Potential for enhanced geothermal systems in low permeability limestones – stimulation strategies for the Western Malm karst (Bavaria)

Hofmann, Hannes; Blöcher, Guido; Börsing, Nele; Maronde, Nico; Pastrik, Nicole; Zimmermann, Günter

doi:10.1016/j.geothermics.2014.03.003

Cited by 20 publications

(16 citation statements)

References 20 publications

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“…The Molasse basin is a foreland basin north of the Alps that formed due to continental collision. As a target geothermal reservoir formation, the Upper Jurassic Malm underlies the Molasse sediments and is confined by the Mesozoic crystalline basement Mavko et al (2003) and the bulk modulus of titanium dioxid is taken from Carmichael (1984 (Hofmann et al, 2014). The massive facies is mainly dolomitized and has a high permeability, due to recrystallization and karstification.…”

Section: Experimental Procedures 41 Sample Materialsmentioning

confidence: 99%

“…The quantitative correlation between static and dynamic moduli in combination with sonic logs and seismic data provide the input elastic parameters to populate geomechanical models. Such geomechanical models can be employed to predict the induced stresses and the resulting deformation, caused by production and injection of water from and into geothermal reservoirs, respectively (Cacace et al, 2013;Hofmann et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Static and Dynamic Moduli of Malm Carbonate: A Poroelastic Correlation

Hassanzadegan

Guerizec

Reinsch

et al. 2016

Pure Appl. Geophys.

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The static and poroelastic moduli of a porous rock, e.g. the drained bulk modulus, can be derived from stress-strain curves in rock mechanical tests and the dynamic moduli, e.g. dynamic Poisson's ratio, can be determined by acoustic velocity and bulk density measurements. As static and dynamic elastic moduli are different a correlation is often required to populate geomechanical models. A novel poroelastic approach is introduced to correlate static and dynamic bulk moduli of outcrop analogues samples, representative of Upper-Malm reservoir rock in the Molasse basin, southwestern Germany. Drained and unjacketed poroelastic experiments were performed at two different temperature levels (30 and 60• C). For correlating the static and dynamic elastic moduli, a drained acoustic velocity ratio is introduced, corresponding to the drained Poisson's ratio in poroelasticity. The strength of poroelastic coupling, i.e. the product of Biot and Skempton coefficients here, was the key parameter. The value of this parameter decreased with increasing effective pressure by about 56% from 0.51 at 3 MPa to 0.22 at 73 MPa. In contrast, the maximum change in Pand S-wave velocities was only 3% in this pressure range. This correlation approach can be used in characterizing underground reservoirs, and can be employed to relate seismicity and geomechanics (seismo-mechanics).

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Section: Experimental Procedures 41 Sample Materialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Static and Dynamic Moduli of Malm Carbonate: A Poroelastic Correlation

Hassanzadegan

Guerizec

Reinsch

et al. 2016

Pure Appl. Geophys.

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“…9). Cacace et al (2013) have investigated the influence of the damage zone on the productivity of the geothermal reservoir, while Hofmann et al (2014) have addressed the potential of a hydraulically induced fracture on the reservoir productivity. The model spans an area of 8730 m times 9760 m and has a maximum vertical extension of 1080 m. It includes a major ENE-WSW striking fossil normal fault surrounded by a damage zone 160 m wide.…”

Section: Virtual Case Study Iii: Fault Dying Out Laterallymentioning

confidence: 99%

“…The model spans an area of 8730 m times 9760 m and has a maximum vertical extension of 1080 m. It includes a major ENE-WSW striking fossil normal fault surrounded by a damage zone 160 m wide. The distance between the assumed fracture and the damage zone is about 98 m at reservoir depth and the fracture has a half-length if 145 m and a total height of 210 m (Hofmann et al 2014). The model domain is constrained by two isohypses along the SW and NE borders and a third fault zone constrains the domain along the NW border.…”

Section: Virtual Case Study Iii: Fault Dying Out Laterallymentioning

confidence: 99%

“…On the one hand, we describe a geometric processing tool to convert models of geological structures (including fault zones and fractures) and well trajectories into a volumetric mesh suitable for dynamic forward reservoir simulations. We have tested its robustness and performance against synthetic (Blöcher et al 2010a;Cherubini et al 2013) and realistic case studies Hofmann et al 2014). …”

Section: Introductionmentioning

confidence: 99%

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MeshIt—a software for three dimensional volumetric meshing of complex faulted reservoirs

Cacace

Blöcher

2015

Environ Earth Sci

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Flow, mass and energy transport processes in natural reservoirs are controlled to a large degree by the presence of geological heterogeneities including structures such as fractures and fault zones embedded in a spatially varying three-dimensional (3D) porous matrix of the reservoir. Despite recent advances, currently, state-of-theart models rely on a number of simplifications partly related to our inability to represent heterogeneities as observed in the field into dynamic model realizations. In this respect, an adequate geometric representation of the discrete system is a basic requirement. In this study, we show how fundamental concept from computational geometry can be assembled and used to bridge the gap between geological and dynamic forward models. The result is an automated, open source software solution (MeshIt) to generate quality 3D meshes suitable for the study of flow and transport processes in faulted and fractured reservoirs. The software enables us to integrate into a 3D volumetric representation dipping structures, comprising fault zones and fractures as well as inclined well paths. This permits us to correctly simulate interactions between discrete flow paths along these interacting components and the 3D flow within the reservoir matrix. The crucial factor that makes the approach applicable to real case reservoirs is that all algorithms are local and scalable parallel and have computing times increasing approximately linearly with data volumes. We test the performance and the robustness of the software against three different scenarios of increasing complexity and further discuss current limitations and range of applicability of the software. Although all examples describe geothermal applications, it is worth mentioning that the approach is equally valid for other applications in geoscience from oil and gas industry to carbon capture and sequestration issues.

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Sustainable design of geothermal energy systems for electric power generation using life cycle optimization

et al. 2019

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This paper addresses the sustainable design of organic Rankine cycle based geothermal binary power systems under economic and environmental criteria. A novel superstructure with multiple heat source temperatures, working fluids, and heat rejection systems is proposed. Based on the superstructure, a life cycle optimization model is formulated as a mixed-integer nonlinear fractional program (MINFP) to determine the optimal design. The nonconvex MINFP is efficiently solved by a tailored global optimization algorithm. Two case studies are considered to demonstrate the proposed modeling framework and solution algorithm. One case is based on a geothermal energy system located in California, and the other one is in New York (NY) State. The results show that the geothermal energy system in California is much more economically competitive than that in NY State. The difference in life cycle environmental impacts is less pronounced because the environmental impacts are less sensitive to geological conditions than the capital investments.

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Potential for enhanced geothermal systems in low permeability limestones – stimulation strategies for the Western Malm karst (Bavaria)

Cited by 20 publications

References 20 publications

Static and Dynamic Moduli of Malm Carbonate: A Poroelastic Correlation

Static and Dynamic Moduli of Malm Carbonate: A Poroelastic Correlation

MeshIt—a software for three dimensional volumetric meshing of complex faulted reservoirs

Sustainable design of geothermal energy systems for electric power generation using life cycle optimization

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