Acquisition of time-lapse, 6-component, P- and S-wave, crosswell seismic survey with orbital vibrator and of time-lapse VSP for CO2 injection monitoring

Using an orbital vibrator source (2-components), and a 40 level 3-component geophone string, a 6-component crosswell survey was acquired before and after a CO2 injection in a saline aquifer. Decomposition of the two source components and component rotation of both source and sensors created good separation of P- and S-wave energy allowing independent analysis of travel time and reflectivity. A time-lapse VSP was also acquired

Rising rural body-mass index is the main driver of the global obesity epidemic in adults

Body-mass index (BMI) has increased steadily in most countries in parallel with a rise in the proportion of the population who live in cities 1,2 . This has led to a widely reported view that urbanization is one of the most important drivers of the global rise in obesity 3�6 . Here we use 2,009 population-based studies, with measurements of height and weight in more than 112 million adults, to report national, regional and global trends in mean BMI segregated by place of residence (a rural or urban area) from 1985 to 2017. We show that, contrary to the dominant paradigm, more than 55 of the global rise in mean BMI from 1985 to 2017�and more than 80 in some low- and middle-income regions�was due to increases in BMI in rural areas. This large contribution stems from the fact that, with the exception of women in sub-Saharan Africa, BMI is increasing at the same rate or faster in rural areas than in cities in low- and middle-income regions. These trends have in turn resulted in a closing�and in some countries reversal�of the gap in BMI between urban and rural areas in low- and middle-income countries, especially for women. In high-income and industrialized countries, we noted a persistently higher rural BMI, especially for women. There is an urgent need for an integrated approach to rural nutrition that enhances financial and physical access to healthy foods, to avoid replacing the rural undernutrition disadvantage in poor countries with a more general malnutrition disadvantage that entails excessive consumption of low-quality calories. © 2019, The Author(s)

SEISMOLOGICAL INVESTIGATIONS IN GEOTHERMAL REGIONS

Seismological methods, including studies of microearthquakes, P- and S-wave velocities and P-wave attenuation were investigated as tools for the exploration and delineation of geothermal resources. Seismograms from explosions and microearthquakes were examined for changes in frequency content and relative arrival times across a known geothermal area, The Geysers, California, and a potential geothermal region, Grass Valley, Nevada. Microearthquakes within the two regions were examined for evidence of spatial variations in radiated P- and S-waves. Additional information concerning Basin and Range structure was provided by regional refraction studies. Detailed structural analysis in Grass Valley was obtained by commercial reflection and refraction work. Heat flow modeling, consistent with structure inferred by seismological techniques, was used to discriminate between conductive and convective heat flow anomalies in Grass Valley. Concentrated observations in Grass Valley around Leach Hot Springs revealed moderate microearthquake activity on a trend crossing the southern end of the valley, with occasional swarms in the area of high heat flow (4 to 6 hfu) at the north end of the 1915 Pleasant Valley earthquake (mag = 7.5) fault trace. Studies in The Geysers steam field reveal significant velocity and attenuation anomalies associated with the production zone. It is concluded that with proper sampling in space and time, P- and S-wave velocity and attenuation data can detect and delineate significant anomalies associated with the static properties of a geothermal resource. Microearthquake data are useful for monitoring the dynamic strain relief processes associated with fluid movement, temperature and pressure gradients in geothermal environments

3-D Seismic Methods for Geothermal Reservoir Exploration and Assessment--Summary

A wide variety of seismic methods covering the spectrum from DC to kilohertz have been employed at one time or the other in geothermal environments. The reasons have varied from exploration for a heat source to attempting to find individual fractures producing hot fluids. For the purposes here we will assume that overall objective of seismic imaging is for siting wells for successful location of permeable pathways (often fracture permeability) that are controlling flow and transport in naturally fractured reservoirs. The application could be for exploration of new resources or for in-fill/step-out drilling in existing fields. In most geothermal environments the challenge has been to separate the ''background'' natural complexity and heterogeneity of the matrix from the fracture/fault heterogeneity controlling the fluid flow. Ideally one not only wants to find the fractures, but the fractures that are controlling the flow of the fluids. Evaluated in this work is current state-of-the-art surface (seismic reflection) and borehole seismic methods (Vertical Seismic Profiling (VSP), Crosswell and Single Well) to locate and quantify geothermal reservoir characteristics. The focus is on active methods; the assumption being that accuracy is needed for successful well siting. Passive methods are useful for exploration and detailed monitoring for in-fill drilling, but in general the passive methods lack the precision and accuracy for well siting in new or step out areas. In addition, MEQ activity is usually associated with production, after the field has been taken to a mature state, thus in most cases it is assumed that there is not enough MEQ activity in unproduced areas to accurately find the permeable pathways. The premise of this review is that there may new developments in theory and modeling, as well as in data acquisition and processing, which could make it possible to image the subsurface in much more detail than 15 years ago. New understanding of the effect of fractures on seismic wave propagation are now being applied to image fractures in gas and oil environments. It now may be appropriate to apply these methods, with modifications, to geothermal applications. It is assumed that to implement the appropriate methods an industry coupled program tightly linked to actual field cases, iterating between development and application will be pursued. The goal of this work is to evaluate the most promising methods and approaches that may be used for improved geothermal exploration and reservoir assessment. It is not a comprehensive review of all seismic methods used to date in geothermal environments. This work was motivated by a need to assess current and developing seismic technology that if applied in geothermal cases may greatly improve the chances for locating new geothermal resources and/or improve assessment of current ones

GTO-DOE/Industry Cost Shared Research; Microseismic Characterization and Monitoring

The application of passive seismic studies in geothermal regions have undergone significant changes in the last 15 years. The primary application is now in the monitoring of subsurface processes, rather than exploration. A joint Geothermal Technology Organization (GTO) industry/DOE, monitoring project involving GEO, Unocal Geothermal, and LBL, was carried out at The Geysers geothermal field in northern California using a special high frequency monitoring system. This several-month-long experiment monitored the discrete and continuous seismic signals before, during, and after a fluid stimulation of a marginal production well. Almost 350,000 liters of water were pumped into the well over a four-hour, and a three-hour time period for two consecutive days in June of 1988. No significant changes in the background seismicity or the seismic noise were detected during the monitoring period. Analysis of the background seismicity did indicate that the earthquakes at The Geysers contain frequencies higher than 50 Hz and possibly as high as 100 Hz. 5 refs., 5 figs

THE APPLICATION OF HIGH FREQUENCY SEISMIC MONITORING METHODS FOR THE MAPPING OF FLUID INJECTIONS

This paper describes experimental work using seismic methods for monitoring the path of fluid injections. The most obvious application is the high pressure fluid injections for the purpose of hydrofracturing. Other applications are the injection of grout into shallow subsurface structures and the disposal of fluids in the geothermal and toxic waste industries. In this paper hydrofracture monitoring and grout injections will be discussed