Field Application of Combined Kinetic Hydrate and Corrosion Inhibitors in the Southern North Sea: Case Studies

Poly(N,N-dimethylhydrazidoacrylamides)s (PDMHAMs) and a series of copolymers of (N,N-dimethylhydrazidoacrylamide) and (N-isopropylacrylamide) were recently investigated as kinetic hydrate inhibitors (KHIs). Poly(Nvinylcaprolactam) (PVCap) and related copolymers have been used as a class of commercial KHIs in the oil and gas industry to prevent plugging of pipelines with gas hydrates. In this study, we have synthesized and investigated the ability of copolymers of DMHAM monomer and VCap monomer to inhibit structure II gas hydrate formation in high-pressure rocking cells at approximately 75 bar. Various polymer molecular weights have been investigated at various pH conditions. It was found that the novel polymers have high cloud points in deionized (DI) water or brine solutions at high or low pH under pressure compared to polyVCap. A 1:2 copolymer of DMHAM/VCap gave the best KHI performance for this class of copolymer with a cloud point at 50°C in DI water. Also, a 1:1 DMHAM/VCap copolymer gave excellent KHI performance, as well as giving no cloud point up to 100°C in DI water or high-salinity solutions (3.6−15 wt % NaCl) at pH 5.0. The cloud point was found to be 67°C at pH 12.0 for the 15 wt % NaCl solution, making it compatible for use in high-salinity water-based deep-water drilling fluids. It was also found that high pH improved the performance of the KHIs compared to otherwise identical tests at pH 5.0. This may be related to removing the structure I (SI)-forming and relatively more soluble acid gas CO 2 from the system at high pH.

Section: Introductionmentioning

confidence: 99%

N,N-Dimethylhydrazidoacrylamides. Part 2: High-Cloud-Point Kinetic Hydrate Inhibitor Copolymers with N- Vinylcaprolactam and Effect of pH on Performance

Mady

Kelland

2015

“…These polymers are being successfully used to prevent gas hydrate formation in pipelines in locations such as the U.K. sector of the North Sea, the Gulf of Mexico, South America, and the Middle East. − Polymers of N -isopropylmethacrylamide have recently been commercialized, and a polyester pyroglutamate KHI is also commercially available, which although it has good biodegradability, has limited performance. − Other biodegradable KHIs have recently been developed. − All these classes of KHI polymers contain amide groups which are particularly useful for hydrogen bonding from both the amino nitrogen atom and the carbonyl oxygen …”

Section: Introductionmentioning

confidence: 99%

Study of the Kinetic Hydrate Inhibitor Performance of a Series of Poly(N-alkyl-N-vinylacetamide)s

Ajiro¹,

Takemoto²,

Akashi³

et al. 2010

Kinetic hydrate inhibitors (KHIs) have been used successfully for about the last 16 years to prevent gas hydrate formation mostly in gas and oilfield production lines. They work by delaying the nucleation and often also the growth of gas hydrate crystals for periods of time dependent mostly on the subcooling in the system. Poly(N-alkyl-N-vinylamide)s have been briefly investigated previously but no work has previously been published detailing a systematic study of structure versus performance. In this paper we report the KHI performance of a series of poly(N-alkyl-N-vinylacetamide)s polymers with alkyl side groups up to five carbon atoms. The study includes hydrate crystal growth tests on structure II tetrahydrofuran hydrate crystals as well as high pressure nucleation and crystal growth studies on a synthetic natural gas mixture giving structure II hydrates. The SII gas hydrate inhibition results correlate well with the THF hydrate crystal growth inhibition results since the polymers with the larger isopentyl or isobutyl groups performed best in both equipments but not significantly better than a commercial low molecular weight Nvinyl caprolactam-N-vinyl pyrrolidone 1:1 copolymer.

“…These polymers are being successfully used to prevent gas hydrate formation in pipelines in locations such as the UK sector of the North Sea, the Gulf of Mexico, South America, and the Middle East. − A polyester pyroglutamate KHI is also commercially available that, although nicely biodegradable, has limited performance. − At the time of writing, only one polymer from these classes is available for use offshore of Norway since the environmental authorities demand at least 20% biodegradability (preferably >60%) in 28 days for new oilfield chemicals and that the products of degradation are also environmentally friendly. We have endeavored to find new polymer classes that are both high performing and have at least 20% biodegradation in the OECD 306 test.…”

Section: Introductionmentioning

confidence: 99%

A Study of the Kinetic Hydrate Inhibitor Performance and Seawater Biodegradability of a Series of Poly(2-alkyl-2-oxazoline)s

Villano¹,

Kommedal²,

Fijten³

et al. 2009

Kinetic hydrate inhibitors (KHIs) have been used successfully in the field for about the last 14 years to prevent gas hydrate formation mostly in gas and oilfield production lines. They work by delaying the nucleation and often also the growth of gas hydrate crystals for periods of time dependent on the subcooling in the system. Poly(2-alkyl-2-oxazoline)s [or poly(N-acylalkylene imine)s] are a known class of KHI, but no work has previously been published detailing a systematic study of structure versus performance. In this paper we report the KHI performance of poly(2-alkyl-2-oxazoline) homopolymers and statistical copolymers with alkyl side groups up to four carbon atoms. The study includes hydrate crystal growth tests on structure II tetrahydrofuran hydrate crystals as well as high pressure nucleation and crystal growth studies on a synthetic natural gas mixture giving structure II hydrates. Seawater biodegradation studies on all the polymers according to the OECD306 procedure indicate that they are all poorly biodegradable (<20% in 28 days).