Browsing by Author "Zong, Jingjing 1990-"
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Item Elastic Properties of Rock Salt: Lab Measurements, Numerical and Physical Modeling, and Gulf of Mexico Well Logs and VSP(2019-05) Zong, Jingjing 1990-; Stewart, Robert R.; Zhou, Hua-Wei; Zheng, Yingcai; Gelinsky, StephanTo achieve high-resolution subsurface imaging and lithology description, the elastic properties of rock salt are investigated using ultrasonic lab measurements, well logs, and a salt proximity VSP survey. In the lab, I analyzed the effects of composition, crystalline structure, pressure, and temperature on the elastic behavior of a variety of rock salt samples, includ- ing pure halite (>95 wt.%) from the Gulf Coast, argillaceous rock salt from the Zipaquir ́a Mine, Colombia, and crystalline salt from the Goderich Mine, Canada. At room-dry conditions, with 0.5-1 MHz transducers, the Gulf Coast cores behave isotropically in general: Vp and Vs range from 4325-4747 m/s and 2655-2730 m/s, respectively. The attenuation quality factor Q for a selection of Gulf Coast salt samples were measured at 34-57 and 34-41 for Qp and Qs at room conditions using a spectral ratio method. The Zipaquira salt samples show velocity and density variations due to their heterogeneous composition. The Goderich crystals display distinct cubic anisotropy: up to 7% and 18% differences in Vp and Vs, respectively. Increasing pressure elevates both V and Q while increasing temperature decreases them. An empirical relationship between the intrinsic Qp and Vp under varying pressure and temperature was established. Further velocity and density values were studied from 147 log suites from boreholes drilled through rock salt in the northern Gulf of Mexico. Within the salt formations, P-wave velocities increase slightly with depth (around 5 m/s per km). In addition, a set of numerical and physical models were studied for the salt flank delineation using VSP acquisition geometries. A single-shot salt proximity VSP survey in Markham salt dome, Texas, was processed to extract salt properties and image the structures inside salt as well as the salt flank. Wave conversion between P- and S-waves in the presence of ultra-high impedance layer (e.g., anhydrite) around salt structures was analyzed and can be significant. These studies further inform us about the physics of rock salt as well as assist with salt structure model building and imaging.Item Elastic properties of salt: laboratory measurements, well-log analysis, and a seismic survey over the Hockley Salt Mine, Texas(2014-08) Zong, Jingjing 1990-; Stewart, Robert R.; Li, Aibing; Leaney, ScottSalt plays a significant part in the geology of the Gulf of Mexico area (GoM). Numerous basins in the world have undergone evaporation sequences that have deposited vast quantities of salt. Sometimes these deposits have remained largely undeformed, which can lead to anisotropic crystal growth, while other salt deposits have undergone significant movement and extrusion. In this thesis, I use lab measurements, well-log data, and surface seismic to determine the properties of salt crystal and rocks. In the lab, we have undertaken ultrasonic measurements on salt samples from various locations. The pure halite crystals from the Goderich salt mine, Canada, demonstrate shear-wave splitting and compressional-wave variations which indicate cubic anisotropy. The stiffness values calculated for that are C_11=48.7 GPa, C_44=13.1 GPa , and C_12=11.9 GPa. Our samples from the Hockley and the Bayou salt mine have fractures, and aligned domains, but no obvious anisotropy. The density ranges from 2.16 - 2.22 g/cc. The confining pressure experiments are conducted on the Louisiana salt cores. The velocities under 0 - 4000 psi are 4.4 - 4.8 km/s for P-waves and 2.5 - 2.8 km/s for S-waves. For a 1 km-thick numerical halite model, the travel-time difference caused by cubic anisotropy is up to 20 ms for P-waves based on the calculated stiffness values. We analyzed 142 well-log from boreholes drilled through salt in the GoM. We find an empirical relationship for P-wave velocity of salt V (km/s) versus depth D (km): V=4.41+0.0145D The RMSE of the fit is 0.10 km/s. This variability may be useful for modeling velocities in “dirty” or inhomogeneous salt deposits. For salt density vs. velocity, our log data are similar to Gardner’s, although we find a cluster, not a monotonic relationship. We acquired a 1.2 km seismic line over Hockley Salt Mine. From refraction crossover analysis of one shot gather, we find depth for the top of anhydrite with the stacking velocity of 5.5 km/s occurs around 50 m (164 ft). These studies of elastic properties of salt provide more information for salt velocity model building and a general understanding of salt properties.