Large natural gas processing plants that rely on Joule–Thomson refrigeration for low-temperature separation face a persistent flow assurance challenge: wax deposition from aromatic compounds can rapidly degrade equipment performance and reduce throughput. A case study at the KS processing facility at TLM oilfield illustrates the severity and solution for this problem.
The facility's troubles began shortly after commissioning when the J-T valve experienced mechanical sticking, followed by excessive pressure buildup in the low-temperature separator. Initial diagnostics ruled out common culprits such as inadequate glycol injection or mineral scaling. Detailed chemical analysis and thermodynamic modeling revealed the true cause: aromatic-based wax, primarily biphenyl and polycyclic aromatic hydrocarbons (PAHs), precipitated under throttle-cooling conditions due to the lean composition of the inlet gas.
The mechanism is straightforward: the feed gas lacked sufficient C5–C8 light hydrocarbons to maintain PAH solubility. Following the principle that "like dissolves like," researchers determined that reintroducing light hydrocarbons could disrupt wax crystal lattices and restore system operability.
The solution deployed was a circulating light hydrocarbon injection technology. Rather than relying on permanent chemical additives, this approach continuously recovers and recirculates the injected hydrocarbons while progressively dissolving and mobilizing deposited wax. HYSYS software modeling optimized injection parameters ahead of field implementation.
Results were dramatic. The facility transitioned from crisis-mode operation with severely constrained throughput to stable continuous production. More than $1.12 million in annual operational cost savings materialized through improved efficiency and reduced intervention requirements.
This approach offers broader applicability to lean gas processing environments where conventional wax inhibitors prove insufficient. It demonstrates how mechanistic understanding of thermodynamic principles can drive practical, cost-effective solutions to persistent flow assurance challenges in hydrocarbon recovery operations.
