las

The las module implements a reader for LAS (Log ASCII Standard) well log files (LAS 2.0).For more information about this format, see the Canadian Well Logging Society web page(https://www.cwls.org/products/).

Example 1

The following file, "example1.las", is from "LAS Version 2.0: A Digital Standard forLogs; Updated January 2014":

~VERSION INFORMATIONVERS.                          2.0 :   CWLS LOG ASCII STANDARD -VERSION 2.0WRAP.                          NO  :   ONE LINE PER DEPTH STEP~WELL INFORMATION#MNEM.UNIT              DATA                       DESCRIPTION#----- -----            ----------               -------------------------STRT    .M              1670.0000                :START DEPTHSTOP    .M              1669.7500                :STOP DEPTHSTEP    .M              -0.1250                  :STEPNULL    .               -999.25                  :NULL VALUECOMP    .       ANY OIL COMPANY INC.             :COMPANYWELL    .       ANY ET AL 12-34-12-34            :WELLFLD     .       WILDCAT                          :FIELDLOC     .       12-34-12-34W5M                   :LOCATIONPROV    .       ALBERTA                          :PROVINCESRVC    .       ANY LOGGING COMPANY INC.         :SERVICE COMPANYDATE    .       13-DEC-86                        :LOG DATEUWI     .       100123401234W500                 :UNIQUE WELL ID~CURVE INFORMATION#MNEM.UNIT              API CODES                   CURVE DESCRIPTION#------------------     ------------              ------------------------- DEPT   .M                                       :  1  DEPTH DT     .US/M           60 520 32 00             :  2  SONIC TRANSIT TIME RHOB   .K/M3           45 350 01 00             :  3  BULK DENSITY NPHI   .V/V            42 890 00 00             :  4  NEUTRON POROSITY SFLU   .OHMM           07 220 04 00             :  5  SHALLOW RESISTIVITY SFLA   .OHMM           07 222 01 00             :  6  SHALLOW RESISTIVITY ILM    .OHMM           07 120 44 00             :  7  MEDIUM RESISTIVITY ILD    .OHMM           07 120 46 00             :  8  DEEP RESISTIVITY~PARAMETER INFORMATION#MNEM.UNIT              VALUE             DESCRIPTION#--------------     ----------------      ----------------------------------------------- MUD    .               GEL CHEM        :   MUD TYPE BHT    .DEGC           35.5000         :   BOTTOM HOLE TEMPERATURE BS     .MM             200.0000        :   BIT SIZE FD     .K/M3           1000.0000       :   FLUID DENSITY MATR   .               SAND            :   NEUTRON MATRIX MDEN   .               2710.0000       :   LOGGING MATRIX DENSITY RMF    .OHMM           0.2160          :   MUD FILTRATE RESISTIVITY DFD    .K/M3           1525.0000       :   DRILL FLUID DENSITY~OTHER     Note: The logging tools became stuck at 625 metres causing the data     between 625 metres and 615 metres to be invalid.~A  DEPTH     DT    RHOB        NPHI   SFLU    SFLA      ILM      ILD1670.000   123.450 2550.000    0.450  123.450  123.450  110.200  105.6001669.875   123.450 2550.000    0.450  123.450  123.450  110.200  105.6001669.750   123.450 2550.000    0.450  123.450  123.450  110.200  105.600

Sample python session:

>>> import las>>> log = las.LASReader('example1.las')>>> log.start1670.0>>> log.stop1669.75>>> log.step-0.125>>> log.null-999.25>>> log.well.COMPLASItem(name='COMP', units='', data='ANY OIL COMPANY INC.', descr='COMPANY')>>> log.well.COMP.value'ANY OIL COMPANY INC.'>>> log.well.FLD.value'WILDCAT'>>> print(log.other)     Note: The logging tools became stuck at 625 metres causing the data     between 625 metres and 615 metres to be invalid.

The log data is stored as a numpy structured array in log.data:

>>> log.dataarray([(1670.0, 123.45, 2550.0, 0.45, 123.45, 123.45, 110.2, 105.6),       (1669.875, 123.45, 2550.0, 0.45, 123.45, 123.45, 110.2, 105.6),       (1669.75, 123.45, 2550.0, 0.45, 123.45, 123.45, 110.2, 105.6)],      dtype=[('DEPT', '<f8'), ('DT', '<f8'), ('RHOB', '<f8'), ('NPHI', '<f8'), ('SFLU', '<f8'), ('SFLA', '<f8'), ('ILM', '<f8'), ('ILD', '<f8')])>>> log.data['RHOB']array([ 2550.,  2550.,  2550.])>>> log.data[0](1670.0, 123.45, 2550.0, 0.45, 123.45, 123.45, 110.2, 105.6)

The data is also available as a two-dimensional numpy array. First we'lladjust numpy's output format. This is not necessary, but it makes the valueseasier to read:

>>> import numpy as np>>> np.set_printoptions(precision=4)

The two-dimensional view of the data is called data2d:

>>> log.data2darray([[  1.6700e+03,   1.2345e+02,   2.5500e+03,   4.5000e-01,          1.2345e+02,   1.2345e+02,   1.1020e+02,   1.0560e+02],       [  1.6699e+03,   1.2345e+02,   2.5500e+03,   4.5000e-01,          1.2345e+02,   1.2345e+02,   1.1020e+02,   1.0560e+02],       [  1.6698e+03,   1.2345e+02,   2.5500e+03,   4.5000e-01,          1.2345e+02,   1.2345e+02,   1.1020e+02,   1.0560e+02]])>>> log.data2d.shape(3, 8)

Example 2

The next example reads a file from the Kansas Geological Survey and makesa plot of the gamma ray data versus depth using matplotlib.

First, the imports:

>>> import numpy as np>>> import matplotlib.pyplot as plt>>> import las>>> import io>>> try:...     from urllib.request import urlopen... except ImportError:...     from urllib import urlopen...

Next, read the file:

>>> url = "http://www.kgs.ku.edu/software/DEWL/HELP/pc_read/Shamar-1.las">>> f = io.StringIO(urlopen(url).read().decode('iso-8859-1'))>>> log = las.LASReader(f, null_subs=np.nan)

Finally, make the plot using matplotlib:

>>> plt.figure(figsize=(9, 5))>>> plt.plot(log.data['DEPT'], log.data['GR'])>>> plt.xlabel(log.curves.DEPT.descr + " (%s)" % log.curves.DEPT.units)>>> plt.ylabel(log.curves.GR.descr + " (%s)" % log.curves.GR.units)>>> plt.title(log.well.WELL.data + ', ' + log.well.DATE.data)>>> plt.grid()>>> plt.show()