Non-Emulsifying, New Anti-Agglomerant Developments

Abstract

Abstract Anti-agglomerant (AA) has emerged over the last decade as a new technology foroffshore hydrate control thanks to its unique hydrate control mechanism andlower application dosage. However, field operational issues, such asfluids separation, water quality and corrosivity in the presence of protic solvents, have prevented the growth of this technology industry-wide as a reliable andefficient hydrate control alternative to methanol and monoethyleneglycol. In this paper, we are reporting a new AA product formulated with anewly-developed proprietary chemistry. The product has been tested under fieldimplementation conditions in hydrate control performance (dose rate, salinity, water cuts and types of hydrocarbon), fluids emulsions and water quality, and corrosiontendency (on both SS304 and SS316). A new method using gas chromatography withflame ionization detector (GC/FID) and gas chromatography withNitrogen/Phosphorus Sensitive Detection (GC/PND) has been developed to quantifyAA partitioning and distribution in the fluids (hydrocarbon and water phases). The relationship between fluids quality and AA actives partitioning in bothaqueous and hydrocarbon phases has also been established to elucidate why the new AAprovides much improved fluids separation and water quality. It also confirmsthe observations made through bottle shaking testing. Under severe lab testing conditions where quaternary ammonium chemistries showcorrosion and pitting on both SS340L and SS316L, the new AA product offerssatisfying material compatibility, although it has the same solvent packageas existing commercial AAs. Comparison of toxicological properties with differentAA chemistries has also been conducted. Under the CEFAS testing protocol, the new AA chemistry presents improvedenvironmental properties over conventional AA chemistries. Introduction Over the last two decades, low dosage hydrate inhibitor (LDHI) has evolved asan alternative method for hydrate control in field applications to provide flowassurance in oil and gas production and transportation systems.1, 2, 3 A widerange of OPEX savings, possible extended field lifetime, and dramatic CAPEXsavings are the ultimate economic drivers for its field implementations.4, 5, 6Based on its hydrate mitigating mechanism, LDHI is divided into two maincategories, kinetic inhibitors (KHI) and anti-agglomerants (AA). The earlier versions of AA technology used in the field are quaternary ammoniumchemistries, with the counter ion normally being chloride.1 Years of fieldimplementation show operation challenges in both fluids separation and waterquality topsides, even though hydrate control performance meets most of therequirements when brine salinity and water cut do not run into therestrictions. Recently, it was also reported that this kind of quat chemistrywas also corrosive, pitting super duplex umbilicals (SDSS2507) and stainless steel storage tanks (SS316L) likelydue to the presence of chloride ions.7 Moreover, the current quat chemistry istoxic, which makes it extremely challenging to meet different HS&Eregulations worldwide. Similar chemistries have rendered a few alternatives over the lastfew years. However, not much improvement has been shown in fluids separationand EcoTox properties. Challenges of quaternary ammonium chemistry are:Poor water quality and treatment difficulty, especially when brine salinityis lowCorrosion due to the large amount of Cl- presentLow thermal stability due to Hoffmann elimination, resulting in limiteddownhole injectionToxicity, poor biodegradation and bioaccumulation.