Use of Magnetic Surveys for Delineation of Paleostructural Morrow Sand Reservoirs in Southwestern Kansas

L. Steven Travis, William E. Full, Chris D. Dilts

Oil and gas-producing Morrow sandstones (Pennsylvanian) are found throughout southeastern Colorado, western Kansas, and western Oklahoma. Valley fill, deltaic, and marine sand bodies of the Morrow Formation make up some of the most productive reservoirs in the southwestern Kansas region. Initial recovery rates are generally in the 300 b/d and 6 MMCFGD ranges. The location and geometry of these sand bodies are controlled largely by the paleostructure of the top of the Mississippian unconformity.

High-resolution ground and air magnetic data were obtained for southwest Kansas. These data were processed using an expert system which incorporated principles of artificial intelligence. The results of this processing were equipotential surfaces reflecting maximum resolution contained in the magnetic data. Using these equipotential maps in conjunction with paleostructure maps of the dominant rock units, the writers observed an excellent visual correlation between the magnetic data and the paleostructure of the Mississippian erosional surface. The implication of this observation is either that the erosion surface of the Mississippian was controlled by movements in the basement rocks or that the basement faults were active when the overlying Morrow Sandstone was deposited.

Evidence supporting the strong correlation between magnetics and paleostructure included the definition of subsurface faults which were suggested by detailed subsurface studies. Additionally, isopach maps of the Morrow sandstones were highly correlatable with the inferred Mississippian paleostructure. The local Morrow depositional environments and rough percentage of clay, hence permeability, were also predicted. Evidence for this interpretation will be presented.

In conclusion, the combination of magnetics, artificial intelligence, and traditional structural data can be used to economically explore large areas which might or might not contain good well control.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.