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Exploration and development of wet steam and hot water fields
NEWS Exploration and Development of Wet Steam and Hot Water Fields A n o t e b y JOSEPH BARNEA * Luncheon Address, 11 May 1973, National ConJerence on Geothermal Energy, Palm Springs, Cali]ornia. 1 would like to concentrate on a type of geothermal development which, by and large, aoes not yet exist in the United States, but undoumedly wnl become of very great significance in the future, namely, the exploration and development of wet steam fields or hot water helds. A proper understanding ot the signifmance of these fields must start with the recognition that at the m o m e n t many people both at the periphery ot geothermal energy, and also reside the industry, are looking for geothermal steam only, not fully realizing that geothermal energy is a heat source and not only a steam source. This prejudice, if 1 may call it that, in favour of steam, has crept even into legal documents and the now famous federal law on geothermal energy ot December 1970 is called the Geothermal bteam Act, w h e n the proper technical term should have been Geothermal Energy Act. It is geothermal heat which we are seeking for a variety of applications, not only geothermal steam Ior power generation. As nas been pointed out earlier, exploration on a global basis appears to indicate that geothermal steam fields are comparatively rare and, as a rule of thumb, it is now expected that for every geothermal steam field about 20 geothermal hot water fields wilt be found. It is likely therefore that The Geysers field, the biggest dry steam field discovered so far, will not be the predominant type of fields to be found in the United States, but hot water fields, and it is with the latter, its problems and its opportunities that this meeting should get involved. Indeed, there appears to be a feeling in this country, as expressed in some journals, that hot water fields are not understood, the technology is u n k n o w n and that they have higher costs than dry steam fields. This is far from being correct. We have now a n u m b e r of hot water fields in the world and for some of them we have operational experience going back over a substantial n u m b e r o~ years, The Wairakei field in New Zealand is a typical hot water field and part of the proper technology for wet steam development was evolved in New Zealand. It was there that the highly efficient separators were developed which are an essential ingredient in the handling of a hot water field. When we drill into a wet steam field we are drilling into a reservoir where there is hot water under high pressure and when this hot water reaches the well-head separator, the pressure is reduced. Part of the hot water flashes into steam, i.e., about 20%, and the steam is then sent to the power station to produce electricity as in a dry steam power station. We are then left with about 80% by weight of very hot water which, depending on the circumstances, can be used for a variety of purposes and which, in most cases, will have to be handled carefully in order to avoid potential environmental problems. The hot water can be channeled to a nearby river, as in the case of Wairakei, which can absorb the 60 million tons of hot water a year. To avoid the wastage of heat involved in this procedure, the water can be reinjected into the formation, a method the United Nations has developed in El Salvador. In this way, we expect that the life of a reservoir can be extended and the heat balance of the reservoir perhaps also improved. The recharge of the hot water back into a reservoir will always need detailed local studies, but where conditions are favourable, the additional costs are very small, below 1 mill/kWh. Much more attractive economically, however, is the use of the hot water f9 r other purposes and they are numerous. First, more of the hot water can be flashed and more electricity * Director o~ the Resources and Transport Division, United Nations, New York. The views expressed are those of the author and not necessarily those of the United Nations. 76
generated, and it is a matter of cost and local conditions to determine how much of the water should be flashed for power generation. There is a further possibility through a binary cycle or otherwise to further increase the power generationl The normal case is at the present stage to flash about 20'11o and then use the hot water for other p u r p o s e s This hot w a t e r :nay be important for three reasons - - its heat content - - its water content - - its mineral and gas content. The hot water, with its heat content, can be used for a large number of different purposes from house, hospital, mine and other heating purposes to air conditioning and refrigeration, and it is likely that in suitable locations the low cost refrigeration which is possible with hot water, may have significant impact on agriculture and other industries. The application and utiiization of the heat content of the water also allows a sequential use of the hot water where its first use would apply to higher temperature heat followed by subsequent use in glasshouses, geothermal fish farming and other purposes where lower temperature heat is required. The next category is the use of the water content of the hot water part of a wet smam field. This, in water short areas. will allow geothermal desalination without energy cost because geothermal water available from a hot water field could be hotter than required for desalination. It is likely that in appropriate localities geothermal desalination will make a very important contribution to water supply problems in the future and in ~he proposed Water Conference of the United Nations in 1977 which will deal with the water problems of the year 2000, geothermal water supply is one of the items on the agenda. The potential of a hot water field as a source of water supply is very significant because of the large amount of water which can be obtained from such a source. Indeed, in looking into the future, as we did at the closing of the International Geothermal Symposium at Pisa, we saw the use of wet steam fields for the production of geothermal water and the use of low quality (contaminated and brackish) water to recharge the geothermal field, and in this way a geothermal reservoir could be used as a boiler for the large-scale production of fresh water. The third element which can often be found in hot water fields consists of minerals and gases. Here we have to mention that we usually also find in geothermal waters from hot water fields, minerals and gases which we cannot allow to enter the river systems of a country, the fresh ground water aquifers o1: the atmosphere because they can damage the environment. Boron, for instance, is bad if added to irrigation water. We also find hydrogen sulphide and other gases and we sometimes find high mercury concentrations, and it is for this and other reasons that a very early and careful trace mineral and gas analysis is vital. Geothermal waters often contain large quantities of salts, many of which in many localities may be in excess of possible local marketing opportunities. It is therefore essential to give attention to the gases as welt as the mineral content which is or may be harmful to the environment or may be unmarketable. A safe disposal system whenever this is a necessity is therefore required, and since there appear to be no insurmountable technical problems involved, it is therefore only a matter of cost. However, the problem of handling the potentially harmful or unmarketable minerals and gases can be very much eased, and perhaps even solved if we are able to find in the water economically attractive minerals and gases. The experience of the United Nations, which has undertaken detailed trace mineral and gas analysis, leads to the conclusion that in a number of cases we will be able to find valuable constituents in the geothermal water. We have begun to understand the relationship between certain minerals and geothermal provinces, significant perhaps, in the case of mercury, porphyry copper, dispersed gold and silver, and so on. Certain gases appear also to occur either frequently in hot water fields like CO: or rarely such as helium. In the Kizildere field in Turkey, a wet steam field in a limestone area, it has been calculated that, if there were a sufficient market for dry
ice cad other applications of CO,, the sale of this gas would bring in a much higher return than all other applications of the hot water field. After this recital of the principal characteristics of a wet steam field and the variety of the different natural resources involved, it will be appreciated that, in suitable locations and conditions, the multipurpose development of a wet steam field may have higher economic significance and profitability than a dry steam field. It may be useful at this stage to compare within the limits of comparability dry steam fields and wet steam fields from the point of view of productivity. Such comparisons need care because one should compare equals - - in other words, a good dry steam well should only be compared with a good hot water well, an average well with an average well and a low productivity well with another low productivity well. It is also essential to compare wells with equal temperature and diameter so that the technical parameters are fairly equal. If we do this, we will reach a conclusion that a good hot water well will produce three to five times the weight of hot water at approximately the same temperature as compared to a steam well. As the heat content of a ton of steam is approximately two to three times that of a ton of hot water, it nevertheless leads to the conclusion that on a comparative basis a hot water well has a total heat output of about double or more than that of a dry steam well. As a result, even if only 20% of the hot water of a wet steam field is flashed into steam, a hot water well has approximately the same electric generating capacity as a comparable dry steam well. A hot water well, therefore, can generate the same quantity of electricity as a dry steam well, but in addition, large quantities of heat in the form of hot water. Depending on the circumstances, this hot water can represent an additional heat source of greater magnitude than the heat used for electricity generation. The utilization of hot water, given its limited transportability, is basically a local problem, but in the right region and under the right conditions the utilization of such hot water may contribute in a variety of forms to the solution of energy problems in a given area. First let us properly understand the great energy savings, cost reductions and reduction in thermal pollution we can obtain wherever we can apply hot water directly. Let us compare air conditioning. We can use geothermal steam to ~enerate electricity and then use such electricity for air conditiopin~. In this case, as the efficiency in using steam for electricity f,en. eratin~ is less than 30%. 70% of the heat is discarded. Tho electricity thus ~enerated entails further energy losses in r~roriding, air conditioning - - so that as a result perhans only 20% of the energv content of geothermal steam is utilized in air conditioning. The direct, one step use of hot geothermal w;,ter for air conditioning_, using standard eouipment, may onerate at about 80% efficiency - - thus allowing, lower cost. hi~her energy utilization and smaller heat relection. The efficlencv and cost advantages of the direct use of hot geothermal wmer anoly to a wide range of agricultural processes, includln~. refri~.eration, drying, he~tinq otc. Here in the Imperial Valley. with its need for a~zricult, r,~l nrocessing, for air eonditionirm, for refri~,eration and for desalinated water, is the re~ion for the multirmrnose develonment of hot water fields. The full develor~ment in the Imperial Vail---, could become a model for trio world for the efficient utilization of the terse heat content of hot water fields. It should be noted here that geothermal water for direct applications tin air conditioninm refrigeration, etc.) does not need the high temnerature reouired for electricitv ~eneratimz. Furthermore. a full mnhirgurpose develorment of a hot water field with its much hi~ber economic return would also Justify deeoer drilling in regions where the demand for hot water exists and o-ola,,ic and hvdro~eologie conditions apoear favnurahle All this annears to be anDlicable to the lmDerial Valley. At *he suggestion of the United Nations. the Governmerit of Nicaraqua is now considering the central air cor~ditionin~ of Manamm and the nrovision of refri~eratlnn in the ind,,atri~l part of the city - - all based on geothermal hot water. This ormortunitv and challenge of a muhipurnose develor~ment of hot water fields poses, however, serious institutional r~roblems. Pnwer comnanies in many states are not nermitted to deal with water desalination mineral e~traction and. in some cases, they are not allowed to provide hot water for Mr conditioning, heating, refrigeration, etc. On the other hand,
the sate of electricity is reserved for power companies. In this dHficuit situation wnere the power companies have a monopoly posiu~,n on tlae one hand and a very narrow area of activities - - racy arc one commodity companies - - the only way out appears to me to grant to multipurpose geothermal companies tnc r~ght to produce and market all ot their products, ~lJcluclirtg eJcc,r~c]ty, this suggestion may appear in the context o, the present institutional structure to be a novel idea - - to me, ~t is a necessary ana a traditional idea. In the history of ,~merican electricity development, shortcomings at each historic stage have led to new institutional arrangements, from rural power co-operatives to municipal power systems, to governmentowned generating and transmission systems and now, with the advent o~ geotiaermal energy, we have a new set of problems. oeothermal wmer and steam are location-bound - - unlike coal, oil and all diner tuels. A geothermal power station must be built near the geothermal field. Now, if the power company possessing the monopoly for power sales is not willing to build such a station or is unwilling to pay a fair price for steam, the owner of the geothermal field is practically helpless. Moreover, if a hot water field is involved, the power company may legally not be able to undertake a multi-purpose development which may economically and nationally be the best type of developlnent. A iree hand for geothermal developers for a broad development is clearly neecled. "Ibis might also have been in the mind of Congress when iL provided in the Geothermal Steam Act of 1970 that governmental units, including, without limitation, municipalities, may acquire geothermal leases. The freedom for geomermal developers may in some cases reintroduce an element of competition - - perhaps at the wholesale level and at the retail level - - in such a vital service industry as the supply of electricity. Such a competition at this stage of the electricity industry can have only beneficial effects, both for the development of a local energy resource and for the economy as a whole. 1 believe that the expansion of the freedom of geothermal developers may, for all concerned, be more acceptable than delays and deformation which in the end may force the government to step in as it has in the case of river basin development in order to achieve multipurpose development. Geothermal energy is too important a natural resource to be considered only a steam source. Hot water fields are bound to become the most important part of the geothermal industry in this country. If the full potential of these hot water fields is to be fully developed, all parties concerned must co-operate in a spirit of new approaches and new initiatives.
United Nations Geothermal Exploration in Kenya Exploration drilling sites were selected last December in the Olkaria prospect located south of Lake Naivasha A thirteen-kilometer long, 6-inch pipe line is now being constructed from Lake Naivasha to the first site in order to provide water for drilling. In April, the United Nations awarded the drilling contract to Foramines. The contract calls for the drilling of 4500 meters distributed among four holes. Drilling is scheduled to begin in August or September of this year. (j. r. m.)
Present Status and Future Prospect of Geothermal Energy Development in Japan A n o t e by the IAPAN NATIONAL NATURAL RESOURCES DEVELOPMENT COMMITTEE - M a y 1973 Geothermal
Energy
D e v e l o p m e n t in J a p a n Y e s t e r -
day and T o d a y History The utilization of hot spas in Japan for purposes of ceremonial ablution, therapeutical treatment for injuries and illnesses, or plain bathing, has always been a popular practice, and 77
generated, and it is a matter of cost and local conditions to determine how much of the water should be flashed for power generation. There is a further possibility through a binary cycle or otherwise to further increase the power generationl The normal case is at the present stage to flash about 20'11o and then use the hot water for other p u r p o s e s This hot w a t e r :nay be important for three reasons - - its heat content - - its water content - - its mineral and gas content. The hot water, with its heat content, can be used for a large number of different purposes from house, hospital, mine and other heating purposes to air conditioning and refrigeration, and it is likely that in suitable locations the low cost refrigeration which is possible with hot water, may have significant impact on agriculture and other industries. The application and utiiization of the heat content of the water also allows a sequential use of the hot water where its first use would apply to higher temperature heat followed by subsequent use in glasshouses, geothermal fish farming and other purposes where lower temperature heat is required. The next category is the use of the water content of the hot water part of a wet smam field. This, in water short areas. will allow geothermal desalination without energy cost because geothermal water available from a hot water field could be hotter than required for desalination. It is likely that in appropriate localities geothermal desalination will make a very important contribution to water supply problems in the future and in ~he proposed Water Conference of the United Nations in 1977 which will deal with the water problems of the year 2000, geothermal water supply is one of the items on the agenda. The potential of a hot water field as a source of water supply is very significant because of the large amount of water which can be obtained from such a source. Indeed, in looking into the future, as we did at the closing of the International Geothermal Symposium at Pisa, we saw the use of wet steam fields for the production of geothermal water and the use of low quality (contaminated and brackish) water to recharge the geothermal field, and in this way a geothermal reservoir could be used as a boiler for the large-scale production of fresh water. The third element which can often be found in hot water fields consists of minerals and gases. Here we have to mention that we usually also find in geothermal waters from hot water fields, minerals and gases which we cannot allow to enter the river systems of a country, the fresh ground water aquifers o1: the atmosphere because they can damage the environment. Boron, for instance, is bad if added to irrigation water. We also find hydrogen sulphide and other gases and we sometimes find high mercury concentrations, and it is for this and other reasons that a very early and careful trace mineral and gas analysis is vital. Geothermal waters often contain large quantities of salts, many of which in many localities may be in excess of possible local marketing opportunities. It is therefore essential to give attention to the gases as welt as the mineral content which is or may be harmful to the environment or may be unmarketable. A safe disposal system whenever this is a necessity is therefore required, and since there appear to be no insurmountable technical problems involved, it is therefore only a matter of cost. However, the problem of handling the potentially harmful or unmarketable minerals and gases can be very much eased, and perhaps even solved if we are able to find in the water economically attractive minerals and gases. The experience of the United Nations, which has undertaken detailed trace mineral and gas analysis, leads to the conclusion that in a number of cases we will be able to find valuable constituents in the geothermal water. We have begun to understand the relationship between certain minerals and geothermal provinces, significant perhaps, in the case of mercury, porphyry copper, dispersed gold and silver, and so on. Certain gases appear also to occur either frequently in hot water fields like CO: or rarely such as helium. In the Kizildere field in Turkey, a wet steam field in a limestone area, it has been calculated that, if there were a sufficient market for dry
ice cad other applications of CO,, the sale of this gas would bring in a much higher return than all other applications of the hot water field. After this recital of the principal characteristics of a wet steam field and the variety of the different natural resources involved, it will be appreciated that, in suitable locations and conditions, the multipurpose development of a wet steam field may have higher economic significance and profitability than a dry steam field. It may be useful at this stage to compare within the limits of comparability dry steam fields and wet steam fields from the point of view of productivity. Such comparisons need care because one should compare equals - - in other words, a good dry steam well should only be compared with a good hot water well, an average well with an average well and a low productivity well with another low productivity well. It is also essential to compare wells with equal temperature and diameter so that the technical parameters are fairly equal. If we do this, we will reach a conclusion that a good hot water well will produce three to five times the weight of hot water at approximately the same temperature as compared to a steam well. As the heat content of a ton of steam is approximately two to three times that of a ton of hot water, it nevertheless leads to the conclusion that on a comparative basis a hot water well has a total heat output of about double or more than that of a dry steam well. As a result, even if only 20% of the hot water of a wet steam field is flashed into steam, a hot water well has approximately the same electric generating capacity as a comparable dry steam well. A hot water well, therefore, can generate the same quantity of electricity as a dry steam well, but in addition, large quantities of heat in the form of hot water. Depending on the circumstances, this hot water can represent an additional heat source of greater magnitude than the heat used for electricity generation. The utilization of hot water, given its limited transportability, is basically a local problem, but in the right region and under the right conditions the utilization of such hot water may contribute in a variety of forms to the solution of energy problems in a given area. First let us properly understand the great energy savings, cost reductions and reduction in thermal pollution we can obtain wherever we can apply hot water directly. Let us compare air conditioning. We can use geothermal steam to ~enerate electricity and then use such electricity for air conditiopin~. In this case, as the efficiency in using steam for electricity f,en. eratin~ is less than 30%. 70% of the heat is discarded. Tho electricity thus ~enerated entails further energy losses in r~roriding, air conditioning - - so that as a result perhans only 20% of the energv content of geothermal steam is utilized in air conditioning. The direct, one step use of hot geothermal w;,ter for air conditioning_, using standard eouipment, may onerate at about 80% efficiency - - thus allowing, lower cost. hi~her energy utilization and smaller heat relection. The efficlencv and cost advantages of the direct use of hot geothermal wmer anoly to a wide range of agricultural processes, includln~. refri~.eration, drying, he~tinq otc. Here in the Imperial Valley. with its need for a~zricult, r,~l nrocessing, for air eonditionirm, for refri~,eration and for desalinated water, is the re~ion for the multirmrnose develonment of hot water fields. The full develor~ment in the Imperial Vail---, could become a model for trio world for the efficient utilization of the terse heat content of hot water fields. It should be noted here that geothermal water for direct applications tin air conditioninm refrigeration, etc.) does not need the high temnerature reouired for electricitv ~eneratimz. Furthermore. a full mnhirgurpose develorment of a hot water field with its much hi~ber economic return would also Justify deeoer drilling in regions where the demand for hot water exists and o-ola,,ic and hvdro~eologie conditions apoear favnurahle All this annears to be anDlicable to the lmDerial Valley. At *he suggestion of the United Nations. the Governmerit of Nicaraqua is now considering the central air cor~ditionin~ of Manamm and the nrovision of refri~eratlnn in the ind,,atri~l part of the city - - all based on geothermal hot water. This ormortunitv and challenge of a muhipurnose develor~ment of hot water fields poses, however, serious institutional r~roblems. Pnwer comnanies in many states are not nermitted to deal with water desalination mineral e~traction and. in some cases, they are not allowed to provide hot water for Mr conditioning, heating, refrigeration, etc. On the other hand,
the sate of electricity is reserved for power companies. In this dHficuit situation wnere the power companies have a monopoly posiu~,n on tlae one hand and a very narrow area of activities - - racy arc one commodity companies - - the only way out appears to me to grant to multipurpose geothermal companies tnc r~ght to produce and market all ot their products, ~lJcluclirtg eJcc,r~c]ty, this suggestion may appear in the context o, the present institutional structure to be a novel idea - - to me, ~t is a necessary ana a traditional idea. In the history of ,~merican electricity development, shortcomings at each historic stage have led to new institutional arrangements, from rural power co-operatives to municipal power systems, to governmentowned generating and transmission systems and now, with the advent o~ geotiaermal energy, we have a new set of problems. oeothermal wmer and steam are location-bound - - unlike coal, oil and all diner tuels. A geothermal power station must be built near the geothermal field. Now, if the power company possessing the monopoly for power sales is not willing to build such a station or is unwilling to pay a fair price for steam, the owner of the geothermal field is practically helpless. Moreover, if a hot water field is involved, the power company may legally not be able to undertake a multi-purpose development which may economically and nationally be the best type of developlnent. A iree hand for geothermal developers for a broad development is clearly neecled. "Ibis might also have been in the mind of Congress when iL provided in the Geothermal Steam Act of 1970 that governmental units, including, without limitation, municipalities, may acquire geothermal leases. The freedom for geomermal developers may in some cases reintroduce an element of competition - - perhaps at the wholesale level and at the retail level - - in such a vital service industry as the supply of electricity. Such a competition at this stage of the electricity industry can have only beneficial effects, both for the development of a local energy resource and for the economy as a whole. 1 believe that the expansion of the freedom of geothermal developers may, for all concerned, be more acceptable than delays and deformation which in the end may force the government to step in as it has in the case of river basin development in order to achieve multipurpose development. Geothermal energy is too important a natural resource to be considered only a steam source. Hot water fields are bound to become the most important part of the geothermal industry in this country. If the full potential of these hot water fields is to be fully developed, all parties concerned must co-operate in a spirit of new approaches and new initiatives.
United Nations Geothermal Exploration in Kenya Exploration drilling sites were selected last December in the Olkaria prospect located south of Lake Naivasha A thirteen-kilometer long, 6-inch pipe line is now being constructed from Lake Naivasha to the first site in order to provide water for drilling. In April, the United Nations awarded the drilling contract to Foramines. The contract calls for the drilling of 4500 meters distributed among four holes. Drilling is scheduled to begin in August or September of this year. (j. r. m.)
Present Status and Future Prospect of Geothermal Energy Development in Japan A n o t e by the IAPAN NATIONAL NATURAL RESOURCES DEVELOPMENT COMMITTEE - M a y 1973 Geothermal
Energy
D e v e l o p m e n t in J a p a n Y e s t e r -
day and T o d a y History The utilization of hot spas in Japan for purposes of ceremonial ablution, therapeutical treatment for injuries and illnesses, or plain bathing, has always been a popular practice, and 77