Reliability and Performance of Vinyl Lactam-Based Kinetic Hydrate Inhibitor Polymers after Treatment under a Range of Conditions

Abstract

Well-known kinetic hydrate inhibitors (KHIs) such as poly­(N-vinylcaprolactam) (PVCap), poly­(N-vinylpyrrolidone) (PVP), and 1:1 N-vinylcaprolactam:N-vinylpyrrolidone (VCap:VP) copolymer have been subjected to a range of treatments to determine their reliability and whether the treatment conditions could affect the KHI performance, both positively or negatively. This included thermal aging (at varying temperatures, at varying pH, and in monoethylene glycol (MEG) solvent), treatment with microwaves or ultrasound, ball-milling, and oxidizing agents (household bleach or hydrogen peroxide, also with heat). In addition, samples of commercial polymer solutions kept for up to 15 years were also tested for KHI performance to determine their long-term reliability. Testing was carried out using a synthetic natural gas mixture in steel rocking cells using slow constant cooling starting at ca. 76 bar. All samples of PVCap and 1:1 VP:VCap showed good KHI performance to the first sign of hydrate formation, but older samples showed a better ability to inhibit crystal growth. KHI polymer testing after treatment with microwaves or ultrasound, or thermal aging (at varying temperatures, varying field pH, and in MEG solvent up to 160 °C) showed little loss of performance. Oxidizing agents, particularly sodium hypochlorite solution, worsened the KHI performance.

Surface Science in the Research and Development of Hydrate-Based Sustainable Technologies

“…Advanced surface science is a prerequisite for the development of targeted LDHIs. ,,− As surface-active reagents, LDHIs adsorb on the surface of ensuing hydrate nuclei and retard their growth and/or aggregation. ,− This necessitates an insightful understanding of the interaction between LDHI molecules and the hydrate surface. , The attractive force between LDHI molecules and the hydrate surface (i.e., the driving force of LDHIs adsorption) acts within a subnanometer range, meaning that the adsorption process is dictated only by a few outmost water layers of the hydrate surface. Carver et al indicated that this driving force arises from the hydrogen bonding between hydrophilic sites of LDHI molecules and water molecules of the hydrate surface. , This mechanism applies to hydrate surfaces contacting a gas or hydrophobic environment.…”

“…First, the QLL alters the adsorption mechanism, for example, changing from a hydrogen-bonding regime (Figure a) to a hydration regime (Figure b). Second, LDHIs are complex molecules containing functional (hydrophilic/charged) sites. , As such, a rigid solid surface can only contact certain sites of LDHI molecules at one time (Figure c), but a premelting surface can deform to reach a larger number of functional sites (Figure d). The latter leads to an improved driving force of the adsorption.…”

A sustainable approach to synthesize phosphonated chitosan using ball milling and its application for oilfield scale management

“…We previously found that extreme mechanical stress from ball-milling can reduce the polymer molecular weight to shorter chain lengths. 52 In addition, it was reported that the phosphonation reaction of original chitosan under conventional conditions led to a decrease in its molecular weight. [53][54][55] It is well known that low molecular weight polymers exhibit optimal scale inhibition performance in petroleum industry applications.…”

Simultaneous inhibition of natural gas hydrate formation and CO2/H2S corrosion for flow assurance inside the oil and gas pipelines

“…KHIs are water-soluble polymers containing imide or amide functional groups, and they are typically used at 0.1-2 wt.% [21][22][23]. Poly(N-vinyl lactam)s, poly(N-isopropylacrylamide), polyvinylpolypyrrolidone, poly(N-alkyl (meth)acrylamide)s, and hyperbranched polyesteramide are commercially available KHIs [24][25][26]. The mechanism action of KHIs is predominantly on the kinetics of gas hydrate formation by delaying nucleation and crystal growth of hydrates [27][28][29].…”