Geochemical Trends in Gas Quality in Kansas

Newell, K. David¹ (1) Kansas Geological Survey, University of Kansas, Lawrence, KS

Analysis of Kansas gas-chemistry data defines several regions that may have reserves of low-BTU gas (i.e., heating value <950 BTU/scf). About one-third of the 4600 compiled chemical analyses are less than 950 BTU/scf. With higher gas prices and new upgrading technologies, utilization of this low-BTU gas may be increasingly possible.

Low-BTU gas in this part of the Mid-Continent is primarily caused by high percentages of nitrogen and subsidiary helium. Argon and carbon dioxide can also be present, but they commonly compose less than 0.5% of the total gas.

Stratigraphic and spatial trends are evident. Percentages of noncombustible component gases and nitrogen-to-helium ratios increase with decreasing age of the producing formation. With several pay zones, low-BTU gas is more common on the Central Kansas uplift than in deeper geological provinces farther south. A rim of low-BTU gas is also present around the giant Hugoton Gas Field in southwestern Kansas.

Some possible low-BTU-gas plays include: Permian Chase Group west of the Central Kansas uplift and on the eastern side of the Hugoton Gas Field; Pennsylvanian Topeka Limestone and Permian Red Cave Sandstone in the vicinity of the Greenwood Gas Field; Cambrian-Ordovician Arbuckle, Pennsylvanian Lansing-Kansas City, Shawnee and Douglas Groups on the perimeter of the Central Kansas uplift and in sporadic localities in the southern Cherokee and Sedgwick basins; and Mississippian chat on the western flank of the Pratt anticline.