Demonstration of a successful soft chemical stimulation in a geothermal sandstone reservoir in Mezőberény (Hungary)

Brehme, Maren; Markó, Ábel; Osvald, Máté; Zimmermann, Günter; Weinzierl, Wolfgang; Aldaz, Santiago; Thiem, Stefan; Huenges, Ernst

doi:10.1016/j.geothermics.2024.102980

Cited by 5 publications

(1 citation statement)

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“…In this work, we review retardation methods currently applied in or developed for geothermal applications with the aim of an extended penetration depth for improved well rejuvenation or even reservoir-wide chemical stimulation. This explicitly excludes works applying acid stimulation without retardation (e.g., Schulz et al 2022;Brehme et al 2024). Reviews on general chemical stimulation with geothermal context can be found in Portier et al (2007), Huenges (2016), Charalambous (2021), Li et al (2022).…”

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Chemical stimulation of geothermal reservoirs using retarded acid systems: current developments and potential directions

Grifka,

Licha,

Heinze

2024

Geotherm Energy

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Stimulation techniques to enhance fluid pathways are an important tool to make geothermal projects economically feasible. So far, hydraulic stimulation is used almost exclusively for reservoir-wide improvement of the permeability, but induced seismicity poses a challenge. Chemical stimulation on the other hand has been limited to the close vicinity of the borehole and has barely been considered for the creation of enhanced geothermal reservoirs. However, retardation mechanisms reducing the chemical reaction rate can be used to increase the radius of the chemical stimulation thus enabling a reservoir-wide enhancement of fluid pathways. In this work, we review the technologies of retardation mechanisms for chemical stimulation in geothermal systems and identify five groups of retardation techniques: (i) causing impaired mobility of the acid, e.g., by gelling agents; (ii) causing an impaired dissociation, e.g., by the in-situ generation of the reactive compounds; (iii) blocking the mineral surface area, e.g., by alternating injections of pad fluids and acids; (iv) reducing the reaction rate constant, e.g., by cooling; and (v) changing the chemical equilibrium through chelating agents. We found that most applications are currently based on the use of impaired dissociation, but present research focuses on the development and application of chelating agents. Most of these retardation techniques are adopted from the hydrocarbon industry, but there are several techniques that have not been applied in the geothermal context so far for various reasons. We identify a distinctive lack of in-depth descriptions of the retardation techniques in various studies—mostly to protect intellectual property. However, in the light of public concern regarding fracking techniques and to independently assess potential environmental hazards, scientific examination of proposed techniques is indispensable.

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