Energy Policy Act of 2005 (Ultra-deepwater and Unconventional Resources Program)
Wax Control in the Presence of Hydrates
University of Utah
SINTEF Petroleum Research
University of Tulsa
Wax precipitation in flow lines is a serious problem. Unique challenges are associated with transporting fluids through long subsea pipelines. One way of preventing wax precipitation in long subsea lines is to insulate them – an expensive solution. One idea that has been tested recently, but not been implemented commercially, is cold flow. The idea is to use a non-heated, uninsulated pipeline to transport oil-water mixtures in cold, subsea environments where both Projects and waxes are likely to form. The concept in cold flow is to create slurry of Project and/or wax particles and transport the oil-water mixture in the presence of this slurry. The seed particles in the slurry act as nucleation sites and prevent or minimize further wax deposition.
A number of other wax control technologies have been proposed, some of which are being commercially used. These include mechanical methods such as pigging, chemical injection technologies and thermal management strategies, which focus on preventing the problem. In previous studies, no single strategy has proven to be completely effective in preventing and/or remediating the problem. There is a necessity to carefully evaluate all available technologies, and select one or two for further evaluation.
This project uses a two-phase approach to identify the most promising technologies and forwarding them for further testing toward commercial maturity. First a comprehensive literature survey will be undertaken on this subject, and all the possible options for wax control in cold-flow subsea pipelines will be considered. This review and analysis will yield two technologies for further evaluation. These technologies will be selected based on our analysis coupled with interaction and feedback from the industrial board and from RPSEA. Testing of deep-sea flow assurance technologies will require good understanding of oil and chemical characterization, properties measurement, fluid rheology (including slurry hydrodynamics) and interfacial and surface properties. The University of Utah is uniquely positioned to undertake this project because of existing facilities and knowledge and experience in all the aspects described above. Comprehensive projects on wax precipitation in the trans-Alaskan pipeline, high-pressure carbon dioxide induced asphaltene precipitation studies, fluid compatibilities with respect of asphaltenes and waxes and chemometric methods development have all been performed at the University in the last ten years. Laboratories at the University are equipped with oil and gas characterization analytical equipment (gas chromatographs, mass spectrometers, liquid chromatographs, elemental analyzers, etc.), rheometers (including constant stress and equipment necessary for slurry characterization), instrumented flow loops and laser and particle imaging velocimetry (PIV) visualization tools. The team at the University will assemble a high pressure flow loop capable of PIV and a high-pressure rheometer for Phase 2 of the project.
Principal Investigator: Prof. Milind D. Deo - University of Utah