Diverters in Acidizing: Steering Acid Where it Needs to Go
In the oil and gas industry, maximizing production from a reservoir often involves injecting acid to dissolve formation damage and improve well productivity. However, in many cases, the acid needs to be directed to specific zones within the reservoir, bypassing others. This is where diverter technology comes into play.
Diverters in acidizing are materials or techniques used to control the flow of acid, forcing it to enter a desired zone while bypassing others. This is crucial for achieving targeted stimulation and avoiding unwanted damage to other formations.
There are two main categories of diverters:
1. Viscosity-based Diverters:
- These rely on the principle of differential viscosity.
- A high-viscosity material, often a gel or polymer solution, is injected first. This viscous material preferentially flows into the desired zone due to its higher resistance to flow.
- Subsequently, the acid is injected, following the path created by the diverter.
- This method works well when there's a significant difference in permeability between the zones.
2. Filter Cake Diverters:
- These involve creating a filter cake, a thin layer of solid material, at the desired zone's entrance.
- The filter cake acts as a barrier, preventing acid from entering the undesired zones.
- This method is commonly achieved using proppants or resin-based materials that form a cohesive cake upon contact with acid.
Advantages of Using Diverters in Acidizing:
- Targeted Stimulation: Diverters allow for precise placement of acid, maximizing its effectiveness on the desired zone.
- Reduced Damage: By preventing acid from reaching unwanted zones, diverters minimize the risk of formation damage and acid leak-off.
- Improved Well Productivity: Focused stimulation leads to higher production rates and longer well life.
Considerations for Diverter Selection:
- Formation Characteristics: The permeability, porosity, and heterogeneity of the reservoir significantly influence diverter selection.
- Acid Type and Concentration: The acid's reactivity and viscosity need to be considered to ensure compatibility with the diverter material.
- Operational Parameters: Injection pressure, temperature, and flow rate affect diverter performance.
Conclusion:
Diverters play a vital role in optimizing acidizing treatments by ensuring targeted acid placement. By selectively steering acid flow, diverters contribute to safer, more effective stimulation, leading to improved well productivity and increased hydrocarbon recovery. Understanding diverter technology is essential for operators seeking to maximize reservoir performance and profitability.
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