Quantitative determination of pore‐structure change and permeability estimation under hydrate phase transition by NMR

Abstract

AbstractQuantitatively characterizing the seepage features is critical important for multi‐fluid flow in gas hydrate accumulations; however, limited researches concern water permeability during hydrate phase transition. In this work, nuclear magnetic resonance (NMR) measurement is employed to observe the in situ formation and dissociation of tetrahydrofuran (THF) hydrate in porous media. Results indicate that the relative free water and bound water consumption during hydrate phase transition can affect the seepage features of sediments. In addition, we investigate the growth habits of THF hydrate in quartz glass sand and find the growth pattern of the hydrate transforms from suspension to cementation when its saturation exceeds approximately 35%. The Tokyo model shows that the hydrate are heterogeneous distribution of pore‐filling and likely to evolve in larger pores; The findings clearly show that NMR is an efficient and direct technique for investigating the seepage characteristics during hydrate phase transition as well as pore fluid distribution in sediments.