A new, field-proven, cost-effective solution for MEG regeneration unit issues in offshore Australia gas production

Abstract

Several gas fields are being developed off the coast of Western Australia. The risk for hydrate blockages in these fields is high and presents several challenges for hydrate inhibition, including high subcoolings, low water salinities, and high system temperatures. The current strategy is to use mono-ethylene glycol (MEG) for hydrate inhibition, which includes MEG regeneration units (MRUs) in the design of the facilities. The installation and maintenance of MRUs capable of handling the large required volumes of MEG is costly and other issues such as scale, foaming, and accumulation are a concern when using an MRU. Therefore, the use of a low dosage hydrate inhibitor (LDHI) is being considered for some developments. Kinetic hydrate inhibitors (KHIs) are typically considered for gas fields, not anti-agglomerate low dosage hydrate inhibitors (AA-LDHIs). KHIs, however, are not effective at high subcoolings and can become unstable when subjected to the high temperatures of the MRUs. Instead, a new generation of AA-LDHI chemistry can be considered for Australian gas fields. Field data will be presented supporting the new AA-LDHI’s effectiveness in inhibiting hydrate blockages in a gas/condensate field, eliminating the need for MEG and the MRU. The new AA-LDHI chemistry is being evaluated for several Australia projects, and data supporting the chemistry’s stability at temperatures greater than 150°C and its effectiveness with low-water salinities will also be presented. The new AA-LDHI chemistry could eliminate the need for MEG or greatly reduce the volume of MEG required for inhibition, which would reduce CAPEX and OPEX.

Experimental and Theoretical Investigation of the Interaction between Hydrate Formation and Wax Precipitation in Water-in-Oil Emulsions

“…Challenges encountered in deep-water fields include colder water, longer subsea tiebacks, higher water cuts, and higher hydrostatic pressure, thereby increasing risks of plugging pipelines because of hydrate formation, wax/asphaltene precipitation, or scaling. , Hydrate flow assurance is a major technical concern by the flow assurance engineers in deep-water fields. Thermodynamic hydrate inhibitors (THIs) injecting or heating have been widely applied in flowlines to shift the operation condition outside of the hydrate formation boundary, making it thermodynamically unfavorable for hydrate formation. − These methods are effective, but a large amount of additives is required to be injected and huge energy is needed for heating, which make them financially unattractive . Alternatively, a risk management method is presented to control hydrate blockage issues.…”

“…3−5 These methods are effective, but a large amount of additives is required to be injected and huge energy is needed for heating, which make them financially unattractive. 6 Alternatively, a risk management method is presented to control hydrate blockage issues. Low dosage hydrate inhibitors (LDHIs) including anti-agglomerants (AAs) and kinetic hydrate inhibitors (KHIs) are gaining more attention for advantages in low dosage and environmental protection.…”

Exacerbation of Hydrate Agglomeration in the Presence of Kinetic Hydrate Inhibitor under High pH Conditions

“…It was estimated that the cost of injecting a thermodynamic inhibitor into the subsea flowlines can reach 50% of the total operating costs for offshore fields producing about 50 000 bbl/day water. 6 Several studies 5,7−9 have proposed a method called "underinhibition", in which the concentration of MEG in the water phase is reduced to a value lower than that required to fully avoid the hydrate formation. Creek et al 5 demonstrated that the hydrate inhibition performance of MEG in an under-inhibition system reduced the required MEG injection rate for the offshore gas field development.…”

“…However, handling a large amount of MEG or methanol in offshore and remote areas where the platforms are located would increase the operating cost significantly. It was estimated that the cost of injecting a thermodynamic inhibitor into the subsea flowlines can reach 50% of the total operating costs for offshore fields producing about 50 000 bbl/day water …”

Experimental Evaluation of Kinetic Hydrate Inhibitors and Mixed Formulations with Monoethylene Glycol for Hydrate Prevention in Pure Water and Brine–Oil Systems

“…A more practical and potentially cheaper solution for hydrate prevention or remediation is the injection of chemicals. This involves two major categories: thermodynamic hydrate inhibitors (THIs), such as methanol and glycol, − and low dosage hydrate inhibitors (LDHIs) covering mainly kinetic hydrate inhibitors (KHIs) and antiagglomerates (AAs). THIs are still widely used in industry with the ability of directly lowering the hydrate–liquid–vapor equilibrium (HLVE) temperature or increasing the HLVE pressure.…”