Application of superparamagnetic nanoparticle-based heating for non-abrasive removal of wax deposits from subsea oil pipelines

Abstract

Flow assurance is a critical problem in the oil and gas industry, as an increasing number of wells are drilled in deep water and ultra-deep water environments. High pressures and temperatures as low as 5°C in these environments hinder flow of hydrocarbon-based fluids by formation of methane hydrate and wax deposits on the inner surface of pipelines. Commonly used methods for removal of deposits from pipelines are chemical injection and foam or gel pigs, which face several limitations. In our work, an application to use superparamagnetic nanoparticle-based heating for flow assurance, in the form of a magnetic nanopaint is presented. Superparamagnetic nanoparticle-based heating has been extensively researched in the biomedical industry for cancer treatment by hyperthermia. Superparamagnetic nanoparticles in dispersions generate heat by application of an oscillating magnetic field as explained by Neel’s relaxation theory. In our application, superparamagnetic Fe₃O₄ nanoparticles are embedded in a thin layer of cured epoxy termed ‘nanopaint’. This nanopaint coating on the internal surface of subsea pipelines could generate heat and thus remove formation of methane hydrates and wax. In our work, the role of key parameters affecting heating performance of superparamagnetic nanoparticles such as particle size, and magnetic field is quantified. Rigorous characterization of physical and magnetic properties of nanoparticles and nanopaint is performed. This is correlated to and used to optimize the heating performance. Heating performance of several samples of Fe₃O₄ nanoparticles varying in size distribution is evaluated in static experiments. Two samples having similar physical and magnetic properties are compared in terms of the correlation between their size distribution and their heating performance. Performance of nanopaint to heat static fluids, flowing fluids and wax deposit is evaluated. Heating performance of superparamagnetic nanoparticles in dispersions and in nanopaint is found to be similar and so it is concluded that Neel’s relaxation theory is applicable to nanopaint. Heating performance of nanopaint in flow experiment is found to be better than in static experiments by a factor greater than 5. A correlation of heating performance of nanopaint at magnetic fields of 100 to 1000 A/m is developed. Finally, implementation issues of nanopaint are addressed. The effect of low ambient temperatures on nanopaint heating performance is evaluated. The theoretical feasibility of generating a magnetic field inside a pipeline is studied. A COMSOL model is used to verify the feasibility of magnetic field propagation inside a steel pipeline and is subsequently used to evaluate nanopaint heating of wax deposits in pipeline. Material and power requirements are analyzed and optimized using the COMSOL model.