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Seismicity, Rock Mechanics and Harnessing Geothermal Energy

Introduction

The geothermal industry faces many challenges that are common to the oil and mining industries. Some of them fall into the category of risks, as in the case of induced seismicity, aquifer contamination and CO2 leakage, while others present a challenge to the operation of geothermal fields and their profitability, such as clogging (mineral precipitations in fractures that close permeable paths) and the presence of corrosive fluids.

A deep synergy between science and industry, with mutual understanding of concerns and respect of interest on both sides, is necessary. One important point is the proper understanding of the risks connected with georesource exploitation in general, not only geothermal energy production.

Mitigating the Risks of Geothermal

Seismicity and Rock Mechanics towards Harnessing of Geothermal Energy

Seismicity

It is well known that increased levels of seismicity are expected with the production of geothermal energy, and there are several aspects that need to be taken into consideration here. First of all, there is safety. This includes the safety of people directly involved in the operation but also the safety of the local community. Secondly, environment. Good care of the environment during operations needs to be taken, considering all of the risks and doing everything possible to minimise them. Monitoring of seismicity can provide an early warning in case of any operations problems. Thirdly, the infrastructure. Monitoring of seismicity can also help with the mitigation of hazards directly affecting the infrastructure of the site (well integrity, casing, boreholes, etc).

Finally, the knowledge. It is extremely important to gather as much information and data as possible during operations. This can be used later by scientists for deeper understanding of the physical processes, performing detailed analyses towards the reduction of potential failures in future operations.

In all of these fields, monitoring seismicity provides quantitative measurements that, when used appropriately, can help mitigate against hazards associated with induced seismicity.

The video above features Piotr Salek from the Institute of Geophysics Polish Academy of Sciences speaking about mitigating the risks and seismic / environmental impact associated with geothermal applications.

Rock Mechanics and Mineral Analysis

Understanding the physical changes in reservoir conditions is a challenging task due to the small amount of information available from the conditions at 2, 3 or 5 kms depth inside the earth. Rock mechanics is a field of research that allows us to understand how fractures behave at those pressure conditions that occur in natural reservoirs. This field of research combines theoretical, experimental and modelling techniques to explain the role of the stress fields in fluid flow and mineralisation in the Earth’s crust, making it crucial to the overall operation. Meanwhile, mineral analysis and geochemistry are tools that allow us to dig into the chemical changes that transform, dissolve or precipitate minerals at depth. The consequences of these changes can deeply affect the efficiency of the whole reservoir. For this reason, it is important to look at the geothermal system as a whole and combine physical-chemical perspectives when exploring, assessing and developing a geothermal field. Catalina Sanchez-Roa from University College London spoke to TWI about rock mechanics and the geological challenges associated with geothermal energy exploitation.

TWI’s Expertise for Geothermal Energy 

TWI’s extended expertise in condition and structural health monitoring can be utilised with relevant techniques that can give major information for the conditions of the reservoir as well as the pipes which are used within the geothermal well. TWI’s expertise in condition and structural health monitoring offers extensive experience in the development of dedicated algorithms which, in combination with appropriate monitoring techniques, can reveal important information for the health of the structure of interest.

TWI’s Involvement with the S4CE Project

TWI is involved in the Science for Clean Energy (S4CE) collaborative project, which is a well-established network of academia, SMEs and end users towards the increased trust of environmental safety of geothermal operations. The project is funded under grant agreement number 764810.

 

The information in this article is taken from the interviews with Piotr Salek and Catalina Sanchez-Roa, which are included in the Insight.

Avatar Sofia Sampethai Project Leader - Condition and Structural Health Monitoring

Sofia is a Project Leader at TWI in the Condition and Structural Health Monitoring section. She is a Chartered Engineer and a Member of the Welding Institute. She has studied Chemical Engineering and her MSc was carried out at ETH Zurich in the department of Process Engineering. Sofia manages funded collaborative projects, including Innovate UK, FP7 and H2020, and the majority of them are in the areas of condition monitoring, sensor development targeting composites failure, and integrity monitoring for casings used in oil and gas industry. She has also been involved in proposal writing for European and national funded projects, and in developing partnerships within industry. Sofia’s work is focused on the research and development of innovative solutions in the area of condition and structural health monitoring.

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