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

Abstract

Hydrate control has always been essential to oil and gas pipeline flow assurance work. To study the decomposition process of the hydrate deposition layer in the gas–water system, the decomposition experiments of the hydrate layer on the gas-phase pipe wall under different heating temperatures, different depressurization rates, and the combined action of heating and depressurization were carried out by using a high-pressure transparent rock-flow cell with a voltage detection system. The dynamic decomposition process was observed, and it was found that the decomposition rate was faster when decomposed by the depressurization method compared to the heating method. The decomposition process of the hydrate layer was quantitatively analyzed based on the voltage signal, and an electrical signal-based method for monitoring the decomposition of the hydrate layer on the pipe wall was proposed. The decomposition mechanism of the hydrate layer in 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 differential ablation with the shedding phenomenon. The impact force generated by the gas release is the main reason for hydrate layer shedding. Shedding of the mixture of ice and hydrate occurs at depressurization rates 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–water flow systems.