Investigation of natural gas hydrate potential of the South Caspian Sea

Mustafayeva, Zhala
Considering the improved technology, increase in demand on energy and limited conventional hydrocarbon resources make researchers look for new clean energy alternatives. Existence of large amount of gas hydrates in continental margins and permafrost regions shows that methane in gas hydrates may be the next clean energy supply of the world. The energy potential of gas hydrates has been encouraged researhers from all around the world to understand conditions for occurrence of gas hydrate and estimate the amount of methane in them. The Caspian Sea, especially the South Caspian Sea, is a convenient environment for generation of gas hydrates. Low geothermal gradient, rapid sedimentation, a great number of mud volcanoes, suitable temperature and pressure conditions and actively generation of hydrocarbons are some unique characteristics of the region which make it worth for exploration. The targeted area lies within the coordinates 39N, 50E - 40N, 50E and 39N, 52E - 40N, 52E, which includes Apsheron area and several mud volcanoes but excluding the parts shallower than 100 m water depth. The total area is subdivided into three sections based on the following characteristics: i) Existence of bottom simulating reflections (BSRs) is observed in Apsheron area from Chevron’s exploration in 1998. This area is studied as gas hydrate concentrated zone at 200-600 m water depths. ii) Since suitable conditions for gas hydrate occurrence spread to a very large area in the Caspian Sea, another area is specified and named as gas hydrate bearing zones between 100-1000 m water depths. iii) 17 mud volcanoes are studied on their gas hydrate potential although more than 60 mud volcanoes show suitable conditions for hydrate formation in the South Caspian Sea. Salinity, gas compositions, and geothermal gradients obtained from literature are utilized in the estimation of gas hydrate potential of all three sections through Monte Carlo simulation. Area, thickness, hydrate saturation, porosity, cage occupancy and volume ratio parameters are needed for volumetric calculations. Area of the gas hydrate concentrated zone is 7.30108 km2 and area of gas hydrate bearing zone is 1.681010 km2. Radii of craters of mud volcanoes are assumed as large as twice of their original radii and theır total area is calculated as 5.94107 km2. Thickness of gas hydrate stability zone (GHSZ) for each zone is determined by temperature-depth diagrams. Hydrate saturation, porosity, cage occupancy and volume ratio are determined from analog studies and literature. The mean of accessible resource volume is estimated as 1.501012, 1.481013, 1.651010 Sm3 of gas for concentrated zone, bearing zone and in and around of craters of mud volcanoes, respectively. The mean of total accessible resource volume of targeted areas is estimated as 1.641013 Sm3. The results show that the area has great potential of gas hydrates and clean energy supply for future.
Citation Formats
Z. Mustafayeva, “Investigation of natural gas hydrate potential of the South Caspian Sea,” M.S. - Master of Science, Middle East Technical University, 2018.