Pressure Traverse

Understanding Pressure Traverse in Oil & Gas: Mapping Pressure Down the Wellbore

In the oil and gas industry, understanding the pressure distribution within a wellbore is crucial for efficient production and safe operations. A pressure traverse is a critical tool used to achieve this understanding.

What is a Pressure Traverse?

A pressure traverse involves measuring the pressure at various depths down the wellbore. This process provides a detailed picture of the pressure gradient, revealing information about the reservoir's pressure, fluid properties, and potential flow patterns. It's essentially a pressure profile of the well, allowing engineers to assess the well's health and make informed decisions about production strategies.

Why is Pressure Traverse Important?

• Reservoir Pressure Estimation: Analyzing the pressure traverse helps determine the reservoir pressure, which is essential for predicting production rates and estimating the remaining reserves.
• Fluid Characterization: The pressure gradient can indicate the presence of different fluid phases (oil, gas, water) and their relative densities.
• Flow Pattern Analysis: Examining the pressure drop along the wellbore allows engineers to assess the flow regime and identify potential bottlenecks or restrictions.
• Wellbore Integrity Assessment: Sudden pressure changes or inconsistencies in the pressure profile can signal potential issues with the wellbore, such as casing leaks or formation damage.

How is a Pressure Traverse Conducted?

Pressure traverses are typically conducted using a downhole pressure gauge or a specialized tool called a pressure-depth recorder (PDR). The PDR is lowered into the wellbore on a wireline, taking pressure readings at predetermined intervals.

Calculating Pressure vs. Depth:

The pressure gradient can be calculated by integrating the pressure readings over different depths. This involves:

1. Collecting Pressure Data: Using the PDR, obtain pressure readings at various depths along the wellbore.
2. Determining Depth Intervals: Divide the wellbore into discrete intervals, typically based on the length of the production tubing or the location of specific formations.
3. Calculating Pressure Difference: Calculate the pressure difference between the top and bottom of each interval.
4. Calculating Pressure Gradient: Divide the pressure difference by the corresponding depth interval.

This process generates a pressure-depth profile, which can then be used to assess the well's performance and identify potential areas of concern.

Example Application:

Imagine a well producing oil from a reservoir located at a depth of 3000 meters. A pressure traverse reveals that the pressure at the bottom of the wellbore (reservoir pressure) is 4000 psi. The pressure gradient, calculated from the pressure readings along the wellbore, shows a gradual decrease as we move upwards. This suggests that the flow of oil is being affected by friction within the tubing and other factors. Based on this information, engineers can adjust the production rate to optimize flow and prevent potential wellbore issues.

Conclusion:

Pressure traverse is an essential diagnostic tool in the oil and gas industry. It provides valuable insights into the wellbore's pressure distribution and helps optimize production operations. By understanding the pressure gradient, engineers can make informed decisions about reservoir management, fluid characterization, and wellbore integrity, ultimately leading to increased production efficiency and safety.