Copyright (C)  2016 Statoil ASA, Norway.

Snapwell is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation, either version 3 of the License, or (at your option)
any later version.

Snapwell is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE.

See the GNU General Public License at <http://www.gnu.org/licenses/gpl.html>
for more details.

Snapwell requires an installation of ert to function. Ert provides the necessary library to read Eclipse grids and restart files.

Make sure to have snapwell in your Python path:

you@host:~$ git clone https://github.com/Statoil/snapwell
you@host:~$ export PYTHONPATH=snapwell:$PYTHONPATH
you@host:~$ python
>>> import snapwell

Snapwell is a project for depth optimizing wellpaths by changing the TVD according to OWC. What exactly defines OWC at a given (x,y)-coordinate can be specified as number r between 0 and 1, and OWC is then the lowest point with SWAT=r. Future implementations might also take the permeability into account.

Changes in TVD are typically done by using a max increase of 0.5 m/30m to avoid making vertical segments.

Should avoid putting the majority of the well path in cells with non producible permeability.

The config file format for snapwell (SnapConfig) is as follows:

• Everything on a line following a "--" is ignored
• A line should start with a keyword and be followed by the keyword's arguments
• Two keywords are mandatory, GRID and RESTART, and should be followed by a path to the grid (GRID/EGRID) and restart files (UNRST), respectively (see example below).
• The INIT keyword is required for permeability output, and should be followed by a path to an init file.
• The following additional header keywords are supported:
  • OUTPUT --- the output directory (path), is set to cwd by default
  • OVERWRITE --- a boolean (True/False) specifying whether the program is allowed to overwrite already existing files. Defaulted to False; use with care.
  • DELTA_Z --- the maximum elevation per 100 meters, given as a float. 0.0167 is 0.5m/30m.
  • OWC --- the saturation of water considered to be the OWC (e.g. 0.7)
  • OWC_OFFSET --- a number (eg. 0.5). Will place the wellpoint 0.5m above OWC
  • LOG --- any number of LOG lines is allowed, and supported are:
    • OWC --- actual OWC for given date and (x,y) coordinate
    • OLD_TVD --- the old TVD specified in the input Wellpath
    • DIFF --- The difference between OLD_TVD and new TVD
    • SWAT, SOIL, SGAS, PERMX --- value in wellpoint cell for keyword
    • LENGTH --- the distance between this (x,y) coordinate and the previous
• then follow n lines containing the keyword WELLPATH followed by two or four literals
  • a filepath (path to the wellpath)
  • a datetime (format specified below)
  • optionally "MD " or "TVD ".

The filepath is relative to the config file, not the current working directory.

A datetime is specified as either

• YYYY
• YYYY-MM
• YYYY-MM-DD If either MM or MM-DD is missing, they will be treated as 01 or 01-01, respectively.

Example:

GRID       NORNE_1996.EGRID
RESTART    NORNE_1996.UNRST
INIT       NORNE_1996.INIT
--
OUTPUT        ../snapout
OVERWRITE     False
DELTA_Z       0.0167 -- 0.5m per 30m
OWC_OFFSET    0.8    -- places well 0.8m above OWC
LOG           SWAT   -- outputs SWAT value for the wellpoint's cell
LOG           OWC    -- outputs actual OWC for date and x,y coordinate
--
--KEYWORD  FILENAME                     DATE        D_TYPE  D_SPEC
WELLPATH   case1/SIMULATION_WELL_D_p.txt  2022-01-01  MD      2000.0
WELLPATH   case1/SIMULATION_WELL_D_q.txt  2022        TVD     1750.0
WELLPATH   case1/SIMULATION_WELL_D_r.txt  2022-05
WELLPATH   case1/SIMULATION_WELL_E_f.txt  2022        MD      2558.5
WELLPATH   case1/SIMULATION_WELL_E_m.txt  2022        MD      2300.0
WELLPATH   case1/SIMULATION_WELL_E_n.txt  2022-12-24

The wellpath format is given as follows: (blank lines and lines starting with -- ignored)

<version>
<well type>
<well name> <x> <y> <rkb>
<number of well logs>
<log name 1> <unit> <scale>
...
<log name n> <unit> <scale>
<x> <y> <z> <p1> ... <pn>
...
<x> <y> <z> <p1> ... <pn>

An example is the following:

1.0
PRODUCTION
TEST_WELL 1068.000 0.000 0.0000
3
MD 1 lin
Incl 1 lin
Az 1 lin
1068.0    0.0    38.0    38.0    109.0    359.0
1069.0    5.0    39.0    50.0    109.0    359.0

Here, the X, Y, and Z numbers are UTM* easting, UTM northing, UTM TVD (true vertical depth), and then follow the three log parameters defined, MD, INC and AZ, being measured_depth, inclination and azimuth.

We safely ignore all but the three first numbers in each row (actually, only x and y are really interesting).

• UTM is Universal Transverse Mercator coordinate system