Assess a well intervention
A production flow test followed by a PBU test before and after a well intervention will help to assess the impact of the intervention on well performance.
The evolution of the DP and derivative plots with a derivative overlay will help to clearly understand the impact on the skin, permeability and flow behaviour around the wellbore.
Let’s assume a very simple example where we add new perforations to a slightly deviated oil well.
As shown in the plot below, the pre-intervention PBU (PBU 1) shows a permeability-thickness value of about 1,970 mD and a total skin St = -0.4 (which accounts for the slight deviation of the well).
If we plot the pressure data from the pre and post intervention PBU tests on the log-log plot, the derivative overlay is obtained below :
The derivative overlay shows a shift of the derivative downwards, which indicates an increase in permeability-thickness KH around the wellbore.
With a quick straight line analysis, we could see that perforating the new layers increased KH by 230mD.ft. Also the post-intervention response shows a decreased vertical separation between the DP and derivative plots, which suggests a slight decrease in skin. This is also confirmed with the straight line analysis.
This was a very simple example but it shows that just by looking at a plot (derivative overlay), you could quickly assess the impact of a well intervention under transient production period.
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Why testing wells ?
- Confirmation of discovery and productivity
- Clean-up and rate measurement
- Large volume fluid sample
- Well and reservoir performance
- (skin, KH, Pi, heterogeneity, boundaries)
- Reservoir connectivity & proven volume
- Flow behaviour around wellbore
- Large scale of investigation (100-1000s ft)
- Use of opportunistic shut-ins
- Track permeability, skin, reservoir pressure
- Monitor performance over time
- Understand performance deviation
- Assess well intervention
- Quality control rate measurement
No other alternative to:
obtain large fluid sample
evaluate permeability over large distances (~100s-1000s feet),
assess well damage (skin)
Investigate connectivity over large volume
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Extensive experience from exploration to production in all types of wells and reservoirs worldwide.
We have expertise in deconvolution.
Deconvolution is a great asset for your team. It helps to improve the understanding of the response, refine initial pressure and add reservoir insights. While deconvolution is not new, it is often misused in the industry.
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