Modeling flow assurance regimes is no easy task, not least for long distance tiebacks, where the need for accurate modeling is crucial. Alexander Belkin outlines a model he has worked on.
During the past several decades, offshore oil and gas production has moved from shallow to deep and ultra deepwater. Also, marginal fields located at substantial distances from host platforms have introduced the need for long subsea flowlines, which are often laid over hilly terrains.
The economics of these types of developments quite frequently do not allow the installation of sophisticated completions and the implementation of subsea processing, so unprocessed reservoir fluids, often imbedded with particulate matter, are transported via the long-distance flowlines. Inevitably, flow assurance problems such as hydrates, paraffin plugging and solids deposition arise. Solids deposition, in particular, is related to insufficient flow velocity.
These problems become more challenging in high-pressure, high-temperature (HPHT) environments where pressure, volume and temperature (PVT) changes are more pronounced and occur very quickly. Flow assurance issues can be very costly to repair, or if unrepaired, can lead to erosion and corrosion and can endanger asset integrity. Furthermore, deposition of solid matter reduces the line throughput, sometimes leading to complete blockages and making profitable production of hydrocarbons practically impossible.
Many researchers have attempted to understand the physics of unprocessed fluid flow, characterized as multiphase flow. Primarily, the scientific efforts were focused on understanding the phase interaction between and its impact on flow dynamics. The greatest difficulty is that the nature of the flow is transient due to constantly changing flow patterns, so it is hard to predict flow behavior.
As part of the development of a comprehensive subsea tieback management strategy, the Well Engineering Research Group at Robert Gordon University in Aberdeen, Scotland, has endeavored to create a model for sand transport in long-distance subsea tiebacks. The ideal model would have the potential to solve problems of pipe and equipment sizing, locate places of sand deposition and improve sand management strategies. The previous particle transport models did not reflect the critical factor of flow pattern transition and therefore can be unreliable under varying operational conditions.
Several experiments were conducted during a study to establish the minimum transport velocity (MTV) for rolling and suspension for different flow patterns. The result of that study (Bello et al (2011)), were empirically derived equations for the MTV and flow velocity profiles under different flow regimes. As a continuation of that study, the subsequent project was to create an analytical model in MS Excel (using the concept of MTV) to locate places of deposition in pipelines and to formulate a method to assess the severity of blockages.
Originally from Komi Republic, Russia, Alexander Belkin earned his first degree in Drilling Well Engineering in 2013 from Ukhta State Technical University. He recently graduated from RGU with an MSc in Oil and Gas Engineering.
Belkin presented this paper at the Energy Institute’s Msc Energy Paper competition, in which he was one of six finalists.