Challenge:
Cairn Energy faced significant flow assurance challenges at the Mangala and Aishwariya oil fields, part of the Rajasthan block, which hold substantial oil reserves but are characterized by heavy, waxy crude with high in-situ viscosity. These reservoirs also had a low Gas to Oil Ratio (GOR), making natural flow difficult. Low reservoir energy and early water breakthrough, combined with the crude’s tendency for wax deposition, required an artificial lift system from the start. The challenge was to select an efficient and cost-effective lift method capable of sustaining high production rates while addressing the complex flow assurance issues posed by these challenging fluid characteristics.
Solution:
After conducting extensive evaluations, Cairn Energy identified Jet Pumps (JP) as the optimal solution. While gas lift (GL) was initially recommended, detailed studies revealed that JP systems were better suited to handle the viscosity of the oil, wax deposition risks, and well deviation. JPs, combined with a hot water circulation system for surface flow assurance, provided a dual solution to manage both downhole and surface flow and prevent wax build-up. JPs offered operational flexibility, easier installation and retrieval via wireline, lower workover frequency, and the ability to lift a wide range of fluid volumes. The system also allowed for chemical injection and worked independently of well deviation, making it ideal for both vertical and deviated wells in the Mangala and Aishwariya fields.
Value Added:
The transition from gas lift to jet pumps delivered significant value, with a $60 million reduction in CAPEX on surface facilities by eliminating the need for gas dehydration, compression, and handling infrastructure. Jet pumps consumed less energy, with power fluid requirements of 0.6 to 0.8 barrels per barrel of fluid lifted, compared to gas lift’s higher energy demand.
The ability of JPs to handle up to 10,000 barrels per day allowed for higher production rates while minimizing workovers. Retrieval of JP systems through wireline meant lower maintenance costs and reduced downtime. Furthermore, the new system led to a 20-30% reduction in well pad footprint, lowering both environmental impact and surface installation costs.
By using hot water to maintain flow and prevent wax build-up, Cairn was able to reduce interruptions and ensure smoother production. This optimized approach is expected to significantly boost long-term recovery rates, potentially unlocking millions of barrels of additional recoverable oil, making it a scalable and economically sound solution for other fields with similar challenges.
