Squeeze cementing represents a critical process in the oil and gas industry, where a cement slurry is squeezed through perforations in casing to create a seal in specific locations, bridging undesired gaps. It is a common misconception that the cement penetrates the pores of the rock. Instead, the cement slurry dehydrates against the formation walls, forming a seal cement filter cake. It must be clear that cement does not infiltrate the pores of the rock. Given that cement slurries have particles with a mean size ranging from 20 to 50 microns, the permeability of the formation must be between 2-100 darcies for cement grains to penetrate the formation successfully.
Reasons for Squeeze Cementing
The necessity for squeeze cementing arises for various reasons during drilling and production phases, including:
- Zone Isolation Before Production Perforations: This ensures that specific zones are sealed off before the commencement of production.
- Rectifying Faulty or Inadequate Primary Cement Jobs: When the primary cementing job does not meet requirement, squeeze cementing comes to the rescue.
- Fixing Casing Leaks: Squeeze cementing is instrumental in addressing any breaches in the casing.
- Shutting off Unwanted Reservoir Water or Gas Inflows: To control and stop the unwanted flow of water or gas.
- Abandoning Non-Productive or Depleted Zones: When zones become unproductive or depleted, squeeze cementing is conducted to ensure their abandonment.
Three Main Techniques for Squeeze Cementing
The hesitation squeeze method involves the gradual buildup of a cement filter cake inside perforation tunnels. This process relies on the application of differential pressure to induce slurry dehydration. Given the minimal amount of filtrate lost from the slurry, continuous pumping becomes impractical. Instead, pressure is intermittently applied, allowing pressure to bleed off as the filter cake develops. This technique proves effective in ensuring that the pressure increases steadily as the filter cake builds up.
Low Pressure Squeeze:
During low-pressure squeeze operations, cement slurry is forced through perforations at pressures below the formation’s fracture pressure. The primary goal here is to fill perforation cavities and interconnected voids with dehydrated cement. Importantly, no slurry is pumped directly into the formation. This technique is commonly recommended in squeeze cementing procedures.
High Pressure Squeeze:
In certain scenarios, a low-pressure squeeze may not suffice to achieve the desired results. High-pressure squeezes are used when channels behind the casing aren’t directly connected to perforations, or when small cracks or micro-annuli permit gas flow but not cement slurry. Furthermore, some low-pressure operations face challenges due to the displacement of plugging fluids, such as drilling muds or solids-carrying completion brines. To carry out high-pressure squeezes, formations close to the perforations are broken down to create space for the cement slurry. This technique is particularly effective when displacing fluids and ensuring that all channels, from fractures to perforations, are filled with cement cake.
What is the Preferred Method?
Among these techniques, the hesitation squeeze is often preferred, involving the pumping of small cement volumes at intervals to allow gelling before squeezing.
Squeeze cementing techniques are essential for ensuring well integrity, addressing various challenges during drilling and production. By understanding and implementing advanced methods like hesitation squeezes, low-pressure squeezes, and high-pressure squeezes, oil and gas professionals can effectively seal undesirable gaps, enhancing the overall efficiency and safety of well operations.
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