Quantitative analysis of CO₂ hydrate formation in porous media by proton NMR

Abstract

Gas hydrate is a nonstoichiometric crystal compound formed from water and gas. Most nonvisual studies on gas hydrate are unable to detect how much water is converted to hydrates, and thus, the hydrate stoichiometry calculations are inaccurate. This study investigated the CO 2 hydrate formation process in porous media directly and quantitatively. The characteristics of the time-variable consumption of hydrate formation indicated a two-stage formation, hydrate enclathration and continuous occupancy. The enclathration stage occurred in the first 20 min of the formation when considerable heat is released. The continuous occupancy stage lasted longer than the hydrate enclathration because the empty cages in previously formed hydrates would also be occupied. The higher formation pressures can accelerate water consumption and increase cage occupancy. The compositions of completely formed CO 2 hydrates at 2.7, 3.0, and 3.3 MPa and 275.15 K were determined as CO 2 Á6.90H 2 O, CO 2 Á6.70H 2 O, and CO 2 Á6.49H 2 O, respectively.

Advances in Characterizing Gas Hydrate Formation in Sediments with NMR Transverse Relaxation Time

“…Given the advances in modern technology, many non-destructive detection techniques (e.g., X-ray computed tomography (CT), magnetic resonance imaging (MRI), Cryogenic scanning electron microscopy (Cryo-SEM), 13 C solid-state NMR, and NMR T 2 ) are used to acquire in situ quantitative and real-time characterization of gas hydrate formation process [47,50,51,[68][69][70][107][108][109][110][111][112][113][114][115][116]. This study compares their application characteristics in the fields of resolution, phase recognition, scanning time, advantages, and drawbacks.…”

“…NMR T 2 test provides a fast, easy, and non-destructive way of detecting hydrogenbearing fluids, which is widely used to monitor the dynamic behavior of gas hydrate formation and pore structure in sediments [30,[45][46][47][48][49][50][51][52][53]56,66,[68][69][70]. Figure 4 shows the schematic diagram of the NMR T 2 method applied to quantitative characterization of gas hydrate formation in sediments.…”

“…Although there have been a lot of excellent studies on the gas hydrate formation in sediments using NMR T 2 method, a few of them combined NMR T 2 with other methods to characterize the formation process of gas hydrate and the pore structure in sediments in a more effective way [30,45,[50][51][52][53]56,[66][67][68][69][70]74,[147][148][149]. The combined use of these techniques can provide more information about the gas hydrate formation in sediments than any single technique.…”

“…The NMR T 2 method is used to determine the petrophysical characteristics of conventional and unconventional porous media in oil and gas fields, such as porosity, pore geometry, pore connectivity, permeability, and even the fluid saturation in reservoirs [37][38][39][40][41][42][43][44]. Therefore, the NMR T 2 method is also widely used for monitoring the pore structure and the formation process of gas hydrate in sediments [45][46][47][48][49][50][51][52][53]. NMR T 2 is an effective method for microscopic detection of hydrate-bearing sediments with considerable advantages (e.g., fast response, high resolution, and no damage) in the quantitative analysis of gas hydrate in sediments by low-field NMR (LF-NMR) [54][55][56].…”

Research Advances, Maturation, and Challenges of Hydrate-Based CO2 Sequestration in Porous Media

“…The range of grain size used for studying hydrate formation in porous media is 0.0007–1000 μm. At the same time, porosity ranges from 0.24 to 0.559 are studied at different water saturation. ,,− ,,,,,− The main hydrate formers studied are pure CO 2 , ,,− ,,,,,− binary mixtures of CO 2 + CH 4 ,− and CO 2 + N 2 , and other guest molecules like C 3 H 8 , C 2 H 6 , THF, TBAB, and cyclopentane . Depending on the guest molecule mixtures, the experimental pressures and temperatures range from 1.13 to 10.50 MPa and 269.65 to 289.95 K, respectively.…”