(74g) Hydrate Plug Location during Depressurization Remediation Technique

During the remediation of hydrate blockage in a pipeline, certain key parameters such as the location of the first plug, the velocity of the plug upon release, the gas volume fraction upstream and downstream of the pig, etc. are important to know for safe handling of the process. Typical remediation of a blocked pipeline would include alternating cycles of depressurization and inhibitor injection to safely handle plug movement.

Utilizing operating information during the remediation process, MSi Kenny has developed a toolkit that estimates the hydrate plug location based on alternating between inhibitor injection and depressurization method of remediation.  The purpose of this model is to determine the plug location and calculated downstream gas volume fraction.

The model uses the pressure rise in the pipeline during the inhibitor injection cycle (with known methanol injected volume), the subsequent pressure drop and liquid offtake volume during the depressurization step.  Using these inputs the model iteratively calculates the first mathematically stable plug location and downstream gas volume fraction.  These calculations are currently based on basic equations of state.  Initial comparison of the model to multiphase flow simulations show the results to be in close agreement.

This model offers a tool to predict potential hydrate plug locations for this particular remediation technique.  With an estimate of the hydrate plug location, operators can have a better idea of hydrate plug movement risks, more specific hydrate remediation locations, or simply a secondary method to verify plug locations.