|
<br />yield on apparent grain density. Apparent grain-
<br />density data were obtained from the apparent grain-
<br />density log for well USGS. Testing of various
<br />regression equation models indicated that the regres-
<br />sion equation that had the largest coefficient of correla-
<br />tion and the smallest standard error of estimate had
<br />specific yield divided by porosity as the dependent
<br />variable. This regression equation was used in this
<br />report; specific yield and specific retention were calcu-
<br />lated by using porosity values from the density porosity
<br />log. The regression equation (fig. 7) has a coefficient
<br />of correlation of 0.90 and a standard error of estimate
<br />of 0.13 (in units of specific yield divided by porosity).
<br />At a porosity of 0.30, this standard error is equivalent
<br />to 0.04 specific-yield units. The correlation is adequate
<br />to enable estimation of specific yield divided by poros-
<br />ity from the apparent grain-density log. Mean values of
<br />specific yield calculated from core and from the appar-
<br />
<br />1,0
<br />
<br />,
<br />,
<br />
<br />
<br />ent grain-density log and density porosity log are listed
<br />in table 3. Values calculated by this technique agree
<br />closely with those calculated from core analyses and
<br />from the effective porosity technique.
<br />
<br />The regression equation of specific yield on
<br />effective porosity was used with geophysical logs for
<br />the lower 200 ft of well USGS to calculate a specific-
<br />yield log for this interval (fig. 8). Except for washout
<br />intervals, a continuous specific-yield log can be calcu-
<br />lated, and log values can be averaged to determine the
<br />mean specific yield of intervals or for entire aquifers.
<br />An estimated mean specific yield of 0.14 was calcu-
<br />lated for this 200-ft interval by using the regression
<br />equation of specific yield on effective porosity. The
<br />specific-yield log produced by using the regression
<br />equation of specific yield divided by porosity on appar-
<br />ent grain density was similar to that in figure 8.
<br />
<br />o
<br />
<br /> " . LINE OF REGRESSION -
<br /> " .
<br /> " .... (SY/l/l =' 6.819 - 2.253 Pfha)
<br /> .. ~.
<br /> 0,8 : :. ....... :t ONE STANDARD ERROR 0,2
<br /> , . , . OF ESTIMATE
<br /> , . . . . ,
<br /> , . . ,
<br />-------- .... ,
<br />~I~ , ,
<br /> , . ,
<br /> , . , . z
<br />--------- 0,6 , . , 0,' 0
<br /> . . , , f=
<br />0 , , .
<br />...J , , Z ~
<br />w ~ , , W
<br />>= , , f- (ii
<br />(ii , , W 0
<br /> . a;
<br />U 0 . . , , a;
<br />u: a; 0,' ,. , 0,6 !,1 0
<br />U 0 . , . , LL. ll.
<br />W ll. ,. , U
<br />ll. , , W
<br />en . , , ll.
<br /> , , en
<br /> , ,
<br /> , ,
<br /> 0,2 , 0,8
<br /> ,
<br /> ,
<br /> ,
<br /> ,
<br /> ,
<br /> ,
<br /> "-
<br /> 0 1,0
<br /> 2.60 2.70 2.80 2,90 3.00
<br /> APPARENT GRAIN DENSITY (Pma), IN GRAMS PER CUBIC CENTIMETER
<br />Figure 7. Unear regression relation of specific yield divided by porosity on apparent grain density.
<br />
<br />
<br />18 Techniques for EsUrnatlng Specific Yield and Specific Ratentlon from Graln-S1za Data and Geophysical Logs from
<br />eluUc Badrock Aquila..
<br />
|