New screens, gravel pack systems among innovations being designed with cost reduction in mind for complex deepwater wells
By Kelli Ainsworth, Associate Editor
As operators continue to drill deeper wells in more remote offshore locations, the traditional wait-and-see approach to sand control is no longer an option in many cases. Operators have recognized that a proactive strategy is needed, and many are actually installing sand control equipment during the well’s initial completion, rather than waiting to do so only when sand production becomes a problem.
This shift has been driven in large part by the type of wells that are being drilled today and the cost of deepwater rigs, said Reggie Boggs, Global Director-Sand Control for Weatherford. “As you get into deepwater markets with subsea completions, it’s very expensive to bring a rig in to do a recompletion,” he said. “If they think they’re going to require sand control in five to 10 years, they’re going to put it in on day one. It’s more cost effective to do it at the initial stage of drilling and completion than to work over the well later.”
Operators are also increasingly demanding sand control technologies for open-hole completions, Mr Boggs said. “In a cased-hole completion, you have to perforate the casing in order to produce, and each one of those perforations creates a restriction in flow area.” Open holes, which are common in horizontal, highly deviated and extended-reach wells, have historically been challenged by inflow control performance and fines migration. However, things are changing. “We’ve developed technologies for the open-hole market that remove the limitations and barriers of open-hole completions.”
Another major driver for the development of sand control completion systems has been the need to treat multiple zones in a single trip, Ed Smith, Vice President of Completion Services for Superior Energy Services, said. “Trip time is one of the biggest causes of NPT,” he said. “What we’re doing is running sand control equipment for the entire section all in one trip and treating each zone independently but, one after the other.”
The more zones to be completed in a wellbore the more savings that can be achieved with a single-trip system. “The number of days that you carve out of a well grows as you add zones. If it’s just two zones, you might carve out two or three days,” Mr Smith explained. “But if you get into four or five zones, you could carve out anywhere from 12 to 14 days from a completion.”
Eliminating runs in open-hole completions
Since 2015, Weatherford has been developing a gravel-pack system to provide cased-hole functionality in an open hole. The result, the WFX0 system, combines existing field-proven technologies with a newly developed open-hole packer and setting tool with quick-connect capability and sliding sleeve technologies.
The system provides completion of multiple open-hole zones in a single trip, from a single position. “The system gives you reliable multizone open-hole gravel packs, and it eliminates the need for immediate deep-set barrier runs,” Mr Boggs said. “It can cut 15 to 20 days off the completion time and $20 million off the cost.”
The system, which was commercialized in May, leverages Weatherford’s TerraForm open-hole packers, commercialized in 2008, which use tension-set cup-sealing technology to create a V3-rated seal without harming the reservoir or creating micro-fractures. On the seals, fingers located every 15° around the cup seal set independently. This allows the packer to set in a hole that is not completely round. Other technologies leveraged to create the WFX0 system include the SST shunt-tube screen and the OptiBarrier ball valve, which were released in 2015.
The setting tool can transmit up to 20,000 ft-lb of torque and allows for circulation at high rates – the system has been tested for up to 18 bbl/min – to get to bottom. At lower pump rates, it can take between 24 and 30 hours to circulate the ball valve to bottom, Mr Boggs said. Because the WFX0 is tolerant of higher pump rates, it can circulate the ball to bottom in a fraction of time of normal gravel-pack systems. There is also no need for a deep-set barrier run because the WFX0 packers are ISO and API V0-rated.
After the system is deployed, the WFX0 packers and TerraForm packers are set, and the setting tool is moved into position for gravel packing, which is done from the top down. During packing, the tool remains in a fixed position. Typically, gravel-pack systems require the tool to be moved from zone to zone during packing, which can cause swabbing or the tool to become stuck. “The system is able to give you the discrete zones in an open hole and then allow you to gravel-pack all those discrete zones from a single position,” Mr Boggs said. “That’s never been done before.”
Once gravel packing is complete, the sleeve and ball valve are closed, and the setting tool is removed from the hole. Because the gravel-pack tools – the packers, quick connect and sliding sleeve technologies – were designed to be API and ISO V0-rated, the system provides a deep-set barrier as soon as the gravel pack is placed, Mr Boggs said. “Normally after you go in and gravel-pack the well, your next run in the well has to be a deep-set API ISO V0 barrier. It’s an extra trip into the well, an extra packer, extra everything.” He estimates that eliminating the deep-set barrier run can save operators three to five days, which could add up to as much as $5 million in savings.
Reducing completion times
While some companies are improving the efficiency of open-hole gravel packing, others are developing technologies that eliminate the need for gravel packing entirely. In Q2 2017, Halliburton released a 6-in. version of its Endurance Hydraulic Screen, which was originally launched in mid-2015 in an 8 ½-in. size.
Once on depth, the screen extends radially in response to surface-applied pressure, closing the annular gap between the screen itself and the formation in an open-hole environment.
Halliburton sees the hydraulic screen technology as a more efficient alternative to traditional gravel-packing operations, Maxime Coffin, Sand Control Product Manager, said. “The screen is able to provide wellbore support and efficient sand control, but it’s much faster, typically in one hour compared to days.” Because the screen not only controls sand production but also provides strong wellbore support, he added, it is particularly effective in poorly consolidated formations.
The tool consists of a base pipe, activation chambers, sand filtration media, a drainage/support layer and an outer shroud. When the screen reaches the desired depth, internal tubing pressure is applied from the surface via the rig’s cement unit. This pressurizes the screen’s activation chambers, causing the screen diameter to increase and fill the annular gap to achieve compliance. “It’s activated by surface-applied pressure without any pumping,” Keith Oddie, Product Champion for the Endurance Hydraulic Screen, said. “That’s what allows us to take away major time from the operation. It lends itself to major cost reduction.”
Once the screen is activated, the pressure is bled off, and the screens are opened to production. Produced hydrocarbons will flow through the tool’s layer sequences, protective shroud, filter media and drainage layer like a standard screen. After it has passed through these layers, produced fluid enters flow channels between activation chambers.
The screen has been tested and qualified for an operator in the Gulf of Mexico in temperatures of up to 375°F (190.5°C) and reservoir pressures reaching 18,000 psi. It was subsequently used for Statoil’s Statfjord field offshore Norway, where there was a specific need for sand control in mature wells, Mr Oddie said. Depletion challenges and the field’s narrowing pore/frac pressure window made pumping gravel packs a challenge, so the operator wanted a pump-free solution. The screen was field-tested and proven on the Statfjord field in 2015.
During this test deployment, the screen was run with standard completion equipment in an 8 ½-in. open hole that was drilled to a depth of 2,580 m with a maximum deviation of 30° and a temperature of approximately 176°F (80°C). The overall completion took six days, compared with a field average of nine days with open-hole gravel packing. “It was in excess of a 30% reduction in overall completion time,” Mr Oddie said.
In addition to faster completion times, this compliant screen technology reduces HSE risk, Mr Coffin said. “When you have to do a gravel-packing operation, typically the equipment is not on the rig,” he said. “Every piece of equipment you have to move is a risk.” Further, deployment of the screen requires only two people, compared with a crew of 10 or more needed for a gravel-packing operation, Mr Oddie added.
Although the system has primarily been deployed in mature fields in the North Sea since its launch, Halliburton believes it can achieve significant cost savings in frontier deepwater operations by reducing the rig time required for installation compared with other sand control methodologies. “All the big IOCS are deeply involved with deep water, and they are all looking at new ways to achieve major cost reduction in their wells. Gravel packing can require two to three days with a rig, and we can do that in one hour,” Mr Coffin said.
The 6-in. version of the Endurance Hydraulic Screen was also developed for Statoil, which needed the smaller size to access a particular reservoir. This reduced screen size was installed for the first time in a North Sea well in Q1 2017. Two further installations were completed in Q2 2017, with time savings comparable with the original version that has been successfully deployed eight times, according to Halliburton.
Alternate path technologies
Alternate path sand control technologies have been in use since the 1990s to help prevent bridging and incomplete open-hole gravel packing in formations with low fracture gradients and in sensitive shales. Schlumberger has been using alternate path shunt tube technologies for years, but in 2016 the company commercialized a new open-hole packer to work in conjunction with the OptiPac Alternate Path open-hole gravel-pack screens. The packer is based on technology developed for the company’s Falcon uncemented multistage stimulation system and allows an uninterrupted flow of gravel between compartmentalized zones of the well, without impacting the sealing element of the packer itself.
It’s activated via hydrostatic pressure, replacing the swellable elastomer packers that are sometimes used in open-hole gravel packing operations. “Previously, you had to wait for the elastomer to swell before the gravel pack could be performed,” said Ezio Toffanin, Sand Control Sales and Marketing Manager, Schlumberger. “Now we have a system we can install and immediately activate and continue with the gravel-pack treatment without delays.”
In the event that a bridge forms anywhere along an interval during gravel packing, the increased pressure forces the slurry down the shunt tubes. Then, when the slurry encounters a nozzle facing a void in the open hole, it flows out and fills empty spaces, ensuring a complete gravel pack, Mr Toffanin said.
In late 2016, the system and the new packer were commercially deployed in a well exceeding 5,000 ft of water offshore Africa for an operator who wanted to bypass a specific zone in a reservoir. “Due to the characteristics of that interval, they were concerned about it potentially affecting the gravel pack and the production,” Mr Toffanin said. Two of the new packers were installed to gravel-pack both above and below the zone.
In early 2017, also in an ultra-deepwater well offshore Africa, the system was utilized to compartmentalize the reservoir in such a way as to allow for potential intervention to shut off one section of the interval. “In that case, it was only one packer, and the gravel pack was placed above and below the packer,” he said. “If one of the zones above or below started producing water, the operator has the ability to go in and shut off that part with the subsequent intervention.”
In 2015, Superior Energy Services was commissioned to fast-track the design, development and validation of a large-bore, 12,500-psi rated multizone single-trip completion system. The system, which consisted of both screens and frac pack equipment, was intended for an ultra-deepwater Gulf of Mexico project with well depths reaching 32,000 ft. Typically, designing and fully validating such a fit-for-purpose system can take more than 24 months, but Superior completed it in 18 months.
One of the major design considerations was ensuring the tools were robust enough to stand up to the differential pressures reaching 12,500 psi and temperatures of 250°F. “We had to be able to build equipment that handles the pressure and temperature and still give the operator significant flow area to get their hydrocarbons to surface,” Mr Smith said.
Bernard Franklin, Director of Technology for Completion Services, added: “Not only was the design important, but you’d better execute flawlessly in the field. Installing reliable sand control completions is critical to deepwater field developments.”
The system was function tested at Superior’s Lafayette and Houston facilities, with key components tested at downhole conditions at the Houston R&D test lab. “The operator also wanted to ensure the downhole equipment could handle the pumping treatments. So we performed erosion testing on the system at elevated rates and volumes to validate the key components,” Mr Smith said. Erosion testing was done at a rate of 35 bbl/min and 1 million lb of high-strength proppant. Finally, the system was run and installed in an onshore completion to simulate all necessary processes and procedures. Based on these tests, the equipment was deemed fully qualified.
Installation of the completion system was done in the first well of a 10-well project early this year. The well had three zones – two in 7 ¾-in. casing and one in 9 7/8-in casing. As with all development systems, lessons learned were documented and analyzed, and minor modifications are being instituted to maximize operational efficiencies and processes on upcoming completions.
The burgeoning of the Lower Tertiary in the deep and ultra-deepwater Gulf of Mexico demands higher operational efficiencies, reliability, and lower overall costs. The key factor in reducing long-term costs in sand control applications is the elimination of costly interventions. This can be enhanced with new technologies, but the methodology and application of completion techniques in the Lower Tertiary are still in an evolutionary and exploratory phase. DC
WFX0, TerraForm and OptiBarrier are registered terms of Weatherford. Endurance Hydraulic Screen is a registered term of Halliburton. OptiPAC and Falcon are registered terms of Schlumberger.