The fight against hydrates has never been more critical in our industry. With the recent increase in deepwater and ultra-deepwater production, maintaining flow assurance demands careful consideration given the increased likelihood that hydrate formation will occur (due to high pressure and low temperature operating conditions).
THIs or LDHIs
Chemical inhibitors, such as Thermodynamic Hydrate Inhibitors (THIs) and to a lesser extent Low Dose Hydrate Inhibitors (LDHIs), are often the key weapon in the fight to maintain flow. Both categories of inhibitor have their benefits and uses. THIs, such as methanol and ethylene glycol, are favoured for their ability to effectively shift the hydrate curve and LDHIs, surfactant based chemical solutions, are known for their ability to reduce hydrate inhibitor chemical consumption.
In an effort to reduce chemical usage, and subsequently chemical costs, some operators have switched from THIs to LDHIs as they are often considered to be a more cost-effective alternative. A recent trend that has emerged off the back of this switch, especially in the Gulf of Mexico, is the use of isopropyl alcohol (IPA) as a carrier fluid for LDHIs. IPA is mixed with the LDHIs before injection to improve the dosing of the LDHIs within the pipeline, given the low % by volume of the chemical required. Injections rates for methanol, for example, are around 30-60% by volume whereas LDHIs are typically 0.5-2.0% by volume.
IPA as a contaminant
Since swapping out methanol for IPA/LDHI inhibition however, operators in the GOM have faced a significant issue downstream. Few were aware that refiners consider IPA to be as much of a contaminant as methanol and, as such, have demanded that the operators declare IPA concentrations in oil before the crude arrives for processing. Importantly, there are currently no known accurate, timely analysis methods for IPA in crude oil.
The importance of being able to provide fast and accurate measurements of contaminants in crude, such as methanol, before it reaches the refinery is widely recognised. Doing so can save an operator $ millions in waiver fees through enabling more accurate reporting of methanol partitioning to the oil phase. With no such solution available for IPA, surely making the switch from methanol to IPA/LDHI is a risky one!
Time to consider the risks
To muddy the waters even further, it is often the case that IPA/LDHI inhibition is not adequate in challenging deepwater conditions and operators will continue to dose methanol, albeit at lower levels. This is due to the fact that LDHIs are not able to completely stop hydrates from forming, as they do not cause a hydrate curve shift, and they are unable to dissolve hydrates that have already formed. As such, operators must continue to accurately determine the amount of methanol in their crude, and use timely, accurate analysis to reduce potential waiver fees. For the operators in the GOM, this is in addition to determining IPA levels in their crude.
Considering these issues, is the amount saved on chemical costs from switching from methanol to IPA/LDHIs worthwhile? It is certainly worth careful consideration.
More on waiver fees, with a particular focus on methanol contaminated crude, coming soon…