Study of Faults and Fractures in Mississippian Carbonate Reservoirs by Multi-scale Data Integration: A Geological Modeling Case in the Dickman Field of Ness County, Kansas State

Fault and fracture analysis is an important step to guide the 3D reservoir property gridding for the Dickman Filed as a potential CO₂ sequestration site. Due to the lack of standard logs and borehole images for such analysis, discontinuity patterns visualized by multiple seismic attributes were displayed in their original geological occurrence and tied to stratigraphic units at the reservoir scale to evaluate their geological integrity. The evaluation was based on the understanding of regional deformation history; the distribution patterns of fault/fracture zones predicted by a carbonate deformation model; the structural-controlled maturity of karst topography; and the fault and fracture indicators from sparse well logs, core descriptions and measurements.

The motion of major faults visualized by the SPICE attribute volume reflects the influence of the latest structural episode. Well tops, thickness and lithology data were used together with seismic images to determine the relative motion of blocks across faults during earlier structure episodes. Indirect indicators of differential up-lifting across faults, such as the relative roughness of karst-topography extracted from attributes, were also used to restore the multi-episode deformation associated with faults. Possible fractured zones extracted from six geometry attributes revealed different vertical and lateral patterns of discontinuity. These patterns were classified into two geometric categories: the unconfined features penetrating multiple litho-zones; and confined features mostly within an individual litho-zone. The former, best viewed by plane-extraction from ANT volumes, are mostly structural and associated with major faults. The latter are mostly none-structural and best viewed as varying density patterns while marching depth slices of Chaos and Variance volumes. These patterns can be more indicative of post-depositional changes, and some could be related to the “intra-strata” features observed in the Middle Mississippian cores in nearby Schaben Field.

Multi-scale data integration improved the confidence of fault and fracture interpretation based on seismic attributes. Such interpretations helped in the reconstruction of multi-episode deformation history of the area. Several major NW-trending faults and associated fractured zones are likely fluid conduits, and a NE-trending fault served as the sealing fault for the hydrocarbon-producing structure.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California