MAPPING SUBSURFACE LINEAMENTS AND PRESENT-DAY STRESSES IN SOUTHERN KANSAS: A NEW APPROACH FOR IDENTIFYING AREAS AT RISK FOR INJECTION-INDUCED SEISMICITY

Kansas, like other parts of the midcontinent, has experienced unprecedented seismicity linked with large-scale injection of wastewater. A major challenge for stakeholders in Kansas is that subsurface faults and stresses are not well known, making it difficult to properly site new disposal wells or make decisions regarding operations of existing wells. This study focuses on using publicly available well data to map subsurface faults/lineaments and present-day stresses in southern Kansas, with the ultimate goal of identifying specific structures and regions that may be at higher risk for injection-induced seismicity. A database of >500,000 stratigraphic well tops from the Kansas Geological Survey was used to create new structure contour maps of 18 stratigraphic boundaries between the Precambrian basement and present-day surface. Most of the boundaries have more than 10,000 well picks associated with them; however, the spatial density of the picks is variable. Outliers in the tops data were visually identified and removed, including from high data density areas where outliers were subtler. Structure contour maps were created using kriging, convergent interpolation, moving average, and minimum curvature data interpolation methods. These maps were then compared against each other and data confidence maps to select the most reasonable data interpolation technique. A range of 3D surface analysis techniques are being employed to tease out discontinuities and lineaments within each unit, including slope, aspect, curvature, edge detection, and residual analysis. The mapped lineaments will be compared to known faults and lineaments from analysis of 3D seismic data, potential field data, satellite data, LiDAR data, and air photos. A concurrent effort is underway to map subsurface stresses using available image, caliper, and dipmeter logs from a large inventory of well data across the state. The findings can be used to assess reactivation potential of mapped faults, and can be evaluated in conjunction with brine disposal data, to identify areas at risk for injection-induced earthquakes.