In the oil and gas industry, well efficiency and longevity depend on several critical components. One of those components is the tubing anchor catcher, or TAC. This essential downhole tool plays a crucial role in stabilizing the production tubing and improving pump efficiency. In this post, we’ll explore what a TAC is, how it is used, and the benefits it provides to well operations.
An Essential Downhole Tool
A tubing anchor catcher is a mechanical downhole device installed in a well’s tubing string to prevent undesirable movement of the tubing. It is designed to anchor the tubing securely within the casing, thereby restricting its vertical movement due to forces such as fluid pressure fluctuations, mechanical vibrations, and cyclical compression and tension loads from the pump system.
TACs typically consist of an expandable slip mechanism that grips the casing when engaged, ensuring a firm hold. The device can be mechanically set and released as needed for well servicing and maintenance operations.
How is a Tubing Anchor Catcher Used?
The installation of a tubing anchor catcher is a strategic decision in well completion and artificial lift systems, particularly in rod-pumped wells. The process generally follows these steps:
- Placement in the Tubing String: The TAC should be installed at an optimal depth within the wellbore where it can effectively prevent tubing movement. In general, the more tubing that is anchored, the better.
- Setting the Anchor: Once in place, the TAC is set by engaging its slip mechanism. This is done by rotating the tubing until the slips contact the casing, usually in 6 to 8 turns. The residual torque is then worked out of the well and a predetermined amount of stretch is placed on the tubing.
- Operational Benefits: Once anchored, the tubing remains stable, improving the efficiency of artificial lift methods such as rod pumping. This stability enhances the pump’s performance by reducing tubing wear, excessive movement, and energy losses.
- Releasing for Maintenance: When necessary, the TAC can be unset by reversing the setting process, allowing for easy retrieval during workover operations or well interventions.
Benefits of Using a TAC
The use of a tubing anchor catcher in oil and gas wells provides several key benefits. These advantages contribute to the efficiency, reliability and longevity of well operations:
1. Reducing Tubing Movement
Tubing movement, particularly in rod-pumped wells, can lead to inefficient pump operation and accelerated equipment wear. A TAC stabilizes the tubing, eliminating unnecessary movement and ensuring smooth operation.
2. Enhancing Pump Efficiency
By preventing tubing movement, TACs improve the efficiency of downhole pumps. In rod-pumped wells, they help maintain consistent plunger travel, leading to improved pump fillage and reduced fluid pound, which can enhance overall production rates.
3. Preventing Excess Wear
Excessive tubing movement can cause friction between the rods, tubing and casing, leading to premature wear and potential failures. A TAC minimizes this movement, reducing mechanical wear and extending the lifespan of wellbore components.
4. Reducing Energy Consumption
Efficient pump operation means less energy is required to lift fluids from the well. A TAC stabilizes the tubing string, allowing for optimized pump strokes and reduced energy losses, ultimately lowering operational costs.
5. Improving Safety and Well Integrity
Uncontrolled tubing movement can lead to mechanical failures, production interruptions and potential safety hazards. TACs mitigate these risks by providing a secure and stable tubing environment, enhancing overall well integrity.
6. Facilitating Workover Operations
Since tubing anchor catchers can be mechanically set and released, they simplify workover operations by allowing easier access to downhole components. This ease of retrieval and reinstallation enhances well serviceability and reduces downtime.
Is Every TAC the Same?
In a word, no. While the traditional TAC provides the benefits noted above, it’s also been linked to some significant challenges. The outside diameter (OD) of a standard B2 TAC is nearly as large as the casing itself. That leaves very little annular area between the anchor and the casing. This “choke point” creates a pressure drop that can lead to the formation of scale, iron sulfide and paraffin. It can also lead to gas locking of the rod pump.
To mitigate the effects of these issues, TechTAC® developed the Slimline® Tubing Anchor Catcher. The design of the Slimline TAC improves the flow-by capacity in the annulus of a well by as much as 245% over a standard B2 anchor. That increased flow-by area allows gas to more easily flow up the well, rather than being trapped around the pump. The Slimline TAC also features tapered flow deflectors on the top and bottom. That tapered design, along with the anchor’s reduced OD, virtually eliminates the risk of sediment or paraffin building up on top of the anchor. As such, it can be safely set above, in or below the perforations, depending on the well design.
Verified by CFD Analysis
A computational fluid dynamics (CFD) study from the independent consulting firm Imaginationeering found that the net pressure drop around a standard B2-style tubing anchor, as fluid/gas passes through the annular cavity around the anchor, is more than double the pressure drop around TechTAC’s Slimline TAC. As noted previously, a significant pressure drop, like that around the standard B2 anchor, is a primary issue causing gas locking in rod pumps and a major contributor in the formation of scale, iron sulfide and paraffin. The Slimline anchor also demonstrated a noticeable advantage over the standard B2 TAC in reducing the overall turbulence and vorticity strengths within the flow field.
To learn more about the Slimline TAC and the unique benefits it offers, download the TechTAC Product Catalog or contact a member of the TechTAC team.
