Experimental Study of Hydrate Decomposition on the Gas-Phase Wall Using a Rock-Flow Cell

Hydrate control has always been essential to oil andgas pipelineflow assurance work. To study the decomposition process of the hydratedeposition layer in the gas-water system, the decompositionexperiments of the hydrate layer on the gas-phase pipe wall underdifferent heating temperatures, different depressurization rates,and the combined action of heating and depressurization were carriedout by using a high-pressure transparent rock-flow cell with a voltagedetection system. The dynamic decomposition process was observed,and it was found that the decomposition rate was faster when decomposedby the depressurization method compared to the heating method. Thedecomposition process of the hydrate layer was quantitatively analyzedbased on the voltage signal, and an electrical signal-based methodfor monitoring the decomposition of the hydrate layer on the pipewall was proposed. The decomposition mechanism of the hydrate layerin different ways is summarized. During decomposition by heating,the hydrate layer decomposes in the mode of shrinkage ablation. During depressurization decomposition, it decomposes in the mode of differentialablation with the shedding phenomenon. The impact force generatedby the gas release is the main reason for hydrate layer shedding.Shedding of the mixture of ice and hydrate occurs at depressurizationrates ranging from 0.026 to 0.056 MPa/s, with the risk of ice blockage.This work provides further insight into hydrate decomposition in gas-waterflow systems.