Paromita Deb Publications Content

Publications

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Underlined names are links to current or past GEG members

REFEREED PUBLICATIONS IN JOURNALS

7. 
Deb, P., G. Giordano, X. Shi, F. Lucci, and C. Clauser, An approach to reconstruct the thermal history in active active magmatic systems: Implications for the Los Humeros volcanic complex, Mexico. , Geothermics, 96/102162, 2021. [Download PDF] [View Abstract]\(Reconstructing the thermal history in active volcanic complexes characterized by multiple magmatic events is challenging due to the limited knowledge of the nature and extent of the transient heat sources. Although understanding of the geometry and architecture of a magmatic system is of prime importance for accurate temperature assessments, it is still one of the most uncertain parameters in numerical models. In this work, we presented a methodology for thermal assessment in active volcanic systems, whereby field-based geological, geochemical and petrological data are integrated to define the transient heat sources of a magma plumbing system. This time-varying heat source conceptual model is applied in the Los Humeros Volcanic Complex, an active Quaternary caldera complex in the Trans Mexican Volcanic Belt, for evaluating the thermal footprint related to the major volcanic events. The site is characterized by two caldera-forming eruptions, the Los Humeros (164 000 years ago) and the Los Potreros (69 000 years ago) and numerous episodes of post-caldera bi-modal volcanism during Holocene period (8 000 – 3 000 years old). The transient nature of the heat sources is implemented as time-varying temperature boundary conditions and the complete temporal evolution for a period of 182 000 years is simulated in 13 modeling stages. The thermal impact due to the voluminous caldera-forming events and the later short-lived magma pockets of Holocene ages is simulated by emplacing heat sources in the numerical model distributed heterogeneously in space and active at different instants of time. The depth, volume and age of the magma pockets are constrained from geochemical, petrological, geochronological and thermo-barometric analysis of erupted material. The present temperature state obtained from this approach agrees well with the temperature data recorded in the geothermal wells. The thermal footprint of the individual volcanic events indicates that almost 80 % of the present-day thermal contribution results from the massive caldera-forming events. The post-caldera Holocene magma pockets had additionally increased temperatures locally by 10 % - 20 % depending on the volumes and ages of the magma pockets. The present-day thermal regime of the younger Holocene magma pockets suggests existence of super-hot resources at shallow depths in the southern part of the geothermal field, making it a potential site for future exploration activities.)\

6. 
Deb, P., S. Salimzadeh, D. Vogler, S. Düber, C. Clauser, and R. R. Settgast, Verification of coupled hydraulic fracturing simulators using laboratory-scale experiments, Rock Mechanics and Rock Engineering, 54, pp. 2881-2902, 2021. [Download PDF] [View Abstract]In this work, we aim to verify the predictions of the numerical simulators, which are used for designing field-scale hydraulic stimulation experiments. Although a strong theoretical understanding of this process has been gained over the past few decades, numerical predictions of fracture propagation in low-permeability rocks still remains a challenge. Against this background, we performed controlled laboratory-scale hydraulic fracturing experiments in granite samples, which not only provides high-quality experimental data but also a well-characterized experimental set-up. Using the experimental pressure responses and the final fracture sizes as benchmark, we compared the numerical predictions of two coupled hydraulic fracturing simulators—CSMP and GEOS. Both the simulators reproduced the experimental pressure behavior by implementing the physics of Linear Elastic Fracture Mechanics (LEFM) and lubrication theory within a reasonable degree of accuracy. The simulation results indicate that even in the very low-porosity (1–2%) and low-permeability ($10^{-18} m^2 - 10^{-19} m^2$) crystalline rocks, which are usually the target of EGS, fluid-loss into the matrix and unsaturated flow impacts the formation breakdown pressure and the post-breakdown pressure trends. Therefore, underestimation of such parameters in numerical modeling can lead to significant underestimation of breakdown pressure. The simulation results also indicate the importance of implementing wellbore solvers for considering the effect of system compressibility and pressure drop due to friction in the injection line. The varying injection rate as a result of decompression at the instant of fracture initiation affects the fracture size, while the entry friction at the connection between the well and the initial notch may cause an increase in the measured breakdown pressure.

5. 
Weydt, L., A. Ramirez-Guzman, A. Pola-Villasenor, B. Lepillier, J. Kummerow, G. Mandrone, C. Comina, P. Deb, and et al., Petrophysical and mechanical rock property database of the Los Humeros and Acoculco geothermal fields (Mexico), Earth System Science Data , 13, pp. 571-598, 2020. [Download PDF] [View Abstract]Petrophysical and mechanical rock properties are key parameters for the characterization of the deep subsurface in different disciplines such as geothermal heat extraction, petroleum reservoir engineering or mining. They are commonly used for the interpretation of geophysical data and the parameterization of numerical models and thus are the basis for economic reservoir assessment. However, detailed information regarding petrophysical and mechanical rock properties for each relevant target horizon is often scarce, inconsistent or distributed over multiple publications. Therefore, subsurface models are often populated with generalized or assumed values resulting in high uncertainties. Furthermore, diagenetic, metamorphic and hydrothermal processes significantly affect the physiochemical and mechanical properties often leading to high geological variability. A sound understanding of the controlling factors is needed to identify statistical and causal relationships between the properties as a basis for a profound reservoir assessment and modeling. Within the scope of the GEMex project (EU H2020, grant agreement no. 727550), which aims to develop new transferable exploration and exploitation approaches for enhanced and super-hot unconventional geothermal systems, a new workflow was applied to overcome the gap of knowledge of the reservoir properties. Two caldera complexes located in the northeastern Trans-Mexican Volcanic Belt-the Acoculco and Los Humeros caldera were selected as demonstration sites. The workflow starts with outcrop analog and reservoir core sample studies in order to define and characterize the properties of all key units from the basement to the cap rock as well as their mineralogy and geochemistry. This allows the identification of geological heterogeneities on different scales (outcrop analysis, representative rock samples, thin sections and chemical analysis) enabling a profound reservoir property prediction. More than 300 rock samples were taken from representative outcrops inside the Los Humeros and Acoculco calderas and the surrounding areas and from exhumed "fossil systems" in Las Minas and Zacatlán. Additionally, 66 core samples from 16 wells of the Los Humeros geothermal field and 8 core samples from well EAC1 of the Acoculco geothermal field were collected. Samples were analyzed for particle and bulk density, porosity, permeability, thermal conductivity, thermal diffusivity, and heat capacity, as well as ultrasonic wave velocities, magnetic susceptibility and electric resistivity. Afterwards, destructive rock mechanical tests (point load tests, uniaxial and triaxial tests) were conducted to determine tensile strength, uniaxial compressive strength, Young's modulus, Poisson's ratio, the bulk modulus, the shear modulus, fracture toughness, cohesion and the friction angle. In addition, X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses were performed on 137 samples to provide information about the mineral assemblage, bulk geochemistry and the intensity of hydrothermal alteration. An extensive rock property database was created (Weydt et al., 2020; https://doi.org/10.25534/tudatalib-201.10), comprising 34 parameters determined on more than 2160 plugs. More than 31 000 data entries were compiled covering volcanic, sedimentary, metamorphic, and igneous rocks from different ages (Jurassic to Holocene), thus facilitating a wide field of applications regarding resource assessment, modeling and statistical analyses.

4. 
Deb, P., D. Knapp, G. Marquart, C. Clauser, and E. Trumpy, Stochastic workflows for the evaluation of Enhanced Geothermal System (EGS) potential in geothermal greenfields with sparse data: the case study of Acoculco, Mexico, Geothermics, 88/101879, 2020. [Download PDF] [View Abstract]\(This paper presents a workflow for resource characterization and assessment of exploration geothermal fields with minimum data. Our approach utilizes stochastic methods to estimate the temperature distribution at potential target depths by focusing on the impact of uncertain input parameters such as thermal conductivity and porosity. We first perform stochastic forward simulations to determine the initial steady-state thermal field and subsequently quantify the uncertainty via a Monte Carlo approach known as Sequential Gaussian Simulation (SGSim). Next, we analyze the in-field likelihood of success for Enhanced Geothermal Systems by simulating hypothetical energy production scenarios based on existing geothermal installations. This approach is applied to the case study of a Hot Dry Rock geothermal field with two exploration wells, located in Acoculco, Mexico. Data scarcity in this field necessitates the use of stochastic methods for plausible prediction of reservoir temperature used to determine the accessible thermal power. Once reliable temperature estimates are obtained at potential target depths, we simulate production scenarios by assuming a prior successful stimulation process in the existing wells. In addition to providing preliminary estimates of thermal power for different injection/production rates, stimulated volumes and created permeability, we present the long-term impact of production on the temperature and pressure fields.)\

3. 
Deb, P., S. Düber, C. Guarnieri Calo’ Carducci, and C. Clauser, Laboratory-scale hydraulic fracturing dataset for benchmarking of enhanced geothermal system simulation tools, Scientific Data, 7/220, 2020. [Download PDF] [View Abstract]\(Successful design of enhanced geothermal systems (EGSs) requires accurate numerical simulation of hydraulic stimulation processes in the subsurface. To ensure correct prediction, the underlying model assumptions and constitutive relationships of simulators need to be verified against experimental datasets. With the aim of generating laboratory-scale benchmark datasets, a state-of-the-art testing facility was developed, allowing for experiments under controlled conditions. Samples of size 30 cm × 30 cm × 45 cm were subjected to confining stresses while high-pressure fluid was injected into the sample through a pre-drilled borehole, where a saw-cut notch was used to initiate a penny-shaped fracture. Fracture growth and propagation was monitored by measuring pressure data and acoustic emissions detected using 32 seismic sensors. Subsequently, samples were split along the fracture plane to outline the created fracture marked by a red-dyed injection fluid. Finally, a 2D fracture contour was generated using photogrammetry. Presented datasets, accessible via a public repository, include experiments on granite and marble samples. They can be used for verifying and improving numerical codes for field stimulation designs.)\

2. 
Aguilar, A., P. Deb, and G. Izquierdo, Conceptual analysis of geothermal neighboring zones characterized with contrasting behavior: case study from a Mexican geothermal field, International Journal of Hydrology, 3/3, pp. 175-183, 2019. [Download PDF] [View Abstract]\(In Mexico, there are many geothermal fields, which are characterized by high temperature but low permeability. In this work one of these fields is studied, which is a producer with high enthalpy but low mass flow production. The scope of this work is to analyze two neighboring areas of Los Humeros geothermal field (LHGF); whose performance is contrasting. According to productivity behavior, it was found that low permeability of rock formation is related with unfavorable balance between exploitation and water entrance as recharge. Analysis of static temperature profiles of some wells of the field provides temperature range between 300 and 360°C at the bottom. During drilling, low fluid circulation loss (no more than 20m3/hr) is observed in wells of this study zone. However, there is a marked difference, in productive characteristics in wells, located in neighboring zone. In this study, the behavior of producer wells located at the western side of the unproductive zone is compared with the unproductive wells. The main conclusion resulting from this study is that the presence of geological structures influences the productive or unproductive behavior of the wells. As a practical application of this study evaluation of stored heat in area of non-producer wells, and its recovery through the use of non- conventional techniques, is proposed. One of these, are related to the methodology of Enhanced Geothermal Systems (EGS).\)

1. 
Weydt, L., K. Baer, C. Colombero, C. Comina, P. Deb, and et al., Outcrop analogue study to determine reservoir properties of the Los Humeros and Acoculco geothermal fields, Mexico, Advances in Geosciences , 45, pp. 281-287, 2018. [Download PDF] [View Abstract]\(The Los Humeros geothermal system is steam dominated and currently under exploration with 65 wells (23 producing). Having temperatures above 380 °C, the system is characterized as a super hot geothermal system (SHGS). The development of such systems is still challenging due to the high temperatures and aggressive reservoir fluids which lead to corrosion and scaling problems. The geothermal system in Acoculco (Puebla, Mexico; so far only explored via two exploration wells) is characterized by temperatures of approximately 300 °C at a depth of about 2 km. In both wells no geothermal fluids were found, even though a well-developed fracture network exists. Therefore, it is planned to develop an enhanced geothermal system (EGS). For better reservoir understanding and prospective modeling, extensive geological, geochemical, geophysical and technical investigations are performed within the scope of the GEMex project. Outcrop analogue studies have been carried out in order to identify the main fracture pattern, geometry and distribution of geological units in the area and to characterize all key units from the basement to the cap rock regarding petro- and thermo-physical rock properties and mineralogy. Ongoing investigations aim to identify geological and structural heterogeneities on different scales to enable a more reliable prediction of reservoir properties. Beside geological investigations, physical properties of the reservoir fluids are determined to improve the understanding of the hydrochemical processes in the reservoir and the fluid-rock interactions, which affect the reservoir rock properties.\)


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PROCEEDINGS REFEREED

4. 
Deb, P., D. Knapp, G. Marquart, and C. Clauser, Numerical Modeling of Production Scenarios for Engineered Geothermal System (EGS) in Acoculco, Mexico, Proceedings WGC 2020+1, 2021. [View Abstract]\(Acoculco has been identified as a potential site for an EGS (Enhanced/Engineered Geothermal System) in Mexico. Within the Horizon 2020 project GEMex, it is investigated as an exploration field. In the present study, we describe the initial steady-state thermal modeling for Acoculco using stochastic forward simulations. We focus on the impact of uncertain input parameters such as thermal conductivity and porosity on the reservoir temperature at different target depths prior to production. Uncertainty is quantified in a Monte Carlo approach, using the algorithm of Sequential Gaussian Simulation (SGS). From the stochastically parametrized model, we extract the mean temperature of our target reservoir rocks from the ensembles of possible realizations. Following this, we analyze the likelihood of success of an EGS in this field by evaluating production scenarios from two different target reservoir rocks, skarn and granite. Simulations are performed using the existing wells as a geothermal doublet. These simulations investigate the impact in the temperature and pressure fields as a result of different injection rates, permeability, and volume of stimulated zone for a production period of 30 years. This study does not attempt to address the technicalities associated with designing a stimulation concept in this field, but rather focuses on the effect of production on the temperature and pressure field considering that a stimulation treatment has successfully resulted in a productive geothermal doublet.\)

3. 
Deb, P., D. Knapp, C. Clauser, and G. Montegrossi, Modeling natural steady-state of super-hot geothermal reservoir at Los hUmeros, Mexico, Proceedings EGC 2019, 2019. [View Abstract]\(Within the framework of GEMex, a Horizon 2020 project (Grant Agreement No. 727550), we model the initial natural state of the super-hot reservoir system of Los Humeros. This is achieved by solving the porous flow and heat transport equations in a gridded, structural 3D model of Los Humeros using the SHEMAT-Suite (Simulator for Heat and Mass Transport) software (Rath et al., 2006, Clauser, 2003). Initially, we perform purely conductive simulations and check the simulated temperatures against the temperatures measured at the well bottoms. We tested several conductive scenarios to obtain an understanding of the pattern of the basal specific heat flow under the Los Humeros caldera complex.\)

2. 
Deb, P., S. Salimzadeh, S. Dueber, and C. Clauser, Laboratory experiments and numerical simulations of hydraulic fracturing for enhanced geothermal systems, Proceedings EGC 2019/ISBN-978-2-9601946-1-6, 2019. [View Abstract]\(Hydraulic fracturing experiments are performed on large igneous and metamorphic rock samples of size 300 mm × 300 mm × 450 mm at controlled conditions in the laboratory. The fractures are created by injecting high-pressure fluid into the rock. The growth and propagation of fractures and the associated micro-fractures are monitored via acoustic emission data recorded by transducers attached to the samples. These data sets then serve as benchmark data for verifying existing or new hydraulic stimulation codes which are used for field-scale stimulation design.\)

1. 
Deb, P., D. Vogler, S. Dueber, P. Siebert, S. Reiche, C. Clauser, R.R. Settgast, and K. Willbrand, Laboratory Fracking Experiments for Verifying Numerical Simulation Codes, 80th EAGE Conference and Exhibition, pp. 1-4, 2018. [Download PDF] [View Abstract]Carefully designed and well monitored experiments are irreplaceable when it comes to producing reliable data sets for a detailed understanding of physical processes, such as hydraulic fracturing. While such experiments provide insight into the governing physical processes, numerical simulations provide additional information on system behaviour by enabling a straightforward study of parameter sensitivity. In this study, we focus on both these aspects. We report on results from (1) a benchmark experimental facility for performing hydraulic fracturing experiments on large rock samples in the laboratory under controlled conditions and (2) numerical simulations of these experiments using programs, which, in future, may be used for designing hydraulic stimulation layouts. We conduct series of experiments in order to ensure reproducibility and accuracy of the measurements. This experimental data set is then shared with several research institutes to be used for verifying their simulation software. Results from the simulation provide further insight regarding parameters, which contribute to uncertainties during measurements. Detailed study of the sensitive parameters help us to improve our experimental set up further and to perform future experiments under even better controlled conditions.