Flow assurance during deepwater gas well testing: Hydrate blockage prediction and prevention

Hydrates cause serious flow assurance problems during deepwater operations (e.g. well testing). In order to efficiently prevent wellbore/pipeline blockage, it is of great importance to have a good understanding of hydrate formation, deposition and blockage behavior in the flowline. In this work, a model is developed to describe the development of hydrate blockage in the wellbore. The results indicate a non-uniform hydrate layer is formed on the inner wall along the testing tubing during deepwater gas well testing. With the proposed model, the position where hydrate blockage is most likely to occur can be identified. The blockage severity in terms of dimensionless hydrate layer thickness can also be assessed. Based on the model, a method is developed to prevent hydrate blockage with lower inhibitor consumption. We recommend that testing operations should be run within the Hydrate Blockage Free Window (HBFW). The HBFW refers to the period from the beginning of testing operations to the moment when a significant pressure drop increase is encountered. Implementation procedure of the proposed method is developed and further illustrated through case studies. The inhibitor consumption is much lower compared with the current over-inhibition THI-based method. This work provides possible ways to overcome the shortcomings of the current over-inhibition THI-based method.