Ann: Webinar for Block 9 Update, page-152

Since the above were just my suspicions I queried my mate chatGPT, and I seemed to be on the right track, here


In open-hole completions in fractured carbonate reservoirs, cement can indeed bypass external packers under certain conditions. Here’s a breakdown of how this can happen and the implications:

1. **Fracture Networks**: In carbonate reservoirs, especially those that are highly fractured, there can be extensive natural fracture networks. These fractures can act as pathways for fluids, including cement slurries, to travel through.

2. **Cement Slurry Behavior**: When cement slurry is pumped into the wellbore during cementing operations, it seeks the path of least resistance. If there are existing fractures in the rock, the cement can be diverted into these fractures rather than sealing off the annular space around the casing.

3. **External Packers**: External packers are typically placed to isolate specific intervals in the wellbore during completion operations. However, if the surrounding rock is highly fractured, cement can bypass these external packers by traveling through the fractures instead of staying within the annular space where it's intended to set and form a seal.

4. **Consequences**: If cement bypasses external packers due to fractures, it can lead to several issues:
- **Zonal Isolation Problems**: Incomplete zonal isolation between different reservoir zones or between the reservoir and the surface can occur, compromising well integrity and potentially allowing crossflow between zones.
- **Casing Corrosion Risks**: Fluids from different zones or the surface can corrode the casing if isolation is not properly achieved.
- **Production and Safety Concerns**: Improper zonal isolation can impact production efficiency and safety, as well as increase operational costs for remediation.

5. **Mitigation**: To mitigate cement bypassing external packers in fractured carbonate reservoirs, several measures can be taken:
- **Pre-job Evaluation**: Conduct thorough geological and geophysical studies to understand the fracture network and plan cementing operations accordingly.
- **Cementing Design**: Use appropriate cementing additives and techniques to minimize fluid loss and enhance cement placement around the casing.
- **Alternative Technologies**: Consider alternative technologies like expandable steel packers or swellable packers that can conform to irregular borehole shapes and provide better zonal isolation in fractured formations.

In summary, cement bypassing external packers in open-hole completions is a significant concern in fractured carbonate reservoirs due to the natural pathways provided by fractures. Careful planning, evaluation of reservoir conditions, and appropriate cementing techniques are essential to mitigate this risk and ensure effective zonal isolation and well integrity.