Resource evaluation of geothermal power plant under the conditions of carboniferous deposits usage in the Dnipro-Donetsk depression

The objective of the work is to substantiate the actualization of the problem of obtaining geothermal energy from oil and gas wells of oil and gas production facilities in the central-eastern part of the Dnieper- Donetsk Depression (DDD). The research methodology is based on the collection and statistical processing geophysical data of the DDD oil and gas deposits, the use of balance equations for energy and substance matter. The main result of the work is that the principal technological scheme of the geothermal system has been developed and the geothermal potential of oil and gas wells in the experimental zone has been analyzed. There have been considered the technological and ecological aspects of geothermal heat usage from depleted deposits of the DDD wells, which were disclosed into сarboniferous deposits productive horizons

Geothermal steam condensate reinjection

Geothermal electric generating plants which use condensing turbines and generate and excess of condensed steam which must be disposed of are discussed. At the Geysers, California, the largest geothermal development in the world, this steam condensate has been reinjected into the steam reservoir since 1968. A total of 3,150,000,000 gallons of steam condensate has been reinjected since that time with no noticeable effect on the adjacent producing wells. Currently, 3,700,000 gallons/day from 412 MW of installed capacity are being injected into 5 wells. Reinjection has also proven to be a satisfactory method of disposing of geothermal condensate a Imperial Valley, California, and at the Valles Caldera, New Mexico

Drilling and testing geothermal wells in an active volcanic domain, Puna geothermal field, Hawaii, USA

Thermal Power Company, Operator for the Puna Geothermal Venture which includes AMFAC and Dillingham, has drilled and tested two geothermal wells in the Puna Geothermal Field, Hawaii, USA. The field is located in the East Rift Zone of Kilauea which is one of the world’s most active volcanoes. The wells were drilled to a depth of 7,290 and 8,005 feet and completed with 9 5/8" production casing to 4,200 feet and 7" perforated liner extending to bottom. A high temperature, 660°F plus, two-phase geothermal reservoir was encountered. Noncondensible gas concentration is only 0.2% by weight but contains 1,100 ppm H2S which must be abated to meet environmental concerns. Flow testing proved to be a complex affair. However, 100% steam production has been identified in both wells with the assistance of a separator. These two wells, along with the U.S. Department of Energy/University of Hawaii HGP-A well which now generates 3 MW of electric power, have defined a 25 MW reserve capacity on the Puna Geothermal Venture leasehold. A third well with substantially improved casing design will be drilled by Thermal later in 1984 to refine plans for the wellfield and generating plant

Sustainable Design of Energy Systems - The Case of Geothermal Energy

Geothermal energy is one of the renewable energy resources with a vast potential. It is extended spatially in many areas, isolated from urban areas and direct uses, whereas its utilisation when it is not for electricity production is many times hampered due to lack of a proper development framework. In this work we present a design framework for sustainable geothermal systems incorporating modules covering the various aspects of exploration, utilisation, end-use and management. The overall framework consists of the following sub modules: a. geophysical model of the assessment of the geothermal reservoir capacity b. model for the management of the geothermal wells, pumping and re-injection c. model for the distribution network d. model for the various end-uses, e. environmental model for sustainable operation The overall framework incorporates the basic axes of sustainable development, i.e. resources, economy, environment, energy, technology, society. The theoretical framework is applied to an existing geothermal reservoir which at the current is being underutilized, from an energy, environmental and economic perspective. The search for an optimum design includes the formulation of different scenarios and the multi-criteria decision analysis of them.

Torre Alfina Deep Geothermal Reservoir

The Castel Giorgio-Torre Alfina (CG-TA, central Italy) is a geothermal reservoir whose fluids are hosted in a carbonate formation at temperatures ranging between 120°C and 210°C. Data from deep wells suggest the existence of convective flow. We present the 3D numerical model of the CG-TA to simulate the undisturbed natural geothermal field and investigate the impacts of the exploitation process. The open source finite-element code OpenGeoSys is applied to solve the coupled systems of partial differential equations. The commercial software FEFLOW® is also used as additional numerical constraint. Calculated pressure and temperature have been calibrated against data from geothermal wells. The flow field displays multicellular convective patterns that cover the entire geothermal reservoir. The resulting thermal plumes protrude vertically over 3 km at Darcy velocity of about  m/s. The analysis of the exploitation process demonstrated the sustainability of a geothermal doublet for the development of a 5 MW pilot plant. The buoyant circulation within the geothermal system allows the reservoir to sustain a 50-year production at a flow rate of 1050 t/h. The distance of 2 km, between the production and reinjection wells, is sufficient to prevent any thermal breakthrough within the estimated operational lifetime. OGS and FELFOW results are qualitatively very similar with differences in peak velocities and temperatures. The case study provides valuable guidelines for future exploitation of the CG-TA deep geothermal reservoir

Seismic response to evolving injection at the Rotokawa geothermal field, New Zealand

Catalogs of microseismicity are routinely compiled at geothermal reservoirs and provide valuable insights into reservoir structure and fluid movement. Hypocentral locations are typically used to infer the orientations of structures and constrain the extent of the permeable reservoir. However, frequency-magnitude distributions may contain additional, and underused, information about the distribution of pressure. Here, we present a four-year catalog of seismicity for the Rotokawa geothermal field in the central Taupō Volcanic Zone, New Zealand starting two years after the commissioning of the 140 MWe Nga Awa Purua power station. Using waveform-correlation-based signal detection we double the size of the previous earthquake catalog, refine the location and orientation of two reservoir faults and identify a new structure. We find the rate of seismicity to be insensitive to major changes in injection strategy during the study period, including the injectivity decline and shift of injection away from the dominant injector, RK24. We also map the spatial distribution of the earthquake frequency-magnitude distribution, or b-value, and show that it increases from ∼1.0 to ∼1.5 with increasing depth below the reservoir. As has been proposed at other reservoirs, we infer that these spatial variations reflect the distribution of pressure in the reservoir, where areas of high b-value correspond to areas of high pore-fluid pressure and a broad distribution of activated fractures. This analysis is not routinely conducted by geothermal operators but shows promise for using earthquake b-value as an additional tool for reservoir monitoring and management

Update Heat Flow Density Map for Portugal

New thermal conductivity, heat production and temperature data obtained in Portugal were used to produce a new heat flow density map. Heat flow density values in Portugal vary between 42 and 115 mW/m2 and allow the extrapolation of temperatures to depths not yet reached by existing boreholes. Additionally, temperature maps at 500 and 1000 m depths and a two-dimensional model constructed along a north-south profile in the area where there is more geothermal information are given

Reconstruction of the Past Climate in Southern Portugal from Geothermal Data

The study of the past climate in the territory of mainland Portugal using geothermal data started in 1996. From an initial set of about 90 temperature logs obtained Portugal, eight were chosen as good for estimating ground surface temperature (GST) in the past. The main results from the analysis of the collected geothermal data show, on average, that there has been an increase of the atmosphere mean surface temperature of about 1 K since the middle of the nineteenth century. This conclusion agrees with the results obtained from the analysis of air temperature records that were obtained in the Lisbon weather station since 1856. With the objective of improving the reconstruction of GST history in Portugal one of the eight wells (the TGQC-1 well) was cased and is being used for repeated temperature logging since 1997. The results of the temperature measurements repetition indicate that the warming trend continues to the present day, accelerating in the last 10 to 15 years. Since 2005 a geothermal climate change observatory was installed in the TGQC-1 well to study the air-ground coupling

Analysis of curtailment at The Geysers geothermal Field, California

Geothermal energy has traditionally been viewed as a baseload energy source, but the rapid growth of intermittent renewable energy has led to a need for more flexibility in power generation to avoid mandatory curtailment imposed by grid operators. This study of curtailment at The Geysers provides insights into the magnitude, duration, frequency, temporal and spatial distribution, and potential causes of curtailment events between 2013 and 2018. Annual levels of curtailment range during this period from 9 to 47 GW h, representing 0.15 to 0.81 % of the net generation. Most curtailments occurred at the power plants connected to a lower capacity transmission line and may result from transmission constriction. There is a clear link between negative pricing and economic curtailment, especially when solar production is higher. Economic curtailment events tend to be only a few hours and vary in magnitude up to almost 300 MW, whereas transmission-related curtailment events can be up to several weeks in duration. It is likely that curtailment of geothermal power will be an increasing concern, and could be mitigated by flexible generation strategies and increases in energy storage. It is critical to know the nature of curtailment events so that flexible generation options can be assessed properly