Reexamination of the values used as constants in calculating rock density from borehole gravity data

Geophysics ◽  
1981 ◽  
Vol 46 (2) ◽  
pp. 208-210 ◽  
Author(s):  
Stephen L. Robbins
Keyword(s):  
Bulk Density ◽  
Research Program ◽  
Gravity Data ◽  
Geological Survey ◽  
Rock Density ◽  
The U.S

The U.S. Geological Survey has a research program in bore‐hole gravimetry (Mast, 1978, p. 17). As part of this program, I have been examining the accuracy of constants F and k used in the formula for determining in‐situ bulk density from borehole gravity data.

On: “GRAVITY AND AEROMAGNETIC EXPLORATION IN THE PARADOX BASIN,” BY NELSON C. STEENLAND (GEOPHYSICS, FEBRUARY, 1961, PP. 73–89)

Geophysics ◽  
1962 ◽  
Vol 27 (3) ◽  
pp. 398-398
Author(s):  
P. Edward Byerly
Keyword(s):  
Gravity Data ◽  
Geological Survey ◽  
Effective Density ◽  
Isostatic Compensation ◽  
Paradox Basin ◽  
The U.S

Following are some comments concerning Dr. Steenland’s discussion of gravity data in Professional Papers 316-A and 316-C of the U.S. Geological Survey. Dr. Steenland’s cylinder calculations are entirely dependent upon the regional anomaly removed. He obtained an anomaly of −40 mgal over Paradox Valley, whereas we obtained a residual anomaly of −32 mgal. The bottom 4,000 ft of Dr. Steenland’s cylinder contribute −5 mgal to the anomaly. Dr. Steenland’s analysis supposes that the only effective density contrasts are those attributable to variations in salt thickness or isostatic compensation.

scholarly journals The Geothermal Research Program of the U.S. Geological Survey

Circular ◽  
1982 ◽  
Author(s):  
Wendell A. Duffield ◽  
Marianne Guffanti
Keyword(s):  
Research Program ◽  
Geological Survey ◽  
The U.S

ACCURACY OF BOREHOLE GRAVITY DATA

Geophysics ◽  
1978 ◽  
Vol 43 (3) ◽  
pp. 538-542 ◽  
Author(s):  
James W. Schmoker
Keyword(s):  
Data Quality ◽  
Gravity Data ◽  
Geological Survey ◽  
Gravity Survey ◽  
Vertical Separation ◽  
Elapsed Time ◽  
Gravity Measurements ◽  
Period Data ◽  
The U.S

Repeated subsurface gravity measurements, obtained with the U.S. Geological Survey‐LaCoste and Romberg borehole gravity meter, were studied to determine the accuracy of the borehole gravity data, the dependence of accuracy upon elapsed time and vertical separation, and the precision of bulk densities calculated from borehole gravity measurements. The likelihood of poor interval gravity measurements increases sharply for vertical intervals greater than 150 ft, and increases approximately linearly with increasing time between readings. After a brief warmup period, data quality does not improve with the passage of time from the beginning of the survey. If the stations of a borehole gravity survey are separated by less than 70 ft, and the time between readings is less than 18 minutes, the gravity difference between two points in a borehole can be measured to ±10 μgals. For intervals greater than 20 ft, this is equivalent to a density error of [Formula: see text] or less.

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