Analysis of exploitation‐induced gravity changes at Wairakei Geothermal Field

Geophysics ◽  
1986 ◽  
Vol 51 (8) ◽  
pp. 1647-1660 ◽  
Author(s):  
Richard G. Allis ◽  
Trevor M. Hunt
Keyword(s):  
Geothermal Field ◽  
Gravity Change ◽  
Gravity Models ◽  
Liquid Temperature ◽  
Surrounding Area ◽  
Liquid Pressure ◽  
Induced Gravity ◽  
Gravity Changes ◽  
Flow Equilibrium ◽  
The 1960S

Gravity changes (corrected for subsidence) of up to -1 000 (±300) μGal have occurred in the [Formula: see text] area of the production bore field at Wairakei, and smaller decreases extend over a [Formula: see text] surrounding area. The largest part of these decreases occurred during the 1960s; since then the net gravity change for the whole field has been zero, indicating mass flow equilibrium. The principal causes of gravity change have been deep liquid pressure drawdown which resulted in formation of a steam zone, subsequent saturation changes in the steam zone, liquid temperature decline, and groundwater level changes. Gravity models suggest saturation of the steam zone was 0.7 (±0.1) in 1962 and decreased to 0.6 by 1972. Gravity increases in the northern and eastern bore field since the early 1970s are attributed to cool water invading the steam zone.

scholarly journals Induced Gravity Models with Exact Bounce Solutions

2018 ◽  
Vol 49 (5) ◽  
pp. 914-917 ◽  
Author(s):  
E. O. Pozdeeva ◽  
S. Yu. Vernov
Keyword(s):  
Gravity Models ◽  
Induced Gravity

scholarly journals Flattening the inflaton potential beyond minimal gravity

2018 ◽  
Vol 168 ◽  
pp. 06001 ◽  
Author(s):  
Hyun Min Lee
Keyword(s):  
Standard Model ◽  
Higgs Field ◽  
Gravity Models ◽  
Induced Gravity ◽  
Consistent Description ◽  
The Standard Model ◽  
Self Consistent ◽  
The Status

We review the status of the Starobinsky-like models for inflation beyond minimal gravity and discuss the unitarity problem due to the presence of a large non-minimal gravity coupling. We show that the induced gravity models allow for a self-consistent description of inflation and discuss the implications of the inflaton couplings to the Higgs field in the Standard Model.

High Order Bubble Dynamics in Incompressible Liquid

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Vasilii Sharipov
Keyword(s):  
Bubble Dynamics ◽  
Pressure Change ◽  
Analytical Approximation ◽  
Industrial Applications ◽  
Oxygen Mixture ◽  
Liquid Temperature ◽  
Computationally Efficient ◽  
Liquid Pressure ◽  
Computer Codes ◽  
Fourier Equation

A semi-analytical approximation to the solution of the radial Fourier equation describing liquid temperature dynamics in the vicinity of a spherical bubble is presented. This approximation opens a possibility to construct a computationally efficient bubble model that is flexible enough to simulate different bubble dynamics behavior like bubble growth, collapse, and oscillations. In turn, it allows development of two-pressure computer codes aiming at simulation of processes in liquid with bubbles that are important for industrial applications. The model is based on the system of ordinary differential equations (ODEs) and is presented together with results of simulations and comparison with some available experimental data. Additionally, scenarios like strong bubble parameter oscillations in largely subcooled water and abrupt liquid pressure change are considered. As respective simulations show, the latter may lead to subsequent hydrogen explosion if hydrogen–oxygen mixture is presented in the bubble. This may be important for boiling water reactor piping safety analysis.

Analytical modelling and joint inversion of surface displacements and gravity changes at volcanoes

2021 ◽  
Author(s):  
Mehdi Nikkhoo ◽  
Eleonora Rivalta
Keyword(s):  
Source Parameters ◽  
Surface Displacement ◽  
Point Sources ◽  
Gravity Change ◽  
Density Estimate ◽  
Mass Change ◽  
Long Valley Caldera ◽  
Gravity Changes ◽  
Surface Displacements ◽  
Volcanic Reservoirs

<p>Gravity change observations at volcanoes provide information on the location and mass change of intruded magma bodies. Gravity change and surface displacement observations are often combined in order to infer the density of the intruded materials. Previous studies have highlighted that it is crucial to account for magma compressibility and the shape of the gravity change and deformation source to avoid large biases in the density estimate. Currently, an analytical model for the deformation field and gravity change due to a source of arbitrary shape is lacking, affecting our ability to perform rapid inversions and assess the nature of volcanic unrest.  </p><p>Here, we propose an efficient approach for rapid joint-inversions of surface displacement and gravity change observations associated with underground pressurized reservoirs. We derive analytical solutions for deformations and gravity changes due to the volume changes of triaxial point-sources in an isotropic elastic half-space. The method can be applied to  volcanic reservoirs that are deep compared to their size (far field approximation). We show that the gravity changes not only allow inferring mass changes within the reservoirs, but also help better constrain location, shape and the volume change of the source. We discuss how the inherent uncertainties in the realistic shape of volcanic reservoirs are reflected in large uncertainties on the density estimates. We apply our approach to the surface displacements and gravity changes at Long Valley caldera over the 1985-1999 time period. We show that gravity changes together with only vertical displacements are sufficient to constrain the mass change and all the other source parameters. We also show that while mass change is well constrained by gravity change observations the density estimate is more uncertain even if the magma compressibility is accounted for in the model.</p>

The Performances of GRACE Mascon Solutions in Studying Seismic Deformations

2020 ◽  
Author(s):  
Lan Zhang ◽  
He Tang ◽  
Le Chang ◽  
Wenke Sun
Keyword(s):  
Tohoku Earthquake ◽  
Gravity Change ◽  
Mathematical Treatment ◽  
Seismic Signals ◽  
Gaussian Filter ◽  
Seismic Deformations ◽  
Gravity Changes ◽  
Grace Data ◽  
Basin Scale ◽  
Large Earthquakes

<p>The GRACE mascon solutions, called the advanced products of GRACE data, are widely used in cryosphere science or hydrology research. It has been demonstrated that the mascon solutions have the same or better performances compared with the spherical harmonic (SH) solutions at the basin scale. However, although the mascon solutions are expected to have the ability to recover the transient gravity signals due to large earthquakes, few studies have investigated the performances of the mascon solutions in studying seismic deformations systematically. In this study, we attempt to examine the performances of the mascon solutions for transient gravity signals induced by three M9 class earthquakes: the 2011 Tohoku-Oki, 2004 Sumatra and 2010 Chile earthquakes, and compare them with the SH solutions and theoretical gravity changes modelled by dislocation theory. We analyse the co-seismic gravity changes and conclude that the mascon solutions contain almost identical information as the SH solutions and can retrieve the co-seismic gravity change signals in the resolutions equivalent to the Gaussian filter radii of 210~270 km. However, the mascon solutions have other strengthening gravity change signals, with magnitudes that are the same order as that of the SH solutions and contain pre-seismic gravity change signals in the Tohoku earthquake. These strengthening and pre-seismic signals are both considered artificially introduced noise due to the mathematical treatment before releasing rather than real geophysical signals.</p>

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