Casing repair in CSS wells
CSS remedial applications may admit the casing patch technology since the latter can handle high temperatures when the well goes back to ‘steam-ulation’. This single-well method consists of injecting steam at high pressure and high temperature in the reservoir during the first phase. The completion of a soaking phase allows the reservoir to heat up evenly through convection, then the team pumps out the heated oil from the same well. When the oil production rate decreases due to reservoir cooling, they initiate another cycle. The process of enhanced oil recovery (EOR) includes a step where the team temporarily shuts-in the well to let heat evenly distribute throughout the reservoir through natural processes such as convection. The aim is to warm up the reservoir to help increase the flow of oil, making it easier to pump out.
Challenges with CSS remedial applications
High-temperature casing remediation poses several challenges due to the harsh operating conditions. These challenges include:
- Extreme temperatures. Temperatures inside the well can reach up to 335°C, requiring casing material and seals to withstand high heat.
- Harsh environment. The presence of hydrogen sulfide (H2S) in high concentrations creates an aggressive environment that can damage or deteriorate casing materials.
- Thermal cycling. The casing must be able to withstand up to 10 thermal cycles, where it is exposed to repeated heating and cooling.
- High and low-temperature seals. The casing must be able to seal effectively at both high and low temperatures without losing its integrity.
- Production rate impact. To keep the well profitable, minimize the impact of the casing remediation process on the production rate by leaving the maximum inside diameter of the casing intact.
Solution
The Saltel Expandable Steel High Temp Patch 335°C/635°F is a solution to repair wells that operate in high-temperature environments. We designed the Saltel Expandable Steel High Temp Patch 335°C/635°F to last the entire lifetime of the well. We modified the design and installation process, based on the standard Patch, to suit high-temperature conditions. Rigorous testing approved the product for use in repairing wells that are outside of their normal operating zone. The tests include 10 thermal cycles under challenging conditions and it has been successfully qualified through these tests.