After cementing, frac plugs are set, and perforation guns are lowered to prepare a zone for hydraulic fracturing. It is a time-consuming and costly operation.
The winch speed, pump rate, and downhole cable head tension must be in sync to maximize perforating run efficiency. Achieving this requires an automated system that monitors these variables.
How It Works
The process involves lowering a plug and perforating the gun into the well to pump down, then removing it. It is typically done after each frac stage to isolate the completed section of the well and prepare it for drilling or other work.
The device lowered into the cased well bore is usually a perforating gun that uses explosive charges to create holes or cracks in the steel casing and fracture the surrounding formation. It is often referred to as pump-and-perf or coiled tubing conveyed perforating. Many different tools can be used in this operation, and methods to improve efficiency are constantly being sought. One example of a tool that can benefit from enhanced control techniques is the plug-deployed perforating tool 100. It is a tool with an upper retrieval portion 110 with a fishing neck 112, an intermediate portion 120 with a firing head 122, and a lower plug deployment portion 130. To learn more about pump-down perforating, click https://renegadewls.com/.
Why It’s Used
During a wireline pump-down perforating operation, coiled tubing conveys a tool string to depth and perforates the casing with explosive charges that create production pathways through the cased wellbore. It is a time-efficient and cost-effective alternative to the tractor or E-coil perforating.
The tool string is then activated with commands transmitted downhole through a wireline perforating gun unit 110 by the conveyance and pumping equipment at the surface. This activation initiates the firing mechanism, causing explosives to blast holes in the steel casing that become entry points for hydraulically fracturing the formation.
This technique also eliminates the need for traditional wireline toe prep operations, which are costly and can cause damage to the tools and casing. And it provides the means to evaluate communication between a just-perforated frac stage and previous stages—a critical factor in treatment control and cement sheath integrity. In addition, pump-down diagnostics optimize winch speed, downhole tension, and pump rate during perforating runs—reducing non-productive wireline time.
Safety
A conventional perforating gun creates a set of holes in the steel casing. It creates a path through the container for fluid to access the wellbore. This perforation allows fracturing operations without running coil tubing and using workover rigs.
Automated monitoring and control of operational parameters may be performed during pump-down perforating. For example, a surface system may monitor a downhole tool string to detect the time since a perforating gun unit was activated. The method may then send a command to the wireline unit 536 to decrease its pump rate in response to that time interval passing.
Pump-down diagnostics field cases from several unconventional plays suggest that evaluating communication to the previous frac stage using pressure trends following perforating and the injection test can offer clues about treatment overlap and cement sheath integrity. A minimal differential between post-perforating and injection test pressure falloffs may indicate behind-pipe communication, while a more significant differential may indicate an isolated interval with nil fracture capacity.
Cost
The pump-down perforation process reduces overall completion costs by allowing the crew to combine cleanout and toe prep runs with perforating. It also allows more frac stages to be run in one run than with traditional perforating guns.
The coiled tubing 20 is pumped down to the perforating gun unit 110, which activates a firing mechanism. It triggers the perforating gun to fire one or more explosive charges that make holes in the casing and cement to provide a fluid path to the formation.
A downhole tension tool is positioned in the coiled tubing to ensure cable tension stays safe during the perforating and pump-down operations. It is crucial in deviated and lateral wells where surface measurements can be misleading and may result in unintentional cable damage. The tool communicates with the surface equipment to provide downhole tension readings and alerts when the plug is set and the perforating gun is fired.
