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It has recently been shown that rather small perturbations in effective stress due to fluid injection or withdrawal may trigger microseismic events. Such events, typically in the magnitude range below magnitude 4 M-L, have similar characteristics to normal tectonic earthquakes, with double-couple focal mechanisms implying a dominant shear motion at the source. In this paper we examine the nature of this mechanical fluid-rock interaction for the case of fluid injection in a hydrocarbon reservoir. Our model is based on the combination of a model of seismicity in dry rocks and a model of pore fluid pressure diffusion. The former involves a finite difference approximation of the equation of motion, and the latter follows;a...
The concept of spatial stochastic processes and the techniques of geostatistics and stochastic inversion are presented as a means for evaluating the spatial variability of thermal properties and temperature in sedimentary basins. Data from the Uinta Basin of NE Utah are used to demonstrate the analysis. Bottom hole temperatures from oil and gas wells provide the best opportunity for a spatial analysis because of the large number and wide distribution of data. Errors in bottom hole temperatures are not too large to preclude their use and stochastic inversion provides an optimum method for removing random noise while retaining spatial resolution. Corrected bottom hole temperatures from 235 wells in the Uinta Basin...
Palaeomagnetic results have been obtained from thirty sites in intrusive and extrusive rocks of Oligocene age from the San Juan Mountains, south-western Colorado. All specimens from each site were subjected to af demagnetization, and the reliability of each site determined. Twenty-three sites gave reliable results. Because five sites from the thick intracaldera part of the La Jara Canyon Member of the Treasure Mountain Tuff appear to have become magnetized during the same small interval of geological time, their results were combined and their mean pole and direction used in the final calculations. The eighteen remaining reliable sites yielded an average Oligocene palaeomagnetic pole at 85�6� N and 298�0� E (?p=...