scholarly journals Assessment of precise surface-gravity measurements for monitoring the response of a geothermal reservoir to exploitation

1981 ◽  
Author(s):  
R.B. Grannell ◽  
J.H. Whitcomb ◽  
P.S. Aronstam ◽  
R.C. Clover
Keyword(s):  
Geothermal Reservoir ◽  
Surface Gravity ◽  
Gravity Measurements

scholarly journals Estimation of Bouguer correction density based on underground and surface gravity measurements and precise modelling of topographic effects – two case studies from Slovakia

2018 ◽  
Vol 48 (4) ◽  
pp. 319-336 ◽  
Author(s):  
Pavol Zahorec ◽  
Juraj Papčo
Keyword(s):  
Laser Scanning ◽  
Airborne Lidar ◽  
Surface Gravity ◽  
Karst Area ◽  
Topographic Effects ◽  
Railway Tunnel ◽  
Detailed Surface ◽  
Active Coal ◽  
Gravity Measurements ◽  
Gravimetric Modelling

Abstract We present a simple and straightforward method for estimating the mean density of topographic masses based on underground gravity measurements along with topography modelling. Two examples under different conditions are given, the first coming from a railway tunnel passing through a Mesozoic karst area and the second from an active coal mine situated in a Neogene sedimentary basin. Relative gravity measurements were processed and corrected by topographic effect modelling based on high-precision airborne LiDAR-derived elevation models. In addition, detailed mining tunnel gravimetric modelling based on terrestrial laser scanning data is presented. Resulted mean (bulk) densities are compared with those obtained from detailed surface gravity measurements as well as with available rock-samples density analysis.

CORRELATING SEA‐SURFACE AND AERIAL GRAVITY MEASUREMENTS

Geophysics ◽  
1966 ◽  
Vol 31 (1) ◽  
pp. 264-266 ◽  
Author(s):  
Stephen Thyssen‐Bornemisza
Keyword(s):  
Ground Surface ◽  
Sea Surface ◽  
Surface Gravity ◽  
Sea Floor ◽  
Gravity Measurements ◽  
Vertical Gradients

When sea‐surface gravity observations were supplemented by corresponding values from the airborne meter, average vertical gradients of gravity could be computed. In a borehole these gradients are observable by moving the borehole gravity meter up and down to another level (Thyssen‐Bornemisza, 1963, 1964, 1965a), but measurements taken on two horizontal profiles separated by the constant vertical interval h could furnish only relative gradient values or variations in the profile direction. Of course, gravity profiles on the ground surface or the sea floor can be likewise supplemented by aerial observations.

Gravity measurements as a calibration tool for geothermal reservoir modelling

Geothermics ◽  
2018 ◽  
Vol 73 ◽  
pp. 146-157 ◽  
Author(s):  
S.C. Pearson-Grant ◽  
P. Franz ◽  
J. Clearwater
Keyword(s):  
Geothermal Reservoir ◽  
Reservoir Modelling ◽  
Gravity Measurements ◽  
Calibration Tool

The problem of hollow space correction in subsurface gravity surveys

Geophysics ◽  
1983 ◽  
Vol 48 (10) ◽  
pp. 1406-1408
Author(s):  
B. V. Satyanarayana Murty ◽  
P. Chandra Reddy
Keyword(s):  
Mineral Exploration ◽  
Gravity Data ◽  
Surface Gravity ◽  
Gravity Method ◽  
Hollow Space ◽  
Additional Correction ◽  
Computational Work ◽  
Gravity Measurements

In spite of the extensive computational work involved in the reduction of data especially in estimating the effects of terrain, the gravity method has earned its own esteemed place in mineral exploration. Measurement of gravity in subsurface openings such as mine shafts, drives, and adits is much more valuable in mineral exploration and also useful in the planning, design, and maintenance of mines. However, because the anomalies being sought in this context are usually of very small magnitudes, accuracy at every stage of the gravity investigation is essential. Besides those corrections which are known for the surface gravity measurements, an additional correction for the subsurface gravity data is the result of hollow spaces.

scholarly journals Gravity monitoring of C O2 movement during sequestration: Model studies

Geophysics ◽  
2008 ◽  
Vol 73 (6) ◽  
pp. WA105-WA112 ◽  
Author(s):  
E. Gasperikova ◽  
G. M. Hoversten
Keyword(s):  
Oil Recovery ◽  
Vertical Section ◽  
Vertical Component ◽  
Time Lapse ◽  
Surface Gravity ◽  
Coal Bed ◽  
Change Analysis ◽  
Model Studies ◽  
Gravity Response ◽  
Gravity Measurements

Sequestration/enhanced oil recovery (EOR) petroleum reservoirs have relatively thin injection intervals with multiple fluid components (oil, hydrocarbon gas, brine, and carbon dioxide, or [Formula: see text]), whereas brine formations usually have much thicker injection intervals and only two components (brine and [Formula: see text]). Coal formations undergoing methane extraction tend to be thin [Formula: see text] but shallow compared to either EOR or brine formations. Injecting [Formula: see text] into an oil reservoir decreases the bulk density in the reservoir. The spatial pattern of the change in the vertical component of gravity [Formula: see text] is correlated directly with the net change in reservoir density. Furthermore, time-lapse changes in the borehole [Formula: see text] clearly identify the vertical section of the reservoir where fluid saturations are changing. The [Formula: see text]-brine front, on the order of [Formula: see text] within a [Formula: see text]-thick brine formation at [Formula: see text] depth with 30% [Formula: see text] and 70% brine saturations, respectively, produced a [Formula: see text] surface gravity anomaly. Such an anomaly would be detectable in the field. The amount of [Formula: see text] in a coal-bed methane scenario did not produce a large enough surface gravity response; however, we would expect that for an industrial-size injection, the surface gravity response would be measurable. Gravity inversions in all three scenarios illustrate that the general position of density changes caused by [Formula: see text] can be recovered but not the absolute value of the change. Analysis of the spatial resolution and detectability limits shows that gravity measurements could, under certain circumstances, be used as a lower-cost alternative to seismic measurements.

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