Low Dosage Hydrate Inhibitors (LDHI): Advances and Developments in Flow Assurance Technology for Offshore Oil and Gas Productions

摘要

The last thing the offshore operators want to see is after all the investments in exploring, drilling and production, they couldrnnot flow the hydrocarbon from underground smoothly and efficiently. Among all the offshore flow assurance challenges, inrna short time period can hydrate restrict flow and even form a solid plug to block all production. Long deepwater subsearntiebacks are especially problematic due to the high pressures and low temperatures, which would require sufficient quantitiesrnof thermodynamic hydrate inhibitors (THI) injection for hydrate mitigation. High THI injection volume can both exacerbaternscaling problems by salting out of high TDS brines, and contaminate the exporting hydrocarbon by methanol. All thesernoffshore production challenges, coupled with complicated logistics and HS&E concerns on THI, have being endorsed therndevelopment and field deployment of low-dosage hydrate inhibitors (LDHI) in the last decade.rnGiven the costs associated with remediating problems in offshore systems and the corresponding deferral of production, eachrnnew LDHI development is put through a series of rigorous qualification process. This paper will detail the challengesrnassociated with LDHI applications for offshore productions. Efforts at developing and deploying new DLHI productsrnsuitable for number of recent offshore applications worldwide with field different requirements will be highlighted.rnUmbilical and capillary line failure is a major concern in the industry. Best practices to qualify products for umbilical andrncapillary injection have been rapidly evolving over the last ten years. Stability of LDHI formulations can depend on bothrntemperature and pressure. In particular, high pressure viscometer measurements have proved to be invaluable forrndetermining whether apparent pressure related stability concerns may exist in formulations at cold deepwater temperatures.rnMoreover, LDHI compatibilities with production fluids, system materials, other production chemicals and no adverse effectrnon their performance are also the key to its successful field implementation. Subsequently, closely monitored topside testsrnand field trials are essential to gain insights to the product performance in real systems.rnFour different LDHI application case histories in GOM, North Sea and Middle East will be presented, illustrating anrnoverview of the successful applicability of LDHIs in offshore gas condensate and oil systems under a variety of conditions.rnThey are involved in hydrate controls for both transient operations (shut-in and start-up) and steady-state productions, and thernproduct qualifications under different field requirements. Emphasis from these applications would demonstrate how LDHIrn(1) to facilitate hydrocarbon production improvement and prolong the field production lifetime; (2) to help meet crudes specs through eliminating MeOH contamination; and (3) to apply in conjunction with corrosion inhibitors (CI), either as individualrnproducts or as combination products for gas condensate systems. (4) Hydrates may form different structures depending onrnthe fluids composition. The nature of the LDHI used needs to take this into account; and recent LDHI product developmentsrnand applications in this area will also be described on field mitigation of structure I hydrate, an uncommon but morernchallenging one.