Stimulation of geothermal energy resources

Kruger, P.

doi:10.2172/5120254

Cited by 3 publications

(2 citation statements)

References 6 publications

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“…A large volume of computational data pertaining to different aspects of mining thermophysics, based on the first of equations (I.1) of the two-temperature model and its simplified versions with closure provided by expressions such as Eq. (I.7) are given in the books [23,24].…”

Section: I1 Equations Of the Two-temperature Modelmentioning

confidence: 99%

Heat Transfer in Dispersions

Buyevich,

Alexandrov

2005

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Section: I1 Equations Of the Two-temperature Modelmentioning

confidence: 99%

Heat Transfer in Dispersions

Buyevich,

Alexandrov

2005

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“…Hydraulic stimulation is a pre‐requisite for the development of deep geothermal reservoirs (enhanced geothermal systems, Kruger 1975; Jung & Weidler 2000; Gérard et al 2006; Zimmermann et al 2006) as well as an often used procedure for tertiary exploitation of hydrocarbon reservoirs (Agarwal et al 1979; Economides & Nolte 2000). During stimulation massive fluid injection into boreholes with successively increasing flow rates gives rise to a number of hydromechanical effects, notably momentary elastic and eventually permanent inelastic deformation of hydraulic conduits.…”

Section: Introductionmentioning

confidence: 99%

Hydromechanical analyses of the hydraulic stimulation of borehole Basel 1

Ortiz

Renner

Jung³

2011

Geophysical Journal International

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S U M M A R YWe analysed the response of the underground penetrated by borehole Basel 1 to two pumping sequences, a pre-stimulation test (flow rate up to 10 L min −1 ) followed by a step-up stimulation (starting from 10 L min −1 up to 3380 L min −1 ), performed to generate a heat exchanger at about 5 km depth. Throughout the test sequences an increase in flow rate resulted in an increase in injection pressure. Yet, sudden pressure drops ( 0.1 MPa) as well as a continuous decrease in pressure occurred at constant flow rates above 100 L min −1 . Analysis of the pre-stimulation record strongly suggests the existence of a vertical fracture prior to stimulation. We focused on two contrasting scenarios in fracture height and normalized fracture conductivity out of the range of possible geometrical characteristics of this pre-existent fracture as constrained by numerical modelling. Independent of chosen scenario, the initially modest pressure increase can only be modelled by hydraulic properties that change with fluid-pressure. The spatiotemporal characteristics of the pressure distributions differ significantly for the two scenarios; the 'formation linear flow'-like pattern found for the scenario with the larger fracture height of 100 m matches geometrically better with the oblate seismic cloud than the 'radial flow'-like pattern found for the smaller fracture height of 10 m. It is problematic to explain the drops in pressure observed at constant flow rate by lateral or vertical extension of the pre-existent vertical fracture in classical tensile hydrofracturing mode considering the persistent increase in pressure with every step-up in flow rate throughout the entire stimulation and the lack of reproducible and distinct instantaneous shut-in pressures. We suggest shearing and wingextension of the pre-existent fracture(s) as an alternative mechanism since this mechanism (a) is consistent with the absence of a distinct breakdown in pressure, (b) can be initiated at fluid pressures below the least principal stress and (c) can explain the pronounced change in hydraulic properties with increasing injection pressure as well as the observed rapid small pressure drops at constant flow rate.

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Permeability changes during the flow of water through westerly granite at temperatures of 100°–400°C

Summers¹,

Winkler²,

Byerlee³

1978

J. Geophys. Res.

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Changes in permeability have been studied during the flow of water through granite for periods of time up to 17 days at temperatures of 100°, 200°, 300°, and 400°C with a constant confining pressure of 500 bars, differential stresses of 0–3500 bars, inlet pore pressure of 275 bars, and outlet pressure of 1 bar. In all cases the initial permeability at elevated temperatures was found to be higher by 1–2 orders of magnitude than the permeability at room temperature, perhaps because of thermal stress cracking. The high initial permeability did not persist with time and in nearly all cases decreased significantly during the first ½ day of water flow. Dissolution of plagioclase and quartz was concentrated near the inlet, where the pore pressure was highest. Precipitation occurred throughout the samples because of oversaturation as the pore pressure dropped, causing significant reduction in permeability. The final permeability after 10 days was less at 300°C than at lower temperatures, and measurable flow stopped in most of the 400°C samples.

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Stimulation of geothermal energy resources

Cited by 3 publications

References 6 publications

Heat Transfer in Dispersions

Heat Transfer in Dispersions

Hydromechanical analyses of the hydraulic stimulation of borehole Basel 1

Permeability changes during the flow of water through westerly granite at temperatures of 100°–400°C

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