Characterizing Seal Bypass Systems Using Seismic Attribute Analysis at the Rock Springs Uplift, Southwest Wyoming
If carbon storage is to be implemented at a potential storage site at the Rock Springs Uplift (southwest Wyoming), there are significant challenges to overcome regarding sealing assessment. Specifically, identifying the potential for leakage of CO2 along natural bypass systems such as faults and fractures. This study evaluates the integrity of strata at a University of Wyoming test well (RSU #1 049–047–07154) using a 25 square mile 3-D survey adjacent to the well. Specifically, we focus on determining potential seal bypass systems using multiple seismic attributes. Two groups of seal bypass systems were recognized within the seismic survey bounds; (1) dispersed sets of orthogonal deformation bands and faults, and (2) isolated fractures and chimneys likely associated with karst collapse features. Deformation bands are associated with folding of the Paleozoic strata and are arranged in patterns related to regional structural deformation. Fracture analysis reveal that lineaments within the study area strike northeast-southwest and northwest-southeast. This observation is consistent with joint orientation in surface outcrops. Isolated, vertically oriented fractures that originate in the Mississippian Madison Limestone were interpreted on coherency horizon slices and within the Rock Integrity attribute volume. These features may result from karst processes such as dissolution, hydrothermal alteration, tectonism, or a combination of these processes. Continuous spectral analysis of wireline logs from the RSU #1 well were used to describe porosity heterogeneity at an intermediate scale of several feet to tens of feet. We found that spectrograms generate useful information that can be utilized for identification of intervals with variable reservoir/sealing capacity within a formation. The amplitude and distribution of spectral peaks appears to correspond with the relative effectiveness of confining layers. Based on the above data, multiple sealing lithologies were identified at the study site though some were associated with seal bypass systems. Additional unknowns include compartmentalization of the reservoirs along fault boundaries and the risk factors for induced seismicity along existing faults and fractures. Hence, it is of great importance to choose reliable rock properties for simulation modeling and, if possible, increase the amount of available subsurface data.
AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015