Water Recirculation in Production Logging interpretations: Apparent Downhole Flow (ADF) or Cros...

Summary

This video explains how to identify and manage water recirculation in oil production logging. Key methods include analyzing inflow zones, apparent velocities, and calibration crossplots to distinguish between recirculation and cross flow. The speaker also discusses using multi-phase flow models, pseudo density, and temperature modeling to accurately assess water movement. The focus is on diagnosing negative velocities caused by water recirculation and refining rate calculations using advanced tools, ensuring more accurate reservoir behavior modeling for better production performance.

Takeaways

• 😀 Water recirculation in production logging can be identified through symmetrical cable speeds and negative velocities, which suggest downward flow.
• 😀 The deepest perforations in the well can show negative velocities, which could indicate water recirculation rather than cross flow.
• 😀 Negative velocities in the well profile may point to recirculation, but it’s essential to differentiate it from actual cross flow between zones.
• 😀 By examining cumulative Q and rate contributions, a 'thief zone' can be identified where one zone is injecting fluid while others are producing.
• 😀 Deviated wells with low velocity intervals are ideal candidates for water recirculation, which affects deeper perforations.
• 😀 Free pseudo density derived from pressure data can help detect water presence in the perforated intervals, confirming water recirculation.
• 😀 A negative productivity index, observed when drawdown increases and rates drop, is a key indication of non-real cross flow and supports the water recirculation hypothesis.
• 😀 Multi-phase conditions, pressure, and density data are critical for distinguishing between cross flow and water recirculation in the reservoir.
• 😀 Using a fluid identification tool and PVT data can refine the water recirculation interpretation, with salinity being a crucial factor in accuracy.
• 😀 Water recirculation can be modeled using multi-phase flow correlations, which help ignore spinner data and calculate the slip velocity, providing more accurate results.

Q & A

What is the primary focus of this video?

The video focuses on identifying and dealing with water recirculation in production logging, particularly in the context of oil wells.

What indicates the presence of water recirculation in a well?

Water recirculation can be identified by negative apparent velocities and unusual patterns in perforation flow, especially when the deepest perforation shows negative contributions despite being a producer well.

How can you distinguish between water recirculation and actual cross flow?

By analyzing the well's dynamic behavior, specifically through pressure and density data, as well as evaluating the negative productivity index and other reservoir zone behaviors, cross flow can be differentiated from recirculation.

What role does the calibration crossplot play in identifying recirculation?

The calibration crossplot helps by showing the intersections of inflow zones and indicating whether the flow is negative, which can signal recirculation.

Why is the deepest perforation more likely to be affected by recirculation?

The deepest perforation is more prone to water recirculation, especially in deviated wells, as it is immersed in water and experiences low velocity intervals, which create ideal conditions for recirculation.

What is the significance of the density analysis in diagnosing recirculation?

Density analysis, especially when corrected for deviation, shows that the deepest perforations are immersed in water, further supporting the theory of water recirculation rather than actual cross flow.

What does the negative contribution in the cumulative Q profile indicate?

A negative contribution in the cumulative Q profile suggests that a zone is injecting water rather than producing oil, which is a classic characteristic of a thief zone, likely due to water recirculation.

How does the concept of a negative permeability relate to the observed flow behaviors?

A negative permeability, while physically impossible, is used as an analogy to explain the behavior of the deepest perforation, where increasing drawdown leads to negative rates, suggesting cross flow is not the cause.

How does using the multi-phase flow model help in the interpretation?

The multi-phase flow model, which uses a multi-phase correlation for water and hydrocarbon behavior, helps in calculating the slipage velocity and provides a more accurate picture of the flow, especially in cases of water recirculation.

What is the purpose of the ADF (Apparent Downflow) setting?

The ADF setting is used to correct for water recirculation by ignoring the spinner's readings in affected zones, allowing for a more accurate calculation of apparent velocity based on multi-phase flow assumptions.