groves said Baker Hughes’ XACT Bi-Directional Acoustic network doesn’t interfere with any component of the drillstring, and no equipment is modified at the surface. That said, there are a few pieces of equipment needed for the network to, well, work.

At the surface, Baker Hughes places the bi-directional acoustic surface tool and the electronic acoustic receiver.A laptop at the surface acts on information received.

Downhole, the acoustic system’s XACT Acoustic telemetry nodes resemble a drill collar, and multiple tools are spaced on the drillstring to boost the signal as it propagates the sound wave up or down the pipe. Groves said a 30,000-ft well might use six or seven XACT acoustic telemetry nodes on the drillstring.

“That gives them bi-directional communication,” Groves said. “It gives them a pathway to see what’s going on.”

And that’s never been more important when it comes to completions, he said.

In the world of completions, acoustic telemetry can be used to monitor downhole pressure, confirm tool position in real-time, improve troubleshooting efficiency, monitor losses and influx and measure tubing and annulus for complete coverage.

Baker Hughes
(Source: Jennifer Pallanich/Hart Energy)

In the field

In the GoM, one of Baker Hughes’ clients had uncertain reservoir pressures in multiple sands. Attempts to perforate the multiple reservoir sands in one run had caused delays since the net downhole pressure was unknown. As a result, the rig had to deal with influxes and losses until the well could be brought into balance. The client elected to make multiple perforation runs until it found a solution that would provide accurate real-time information.

Groves said the client chose Baker Hughes’ XACT bi-directional telemetry system because it was simple to mobilize, required minimal rig time to implement and enabled them to rapidly fine-tune completion fluid weights to trip safely.

“They just changed the risk profile of the well. That saved them five days of rig time,” Groves said.

Now, he said, running real-time data during tubing-conveyed perforating operations is standard with the operator, which has operations in 6,000 ft to 10,000 ft water depth.

Elsewhere in the GoM, a client was dealing with a narrow formation fracture to collapse pressure window in the reservoir. While the well could be drilled with managed pressure drilling, the ideal completion system was deemed too risky to be achievable. The client elected to use a different completion system that could have led to a shorter production life or shorter time to intervention.

The client deployed XACT and integrated real-time pressure data into decision-making on the initial wells.

“The downhole data completely changed what they were going to do,” he said.

Based on confidence in the system performance, the client switched the completion type from standalone screens to a gravel pack and used real-time downhole data to manage the installation and pressure pumping operations.

The client was able to keep the downhole pressures within an extremely tight window using the real-time data. Multiple wells were successfully gravel packed, and the client plans other wells in a field that was initially deemed as unable to be completed. As a result, significant new production will be brought online to an existing production facility, according to Groves.

Duncan Groves, Baker Hughes
(Source: Baker Hughes)

“The downhole data completely changed what they were going to do.” – Duncan Groves, Baker Hughes

In another case, a client wanted better operational control on deepwater frac pack wells, which require manipulation of downhole service tools between several critical positions. The challenge: tools have to be moved up and down several feet — but are 30,000 ft away from the surface where the parameters are being controlled. An incorrect interpretation of what happened downhole can lead to delays and poor production from a suboptimal frac pack.

Groves said the client used the XACT system to understand downhole weight, pressures and temperatures during the entire frac pack process. The downhole data provided clear and concise visibility so decisions could be made efficiently. He said other possible efficiencies and risk reductions were identified that could enable more stages to be completed in a single run with a reduced completion time.

Acoustical actuation

With bi-directional communication, Groves said, it is possible to actuate downhole equipment in the completions’ environment. The acoustic system operates without the need to pressure up or drop actuation tools, he noted.

A new acoustic Sonus Liner Hanger System is still awaiting field trial with multiple clients in discussion to run it. Baker Hughes is evaluating what the next actuated tool system will be and are kicking that project off in 2023.