Schlumberger

Case Study: Frac Balls Made with ELEMENTAL Degradable Technology Dissolve in Low-Temperature Wells

Journey Energy optimizes well productivity and minimizes time and costs in seven Cardium shale wells in Canada by using frac balls that degrade predictably

Challenge: Ensure full production in openhole, multistage wells with bottomhole temperatures as low as 40 degC [104 degF].

Solution: Use frac balls made with ELEMENTAL degradable technology to eliminate well interventions for milling out conventional balls and to ensure full production.

Result: Successfully isolated and activated multiple zones individually within the time planned and to the pressures and flow rates required, ensuring optimal well productivity and minimizing time and costs.

Conventional frac balls can fracture, jam, and fail to flow back

Journey Energy planned to hydraulically fracture seven openhole monobore oil wells, each having from 12 to 25 stages, in the Cardium shale formation in Alberta, Canada. The oil was located in a shallow reservoir surrounded by thick layers of tight shale.

Conventional multistage stimulation involves placing a completion string in the open hole with a series of ball-actuated stages isolated by hydraulically set packers. Composite or other nondegradable frac balls are then pumped from the surface to isolate and selectively access individual zones. When all the stages have been treated, the balls are flushed back to surface to allow production to begin.

With nondegradable balls, production can become obstructed if even one ball deforms or fractures during treatment because of the increased hydraulic pressure or fails to flow back because of low reservoir pressure. A ball can also become jammed on its seat and choke back production from all treated stages below. These problems require a workover rig to be brought onsite so that the balls and seats can be milled out, adding time, costs, and risks to the project. Moreover, reservoir conditions that can hinder production can also exhibit production profiles similar to that of stuck frac balls, complicating any decision to mill out the balls. Journey Energy wanted to avoid these risks and ensure that production reached its full potential.

Degradable frac balls allow unobstructed production

Journey Energy opted to use Schlumberger frac balls made using ELEMENTAL degradable technology, together with the Falcon multistage stimulation system for uncemented wells. The patented aluminum-based alloy is designed to hold its shape during stimulation and then degrade predictably within hours or days after making contact with a well fluid, even in low-temperature formations, which can slow degradation beyond the available time.

The frac ball does not have to degrade completely before flowing back because once its outer diameter is smaller than the seat’s inner diameter, the ball passes through to the bottom, where it continues to degrade until it disappears. With a compressive strength comparable to that of mild steel, the balls can withstand differential well pressures up to 10,000 psi [69 MPa] and temperatures up to 300 degF [150 degC] without fracturing or deforming, and they degrade predictably in low bottomhole temperatures. Frac balls made with ELEMENTAL degradable technology never jam or get stuck, so they never need to be milled, they never restrict the flow path, and they never cause production to be delayed or lost after fracturing. Since their introduction in 2012, these degradable frac balls have been run successfully in more than 500 stimulation stages and have degraded predictably in a wide variety of well depths, temperatures, pressures, and fluids.

Eliminating risk of stuck frac balls ensured full production potential

After the balls were launched and seated, job plots demonstrated clear pressure signatures, indicating that the frac balls had successfully isolated each stage. Further analysis of the differing pressure profiles throughout the stimulation confirmed that each stage remained isolated from the others for the duration of the treatment. The alloy balls performed as expected in the low-temperature wells, successfully isolating and activating individual zones during stimulation and then degrading predictably and completely after stimulation, all within the time planned and to the pressures and flow rates required. As a result, Journey Energy was assured that the seven wells were producing at their full potential.


Download: Frac Balls Made with ELEMENTAL Degradable Technology Dissolve in Low-Temperature Wells (0.54 MB PDF)

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Degradable Frac Balls Ensure That Production in the Cardium Shale Reaches Full Potential

ELEMENTAL degradable alloy frac ball
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Patented Material Degrades Fully and Predictably

Degradable alloy
Frac balls made of high-strength, impact-resistant material using ELEMENTAL degradable technology disintegrate into a fine powder that does not interfere with production.
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