A new approach to upscaling fracture network models while preserving geostatistical and geomechanical characteristics

A new approach to upscaling two-dimensional fracture network models is proposed for preserving geostatistical and geomechanical characteristics of a smaller-scale “source” fracture pattern. First, the scaling properties of an outcrop system are examined in terms of spatial organization, lengths, connectivity, and normal/shear displacements using fractal geometry and power law relations. The fracture pattern is observed to be nonfractal with the fractal dimension D ≈ 2, while its length distribution tends to follow a power law with the exponent 2 < a < 3. To introduce a realistic distribution of fracture aperture and shear displacement, a geomechanical model using the combined finite-discrete element method captures the response of a fractured rock sample with a domain size L = 2 m under in situ stresses. Next, a novel scheme accommodating discrete-time random walks in recursive self-referencing lattices is developed to nucleate and propagate fractures together with their stress- and scale-dependent attributes into larger domains of up to 54 m × 54 m. The advantages of this approach include preserving the nonplanarity of natural cracks, capturing the existence of long fractures, retaining the realism of variable apertures, and respecting the stress dependency of displacement-length correlations. Hydraulic behavior of multiscale growth realizations is modeled by single-phase flow simulation, where distinct permeability scaling trends are observed for different geomechanical scenarios. A transition zone is identified where flow structure shifts from extremely channeled to distributed as the network scale increases. The results of this paper have implications for upscaling network characteristics for reservoir simulation

Methods and standards development for three-dimensional mapping of the Antioch Quadrangle, Lake County, Illinois a pilot study

The Pilot Study for the Central Great Lakes Geologic Mapping Coalition (CGLGMC) focused on the Antioch Quadrangle, Lake County, Illinois developing a series of maps and digital products, several protocols for database development and maintenance and field procedures to acquire and integrate drilling and geophysical data from a quadangle area featuring complex glacial geology over a 25,000 year period.U.S. Geological Survey, Central Great Lakes Geologic Mapping CoalitionOpe

Characterisation of the transmissivity field of a fractured and karstic aquifer, Southern France

International audienceGeological and hydrological data collected at the Terrieu experimental site north of Montpellier, in a confined carbonate aquifer indicates that both fracture clusters and a major bedding plane form the main flow paths of this highly heterogeneous karst aquifer. However, characterising the geometry and spatial location of the main flow channels and estimating their flow properties remain difficult. These challenges can be addressed by solving an inverse problem using the available hydraulic head data recorded during a set of interference pumping tests.We first constructed a 2D equivalent porous medium model to represent the test site domain and then employed regular zoning parameterisation, on which the inverse modelling was performed. Because we aim to resolve the fine-scale characteristics of the transmissivity field, the problem undertaken is essentially a large-scale inverse model, i.e. the dimension of the unknown parameters is high. In order to deal with the high computational demands in such a large-scale inverse problem, a gradient-based, non-linear algorithm (SNOPT) was used to estimate the transmissivity field on the experimental site scale through the inversion of steady-state, hydraulic head measurements recorded at 22 boreholes during 8 sequential cross-hole pumping tests. We used the data from outcrops, borehole fracture measurements and interpretations of inter-well connectivities from interference test responses as initial models to trigger the inversion. Constraints for hydraulic conductivities, based on analytical interpretations of pumping tests, were also added to the inversion models. In addition, the efficiency of the adopted inverse algorithm enables us to increase dramatically the number of unknown parameters to investigate the influence of elementary discretisation on the reconstruction of the transmissivity fields in both synthetic and field studies.By following the above approach, transmissivity fields that produce similar hydrodynamic behaviours to the real head measurements were obtained. The inverted transmissivity fields show complex, spatial heterogeneities with highly conductive channels embedded in a low transmissivity matrix region. The spatial trend of the main flow channels is in a good agreement with that of the main fracture sets mapped on outcrops in the vicinity of the Terrieu site suggesting that the hydraulic anisotropy is consistent with the structural anisotropy. These results from the inverse modelling enable the main flow paths to be located and their hydrodynamic properties to be estimated

Thermodynamic and geomechanical processes research in the development of gas hydrate deposits in the conditions of the Black Sea

Purpose. Research of thermodynamic and geomechanical processes occurring in a gas hydrate body under the influence of an activating agent (sea water from surface layers) in the conditions of the Black Sea by mathematical modeling using finite element method. Methods. The modeling of thermodynamic and geomechanical processes is performed with the use of ANSYS v17.0 software and in accordance with the climatic, hydrogeological and physic-mechanical properties of the numerical model elements in the Black Sea gas hydrate deposit under consideration, which are similar to natural ones. The thermodynamic processes were studied in the section “Steady-State Thermal”, and the geomechanical (stress-strain state) in “Static Structural”. Findings. The spatial model is developed, which allows to simulate thermodynamic and geomechanical processes in a gas hydrate body under the influence of a thermal agent. As a result of modeling, it was determined that under these conditions the temperature in the gas hydrate body varies with the distance from the production well similarly in both directions according to the polynomial dependence. What is more, at a distance from the well of 18.7 m the temperature is stable and equals +22°С, and in the range of 18.7 – 24.9 m – decreases by 3.1 times and reaches a value of +7°С. It was found out that deformations in a gas hydrate body under the influence of an activating agent, which is fed under pressure above the initial, are directed from the lateral boundaries to the center of the gas hydrate body in the direction of productive dissociation zones. This, in its turn, results in the displacement of the gas hydrate volume to the reaction proceeding center, improving the quality of the decomposition process and allows mining of 87 – 91% gas hydrate volume, which is presented in the model. Originality. For the first time, for the conditions of the Black Sea gas hydrate deposits, an analytical assessment of the dissociation zone distribution from the production well under the influence of the thermal agent and the changes of the stress-strain state of the gas hydrated body during its decomposition, has been carried out. This allows to improve the technology of the gas hydrate deposits development in the conditions under consideration. Practical implications. The technological scheme for the development of a gas hydrate body based on the combined approach to the effects of activators (temperature and pressure) is proposed, which eliminates the need to warm the boundary sections of the deposit and increases the amount of the supplied activating agent and its temperatures, which in its turn leads to a decrease in the resource and energy consumption.Мета. Дослідження термодинамічних і геомеханічних процесів, що протікають у газогідратному тілі при впливі активуючого агента (морської води з поверхневих шарів) в умовах Чорного моря шляхом математичного моделювання методом кінцевих елементів. Методика. Моделювання термодинамічних і геомеханічних процесів виконано за допомогою програмного забезпечення ANSYS v17.0 з відповідністю кліматичних, гідрогеологічних та фізико-механічних властивостей елементів чисельної моделі у розглянутому газогідратному родовищі Чорного моря, які є аналогічними натурним. Термодинамічні процеси досліджувалися у розділі програми “Steady-State Thermal”, а геомеханічні (напружено-деформований стан) – в “Static Structural”. Результати. Розроблена просторова модель, що дозволяє моделювати термодинамічні та геомеханічні процеси у газогідратному тілі при впливі теплового агента. В результаті моделювання встановлено, що у розглянутих умовах температура в газогідратному тілі змінюється з відстанню від видобувної свердловини аналогічно в обидві сторони за поліноміальною залежністю, причому на відстані від свердловини 18.7 м температура стабільна і становить +22°С, а в інтервалі 18.7 – 24.9 м – знижується у 3.1 рази і досягає значення +7°С. Виявлено, що деформації у газогідратному тілі при впливі активуючого агента, який подається під тиском, що перевищує початковий, спрямовані від бокових меж у центр газогідратного тіла у напрямі продуктивних зон дисоціації, що, в свою чергу, призводить до зміщення об’єму газогідрату в центр протікання реакції, покращуючи якість процесу розкладання і дозволяючи відпрацювати 87 – 91% об’єму газогідрата, представленого в моделі. Наукова новизна. Вперше для умов газогідратних родовищ Чорного моря проведена аналітична оцінка характеру поширення зони дисоціації від видобувної свердловини при впливі теплового агента та змін напружено-деформованого стану газогідратного тіла при його розкладанні, що дозволяє удосконалити технологію розробки газогідратних покладів у розглянутих умовах. Практична значимість. Запропоновано технологічну схему розробки газогідратного тіла на основі комбінованого підходу до впливу активаторами (температурою та тиском), що усуває необхідність прогріву граничних ділянок покладу і збільшення кількості активуючого агента, що подається, та його температури, що, в свою чергу, веде до зниження ресурсо- й енерговитрат.Цель. Исследование термодинамических и геомеханических процессов, протекающих в газогидратном теле при воздействии активирующего агента (морской воды с поверхностных слоев) в условиях Черного моря посредством математического моделирования методом конечных элементов. Методика. Моделирование термодинамических и геомеханических процессов выполнено при помощи программного обеспечения ANSYS v17.0 с соответствием климатических, гидрогеологических и физико-механических свойств элементов численной модели в рассматриваемом газогидратном месторождении Черного моря, которые являются аналогичными натурным. Термодинамические процессы исследовались в разделе программы “Steady-State Thermal”, а геомеханические (напряженно-деформированное состояние) – в “Static Structural”. Результаты. Разработана пространственная модель, позволяющая моделировать термодинамические и геомеханические процессы в газогидратном теле при воздействии теплового агента. В результате моделирования установлено, что в рассматриваемых условиях температура в газогидратном теле изменяется с расстоянием от добывающей скважины аналогично в обе стороны по полиномиальной зависимости, причем на расстоянии от скважины 18.7 м температура стабильна и составляет +22°С, а в интервале 18.7 – 24.9 м – снижается в 3.1 раза и достигает значения +7°С. Выявлено, что деформации в газогидратном теле при воздействии активирующего агента, подаваемого под давлением, превышающее начальное, направлены от боковых границ в центр газогидратного тела в направлении продуктивных зон диссоциации, что, в свою очередь, приводит к смещению объема газогидрата в центр протекания реакции, улучшая качество процесса разложения и позволяя отработать 87 – 91% объема газогидрата, представленного в модели. Научная новизна. Впервые для условий газогидратных месторождений Черного моря проведена аналитическая оценка характера распространения зоны диссоциации от добывающей скважины при воздействии теплового агента и изменений напряженно-деформированного состояния газогидратного тела при его разложении, что позволяет усовершенствовать технологию разработки газогидратных залежей в рассматриваемых условиях. Практическая значимость. Предложена технологическая схема разработки газогидратного тела на основании комбинированного подхода к воздействию активаторами (температурой и давлением), устраняющая необходимость прогрева граничных участков залежи и увеличения подаваемого количества активирующего агента и его температуры, что, в свою очередь, ведет к снижению ресурсо- и энергозатрат.The results of the current researches were obtained within the framework of the research works of GP-473 Development of scientific principles of phase transformations of technogenic and natural gas hydrates and creation of the newest technologies of their extraction” (State Registration No.0115U002294) and GP-487 “Scientific substantiation and development of energy saving and low waste technologies of hydrocarbon and mineral raw materials extraction” (State Registration No.0116U008041)

Three-dimensional distribution of primary melt inclusions in garnets by X-ray microtomography

open6X-ray computed microtomography (X-mu CT) is applied here to investigate in a non-invasive way the three-dimensional (3D) spatial distribution of primary melt and fluid inclusions in gamets from the metapeitic enclaves of El Hoyazo and from the migmatitcs of Sierra Alpujata, Spain. Attention is focused on a particular case of inhomogeneous distribution of inclusions, characterized by inclusion-rich cores and almost inclusion-free rims (i.e., zonal arrangement), that has been previously investigated in detail only by means of 2D conventional methods. Different experimental X-mu CT configurations, both synchrotron radiation- and X-ray tube-based, are employed to explore the limits of the technique. The internal features of the samples are successfully imaged, with spatial resolution down to a few micrometers. By means of dedicated image processing protocols, the lighter melt and fluid inclusions can be separated from the heavier host garnet and from other non-relevant features (e.g., other mineral phases or large voids). This allows evaluating the volumetric density of inclusions within spherical shells as a function of the radial distance from the center of the host garnets. The 3D spatial distribution of heavy mineral inclusions is investigated as well and compared with that of melt inclusions. Data analysis reveals the occurrence of a clear peak of melt and fluid inclusions density, ranging approximately from 1/3 to 1/2 of the radial distance from the center of the distribution and a gradual decrease from the peak outward. heavy mineral inclusions appear to be almost absent in the central portion of the garnets and more randomly arranged, showing no correlation with the distribution of melt and fluid inclusions. To reduce the effect of geometric artifacts arising from the non-spherical shape of the distribution, the inclusion density was calculated also along narrow prisms with different orientations, obtaining plots of pseudo-linear distributions. The results show that the core-rim transition is characterized by a rapid (but not step-like) decrease in inclusion density, occurring in a continuous mode. X-ray tomographic data, combined with electron microprobe chemical profiles of selected elements, suggest that despite the inhomogeneous distribution of inclusions, the investigated garnets have grown in one single progressive episode in the presence of anatectic melt. The continuous drop of inclusion density suggests a similar decline in (radial) garnet growth, which is a natural consequence in the case of a constant reaction rate. Our results confirm the advantages of high-resolution X-mu CT compared to conventional destructive 2D observations for the analysis of the spatial distribution of micrometer-scale inclusions in minerals, owing to its non-invasive 3D capabilities. The same approach can be extended to the study of different microstructural features in samples from a wide variety of geological settings.openParisatto, Matteo; Turina, Alice; Cruciani, Giuseppe; Mancini, Lucia; Peruzzo, Luca; Cesare, BernardoParisatto, Matteo; Turina, Alice; Cruciani, Giuseppe; Mancini, Lucia; Peruzzo, Luca; Cesare, Bernard

An overview of current status of carbon dioxide capture and storage technologies

AbstractGlobal warming and climate change concerns have triggered global efforts to reduce the concentration of atmospheric carbon dioxide (CO2). Carbon dioxide capture and storage (CCS) is considered a crucial strategy for meeting CO2 emission reduction targets. In this paper, various aspects of CCS are reviewed and discussed including the state of the art technologies for CO2 capture, separation, transport, storage, leakage, monitoring, and life cycle analysis. The selection of specific CO2 capture technology heavily depends on the type of CO2 generating plant and fuel used. Among those CO2 separation processes, absorption is the most mature and commonly adopted due to its higher efficiency and lower cost. Pipeline is considered to be the most viable solution for large volume of CO2 transport. Among those geological formations for CO2 storage, enhanced oil recovery is mature and has been practiced for many years but its economical viability for anthropogenic sources needs to be demonstrated. There are growing interests in CO2 storage in saline aquifers due to their enormous potential storage capacity and several projects are in the pipeline for demonstration of its viability. There are multiple hurdles to CCS deployment including the absence of a clear business case for CCS investment and the absence of robust economic incentives to support the additional high capital and operating costs of the whole CCS process

Institute of Northern Engineering 2006 Annual Report

MESSAGE FROM THE DIRECTOR -- OVERVIEW AND MISSION -- CENTER PROFILES -- ORGANIZATION & CENTER LEADERS -- ARCTIC ENERGY TECHNOLOGY DEVELOPMENT LABORATORY -- ALASKA UNIVERSITY TRANSPORTATION CENTER -- MINERAL INDUSTRY RESEARCH LABORATORY -- PETROLEUM DEVELOPMENT LABORATORY -- WATER & ENVIRONMENTAL RESEARCH CENTER -- INE GENERAL RESEARCH -- ACCOMPLISHMENTS 2006 -- GOALS 2007 -- RESOURCES, FUNDING, AND EXPENDITURE

Aspects of the tectonics of the Greater Caucasus and Western South Caspian Basin

The main objectives of this project are to (a) understand the relationship between climate, topography and the tectonics in the Greater Caucasus belt, (b) construct regional geological cross-sections showing major stratigraphic sequences and structures along the belt using the focal mechanisms of the earthquakes events, (c) evaluate the evolution and development of a single fold structure (Yasamal anticline) and (d) investigate strain accommodation mechanisms using 3D Move to unfold the Yasamal structure. Topographic variations were investigated to understand the interplay between topography, climate and the tectonics of the Greater Caucasus range and compare the findings with other active and inactive belts (Pyrenees, Northern Tibetan Plateau and Himalayas). There is a correlation between elevation changes and climate along the Greater Caucasus belt, where the gradual reduction of the mean altitude, has a close relationship with a wetter climate, and the sharper altitude decrease with a drier climate. And the elevation changes are strongly correlated with the Moho depths underneath the region. The relief along the belt is extremely high, with a strong correlation between the high relief and the large thrusts in the region. And the relief of the eastern part is slightly low compared with the western part of the belt, even though the eastern part is more active than the western part. The structural study undertaken at regional scale for the Caucasus belt and the western side of the South Caspian Basin gave insights on the style of deformation in the basin and the evolution of the Greater Caucasus belt and the preferred distribution, geometry and formation mechanism of the structural elements. The regional cross-sections along the Greater Caucasus were constructed and constrained by using focal mechanisms show that the belt is deformed by active thrust faults that dip inwards from the margins of the range where the northern thrusts are dipping south, and the southern thrusts are dipping to the north, these results have contrary to some previous models that emphasise only south-directed thrusting. The spatial arrangement, geometry and temporal evolution of spectacular kilometre-amplitude fold structures actively forming in Cenozoic sediments on the uplifted western margin of the South Caspian Basin are described and strain accommodation mechanisms established using 3D Move to unfold the Yasamal structure enabled a reconstruction of pre-folding templates and predictively model the fold-related deformation at small-scale. The 3D model of the Yasamal anticline shows that the anticline hinge has about 30° south-directed plunging. The area was characterized by a low rate of sedimentation and high rate of uplift in the Upper Pliocene. The minor structures (accommodating the overall strain in the anticline) are developed throughout the entire anticline. Compressional strain is present at the anticline hinge line, and the extensional strain dominates the anticline limbs. Suggesting potential extensional structures development in the anticline flanks, which correspond with the field observations in the Yasamal valley confirming that; the small normal faults are concentrated within the anticline flanks, and the contractional deformation bands along the hinge area of the anticline

Generating Irregular Models for 3D Spherical-Particle-Based Numerical Methods

The realistic representation of an irregular geological body is essential to the construction of a particle simulation model. A three-dimensional (3D) sphere generator for an irregular model (SGIM), which is based on the platform of Microsoft Foundation Classes (MFC) in VC++, is developed to accurately simulate the inherent discontinuities in geological bodies. OpenGL is employed to visualize the modeling in the SGIM. Three key functions, namely, the basic-model-setup function, the excavating function, and the cutting function, are implemented. An open-pit slope is simulated using the proposed model. The results demonstrate that an extremely irregular 3D model of a geological body can be generated using the SGIM and that various types of discontinuities can be inserted to cut the model. The data structure of the model that is generated by the SGIM is versatile and can be easily modified to match various numerical calculation tools. This can be helpful in the application of particle simulation methods to large-scale geoengineering projects