Browsing by Subject "Gas hydrates"
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Item Analysis of the Development of Messoyakha Gas Field: A Commercial Gas Hydrate Reservoir(2012-12-11) Omelchenko, Roman 1987-Natural gas is an important energy source that contributes up to 25% of the total US energy reserves (DOE 2011). An increase in natural gas demand spurs further development of unconventional resources, including methane hydrate (Rajnauth 2012). Natural gas from methane hydrate has the potential to play a major role in ensuring adequate future energy supplies in the US. The worldwide volume of gas in the hydrate state has been estimated to be approximately 1.5 x 10^16 m^3 (Makogon 1984). More than 230 gas-hydrate deposits have been discovered globally. Several production technologies have been tested; however, the development of the Messoyakha field in the west Siberian basin is the only successful commercial gas-hydrate field to date. Although the presence of gas hydrates in the Messoyakha field was not a certainty, this current study determined the undeniable presence of gas hydrates in the reservoir. This study uses four models of the Messoyakha field structure and reservoir conditions and examines them based on the available geologic and engineering data. CMG STARS and IMEX software packages were used to calculate gas production from a hydrate-bearing formation on a field scale. Results of this analysis confirm the presence of gas hydrates in the Messoyakha field and also determine the volume of hydrates in place. The cumulative production from the field on January 1, 2012 is 12.9 x 10^9 m^3, and it was determined in this study that 5.4 x 10^9 m^3 was obtained from hydrates. The important issue of pressure-support mechanisms in developing a gas hydrate reservoir was also addressed in this study. Pressure-support mechanisms were investigated using different evaluation methods such as the use of gas-injection well patterns and gas/water injection using isothermal and non-isothermal simulators. Several aquifer models were examined. Simulation results showed that pressure support due to aquifer activity was not possible. Furthermore, it was shown that the water obtained from hydrates was not produced and remained in the reservoir. Results obtained from the aquifer models were confirmed by the actual water production from the field. It was shown that water from hydrates is a very strong pressure-support mechanism. Water not only remained in the reservoir, but it formed a thick water-saturated layer between the free-gas and gas-hydrate zone. Finally, thermodynamic behavior of gas hydrate decomposition was studied. Possible areas of hydrate preservation were determined. It was shown that the central top portion of the field preserved most of hydrates due to temperature reduction of hydrate decomposition.Item Pore size distribution and methane equilibrium conditions at Walker Ridge Block 313, northern Gulf of Mexico(2016-05) Bihani, Abhishek Dilip; Daigle, Hugh; Okuno, RyosukeIn-situ pressure, temperature, salinity and pore size may allow coexistence of three methane phases: liquid (L), gas (G), hydrate (H) in marine gas hydrate systems. A discrete zone of three-phase equilibrium may occur near the base of the gas hydrate stability zone (GHSZ) in sediments with salinity close to seawater due to capillary effects. The existence of a three-phase zone affects the location of the bottom-simulating reflection (BSR) and also has repercussions for methane fluxes at the base of the GHSZ. This project studied the hydrate stability conditions in two wells, WR313-G and WR313-H, at Walker Ridge Block 313 in the northern Gulf of Mexico. The pore size distributions were determined by constructing a synthetic nuclear magnetic resonance (NMR) relaxation time distribution. Correlations were obtained by non-linear regression on NMR, gamma ray, and bulk density logs from well KC-151 at Keathley Canyon. The correlations enabled construction of relaxation time distributions for WR313-G and WR313-H, which were used to predict pore size distribution through comparison with mercury injection capillary pressure measurements. With the computed pore size distribution, L+H and L+G methane solubility was determined from in-situ pressure and temperature. The intersection of the L+G and L+H curves for various pore sizes allowed calculation of the depth range of the three-phase equilibrium zone. In previous studies at Blake Ridge and Hydrate Ridge, the top of the three-phase zone moves upwards with increasing water depth and overlies the bulk three-phase equilibrium depth but this was not observed at Walker Ridge. In clays at Walker Ridge, the predicted thickness of the three-phase zone is approximately 5 m, but in coarse sands it is only a few centimeters due to the difference in absolute pore sizes and the width of the pore size distribution. The thick three-phase zone in the clays may explain in part why the BSR is only observed in the sand layers at Walker Ridge, although other factors may influence the presence or absence of a BSR.