Variable-rate, variable-pressure production from a fractured gas well with large viscosity and compressibility variation: applicability of superposition time

Gül Ertunç, Kıymet Gizem
In this study, it was estimated that 71.8 standard tcm of methane can be available in the Black Sea gas hydrates. However, only 13.6 tcm of this amount was calculated as energy sources. With HydrateResSim simulator, gas production potentials from a hypothetical Class 1 hydrate in the Black Sea conditions by depressurization and depressurization with wellbore heating were simulated. Wellbore heating might be necessary to avoid hydrate reformation along the wellbore during production. For comparison with the data of Class 1 hydrate simulations, hypothetical Class 3 hydrate simulations by depressurization with and without wellbore heating were conducted by HydrateResSim. Experimental set-up for gas production from the Black gas hydrates by depressurization was designed according to the results of HydrateResSim. HEP.m code was written with Matlab to predict hydrate properties. This code was integrated with other codes written to calculate gas compositional change (HEPComp.m) during hydrate formation of gas mixtures, the amount of gas and water to obtain target saturations in experimental studies of hydrate in sediments inside high pressure reactors (SM.m and SMmix.m). BSR.m code was written to predict gas composition near the bottom simulating reflectance in marine sediments. These codes were tested and compared with literature experimental, numerical data, and other software, consistent results were obtained. The Black Sea sediments were investigated and it was observed that clay content is high and turbidites include fine silty sand and sandy silt. However, there might be thin coarse sand sections that might be good hydrate reservoirs for gas production.