Historic Seismicity in and Around the Texas Panhandle

At least twenty earthquakes have occurred in the Texas Panhandle north of 34°N since 1907. The largest earthquakes had magnitudes up to 4.8, and the intensities throughout the Panhandle have ranged from IV to VI (Modified Mercalli), corresponding to accelerations from 6.8 cm/s² to over 31.6 cm/s². The record of seismicity in the Texas Panhandle dates back to 1907 when the first reported event occurred near Amarillo. Since then, numerous events have been reported or instrumentally recorded from the Panhandle. In the most complete survey of seismicity in the Panhandle (north of 34° latitude) to be undertaken, 20 earthquakes were identified from 1907 through July 1982. Slightly more than half of the events have locations determined from felt reports, and the others from instrumental locations. During the process of identifying earthquakes, contemporary newspaper accounts, weather bulletins, seismological reports, and other sources were reviewed. Several reported events were found to be in error. Specifically, the published locations of some events are erroneous by tens or hundreds of kilometers, one event was, in fact, a sonic boom, and one "event" near the Panhandle resulted from spurious data reported from seismological observatories nearby. The largest earthquakes in the Texas Panhandle had magnitudes of 4.7 to 4.8 (determined by maximum intensity and felt areas); there were five such events between 1917 and 1951. Since instrumental recording became widespread in about 1962, only two events of magnitude greater than 4.0 have occurred. Although some of the earthquakes reported have been assigned magnitudes of 3.0 or less, the detection threshold is probably considerably higher. As evidence, it is noted that a magnitude 3.4 event in 1983 would have been undetected by conventional procedures, had there not been a specific interest in modern seismicity. Since this interest did not exist until recently, it is probable that many earthquakes of magnitude up to 3.5 have gone unrecognized, and it is likely that some larger events have been missed as well.Bureau of Economic Geolog

Calibration of Seismic Attributes for Reservoir Characterization

The project, "Calibration of Seismic Attributes for Reservoir Characterization," is now complete. Our original proposed scope of work included detailed analysis of seismic and other data from two to three hydrocarbon fields; we have analyzed data from four fields at this level of detail, two additional fields with less detail, and one other 2D seismic line used for experimentation. We also included time-lapse seismic data with ocean-bottom cable recordings in addition to the originally proposed static field data. A large number of publications and presentations have resulted from this work, inlcuding several that are in final stages of preparation or printing; one of these is a chapter on "Reservoir Geophysics" for the new Petroleum Engineering Handbook from the Society of Petroleum Engineers. Major results from this project include a new approach to evaluating seismic attributes in time-lapse monitoring studies, evaluation of pitfalls in the use of point-based measurements and facies classifications, novel applications of inversion results, improved methods of tying seismic data to the wellbore, and a comparison of methods used to detect pressure compartments. Some of the data sets used are in the public domain, allowing other investigators to test our techniques or to improve upon them using the same data. From the public-domain Stratton data set we have demonstrated that an apparent correlation between attributes derived along 'phantom' horizons are artifacts of isopach changes; only if the interpreter understands that the interpretation is based on this correlation with bed thickening or thinning, can reliable interpretations of channel horizons and facies be made. From the public-domain Boonsville data set we developed techniques to use conventional seismic attributes, including seismic facies generated under various neural network procedures, to subdivide regional facies determined from logs into productive and non-productive subfacies, and we developed a method involving cross-correlation of seismic waveforms to provide a reliable map of the various facies present in the area. The Wamsutter data set led to the use of unconventional attributes including lateral incoherence and horizon-dependent impedance variations to indicate regions of former sand bars and current high pressure, respectively, and to evaluation of various upscaling routines. The Teal South data set has provided a surprising set of results, leading us to develop a pressure-dependent velocity relationship and to conclude that nearby reservoirs are undergoing a pressure drop in response to the production of the main reservoir, implying that oil is being lost through their spill points, never to be produced. Additional results were found using the public-domain Waha and Woresham-Bayer data set, and some tests of technologies were made using 2D seismic lines from Michigan and the western Pacific ocean

Elastic waves push organic fluids from reservoir rock

Elastic waves have been observed to increase productivity of oil wells, although the reason for the vibratory mobilization of the residual organic fluids has remained unclear. Residual oil is entrapped as ganglia in pore constrictions because of resisting capillary forces. An external pressure gradient exceeding an ‘‘unplugging’’ threshold is needed to carry the ganglia through. The vibrations help overcome this resistance by adding an oscillatory inertial forcing to the external gradient; when the vibratory forcing acts along the gradient and the threshold is exceeded, instant ‘‘unplugging’’ occurs. The mobilization effect is proportional to the amplitude and inversely proportional to the frequency of vibrations. We observe this dependence in a laboratory experiment, in which residual saturation is created in a glass micromodel, and mobilization of the dyed organic ganglia is monitored using digital photography.We also directly demonstrate the release of an entrapped ganglion by vibrations in a computational fluid-dynamics simulation

Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study

Introduction: The multiorgan impact of moderate to severe coronavirus infections in the post-acute phase is still poorly understood. We aimed to evaluate the excess burden of multiorgan abnormalities after hospitalisation with COVID-19, evaluate their determinants, and explore associations with patient-related outcome measures. Methods: In a prospective, UK-wide, multicentre MRI follow-up study (C-MORE), adults (aged ≥18 years) discharged from hospital following COVID-19 who were included in Tier 2 of the Post-hospitalisation COVID-19 study (PHOSP-COVID) and contemporary controls with no evidence of previous COVID-19 (SARS-CoV-2 nucleocapsid antibody negative) underwent multiorgan MRI (lungs, heart, brain, liver, and kidneys) with quantitative and qualitative assessment of images and clinical adjudication when relevant. Individuals with end-stage renal failure or contraindications to MRI were excluded. Participants also underwent detailed recording of symptoms, and physiological and biochemical tests. The primary outcome was the excess burden of multiorgan abnormalities (two or more organs) relative to controls, with further adjustments for potential confounders. The C-MORE study is ongoing and is registered with ClinicalTrials.gov, NCT04510025. Findings: Of 2710 participants in Tier 2 of PHOSP-COVID, 531 were recruited across 13 UK-wide C-MORE sites. After exclusions, 259 C-MORE patients (mean age 57 years [SD 12]; 158 [61%] male and 101 [39%] female) who were discharged from hospital with PCR-confirmed or clinically diagnosed COVID-19 between March 1, 2020, and Nov 1, 2021, and 52 non-COVID-19 controls from the community (mean age 49 years [SD 14]; 30 [58%] male and 22 [42%] female) were included in the analysis. Patients were assessed at a median of 5·0 months (IQR 4·2–6·3) after hospital discharge. Compared with non-COVID-19 controls, patients were older, living with more obesity, and had more comorbidities. Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p<0·0001) and independently associated with COVID-19 status (odds ratio [OR] 2·9 [95% CI 1·5–5·8]; padjusted=0·0023) after adjusting for relevant confounders. Compared with controls, patients were more likely to have MRI evidence of lung abnormalities (p=0·0001; parenchymal abnormalities), brain abnormalities (p<0·0001; more white matter hyperintensities and regional brain volume reduction), and kidney abnormalities (p=0·014; lower medullary T1 and loss of corticomedullary differentiation), whereas cardiac and liver MRI abnormalities were similar between patients and controls. Patients with multiorgan abnormalities were older (difference in mean age 7 years [95% CI 4–10]; mean age of 59·8 years [SD 11·7] with multiorgan abnormalities vs mean age of 52·8 years [11·9] without multiorgan abnormalities; p<0·0001), more likely to have three or more comorbidities (OR 2·47 [1·32–4·82]; padjusted=0·0059), and more likely to have a more severe acute infection (acute CRP >5mg/L, OR 3·55 [1·23–11·88]; padjusted=0·025) than those without multiorgan abnormalities. Presence of lung MRI abnormalities was associated with a two-fold higher risk of chest tightness, and multiorgan MRI abnormalities were associated with severe and very severe persistent physical and mental health impairment (PHOSP-COVID symptom clusters) after hospitalisation. Interpretation: After hospitalisation for COVID-19, people are at risk of multiorgan abnormalities in the medium term. Our findings emphasise the need for proactive multidisciplinary care pathways, with the potential for imaging to guide surveillance frequency and therapeutic stratification

Observations from the East Texas seismic network (June 1981-August 1982)

UT Librarie

The rapid rise of reservoir geophysics

1980 and again in 1985, on the occasions of the 50th anniversary of the Society of Exploration Geophysicists and the 50th anniversary of publication of GEOPHYSICS, special issues of that journal were published. In both those times, as now, the science was flourishing. The science described in those issues was directed toward exploration, but many of the methods were to form the basis for a new application, here called reservoir geophysics. In 1980, oil prices were at record highs, and in 1985 they were about to plummet; at the time of this writing, prices are again at local highs, accompanied by a renewed enthusiasm for the sound application of the science

Do no harm! - Seismic petrophysical aspects of time-lapse monitoring

© 2000 Society of Exploration Geophysicists. Time-lapse seismic studies of oil and gas reservoirs depend on understanding the seismic response to changing reservoir conditions. By providing erroneous predictions, however, geophysicists have the ability to actually harm future production. The steps involved in time-lapse seismic petrophysical modeling are simple; the details, however, are imposing. To predict future reservoir seismic response accurately, one must know the future reservoir conditions that may be encountered, including: changes in fluid saturation; changes in the properties of the fluids themselves; changes in the dry-frame moduli; and changes in the whole-rock response (usually modeled by Gassmann theory). Simple applications of the modeling procedure described above can lead to highly misleading interpretations of timelapse seismic observations; extreme care must be taken to include all appropriate parameters and to model the response correctly

Geophysics in the eighth grade: Earthquake waves right in their own backyard

© 1998 Society of Exploration Geophysicists. All rights reserved. High-quality broadband earthquake seismographs are now available that can be used for teaching and research purposes by interested Middle and High School teachers, right in their own classrooms, bringing geophysics to life for the students. Some seismographs (purchased through a grant from SEG) are deployed for 2-3 months at a time in various schools throughout Michigan’s rural Upper Peninsula, and the Houghton (MI) Middle School has constructed a dedicated pier for permanent placement of a dedicated seismograph. The involvement of the students in recording and interpreting earthquake waves on a machine sitting in their own classroom, and the visit of a local “expert” to help in interpretation, stimulates interest in global geology, geophysics, and seismology in particular