Multiphase Transportation: Hydrate Plugging Prevention Through Crude Oil Natural Surfactants

Abstract

Abstract Multiphase transportation is more and more contemplated in the development of oil and gas fields both in conventional and frontier areas (from remote satellite fields to deep offshore). This new environment has set forward new challenges in the field of hydrate plugging prevention in subsea flowlines. Increases of transportation distances and water depths place the fluids well inside the hydrate formation domain, and hence threaten flow in multiphase export lines. In such conditions, conventional hydrate prevention (alcohols, insulation, heating) can become very expensive and can in some cases jeopardize the economy of the project. To challenge this anticipated situation, the oil and gas industry has been looking for low dosage inhibitors: kinetic inhibitors which can delay hydrate crystallization, anti-agglomerants which let the hydrate crystallize but ensure their transportability in a slurry. This second process creates a water-in-oil emulsion which remains a transportable suspension after crossing the hydrate equilibrium curve. We have investigated whether this process could occur by itself with some surfactants naturally present within some crudes. Some research works have confirmed that some "natural surfactants" such as resins and asphaltenes have properties similar to synthetic surfactants. Since 95, extensive experimental work has been done at the University of Bergen (1, 2) and Elf research center (3) on a 1" loop with different crudes and fluid blends. The hydrodynamic tests have demonstrated the capability of natural surfactants to prevent hydrate plugging. Based on these results, an experimental methodology to evaluate hydrate transportability of a given crude has been developed. This method could reduce the need of inhibitors during the first years of production and thus result in large savings. With the present development of subsea-water separation technology, this process could further become a standalone alternative. P. 509