Under Travel

Understanding "Under Travel" in Oil & Gas: A Deeper Dive into Rod String Movement

In the world of oil and gas production, the term "under travel" refers to a specific phenomenon related to the movement of the rod string within a well. It occurs when the travel of the rod string at the pump (bottom of the well) is less than the surface rod travel. This discrepancy can have significant implications for well productivity and requires careful monitoring and troubleshooting.

What is Rod String Travel?

Imagine a fishing rod. When you cast the line, the rod bends and the line travels a certain distance. Similarly, in an oil well, the rod string – a series of connected rods that act like a piston – is pumped up and down to lift the oil to the surface. The rod string travel refers to the total distance the rod string moves within the wellbore.

Why Under Travel Happens

Under travel occurs due to various factors, including:

• Pump Efficiency: If the pump at the bottom of the well is not operating efficiently, it may not be able to lift as much oil as expected, leading to less rod string movement.
• Fluid Conditions: High fluid viscosity, gas interference, or the presence of sand can hinder the pump's ability to move the fluid efficiently.
• Rod String Issues: Broken rods, worn out couplings, or stuck rods can cause the rod string to move less than expected.
• Wellbore Geometry: Significant deviations in the wellbore, like sharp bends, can restrict the rod string movement and lead to under travel.

Impact of Under Travel

Under travel can significantly impact well production:

• Reduced Oil Production: Less rod string movement means less oil is lifted to the surface, impacting overall production rates.
• Increased Pumping Costs: Since the pump is working inefficiently, it consumes more energy to lift the same amount of oil, leading to increased operating costs.
• Potential Damage to Equipment: If the issue is related to the pump or rod string, under travel can lead to wear and tear, ultimately requiring expensive repairs or replacements.

Monitoring and Addressing Under Travel

Early detection of under travel is crucial to mitigating its negative impact. Regular monitoring through:

• Surface Rod Travel Measurement: Tracking the movement of the rod string at the surface using sensors and recording devices.
• Downhole Pressure Readings: Monitoring the pressure at the bottom of the well to assess the pump's efficiency.
• Production Rate Analysis: Examining changes in oil production to identify any potential issues.

Once detected, addressing under travel requires careful investigation and analysis to determine the root cause. This may involve:

• Pump Inspection and Repair: Evaluating the condition of the pump and making necessary repairs or replacements.
• Rod String Inspection and Maintenance: Checking the rod string for wear and tear, broken rods, or stuck sections.
• Wellbore Assessment: Investigating any potential issues with the wellbore geometry that might restrict rod string movement.

Conclusion

Understanding the concept of "under travel" in oil and gas production is essential for optimizing well performance and minimizing operational costs. By monitoring rod string travel, analyzing well production data, and effectively addressing the underlying causes, operators can ensure optimal well performance and minimize the negative consequences of under travel.