Sumit Mukhopadhyay - Academia.edu (original) (raw)

Papers by Sumit Mukhopadhyay

Transport in Porous Media, Feb 1, 2011

Injecting CO 2 into a subsurface formation causes a buildup of pressure in the vicinity of the in... more Injecting CO 2 into a subsurface formation causes a buildup of pressure in the vicinity of the injection well. While a large injection rate can reduce the cost associated with injection, an indefinitely large injection rate can result in excessive formation damage. To obtain an optimal injection rate without exceeding the safe pressure limits, one will like to have some knowledge of the transient pressure buildup characteristics resulting from a particular injection rate. While elaborate numerical simulations can provide reliable pressure buildup predictions, they require extensive knowledge about the formation, which is normally not available at the start of an injection process. To alleviate this problem, using some simplifying assumptions, we have developed a solution to predict the transient buildup of pressure resulting from injection of supercritical carbon dioxide from a partially penetrating well into a gas reservoir. The solution in space and time is first obtained in the Fourier-Laplace transform space, and then inverted back into real space (in cylindrical coordinates) and time. We use the solution to study pressure transient characteristics for different formation permeabilities and anisotropy ratios. Results obtained using the solution compared well with those from numerical simulations.

Lawrence Berkeley National Laboratory, Jun 4, 2008

... Page 2. 1 Estimation of Host Rock Thermal Conductivities Using the Temperature Data From the ... more ... Page 2. 1 Estimation of Host Rock Thermal Conductivities Using the Temperature Data From the Drift Scale Test at Yucca Mountain, Nevada S. Mukhopadhyay and YW Tsang Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California Abstract ...

Lawrence Berkeley National Laboratory, Feb 26, 2009

Flowing fluid temperature logging (FFTL) has recently been proposed as a method to locate flowing... more Flowing fluid temperature logging (FFTL) has recently been proposed as a method to locate flowing fractures. We argue that FFTL, backed up by data from high-precision distributed temperature sensors, can be a useful tool in locating flowing fractures and in estimating the transport properties of unsaturated fractured rocks. We have developed the theoretical background needed to analyze data from FFTL.

This paper investigates the impact of proposed repository thermal-loading on mountain-scale flow ... more This paper investigates the impact of proposed repository thermal-loading on mountain-scale flow and heat transfer in the unsaturated fractured rock of Yucca Mountain, Nevada. In this context, a model has been developed to study the coupled thermal-hydrological (TH) processes at the scale of the entire Yucca Mountain. This mountain-scale TH model implements the current geological framework and hydrogeological conceptual models, and incorporates the latest rock thermal and hydrological properties. The TH model consists of a two-dimensional north-south vertical cross section across the entire unsaturated zone model domain and uses refined meshes near and around the proposed repository block, based on the current repository design, drift layout, thermal loading scenario, and estimated current and future climatic conditions. The model simulations provide insights into thermally affected liquid saturation, gas-and liquid-phase fluxes, and elevated water and rock temperature, which in turn allow modelers to predict the changes in water flux driven by evaporation/condensation processes, and drainage between drifts.

Prediction of the amount of water that may seep into the waste emplacement drifts is an important... more Prediction of the amount of water that may seep into the waste emplacement drifts is an important aspect of assessing the performance of the proposed geologic nuclear waste repository at Yucca Mountain, Nevada. The repository is to be located in thick, partially saturated fractured tuff that will be heated to above-boiling temperatures as a result of heat generation from the decay of nuclear waste. Since water percolating down towards the repository will be subject to vigorous boiling for a significant time period, the superheated rock zone (i.e., rock temperature above the boiling point of water) can form an effective vaporization barrier that reduces the possibility of water arrival at emplacement drifts. In this paper, we analyze the behavior of episodic preferential flow events that penetrate the hot fractured rock, and we evaluate the impact of such flow behavior on the effectiveness of the vaporization barrier.

Nuclear technology

... Résumé / Abstract. Predicting the amount of water that may seep into waste emplacement drifts... more ... Résumé / Abstract. Predicting the amount of water that may seep into waste emplacement drifts is important for assessing the performance of the proposed geologic repository for spent nuclearfuel and high-level radioactive waste at Yucca Mountain, Nevada. ...

International Journal of Heat and Mass Transfer, 2014

ABSTRACT A theoretical model for carbon dioxide (CO2) migration in tilted aquifers with groundwat... more ABSTRACT A theoretical model for carbon dioxide (CO2) migration in tilted aquifers with groundwater flow is presented to evaluate the injection of CO2 into a geological formation. Capillary force in the flow of two immiscible fluids in a porous medium creates a saturation transition zone, where the saturation changes gradually. A vertical equilibrium assumption is employed to solve for the capillary pressure. Initially we verify our analytical model without slope and incoming ground water. Next the effects of sloped angle and an incoming ground water are studied. The asymmetrical distribution is fully incorporated in our analysis presented in this work, which provides essential information for CO2 injection period and reservoir capacity. In the limiting case of no sloped stratum and no incoming groundwater flow as well as no transition zone, the results for our analysis compare very well with prior works. For the stratum with a slope angle, CO2 will migrate further in the upper side of CO2 injection point. The incoming underground water helps CO2 move further on the up-dip side of the CO2 injection point where CO2 flow direction is the same as the incoming underground water. The existence of a critical velocity when the incoming CO2 at the injection point will only move to the up-dip side is established. In this work, for the first time we account for the injection velocity and the saturation transition zone as well as a sloped incoming groundwater flow.

$Research paper thumbnail of Determination of transport properties from flowing fluid temperature logging in unsaturated fractured rocks: Theory and semi-analytical solution$

Water Resources Research, 2008

Environmental Earth Sciences, 2012

Because of the complex nature of subsurface flow and transport processes at geologic carbon stora... more Because of the complex nature of subsurface flow and transport processes at geologic carbon storage (GCS) sites, modelers often need to implement a number of simplifying choices while building their conceptual models. Such simplifications may lead to a wide range in the predictions made by different modeling teams, even when they are modeling the same injection scenario at the same GCS site. Sim-SEQ is a new model comparison initiative with the objective to understand and quantify uncertainties arising from conceptual model choices. While code verification and benchmarking efforts have been undertaken in the past with regards to GCS, Sim-SEQ is different, in that it engages in model comparison in a broader and comprehensive sense, allowing modelers the choice of interpretation of site characterization data, boundary conditions, rock and fluid properties, etc., in addition to their choice of simulator. In Sim-SEQ, 15 different modeling teams, nine of which are from outside the USA, are engaged in building their own models for one specific CO 2 injection field test site located in the southwestern part of Mississippi. The complex geology of the site, its location in the water leg of a CO 2 -EOR field with a strong water drive, and the presence of methane in the reservoir brine make this a challenging task, requiring the modelers to make a large number of choices about how to model various processes and properties of the system. Each model team starts with the same characterization data provided to them but uses its own conceptual models and simulators to come up with model predictions, which can be iteratively refined with the observation data provided to them at later stages. Model predictions will be compared with one another and with the observation data, allowing us to understand and quantify the model uncertainties.

Volatile organic chemicals from nonaqueous phase liquids trapped in soil spread quickly both into... more Volatile organic chemicals from nonaqueous phase liquids trapped in soil spread quickly both into the atmosphere and the groundwater system, resulting in long-lasting pollution of the environment. The extent and speed of spread is strongly influenced by the heterogeneities present in the soil, which interact with the various mechanisms of transport in a complex manner. A semianalytical model is presented to investigate the effect of soil-heterogeneities on the spreading of pollutants from a nonaqueous phase liquid trapped in a soil. Based on field evidence, soil heterogeneities are modeled as a self-similar fractal process, and diffusive transport of organic chemicals in such a substrate is studied. Various mechanisms of, and resistance to, transport of these contaminants are considered, and it is illustrated how each of these are altered by the presence of heterogeneities. More specifically, it is shown that, while the transport processes at early time are governed by volatilization and dissolution and are quite unaffected by the heterogeneities, the transport processes at late time are strongly dependent on the heterogeneities of the soil and its sorption characteristics. In addition, how failure to recognize these heterogeneities in the soil may result in unsuccessful design of appropriate remediation techniques is discussed.

A large-scale in situ heater test was conducted at Yucca Mountain, Nevada, in order to better und... more A large-scale in situ heater test was conducted at Yucca Mountain, Nevada, in order to better understand the coupled thermal, hydrological, mechanical, and chemical processes that may occur in the fractured rock mass around a geologic repository for high-level radioactive waste. During and after the four-year heating phase of the test, time-lapse geophysical measurements (e.g., cross-borehole ground-penetrating radar) and thermal-hydrological data (e.g., temperature and neutron-probe-derived water content) were collected, making possible a novel application of hydrogeophysics. Here we describe a joint inversion methodology that combines geophysical and thermal-hydrological data to estimate (1) the thermal-hydrological parameters (such as permeability, porosity, thermal conductivity, and parameters describing the capillary pressure and relative permeability functions) that are necessary for modeling the flow of fluids and heat in the subsurface, and (2) the parameters of the petrophy...

$Research paper thumbnail of Parameter estimation from flowing fluid temperature logging data in unsaturated fractured rock using multiphase inverse modeling$

Water Resources Research, 2009

1] A simple conceptual model has been recently developed for analyzing pressure and temperature d... more 1] A simple conceptual model has been recently developed for analyzing pressure and temperature data from flowing fluid temperature logging (FFTL) in unsaturated fractured rock. Using this conceptual model, we developed an analytical solution for FFTL pressure response, and a semianalytical solution for FFTL temperature response. We also proposed a method for estimating fracture permeability from FFTL temperature data. The conceptual model was based on some simplifying assumptions, particularly that a single-phase airflow model was used. In this paper, we develop a more comprehensive numerical model of multiphase flow and heat transfer associated with FFTL. Using this numerical model, we perform a number of forward simulations to determine the parameters that have the strongest influence on the pressure and temperature response from FFTL. We then use the iTOUGH2 optimization code to estimate these most sensitive parameters through inverse modeling and to quantify the uncertainties associated with these estimated parameters. We conclude that FFTL can be utilized to determine permeability, porosity, and thermal conductivity of the fracture rock. Two other parameters, which are not properties of the fractured rock, have strong influence on FFTL response. These are pressure and temperature in the borehole that were at equilibrium with the fractured rock formation at the beginning of FFTL. We illustrate how these parameters can also be estimated from FFTL data. from flowing fluid temperature logging data in unsaturated fractured rock using multiphase inverse modeling, Water Resour. Res., 45, W04414,