# Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics
## 2 An Overview of Published Articles
(contribution 4) discusses the importance of tracking temperature changes by measuring resulting resistivity changes within low-enthalpy geothermal reservoirs to ensure sustainable energy production and avoid early thermal breakthroughs. While the controlled-source electromagnetic method (CSEM) allows for the estimation of subsurface resistivity, its capability to monitor subtle resistivity changes typical of low-enthalpy reservoirs has not been proven. The study presents a feasibility study examining CSEM monitoring of 4-8 \(\Omega\cdot\)m resistivity changes in a deep low-enthalpy reservoir model, focusing on the TU Delft campus geothermal project. Utilizing a surface-to-borehole CSEM setup, this study investigates the sensitivity of CSEM data to disk-shaped resistivity changes to various radii and return temperatures. The results indicate that CSEM monitoring is robust against undesired effects such as random noise and survey repeatability errors. Modeled differences in electric field suggest successful detection of resistivity changes in the low-enthalpy reservoir, with greater changes in monitoring data observed with increasing resistivity change radius or magnitude. The findings suggest that CSEM could be a promising geophysical tool for monitoring small resistivity changes in low-enthalpy reservoirs, offering potential benefits for geothermal energy production. \"Feasibility Assessment of Acid Gas Injection in an Iranian Offshore Aquifer\" by [PERSON] et al. (contribution 5) explores the feasibility of acid gas injection (AGI) operations in an offshore saline aquifer in Iran. AGI serves as a means of disposing of acid gas, primarily composed of H\({}_{2}\)S and CO\({}_{2}\), often originating from petroleum production or processing. This study outlines a comprehensive procedure for evaluating the suitability of a field or formation for AGI, incorporating sensitivity analysis of various parameters to minimize costs and time. The key aspects of the feasibility assessment include examining reservoir properties, geomechanical aspects, caprock integrity, and gas plume dynamics. The Surmeh formation emerges as a promising candidate for AGI due to its composition of upper dolomite and lower carbonate rock formations. Geomechanical analysis reveals critical parameters such as pore pressure and fracture pressure, while caprock integrity, particularly within the Hith formation, is identified as crucial for containment and long-term stability. Seismic mapping is employed to assess variations in caprock thickness, which influence containment effectiveness. This study also highlights the role of capillary trapping in short-term gas entrapment and plume distribution, with numerical simulations being used to elucidate the impact of heterogeneous rock properties on these processes. The paper projects approximately 2 trillion cubic feet (TCF) of acid gas injection into the Surmeh formation, with a recommended injection rate of 180 million standard cubic feet per day (MMSCFD). The formation's tightness limits injectivity, with a maximum achievable rate of 7 MMSCFD at a permeability of 1 millidarcy (mD). However, higher porosity and permeability enable more efficient injection without fracturing the formation, necessitating the implementation of two injection wells, each with a capacity of 90 MMSCFD. \"Application of Bonded-Block Models to Rock Failure Analysis\" by [PERSON] (contribution 6) explores the use of bonded-block models in the analysis of rock failure processes. Discrete element models, particularly bonded-particle models, have been widely utilized for this purpose, but bonded-block models have emerged as a promising alternative in recent years. These models employ polygonal or polyhedral elements instead of circular or spherical particles. The paper outlines the fundamental principles of bonded-block models and their application in simulating failure in rock materials. It identifies critical governing parameters and discusses their influence on the modeling outcomes.