South-central United States well-bore breakout-data catalog

National Earthquake Hazards Reduction Program, summaries of technical reports volume XXX

“…The distributions of localities of post-late Pleistocene faulting suggest that they, too, might have formed as a surficial response to seismogenic displacement at depth, possibly on the Anacapa fault, rather than being produced as intrinsic parts of seismogenic displacement on the Malibu Coast fault. Yerkes and Campbell, 1980) (Dart, 1987;Dart and Zoback, 1989), little information is currently available regarding the state of stress in parts of southern Oklahoma. Knowledge of the magnitude and orientation of the stress field may provide insight into the contemporary tectonics and seismic potential of individual faults in the Wichita Frontal fault system.…”

In situ stress analysis of wellbore break-outs from Oklahoma and the Texas Panhandle

“…Statistically, wellbore enlargement data sets are treated as axially symmetric, circular-normal distributions of two-dimensional vectors (Batschelet, 1965;Dart, 1987). The results of standard statistical calculations for mean direction, mean deviation, and standard deviation are displayed as rose diagrams of data sets (figs.…”

“…This model predicts that induced components of horizontal stress can vary in magnitude between rock units, either less or more than the vertical stress. Formation of randomly oriented wellbore enlargements associated with lower confining pressures at shallow depths (Dart, 1987;Springer, 1987) can generally be ruled out as a contributor to data scatter because near-surface (< 1,000 ft subsea) wellbore enlargements are commonly washed out and enlarged in both orthogonal directions. These data were not considered reliable and were not used.…”

“…In a seismically active area where S1 is horizontal, such as the New Madrid area of the Mississippi Embay- (Zoback and Zoback, 1980), stress-induced wellbore enlargements from two wells (Dart, 1987) appear to be of greater vertical length (table 9) and have a distinct, characteristic shape (as seen on the dipmeter log). In contrast, in a relatively aseismic area such as the Palo Duro basin (Stone and Webster Corporation, 1983), where Sj is vertical and where in the near surface S2 may not be significantly greater than S3 (table 7) (Borjeson and Lamb, 1987), wellbore enlargements in nearby wells (Bravo dome area), on average, appear to have shorter vertical lengths (table 9) and less well defined trace character on the dipmeter log (log quality on table 4).…”

“…This paper offers a more detailed analysis of data presented in earlier reports (Dart, 1987;Dart and Zoback, 1987).…”