SuperWell. A Simple Well Bore Flow Simulator in Spreadsheet Format. Mike Timlin

Transcription

1 SuperWell A Simple Well Bore Flow Simulator in Spreadsheet Format Mike Timlin TerraThermal 8 Pelican Lane Redwood City, CA USA MTimlin@TerraThermal.Com January, 28 Stanford Geothermal Reservoir Engineering Workshop 1

2 ABSTRACT Well testing is a key tool for the initial measurement and ongoing monitoring of well properties. By coupling it with well bore flow simulation, we can gain valuable information about well and reservoir properties. We can use this information to maintain the health of our reservoirs and wells. We can improve and optimize well and reservoir productivity, providing significant return on our geothermal investments. This report outlines the specification, development and testing of a simulator that solves geothermal problems. January, 28 Stanford Geothermal Reservoir Engineering Workshop 2

3 INTRODUCTION Well testing is a very broad topic, comprising a variety of transient and steady state tests, such as injection, warm-up, flow and interference. Situations can be classified by well status and fluid flow. Well bore flow simulation can provide: Rapid calculation of well output curves Low cost, precise, well sizing studies Down hole pump benefit analysis Well test robustness checking Detection of well damage Decline curve analysis Scaling risk analysis Well histograms January, 28 Stanford Geothermal Reservoir Engineering Workshop 3

4 SURVEY Measured well head values are generally available. Casing shoe, slotted liner, and bottom hole values are wanted: not difficult to extremely difficult to calculate. Multiple feed zones, a distributed feed zone, or a combination of multiple, distributed feed zones complicate calculations. Thermodynamic properties of pure water are very well known. Two-phase flow of geothermal water is prevalent, with liquid flashing into vapour and/or vapour condensing into liquid. CO 2 and NaCl can proxy for dissolved gas and solid species. Many simulators exist; SuperWell implements the ESDU methodology in a spreadsheet approach. January, 28 Stanford Geothermal Reservoir Engineering Workshop 4

5 PROCEDURES Stepping down Haaland equation Stepping up Output curve P( z + dz) = P( z) + f dp dz g dpf + dz 1 = ε D Log 3.7 dp P( z dz) = P( z) dz g 1.11 dpf + dz dpa + dz Re dpa dz dz 2 dz January, 28 Stanford Geothermal Reservoir Engineering Workshop 5

6 STEPPING DOWN Hypothetical Geothermal Well, SuperWell vs. WELL, Stepping Down Pressure (bara), Temperature ( o C) Depth (m) SuperWell Pressure WELL Pressure SuperWell Temperature WELL Temperature January, 28 Stanford Geothermal Reservoir Engineering Workshop 6

7 STEPPING UP Hypothetical Geothermal Well, SuperWell vs. WELL, Stepping Up Pressure (bara), Temperature ( o C) Depth (m) SuperWell Pressure WELL Pressure SuperWell Temperature WELL Temperature January, 28 Stanford Geothermal Reservoir Engineering Workshop 7

8 R831, STEPPING DOWN R831, SuperWell vs. Measured, Stepping Down Depth (m) Pressure (bara), Temperature ( o C) SuperWell Pressure SuperWell Temperature Measured Pressure Measured Temperature January, 28 Stanford Geothermal Reservoir Engineering Workshop 8

9 R831, STEPPING UP, 26 o C Depth (m) R831, SuperWell vs. Measured, Stepping Up 26 o C Bottom Hole Temperature Pressure (bara), Temperature ( o C) SuperWell Pressure SuperWell Temperature Measured Pressure Measured Temperature January, 28 Stanford Geothermal Reservoir Engineering Workshop 9

10 R831, STEPPING UP, 199 o C Depth (m) R831, SuperWell vs. Measured, Stepping Up 199 o C Bottom Hole Temperature Pressure (bara), Temperature ( o C) SuperWell Pressure SuperWell Temperature Measured Pressure Measured Temperature January, 28 Stanford Geothermal Reservoir Engineering Workshop 1

11 R831, OUTPUT CURVE 14 R831, SuperWell vs. Measured, Output Curve 12 Mass Flow Rate (kg/s) Well Head Pressure (bara) SuperWell, 26oC SuperWell, 199oC WELL Measured January, 28 Stanford Geothermal Reservoir Engineering Workshop 11

12 WK232, STEPPING DOWN WK232, SuperWell vs. Measured, Stepping Down Pressure (bara), Temperature ( o C) Depth (m) SuperWell Pressure Measured Pressure SuperWell Temperature Measured Temperature January, 28 Stanford Geothermal Reservoir Engineering Workshop 12

13 WK232, STEPPING UP WK232, SuperWell vs. Measured, Stepping Up Pressure (bara), Temperature ( o C) Depth (m) SuperWell Pressure Measured Pressure SuperWell Temperature Measured Temperature January, 28 Stanford Geothermal Reservoir Engineering Workshop 13

14 WK232, OUTPUT CURVE 25 WK232, SuperWell vs. Measured, Output Curve Mass Flow Rate (kg/s) Well Head Pressure (bara) SuperWell Leaver Measured January, 28 Stanford Geothermal Reservoir Engineering Workshop 14

15 CONCLUSIONS High quality results are easily obtained. Further testing is needed to validate robustness. Multiple and/or distributed feed zones can be handled. Spreadsheet format is very popular; it improves productivity. There are still a number of improvements that can be made: Down hole pumps need to be addressed. Gases and solids may need to be addressed. Water phase transitions need to be addressed: from subcooled liquid to saturated liquid, to two-phase flow of liquid and vapour, to saturated vapour, to superheated vapour. January, 28 Stanford Geothermal Reservoir Engineering Workshop 15

16 ACKNOWLEDGEMENTS The Geothermal Institute, University of Auckland, NZ Dr. Sadiq Zarrouk, my advisor Greg Ussher and Peter Barnett of Sinclair Knight Merz Technical staff and management at Boart Longyear, Century Resources, Contact Energy, and GNS Sciences Electronic steam table functions from Paul Bixley of Bixley Geothermal Consultants and Roland Horne of Stanford University The entire staffs of Grafton Hall, the Geothermal Institute, and the University of Auckland January, 28 Stanford Geothermal Reservoir Engineering Workshop 16

17 REFERENCES BRENNAND, A.W. AND WATSON, A. (1987) ENGINEERING SCIENCES DATA UNIT (1971) FREESTON, D.H. AND HADGU, T. (1987) HAALAND, S.E. (1983) HADGU, T. (1989) KARAALIOGLU, H. (1998) LEAVER, J.D. AND FREESTON, D.H. (1987) ROTORUA GEOTHERMAL TASK FORCE (1985) SUBARKAH, F. (21) SUGANDHI, A. (1997) SUTOYO (21) January, 28 Stanford Geothermal Reservoir Engineering Workshop 17