NESC0893 SHAFT79.

1. NAME OR DESIGNATION OF PROGRAM:  SHAFT79.

3. DESCRIPTION OF PROBLEM OR FUNCTION

SHAFT79 (Simultaneous Heat And  Fluid Transport) is an integrated finite difference program for computing two-phase non-isothermal flow in porous media. Although designed for simulating production and injection in geothermal reservoirs, it is, or can be readily modified to be, applicable to other two-phase problems. SHAFT79 solves coupled mass and energy balance equations based on the following major assumptions: the physical system is a system of porous rock saturated with a one- component fluid in liquid and vapor form; all rock properties, except porosity, i.e., density, specific heat, thermal conductivity, and absolute permeability are independent of temperature, pressure,  or vapor saturation: and liquid, vapor, and rock matrix are at the same temperature and pressure at all times. Capillary pressure is neglected.

4. METHOD OF SOLUTION

The solution method is an explicit-implicit integrated finite difference approach which allows a flexible geometric description because it does not distinguish between one-,  two-, or three-dimensional regular or irregular geometries. The non- linear finite difference equations are solved using the Newton- Raphson method. In SHAFT79 a fluid table is used to provide the equilibrium thermodynamic properties of the fluid filling the void space - temperature, pressure, vapor saturation, heat conductivity,  liquid and vapor viscosities, densities, specific interval energies  - as functions of fluid density and fluid specific internal energy.  All thermodynamic information including derivatives is obtained from the fluid table by bivariate interpolation.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

SHAFT79 has been developed only for systems of water and rock. The fluid table covers most of the equation of state of water substance in the temperature  range of 5 to 400 degrees C and the pressure range of 0.5 to 220 bar, which is adequate for most geothermal applications.

6. TYPICAL RUNNING TIME

Typical problems require about 10 to 25 CP seconds on a CDC7600.

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS

The fluid table is generated by executing two auxiliary programs included in the package, WATER and  PROPER. WATER computes and tabulates the steam table equations as given by the International Formulation Committee (IFC,1967). PROPER  numerically inverts these tables into functions of viscosities and densities and appends parameters other than temperature, pressure and vapor saturation. The tabulation is done in such a way that interpolation does not occur across the saturation line, where derivatives change in discontinuous fashion.
SHAFT79 is one of a set of five geothermal codes. The others are: ANALYZE for multiwell, multirate well test parameter determination (NESC Abstract 891); CCC for one-phase conduction, convection; and compaction (NESC Abstract 892); TERZAGI for isothermal fluid flow and subsidence (NESC Abstract 894); and WELBORE for steady and transient geothermal wellbore flow (NESC Abstract 895).

10. REFERENCES

- K. Pruess, J.M. Zerzan, R.C. Schroeder, and P.A. Witherspoon,
  Description of the Three-dimensional Two-phase Simulator SHAFT78
for Use in Geothermal Reservoir Studies, Paper SPE-7699, presented    at the Fifth Symposium on Reservoir Simulation, Denver, Colorado,
  1979.
- K. Pruess, G. Bodvarsson, R.C. Schroeder, P.A. Witherspoon, R.
  Marconcini, G. Neri, and C. Ruffilli,
  Simulation of the Depletion of Two-phase Geothermal Reservoirs,
Paper SPE-8266, presented at the 54th Annual Technical Conference,    Society of Petroleum Engineers, Las Vegas, Nevada, 1979, also
  printed as,
  LBL-9606, August 1979.
- K. Pruess, R.C. Schroeder,
  Geothermal Reservoir Simulation with SHAFT79,
  5th Geothermal Reservoir Engineering Workshop, Stanford,
  California, 1979,
  LBL-10066.

-  K. Pruess et al.:
    SHAFT-78, A Two-phase Multidimensional Computer Program for
    Geothermal Reservoir Simulation. LBL-8264 (November 1979).
-  K. Pruess and R. C. Schroeder:
    SHAFT-79, USER'S MANUAL. LBL-10861 (March 1980).
-  NESC Note 81-35 (May 9, 1981).

11. MACHINE REQUIREMENTS:  725,000 (octal) words of storage are required

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  SCOPE2.1.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

The
SHAFT79 program uses subroutine MA28A and associated routines from the U.K.A.E.A. Harwell Subroutine Library to solve a general sparse  n x n system of linear equations. These routines, included as part of the package with Harwell's permission, are not in the public domain and extraction for other use is not permitted.

15. NAME AND ESTABLISHMENT OF AUTHOR

             K. Pruess* and R.C. Schroeder
             Lawrence Berkeley Laboratory
             University of California
             Berkeley, California 94720
* Contact

File name	File description	Records
NESC0893_01.001	SHAFT-79 FORTRAN SOURCE	5599
NESC0893_01.002	FLUTAB3 LIBRARY DATA	18297
NESC0893_01.003	BRIGHAM & MORROW HALF-WATER HALF-STEAM	24
NESC0893_01.004	NATURAL HYDROTHERMAL CONVECTION SYSTEM	109
NESC0893_01.005	GARG'S RADIAL FLOW	118
NESC0893_01.006	WATER FORTRAN SOURCE	273
NESC0893_01.007	WATER SAMPLE INPUT	5
NESC0893_01.008	PROPER FORTRAN SOURCE	1734
NESC0893_01.009	PROPER SAMPLE INPUT	364
NESC0893_01.010	ISOT1 FILE	4937
NESC0893_01.011	OGRE FORTRAN SOURCE	1014
NESC0893_01.012	TEST CASE OUTPUT1	380
NESC0893_01.013	TEST CASE OUTPUT2	883
NESC0893_01.014	TEST CASE OUTPUT3	1223