What Is a Formation Integrity Test (FIT) and Why is it performed?

In drilling operations, maintaining wellbore integrity is critical for safe and efficient operations. One of the key checks performed after setting casing is the Formation Integrity Test (FIT). This test helps confirm that the well can safely withstand planned drilling pressures before moving ahead. What Is a Formation Integrity Test (FIT)?

A Formation Integrity Test (FIT) is a pressure test conducted at the casing shoe to evaluate how the formation responds when pressure is applied. The test is performed by gradually increasing pressure in the wellbore to a predetermined value.

The primary purpose of an FIT is to verify formation and casing integrity, ensuring the well can safely handle the pressures expected during the next phase of drilling.

When Is an FIT Performed?

An FIT is typically carried out:

• After casing is run and cemented

• Once cement has achieved sufficient strength

• Before drilling the next hole section

This timing ensures the well is prepared to handle operational pressures before deeper drilling begins.

Why is a Formation Integrity Test Performed?

The FIT plays an important role in drilling safety and planning. It is performed to:

• Confirm the integrity of the casing shoe and surrounding formation

• Ensure the formation can tolerate planned drilling pressures

• Support safe mud weight selection

• Reduce the risk of losses, kicks, or well control incidents

• Provide confidence to proceed with the next hole section

By verifying integrity early, potential problems can be identified before they escalate.

How is an FIT Conducted?

Although procedures may vary slightly by company or location, an FIT generally involves:

1. Closing the BOP and isolating the well

2. Pumping drilling fluid at a controlled rate

3. Increasing pressure gradually to the planned test value

4. Holding and monitoring pressure for stability

Any abnormal pressure behavior may indicate issues with the formation or cement job.

FIT vs Other pressure tests

The FIT is often discussed alongside other wellbore pressure tests. However, it serves a specific purpose focused on confirmation, not exploration of limits. Understanding this distinction is essential for proper well planning and well control decisions.

Importance of FIT in well control

From a well control perspective, the FIT provides critical information that helps:

• Maintain safe pressure margins

• Prevent formation breakdown

• Support controlled drilling operations

• Enhance overall well integrity

Accurate interpretation of FIT results contributes directly to safer drilling outcomes.

Final Thoughts

A Formation Integrity Test is a vital checkpoint in drilling operations. By confirming formation and casing integrity before deeper drilling, an FIT helps protect personnel, equipment, and the well itself.

Whether you are new to the oilfield or advancing into supervisory roles, understanding FITs is essential knowledge for safe and effective drilling operations. Learn more on Drilling operations & Safety