Multiphase Migration Research Articles

Multiphase migration and transformation of BTEX on groundwater table fluctuation in riparian petrochemical sites

Light non-aqueous phase liquids (LNAPL) are considered to be a composition-based risk, containing multiple chemical ingredients that release dissolved- and vapor-phase plumes. In dissolved form, there is a saturation-based risk as the water source expands, affecting groundwater aquifers on a larger scale in the aquifer. As a typical pollutant found in petrochemical contaminated sites, the migration and transformation of benzene, toluene, ethylbenzene, and o-xylene (BTEX) between gas, aqueous, and NAPL phases are distinctly affected by groundwater table fluctuation (GTF). BTEX multiphase migration and transformation pattern in a petrochemical factory at the riverside was simulated based on the TMVOC model in differentiating pollution distribution and interphase transformation under stable or fluctuating groundwater tables conditions. TMVOC model performed an excellent simulation effect on the migration and transformation of BTEX in GTF circumstances. In comparison with the stable groundwater table condition, the BTEX pollution depth under GTF increased by 0.5m, the pollution area increased by 25%, and the total mass increased by 0.12 × 102kg. In both cases, the mass reduction of NAPL-phase pollutants was more significant than the total mass reduction of pollutants, and GTF further promoted the mass conversion of NAPL-phase pollutants to water pollutants. Prominently, as the groundwater table rises, the GTF can correct for evacuation, and the transport flux of gaseous pollutants at the atmospheric boundary decreases with increasing transport distance. Furthermore, descended groundwater table will intensify the transmission flux of gaseous pollutants at the atmospheric boundary with the transmission range expanding, which can be harmful to human health on the surface due to gaseous pollutants entering into the air.

Exsolution effects in CO2 huff-n-puff enhanced oil recovery: Water-Oil-CO2 three phase flow visualization and measurements by micro-PIV in micromodel

CO2 huff-n-puff is one of the most important methods to enhanced oil recovery, which can simultaneously improve oil production and achieve CO2 geological storage. Due to the fluctuation of formation pressure, water-oil-CO2 three phase migration in porous structures was affected significantly by supercritical CO2 exsolution and expansion. However, the existing research on phase distribution is not enough to understand the mechanism of three-phase migration and the essential processes beneath the phase distribution are still not clear. Here, we developed a high-temperature and high-pressure micro-PIV (Particle Image Velocimetry) and fluorescence visualization experimental system (10 MPa, 50°C), which realized the simultaneous measurement of the velocity field and phase distribution of the water-oil-CO2 three-phase. The multiphase migration process under different wettability conditions during the supercritical-subcritical CO2 exsolution were captured. The results showed that the exsolution induced CO2 bubbles expansion in aqueous and oil phase blocked the preferential migration passage and dominated different multiphase migration mechanisms under different wettability. It was found that in water-wet condition, the aqueous phase can still migrate downstream through the water film between the CO2/oil and the wall, unable to further drive CO2/oil downstream. While in oil-wet condition, the aqueous phase eventually broke through the oil phase blocked at throats and formed a new preferential migration passage, pushing part of the oil phase encapsulating CO2 bubbles downstream. Our research reveals the multiphase migration mechanism beneath the phase distribution under different wettability during the exsolution process of the huff-n-puff, which provides a new insight for CO2 enhanced oil recovery and geological storage.

A systematic methodology to migrate complex real-time software systems to multi-core platforms

This paper proposes a systematic three-stage methodology for migrating complex real-time industrial software systems from single-core to multi-core computing platforms. Single-core platforms have limited computational capabilities that prevent integration of computationally demanding applications such as image processing within the existing system. Modern multi-core processors offer a promising solution to address these limitations by providing increased computational power and allowing parallel execution of different applications within the system. However, the transition from traditional single-core to contemporary multi-core computing platforms is non-trivial and requires a systematic and well-defined migration process. This paper reviews some of the existing migration methods and provides a systematic multi-phase migration process with emphasis on software architecture recovery and transformation to explicitly address the timing and dependability attributes expected of industrial software systems. The methodology was evaluated using a survey-based approach and the results indicate that the presented methodology is feasible, useable and useful for real-time industrial software systems.

Application of Inert Gas Tracers to Identify the Physical Processes Governing the Mass Balance Problem of Leaking CO2 in Shallow Groundwater System

The CO2, leaked from a deep storage reservoir, can arrive at the shallow groundwater system. In shallow aquifer, the leaked CO2 forms a multi-phase plume and its mass balance will be controlled by various physical, chemical and biological processes. Inert gases such as sulfur hexafluoride (SF6) and noble gases are biochemically stable in groundwater system which can separate and explain the physical process governing the mass balance of the multi-phase plume. In this study, two pilot tests were conducted using inter gas tracers to evaluate the influence of physical processes on multi-phase plume migration. First injection test was made in Wonju, Korea. Three different tracers including chlorine, helium and argon tracer were jointly injected in 7.5 – 10.5 m below water table and recollected at same point after 1 day drift time in groundwater system. The mass recovery of the Single-Well Tracer Test (SWTT) was 49.3% for SF6, 58.1% for helium, 78.2% for argon, and 73.1% for chlorine. The recovery of inert gas tracers was relative to their solubility. Second injection test was made in Eumseong, Korea. Four tracers such as chlorine, helium, argon, and krypton were released along an induced pressure gradient where 0.0135% of helium, 0.0137% of argon, 0.0602% of krypton, and 75.0% of chlorine were retrieved. In this Inter-Well Tracer Test (IWTT), the recovery of inert gas tracer was also relative to tracer’s solubility. This study suggested the applicability of inert gas tracers to evaluate the mass balance of leaking CO2 plume in shallow aquifer system.

Középső-triász dolomitok képződésének története és töréses deformációja a Szegedi-medence területén

A Pannon-medence aljzatának egyik részmedencéje a Szegedi-medence, mely szénhidrogén-földtani szempontból hazánk egyik kiemelt fontosságú területe. A prekainozoos aljzat legelterjedtebb mezozoos képződményei a középső-triász dolomitok, melyek fontos szerepet töltenek be a terület szénhidrogén-rendszerének felépítésében. Jelen tanulmány célja, hogy az évtizedek óta nem vizsgált képződmények képződéséről és deformációtörténetéről új, korszerű leírást nyújtson. Értelmezésünket általános petrográfiai leírásra, fluoreszcens és katódlumineszcens vizsgálati módszerekre, valamint a területről szóló szakirodalomra alapozzuk.A vizsgált anisusi képződmények változatos partszegélyi, sekélytengeri környezetben ülepedtek le. Ezek a leülepedést követő süllyedés következtében, a sekély és közepes betemetődés után, a kora-krétára juthattak a mély betemetődési diagenezis zónájába. Ezen zónákban a képződmények feltehetően többfázisú, részben szövetmegőrző, részben szövet -romboló dolomitosodási folyamatokon mentek keresztül. A petrográfiai alapon elkülönített dolomit típusok közülközepes vagy mély betemetődési környezetet jeleznek a porfirotópos és cukorszövetű dolomitok, valamint a póruskitöltő nyeregdolomit, de ezek szerepe alárendelt a korábbi dolomitosodási folyamatokhoz viszonyítva. A középső-miocént megelőzően a kőzeteket többször is töréses deformáció érte, melynek hatására breccsa, ezt követően pedig üreg- és repedéskitöltő nyeregdolomit képződött. A nyeregdolomit kristályai több esetben kőolajtartalmú fluidumzárványokat csapdáztak. A dolomittestek felszínközeli helyzetét középső-miocén, abráziósparti kör -nyezetben leülepedett fedőkőzetek jelzik, továbbá dedolomitosodás is kapcsolódhat ehhez a szakaszhoz. A Pannon-medence kialakulásával párhuzamos süllyedés és eltemetődés hatására a képződmények ismét nagy mélységbe kerültek, mely során újabb töréses deformáció és cementáció folyt. A legfiatalabb repedéskitöltő ásványegyüttest fluoreszcens tulajdonságú dolomit, valamint pirit és szilárd bitumen alkotja.A vizsgált dolomitok többfázisú diagenezis- és deformációtörténetéhez többfázisú szénhidrogén-migrációs események kapcsolhatóak, melyek pontosabb megismerése és elhelyezése a medence fejlődéstörténetében kulcsfontosságú. Az erősen átalakult nyeregdolomit tartalmú minták további vizsgálata rezervoárgeológiai szempontból a jövőben szintén fontos feladat.

Effect of subsurface soil moisture variability and atmospheric conditions on methane gas migration in shallow subsurface

A major concern resulting from the increased use and production of natural gas has been how to mitigate fugitive greenhouse gas emissions (predominantly methane) from natural gas infrastructure (e.g., leaky shallow pipelines). Subsurface migration and atmospheric loading of methane from pipeline leakage is controlled by source configurations and subsurface soil conditions (e.g., soil heterogeneity and soil moisture) and are further affected by atmospheric conditions (e.g., wind and temperature). However, the transport and attenuation of methane under varying subsurface and atmospheric conditions are poorly understood, making it difficult to estimate leakage fluxes from methane concentration measurements at and above the soil surface. Based on a series of controlled bench-scale experiments using a large porous media tank interfaced with an open-return wind tunnel, this study investigated multiphase processes controlling migration of methane from a point source representing a buried pipeline leaking at fixed flow rate (kg/s) under various saturation and soil-texture conditions. In addition, potential effects of atmospheric boundary controls, wind (0.5 and 2.0ms−1) and temperature (22 and 35°C), were also examined. Results showed the distinct effects of soil heterogeneity and, to a varying degree, of soil moisture on surface methane concentrations. In addition, results also showed the pronounced effects of wind and, to a lesser degree, of temperature on surface methane concentrations in the presence of varying soil and moisture conditions. The observed subsurface methane profiles were simulated using the multiphase transport simulator TOUGH2-EOS7CA. Observed agreement between measured and simulated data demonstrates that for the conditions studied, multiphase migration of a multicomponent gas mixture (including methane) under density-dependent flow can be adequately represented with a Fickian advection-diffusion (or dispersion) model (ADM) framework. The dominant effect of saturation over the soil texture, could also be inferred from numerical characterization.

Numerical study based on one-year monitoring data of groundwater-source heat pumps primarily for heating: a case in Tangshan, China

Thermal breakthrough is the main factor that affects the long-term efficiency of groundwater heat pump systems that predominantly for heating, particularly in northern China. A large water-source heat pump engineering project in Tangshan, China, is examined in this study. The project involves 18 pumping wells with a yield of 80 m3/h and 40 injection wells, covering a total planning area of 445,000 m2. In the third year, a groundwater monitoring system is installed in 23 wells to monitor the groundwater temperature. A hydrothermal coupling numerical model is established with the non-isothermal multiphase migration software TOUGH2. The model is analyzed by applying it to simulations. Simulation results are validated through a comparison with monitoring data. Results of the 10-year operation simulation show that the A3 and A4 well groups experience severe cold accumulation. Three optimization scenarios are thus presented to improve the groundwater temperature. Simulation results show that using the aquifer thermal energy storage method could fully meet the future requirements of heating during winter; however, the cost of this method is high. The optimization effect of alternating the pumping and the injection wells is insignificant. Adopting different pumping and injection layers can effectively control the water temperature decrease in the pumping wells; however, the breakthrough of cold plume should be prevented. The results of this study could provide a reference for the numerical prediction of large-scale water-source heat pump engineering projects in northern China.

State-of-the-Art of Gas Hydrates and Relative Permeability of Hydrate Bearing Sediments

The methane gas production potential from its hydrates, which are solid clathrates, with methane gas entrapped inside the water molecules, is primarily dependent on permeability characteristics of their bearing sediments. Moreover, the dissociation of gas hydrates, which results in a multi-phase fluid migration through these sediments, becomes mandatory to determine the relative permeability of both gaseous and aqueous fluids corresponding to different hydrate saturations. However, in this context, the major challenges are: (1) obtaining undisturbed in-situ samples bearing gas hydrates; and (2) maintenance of the thermodynamic conditions to counter hydrate dissociation. One of the ways to overcome this situation is synthesis of gas hydrates in laboratory conditions, followed by conducting permeability tests on them. In addition, empirical relationships that relate permeability of the gas hydrate bearing sediments to pore-structure characteristics (viz., pore size distribution and interconnectivity) can also be conceived. With this in view, a comprehensive review of the literature dealing with different techniques adopted by researchers for synthesis of gas hydrates, permeability tests conducted on the sediments bearing them, and analytical and empirical correlations employed for determination of permeability of these sediments was conducted and a brief account of the same is presented in this article.

Influence of rain on tetrachloroethylene’s multiphase migration in soil

For the increasingly serious soil and groundwater pollution by volatile organic compounds, tetrachloroethylene (PCE) was selected as the research object in this study. With the in-situ soil column physical simulation experiments, migration law of PCE in soil under rain conditions was studied by monitoring precipitation and soil parameter as well as sampling and analyzing soil and soil gas, and influence of rain on the multiphase migration process of PCE was preliminarily discussed. Research shows that migrations of PCE and soil moisture were not synchronous, and the rate of the former was speeded up by the latter caused by rain. Preliminary analysis indicates that migration of volatile chlorohydrocarbon in soil was not only driven by soil moisture, but also controlled by the nature of volatility of their own, that is to say, volatilization into gas phase was an important way of migrating and diffusing in pore medium, and the rate of migration and diffusion of gaseous PCE was faster than that of solid, resulting in more abroad distribution of gas phase than that in solid phase.

Review: Approaches to research on CO2/brine two-phase migration in saline aquifers

Understanding CO2/brine multiphase migration processes is critical for effectively evaluating potential storage capacity, ensuring storage security, and predicting the long-term fate of CO2 storage in saline aquifers. Success depends on the development and application of appropriate research methods. This paper accordingly reviews the progress made in research methods on CO2/brine two-phase migration. Due to intrinsic linkage between CO2 migration and trapping in saline aquifers, prediction of CO2/brine migration processes requires an accurate understanding of CO2 trapping mechanisms. Six recognized physical or geochemical mechanisms, including structural and stratigraphic trapping, residual gas trapping, hydrodynamic trapping, solubility trapping, local capillary trapping and mineral trapping, can impede or prevent CO2 migration according to different dominating variables, and consequently immobilize CO2 in brine formations at varying time and spatial scales. Laboratory experiments, field-scale monitoring and computational modeling are the main approaches in studies on CO2/brine multiphase migration. Different techniques have been designed and developed within each of these methods in terms of physical conditions and spatial scales of multiphase migration phenomena. Due to multi-scale characteristics of CO2/brine multiphase migration processes and complementary relationships among these methods and techniques, different research methods and techniques are often used in combination. Based on a systematic analysis of limitations and weaknesses, improvements are recommended which could potentially increase the accuracy, reliability and applicability of the approaches.

Overpressures in the Uinta Basin, Utah: Analysis using a three‐dimensional basin evolution model

High pore fluid pressures, approaching lithostatic, are observed in the deepest sections of the Uinta basin, Utah. Geologic observations and previous modeling studies suggest that the most likely cause of observed overpressures is hydrocarbon generation. We studied Uinta overpressures by developing and applying a three‐dimensional, numerical model of the evolution of the basin. The model was developed from a public domain computer code, with addition of a new mesh generator that builds the basin through time, coupling the structural, thermal, and hydrodynamic evolution. Also included in the model are in situ hydrocarbon generation and multiphase migration. The modeling study affirmed oil generation as an overpressure mechanism, but also elucidated the relative roles of multiphase fluid interaction, oil density and viscosity, and sedimentary compaction. An important result is that overpressures by oil generation create conditions for rock fracturing, and associated fracture permeability may regulate or control the propensity to maintain overpressures.

Modeling Multiphase Migration of Organic Chemicals in Groundwater Systems. A Review and Assessment

Modeling Multiphase Migration of Organic Chemicals in Groundwater Systems. A Review and Assessment

Modeling multiphase migration of organic chemicals in groundwater systems--a review and assessment.

Over the past two decades, a number of models have been developed to describe the multiphase migration of organic chemicals in the subsurface. This paper presents the state-of-the-art with regard to such modeling efforts. The mathematical foundations of these models are explored and individual models are presented and discussed. Models are divided into three groups: a) those that assume a sharp interface between the migrating fluids; b) those that incorporate capillarity; and c) those that consider interphase transport of mass. Strengths and weaknesses of each approach are considered along with supporting data for model validation. Future research directions are also highlighted.

Soil pollution by petroleum products, I. Multiphase migration of kerosene components in soil columns

A laboratory study of soil contamination by a synthetic “kerosene” is reported. Soil (Mediterranean red sandy clay) samples with different moisture contents (0.0, 0.8, 4.0, and 12%, w/w) were contaminated by vapors and/or liquid from a mixture containing 5 kerosene components (m-xylene, pseudo-cumene, t-butylbenzene, n-decane and n-dodecane). The contribution of the different kerosene components to the adsorption, volatilization and transport processes is described. Vapor adsorption was found to be dependent on the vapor concentration of each component (except for the n-decane), and on the soil moisture content. The sorption coefficients of the kerosene components decreased with increasing temperature but showed only a very slight variability between 20 and 34°C, in air-dried soil. The volatilization from soil was high: more than 90% of the aromatic components were desorbed in less than 2 h. The transport of the kerosene, in liquid and vapor phases, through the soil columns, was studied using amounts of kerosene which were less (1 mL) or more (10 mL) than the retention capacity of the soil columns. The increase in the moisture content of the soil increased the rate and the depth of kerosene downward penetration. It stopped however, the vapor movement (at 4%) and the upward liquid movement (at 12%). Among the properties of the kerosene components, volatility seems to be the prime factor which determines kerosene movement once liquid phase movement has ceased.

A Multiphase Approach to the Modeling of Porous Media Contamination by Organic Compounds: 2. Numerical Simulation

A system of equations, derived in part 1 of this paper, which describes the multiphase migration of an organic contaminant in the subsurface is presented. Although this system is not amenable to solution by analytical means, an approximate solution can be sought by a finite difference discretization of the governing equations. A one‐dimensional, implicit numerical model is developed in this manner. To handle the solution of the resultant system of nonlinear algebraic equations, a Newton‐Raphson iteration scheme is employed. In order to apply the finite difference model to a specific problem a number of parameters must be evaluated. These include three‐phase relative permeabilities, saturation‐pressure relations, partition coefficients, and mixture densities and viscosities. As a demonstration of the model's applicability, the migration of a two‐component hydrocarbon mixture in a soil column is simulated. A mass balance is performed, and convergence of the iteration scheme as well as convergence of the difference scheme in space and time are examined heuristically.