A downhole heat exchanger for horizontal wells in low-enthalpy geopressured geothermal brine reservoirs

Abstract

Geothermal energy is a clean, renewable energy resource that is widely available and reliable. Improved drilling and heat conversion systems make geothermal energy an increasingly attractive alternative. Downhole heat exchangers (DHEs) can accelerate the development of geothermal energy by reducing the capital cost and the risk of microquakes or subsidence. However, lowenthalpy geothermal resources are difficult to develop economically because of low heat extraction efficiency. In this study, a coaxial DHE concept is proposed to exploit forced convection driven by a downhole pump inside a horizontal wellbore. Two configurations of the proposed design are introduced, each having different flow paths for working and reservoir fluids. One system-which circulates working fluid through the innermost tubing in the coaxial arrangement has better thermal exchange efficiency of about 29%, and is evaluated by coupling it to a simple model for a binary power generation plant and a geothermal reservoir simulator. Thermodynamic analysis evaluates the DHE performance for electricity generation. A field case study of the Camerina A reservoir (Vermillion Parish, Louisiana) demonstrates a net power of about 350kW can be generated by a turbine even after 30 years of production.

Producing geothermal energy with a deep borehole heat exchanger: Exergy optimization of different applications and preliminary design criteria

“…Some authors consider the DBHE very promising for unexploited geothermal systems where the extraction of brines entails several issues, like volcanic ones (Galoppi et al 2015;. Furthermore, many works have proposed the use of the DBHE to repurpose depleted oil&gas wells Davis and Michaelides 2009;Templeton et al 2014;Feng et al 2015;Noorollahi et al 2015;Wight and Bennet, 2015), where a great amount of hot water is often present and the expensive phases of exploration, drilling and construction have already been concluded. Regarding the final use of the extracted heat, some authors have evaluated the potential electricity production via ORC plants (see Nalla et al 2005;Wang et al 2009;David and Michaelides 2009;Akhmadullin and Tyagi 2014;Noorollahi et al 2015;Wight and Bennet 2015; whereas others of them (see Morita et al 1992;Kohl et al 2002;Mottaghy and Dijkshoorn 2012;Templeton et al 2014;Le Lous et al 2015;Caulk and Tomac 2017;Macenić and Kurevija 2018) recommend the direct use of the heat.…”

“…The literature regarding the deep borehole heat exchanger reports only a few works that include a thermodynamic assessment based on exergy balance (Feng et al 2015;Mokhtari et al 2016;Alimonti et al 2019): all of them analyze a DBHE connected to an Organic Rankin Cycle plant.…”

Numerical Analysis of Enhanced Conductive Deep Borehole Heat Exchangers

“…EGS single-well methods can provide an alternative solution to make stimulation unnecessary, by circulating a working fluid in a sealed well, or by connecting the wellbore to pre-existing fractures or in-situ geothermal fluids [6][7][8][9]. Closed wellbores such as borehole heat exchangers have been conventionally investigated for depths less than 1000 m [10,11].…”

Selecting the Optimal Use of the Geothermal Energy Produced with a Deep Borehole Heat Exchanger: Exergy Performance

“…Five pilot tests have been realized [9][10][11][12][13][14]; in consideration of these tests, the DBHE may be considered to be a very promising technology for volcanic geothermal systems where the extraction of brine entails several issues. The use of the DBHE to repurpose depleted oil and gas wells was also proposed by [15][16][17][18][19][20]. In fact, in hydrocarbon fields, a great amount of hot water is often present and the exploration, drilling and construction steps have been concluded.…”

“…It includes the classification of resources with exergy [25][26][27] the exergy analysis of geothermal power plants [23,[28][29][30], and the low enthalpy applications (ground source heat pumps, district heating and cooling, and thermal storage), see [31][32][33][34][35]. The literature regarding the deep borehole heat exchanger reports only a few works [6,18,36] that include a thermodynamic assessment based on exergy balance: all of them analyze a DBHE connected to an organic Rankine cycle plant.…”