Deepwater gas field development and/or gas field's production in remote locations require long tiebacks with low temperature and high pressure flow paths and complex seabed topographies.
Hydrate formation and plugging is one of the most probable Flow Assurance risks under those conditions, and there is an urgent need for a better knowledge of these gas dominant systems behaviour regarding hydrate plug formation as well as effects of additives (Thermodynamic, KHI- and AA). Indeed, during the design phase of new field development, oil companies have to choose a hydrate mitigation strategy. To do that, important questions rapidly arise:
What about the gas layer protection?
How can non-volatile additives act/protect the non-wetted top of the line from condensed water hydrate formation in stratified flow?
Is there a need to take/run some specific procedures (such as slug of additives) to avoid hydrate problems?
The AHToL JIP phase 1 project's objective was to acquire knowledge and data in multiphase Lyre pilot loop in such gas dominant conditions.
The paper presents Lyre loop pilot tests performed with gas dominant systems without additive. The hydrate formation was performed in multiphase flow. The pilot and tests results flow are shown. The influence of the flow pattern on the hydrate formation and plugging were investigated. Tests were performed in stratified flow and in annular flow.
The water to hydrate conversion rates are calculated. Photos of hydrate deposits inside the flow loop are shown. The plugging mechanisms identified show a direct correlation with the flow pattern inside the line.
