Low Enthalpy Geothermal Energy Research Articles

Thermomineral waters and hydrogeothermal resources in the western part of the Chalkidiki Peninsula (Northern Greece)

The geologic conditions in the western part of the Chalkidiki Peninsula are favourable for the formation, reproduction and accumulation of six to seven types of mineral waters, and of considerable resources of low-enthalpy geothermal energy and endogeneous CO2. Low-mineralized thermal waters with nitrogen gas composition and comparatively low (25-45°C) temperatures form small accumulations related to fault structures in ophiolitic bodies and metamorphic rocks in the NW of the peninsula. Within the other, bigger part of the peninsula, deposits and regional reservoirs of carbonated (saturated in endogenous CO2) mineral waters with bicarbonate (HCO3), bicarbonate-chloride (HCO3-Cl) or chloride (Cl) composition have been formed. The total mineralisation of these waters increase from 2-5 to 30-40 g/l in function of the depth of the reservoirs, and the temperature increase is from 20-30° to 80-90°, correspondingly. The principal reservoir of carbonated mineral waters and geothermal resources is a considerably tectonised formation of Upper Jurassic limestones which has been buried under Neogene marine sediments at depth from 200-300 to 2000-3000 m. The study and prospects for development of Chalkidiki centers of multiseasonal and curative tourism and a parallel industrial exploitation of geothermal energy and natural CO2.

French low enthalpy geothermal energy, assessment of 10 years of operation

The utilization of geothermal energy saw a period of great expansion during the 1980's in a particularly favourable economic and energy environment. Some 50 projects were set up, delivering heat to more than 250,000 dwelling equivalents. The financial health of a geothermal project, however, is not immutable, and changes with the variations in a number of parameters such as the price of imported energy, inflation, the interest rate on loans, etc. The purpose of this article is to attempt to measure the consequences of variations in these parameters and to assess the present and foreseeable profitability of operating geothermal projects.

Developments in geothermal energy in Mexico—Part twenty six: Experimental assessment of an ammonia/water absorption cooler operating on low enthalpy geothermal energy

Mexico possesses large amounts of geothermal brine at temperatures which are too low to enable electricity to be generated efficiently and economically. Most of the geothermal fields in Mexico are located near important agricultural areas. Perishable food losses in Mexico, resulting from inadequate handling and cold storage facilities, vary from 35 to 50%. In order to prove the technical feasibility of operating heat-driven absorption cooling systems on low enthalpy geothermal energy, a prototype ammonia/water absorption cooler was installed in the Cerro Prieto geothermal field, where the ambient temperatures exceed 40°C and the cooling water temperatures reach 30°C. The unit has operated successfully with evaporative cooling loads exceeding the design value. The experimental data obtained will provide an excellent basis for the design of large scale heat-driven absorption refrigeration systems.

Comparison of U.K. geothermal and U.S. oil well costs

As part of the development of a complete cost model for low-enthalpy geothermal energy systems, a detailed investigation was carried out on the major cost components involved in drilling wells in sedimentary regions. A drilling cost model, WDCM, was produced as a result of this work. This paper reports the use of the model in explaining differences in the cost of U.S. oil and gas wells and U.K. low-enthalpy geothermal wells, in particular. A comparison with the cost of French low-enthalpy geothermal wells is included.

Offset-dependent seismic amplitudes from karst limestone in northern Belgium

In northern Belgium, karst limestones at the top of the Lower Carboniferous form a water-bearing reservoir at depths varying from 1000 to more than 2000 m. The temperature of the water and the hydrological characteristics make it an attractive reservoir for low enthalpy geothermal energy extraction. The depth range of the reservoir, its structure, and the sealing characteristics of the overlying rocks imply that it might form a trap for natural gas. The hypothesis that natural gas might he present in this Lower Carboniferous reservoir was recently confirmed by the discovery of a dissolved gas mixture, with methane, at the Merksplas-Beerse well. In the light of this varied economic potential of the reservoir, a preliminary seismic exploration programme was carried out by the Belgian Geological Survey. The reservoir properties, however, are rather heterogeneously distributed, as the pore space is made up of dissolution pockets and fractures. Therefore, a detailed analysis of the seismic reflection data was instigated in order to assess the potential of the seismic method for the detection of the karst distribution. This paper deals with the results of this analysis.

Developments in geothermal energy in Mexico—Part five: The commissioning of an ammonia/water absorption cooler operating on low enthalpy geothermal energy

An attractive way of using low enthalpy geothermal energy is to produce refrigeration using heat driven absorption coolers. This would enable food to be stored for long periods for use in national emergencies. Research and development is required on small systems before large scale systems can be designed with confidence. An experimental ammonia/water absorption cooler has been designed with a cooling capacity of 10.5 kW and installed at the Los Azufres geothermal field. The unit has operated successfully with generator temperatures as low as 91°C and with cooling chamber temperatures down to −5°C.

Topography and the subsurface temperature regime in the western canadian sedimentary basin: implications for low-enthalpy geothermal energy recovery

Bottom-hole temperature data have been used to investigate the relationship between topographic relief and the sub-surface temperature regime in the Alberta part of the western Canadian sedimentary basin. Five sections through the basin have been considered, and temperature gradients from both above and below the Paleozoic erosional surface have been correlated with surface topography. The results indicate that for regions of higher surface elevation the temperature gradients above the Paleozoic surface are less than those in regions of low elevation. Below the Paleozoic surface, the relationship between temperature gradient and surface topography is much less certain, but it appears that there is a general increase of gradient associated with high relief. These results are consistent with those expected to be associated with gravity imposed water motion related to recharge and discharge areas. Cross-sections showing temperature as a function of depth and distance indicate that the effect of regional changes in surface topography is felt to great depth, and perturbations to the thermal regime are caused by both local and regional water flow patterns. As a consequence, the influence of topography on the hydrodynamics and the temperature regime greatly affects the geothermal energy potential of the area.

GEOTHERMAL ENERGY: REPORT OF A SYMPOSIUM

( Symposium held at the University of Durham on 15 th November, 1980) I. INTRODUCTION The aims of the symposium were to summarise the current state of knowledge concerning geothermal energy and the possibilities for its economic extraction in the United Kingdom. The interpretation of geochemical data on the thermal fluids in certain prospective areas was also discussed. The President, Dr G. A. L. JOHNSON, opened the meeting and presented an introductory contribution on behalf of Professor SIR KINGSLEY DUNHAM who was indisposed and unable to be present. Professor M. H. P. BOTT (University of Durham) gave details of the origins of the escaping heat in the earth and of the possible reasons for the differences in heat flow in various parts of the crust. He made particular reference to heat flow over the Alston Block originating in the Weardale Granite. Dr R. A. DOWNING (Institute of Geological Sciences) discussed the potential geothermal systems in the United Kingdom and referred to the results of drilling the first geothermal test well at Marchwood, near Southampton. Dr W. M. EDMUNDS (Institute of Geological Sciences) explained how geochemical techniques gave important information on likely reservoir temperatures at depth, the source of the thermal fluids and highlighted problems such as corrosion and difficulties in disposing of the fluids once they had reached the surface. II. THE EXPLOITATION OF THE EARTH’S CRUSTAL HEAT FLOW In giving Professor Sir Kingsley Dunham’s introductory contribution the President explained the differences between high- and low-enthalpy geothermal energy. In the former case, ...

Low enthalpy geothermal energy resources in Denmark

The deep oil exploration drillings in Denmark have shown that especially the Danish Embayment contains low enthalpy geothermal resources associated with warm aquifers. The most promising reservoirs have been found in highly permeable Upper Triassic sand and sandstone beds, which cover at least 5000 km2 at depths of 2000–3000 m and at temperatures of 60–100°C. The porosity of the main reservoir is of 15–25%, and the permeability is presumed to be approximately 1 darcy (≃ 10−12 m2) or higher. A layer thickness of 30–60 m has been observed on a number of localities. Also the Middle Jurassic and the Lower Triassic contain reservoirs of interest. A major geothermal exploration work is planned with seismic investigations, drillings to depths of 2000–4000 m and probably establishment of pilot district heating plants.