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U.S. Geological Survey
Open-File Report 2005-1451

Methane Gas Volume Expansion Ratios and Ideal Gas Deviation Factors for the Deep-Water Bering Sea Basins



Tables and Graphs

For General P-T Conditions In The Deep-Water Bering Sea Basins:

These 4 graphs and 1 data table provide calculated reference points for pressures between 30 and 52 MPa, temperatures between 4° and 80°C. Differences at a constant temperature can be viewed as the effect of water depth differences on gas compression at a constant depth below sea floor. Differences at a constant pressure can be viewed as the effect of differing geothermal gradients on gas compression at a constant depth below sea surface, or at a constant depth below sea floor if water depth is also constant.

Link to Figure 1 Figure 1. Volume Ratio as a Function of Pressure

(84 Kb)
Link to Figure 2 Figure 2. Z-Factor as a Function of Pressure

(68 Kb)
Link to Figure 3 Figure 3. Volume Ratio as a Function of Temperature

(96 Kb)
Link to Figure 4 Figure 4. Z-Factor as a Function of Temperature

(76 Kb)
Link to Table 2 Table 1. Calculated Values: Volume Expansion Ratio and Z-Factor

(80 Kb)

For the Specific P-T Conditions in the Central Aleutian Basin:

This suite of graphs and associated table provide calculated points of specific relevance to the pressure-temperature conditions expected in the central Aleutian Basin, as a function of depth below sea floor. Sea floor depth is taken to be 3600 m for this example. Geothermal temperature gradient of 60°C/km is based on Hein et al. (1978) and Langseth et al. (1980). Hydrostatic pressure is approximated to be linear with depth. The base of natural gas hydrate stability under these conditions is ~360 m below seafloor , at ~25.6 °C and 39.6 MPa.

Link to Figure 5 Figure 5. Aleutian Basin P-T Path: Pressure, Temperature, Volume Ratio and Z-Factor as a function of Depth Below Sea Floor

(100 Kb)
Link to Table 2 Table 2.Calculated Values: Aleutian Basin P-T Path

(68 Kb)

For General Reference (0-80°C, 1-60 MPa):

These volume expansion ratio contours are presented for general reference for 100% methane gas. Values express the ratio of free gas volume at STP to free gas volume at the specified pressures and temperatures. For comparison, note that the expected gas yield for dissociation of natural gas hydrate is ~164 volumes of free gas at STP for every volume of solid hydrate (Collett, 2000).

Link to Figure 6 Figure 6. Volume Ratio Contours 0°-80°C, 1-60 MPa

(144 Kb)


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URL: http://pubs.usgs.gov/of/2005/1451/tables_and_graphs.html
For more information, contact: Ginger Barth
maintained by Michael Diggles
last modified January 6, 2006 (mfd)