SPE-189112-MS A Model for the Prediction of Hydrate Growth Initiation Point by Determining Quasi Liquid Layer Temperature Akinsete O. Oluwatoyin, Elizabeth I. Obode, Ibadan Ibadan, and Sunday O. Isehunwa, University of Ibadan Copyright 2017, Society of Petroleum Engineers This paper was prepared for presentation at the Nigeria Annual International Conference and Exhibition held in Lagos, Nigeria, 31 July – 2 August 2017. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright. Abstract Hydrates constitute a major flow assurance challenge in the transportation of unprocessed gas through flowlines. Its undesirability stems from the fact that these solids reduce pipe diameter open to gas flow, challenge pipeline integrity, possibly leading to burst pipe – and increasing costs. Hydrates undergo four stages of maturation – entrainment, growth, agglomeration and plugging – and do not usually constitute a flow assurance challenge until agglomeration. These challenges are even more pronounced in the presence of gas-condensate in the flowline. This paper proposes a model to predict the point in the flowline where hydrates start to form in the presence of gas-condensate. This is done by predicting the temperature at which quasi liquid layer starts to form on the hydrate seed. Quasi liquid layer refers to a film of pure water that forms around the hydrate seeds at a particular temperature drop within the system. When two seeds with this layer come together, they become joined together via capillary bridging – and the resulting crystal is bigger than the component seeds – thus leading to growth. The developed analytical model relates mass of hydrate, length of the flowline, time taken for fluid flow in the system, the percentage of hydrate in the fluid composition, density of the hydrate, change in enthalpy and the velocity at which hydrate is flowing in the system to the temperature at which hydrates would start growing – that is the quasi liquid layer temperature. The developed model was validated with field data, and the model was in agreement with field observations. Key words: Hydrate growth, gas-condensate, maturation stages, analytical model, hydrate temperature Introduction Natural gas hydrates are non-stoichiometric, solid substances that consist of a low amount of gas molecules captured in a mesh cage system made up of water molecules (Sloan, 1997, 1998; Sloan and Koh, 2008). When the constituents of hydrates come into contact under high pressure and low temperature conditions a solid structure at different types of crystals with higher densities than typical fluid hydrocarbons is formed.