Report 2, 1993 GEOTIlERMAL DEVELOPMENT IN TIlE PHILIPPINES Zosimo F. Sarmiento, UNU Geothermal Training Programme, Orkustofnun - National Energy Authority, Grensasvegur 9, 108 Reykjavik, ICELAND Work address: Reservoir Engineering and Resource Management, Geothermal Division, PNOC - Energy Development Corporation, PNPC Complex .. Merritt Road, Ft. Bonifacio, Makati, Metro Manila, PHILIPPINES 3 PREFACE Since the fou ndation of the UNU Geothermal Training Programme in Iceland in 1979, it has been customary to invite annually one geothermal expert to come to Iceland as a UNU Visiting Lecturer. The UNU Visiting Lecturers have been in residence in Reykjavik from one to eight weeks. They have given a series of lectures on their speciality and held discussion sessions with the UNU Fellows attending the Training Programme. The lectures of the UNU Visiting Lecturers have also been open to the geothermal community in Iceland, and have always been well attended. It is the good fortune of the UNU Geothermal Training Programme that so many distinguished geothermal specialists with an international reputation have found time to visit us. Following is a list of the UNU Visiting Lecturers during 1979-1993: 1979 Donald E. White United States 1980 Christopher Armstead United Kingdom 1981 Derek H. Freeston New Zealand 1982 Stanley H. Ward United States 1983 Patrick Browne New Zealand 1984 Enrico Barbier Italy 1985 Bernardo S. Tolentino Philippines 1986 C. Russel James New Zealand 1987 Robert Harrison United Kingdom 1988 Robert O. Fournier United States 1989 Peter Ottlik Hungary 1990 Andr. Menjoz France 1991 Wang Ii.yang P_R. China 1992 Patrick Muffler United States 1993 Zosimo F. Sarmiento Philippines The UNU Visiting Lecturer of 1993, Mc. Zosimo F. Sarmiento is the manager of the Reservoir Engineering and Management Section of the Geothermal Division of the Philippine National Oil Company (PNOC). He was a UNU Fellow in Iceland in 1980, and is the first former trainee to be invited to join the distinguished list of UNU Visiting Lecturers. The Studies Board of the Training Programme decided to invite him on the occasion of the 15th anniversary of the Training Programme. The Philippines are amongst the leading users of geothermal energy in the world for electricity production. The Geothermal Division of the PNOC is probably the organization with the largest number of staff and the largest amount of activity in geothermal exploration and development in the world at present. It is therefore of great value for the participants of the UNU Geothermal Training Programme to learn from the experience of the Philippines. We are grateful to Sammy Sarmiento for giving us an insight into the various aspects of the exploration and management of the geothermai resources of the Philippines in his five lectures in Reykjavik in August 1993, and for preparing the lecture notes that are presented here. Ingvar Birgir Fridleifsson, director, United Nations University, Geothermal Training Programme. 4 TABLE OF CONlENTS Page PREFACE . ... .... .... ..... .... .... ... .. ... .. ........ ........ 3 1. UPDATE ON GEOTHERMAL DEVELOPMENT IN THE PHILIPPINES ....... 8 1.1 Introduction . .... ......... .... ........... ... .. .... ... 8 1.2 Geothermal historical performance .... .................... ........ 9 1.3 Geothermal power development plan 1992-2000 ... .. •. .• . ..... 10 1.4 PNOC-EDC steam field development plan .. ..... ... • .. .... ..... 13 1.5 Non-electrical application ........... ... ..... .. .. ... 21 1.6 PG! steam field development plan ..... .... ....... .. .• . • ....... 21 1.7 Geothermal manpower development . .. .. .. ... .. .. ...... 22 1.8 Build-operate-transfer projects. .. 25 1.9 Drilling programme .......... ..... .. .. ... .. ..... 25 1.10 Funding requirements ........ ... .. .. .. .. ..... 25 1.11 Environmental management programme . ....... .. .. • .. ...... 26 1.12 Conclusions ... ............ .. .... .... ... .. .. .. .... ....... 27 2. RESERVOIR ENGINEERING ASPEcrs OF ASSESSING GEOTHERMAL RESOURCES IN THE PHILIPPINES . .. 29 2.1 Introduction. .. 29 2.2 Downhole measurements . .. 29 2.3 Discharge stimulation. .. 35 2.4 Bore output measurements .... ..... ............. .... ... ..... 39 2.5 Reserve estimation .......... ..... .......... .. .. ..... .... 42 2.6 Lumped parameter modelling reservoir simulation .... .. ..... .. 47 2.7 Conclusions. .. 49 3. STRATEGIES IN THE DEVELOPMENT AND MANAGEMENT OF GEOTHERMAL RESOURCES IN THE PHILIPPINES . • . 50 3.1 Introduction . .................... .................... .... 50 3.2 Resource development strategies ...... ........... .. .... 50 3.3 Production philosophy ........ ... ...•........ .. .. •. ..... 51 3.4 Resource management strategies ...... ........ ......... .. ..... 54 3.5 Conclusions. .. 70 4. OPTIMIZATION OF THE TONGONAN GEOTHERMAL RESERVOIR .. .... 71 4.1 Introduction . .......... .......... ............ ....... ....... 71 4.2 Characteristics and performance of the Tongonan reservoir ....... .. 72 4.3 Performance forecast of the field . .. 73 4.4 Power station models. 75 4.5 Conclusions. .. 79 5. A CASE OF RESERVOIR RESPONSE TO CHANGE IN REINJECTION STRATEGY: THE PALINPINON I PRODUCTION FIELD ........ ...... 80 5.1 Introduction . .... ................ ........ ... ....... ....... 80 5.2 Reservoir description . .. 80 5.3 Initial development strategy ... ..... .... .. .. ....... .... .. 80 5.4 Palinpinon I power station loading . .. 83 5.5 Palinpinon I mass withdrawal and reinjection ............ ..... ....... 84 5 Page 5.6 Reservoir pressure response. • . • . .. 85 5.7 Changes in downhole temperatures . ..• . .. ...... .. ... 87 5.8 Changes in bore output .............. .... • ....... ... .. .... 91 5.9 Field output response .... .... .. .... • .. ........ ..... .. .... 93 5.10 Conclusions . .. .... ........• . ... ..•.. .... .. ..... .. .... 95 ACKNOWLEDGEMENTS. • • . • . • . • . .. % REFERENCES .. ..... .. ... • . • . .•. • . •. .... .. .. • . ..... 97 usr OF HGURES 1. Geothermal areas in the Philippines ...... ...................... ........ 8 2. Historical statistics of various energy sources in the energy mix of the Philippines .... 9 3. Power generation mix of various energy sources in the Philippines. .. 10 4. Target power generation mix of various sources of energy (1992-2000) ... .. ... 12 5. The share of geothermal energy in the country's energy and power generation mix .. 12 6. Target energy mix of various sources of energy (1992-2000) . .......... ...... 13 7. Islands to be interconnected through submarine cables .... ........ .. .. 13 8. The location of wells at the Bacman geothermal field ................ ..... 14 9. Proposed Bacman I binary power plant scheme ..................... ...... 15 10. Proposed scheme for bi-phase power plant in Bacman well PAL-14D .. ....... 16 11. Well location map of the Palinpinon geothermal field ................ ..... 16 12. Location map of Northern Negros geothermal project . .. 17 13. Well location map of the greater Tongonan geothermal field. .. 18 14. Well location map of Ml. Apo geothermal field .................. .. ....... 19 15. Schematic diagram of the drying plant facility in Palinpinon geothermal field . .. 22 16. Examples of static formation temperature test results . ... .. .. .. ... ...... 30 17. Examples of results from injectivity tests before and after hydrofracturing . ...... 31 18. Examples of heat-up data identifying permeable zones ...... ......... .. .... 32 19. Example of temperature profiles showing boiling in the wellbore . .. 32 20. Example of temperature profiles showing downflow in the wellbore . .. 32 21. Examples of temperature profiles with reversals at the bottom. .. 33 22. Examples of wells with linear temperature gradient . .. .... ....... .. .. 33 23. Reservoir pressures in Philippine geothermal fie lds .. .......... .. .. 34 24. Analysis of temperature profiles for the application of air compression techniques in discharge stimulation. .. 36 25. Examples of wells successfully stimulated by steam injection . .. 37 26. Examples of wells where boiler stimulation attempts failed . .. 38 27. A typical set-up of a coiled tubing unit for gas lift ing stimulation . ... .. .. .... 39 28. Examples of output trends of two big wells in the Philippines .... ..... .. .... 41 29. Examples of wells with wellbore and formation controlled output ....... ....... 43 30. Different uncertainty distribution models used in Monte Carlo reserve estimation ... 44 31. Malitbog, frequency distribution of the reserve estimate . ....... .. ... .... .. 46 32. Malitbog, reserve cumulative frequency distribution . .. 46 33. The Palinpinon reservoir grid model used in reservoir simulation. .. 47 6 Page 34. Schedule of make-up and replacement well drilling for Sogongon, Palinpinon field 48 35. The conceptual model of Tongonan geothermal field. .. 48 36. Simulated performance prediction of Tongonan in two production scenarios ....... 49 37. Schematic diagram of the cold injection scheme for Baeman I production field ..... 52 38. An alternative steam condensate disposal scheme ................. _ . ..... 52 39. The total field output curve of Tongonan I showing optimum pressure ... ....... 53 40. Comparison of wells' output at two casing size configurations ........ .. ....... 54 41. Comparison of field capacity estimates based on James' method and station plant metering ......... .... .. 56 42. Magnesium tracer breakthrough used in estimating waterflows . .. 57 43. Comparison of waterflow measurements using downhole flowmeter and magnesium