nsl_dmo.m

%% Shut-in slug test (pulse)
% This demonstrates the interpretation of a pulse test with the
% Neuzil (1982) solution
%
% MIT License
% Copyright (c) 2017 Philippe Renard - University of Neuchâtel (CHYN)

%%
% The data set for this example comes from the following reference: 
% Batu, V., Aquifer Hydraulics: A Comprehensive Guide to Hydrogeologic
% Data Analysis, John Wiley, New York, 1998.
% Example 13-2, Pages 689-692
% Example adapted from Neuzil (1982) 
%
% Let us first load the data and plot them.

[t,s]=ldf('nsl_ds1.dat');
clf
plot(t,s)

%% 
% We then define the values of the parameters that are required for the
% interpretation:
%
% rw   represents the radius of the well
% Ceff the effective compressibility
% Vs   the volume of the tested section

rw=0.067;                    % Radius of the well in m
Ceff=2.723e-09;              % effective compressibility in Pa-1
Vs=1.59;                     % vol. of the test section in m3

%%
% Once the data have been loaded and the parameter defined, we can
% interpret the data. We do that as usually in two steps. First the
% parameters p of the model are estimated with the function nsl_gss. Then
% the non linear least squares nsl_fit is used to find an optimum fit.
%

p=nsl_gss(t,s);
p=fit('nsl',p,t,s);

%%
% We can then display the result of the interpretation.
% Hytool find that the folowing values for the transmissivity and
% storativity:
%
% T = 6.7 e-10 m2/s and S = 1.0 e-4
%

figure(1)
nsl_rpt(p,t,s,[Ceff,Vs,rw],'Pierre Shale example - automatic fit');

%%
% The results are in reasonable agreement with the values found by Batu
% (1998):
% T  = 1.0 e-9 m2/s and S = 3.0 e-5
%
% In order to compare the fits between the two solutions, we compute the
% fitting parameter values Cd and t0 from the values of T and S provided
% by Batu and plot the solution.
%

cd = 50; t0 = 6750;
nsl_rpt([cd,t0],t,s,[Ceff,Vs,rw],'Pierre Shale example - according to Batu (1998)');

%%
% We then find that the fits are rather similar and both acceptable.