Connecting microstructural attributes and permeability from 3D tomographic images of in situ shear-enhanced compaction bands using multiscale computations

Tomographic images taken inside and outside a compaction band in a field specimen of Aztec sandstone are analyzed by using numerical methods such as graph theory, level sets, and hybrid lattice Boltzmann/finite element techniques. The results reveal approximately an order of magnitude permeability reduction within the compaction band. This is less than the several orders of magnitude reduction measured from hydraulic experiments on compaction bands formed in laboratory experiments and about one order of magnitude less than inferences from two-dimensional images of Aztec sandstone. Geometrical analysis concludes that the elimination of connected pore space and increased tortuosities due to the porosity decrease are the major factors contributing to the permeability reduction. In addition, the multiscale flow simulations also indicate that permeability is fairly isotropic inside and outside the compaction band

Poroelastic modeling of basement fault reactivation caused by saltwater disposal near Venus, Johnson County, Texas

Presented at the 54th US Rock Mechanics/Geomechanics Symposium held online, 28 June-1 July 2020To assess the potential for fault reactivation in response to wastewater injection near Venus, Texas, we conducted fully coupled 3D poroelastic finite element simulations for a site-specific geomechanical analysis. We find that simulations using the best estimates of in situ stress azimuth and fault orientation, and the Byerlee’s friction coefficient of 0.6 do not predict fault reactivation, in contrast to observed seismicity patterns. Increasing the maximum horizontal stress azimuth by 10° and the basement fault dip by 5°, both within the uncertainty space of the input parameters, and lowering the friction coefficient of the fault in the basement to 0.35, leads to fault reactivation in the basement as observed. Using the same model geometry but a friction coefficient of 0.6 leads to fault reactivation within Ellenburger, which is inconsistent with observed hypocenter depths at Venus. Expanding the model domain from 5 disposal wellbores to 35 increases the excess pore pressure which favors basement fault reactivation. These simulations demonstrate the sensitivity of geomechanical models of fault reactivation in response to injection requiring high-quality field parameters and help refine the azimuths of the horizontal stresses, the basement fault dip, and the basement fault friction coefficient on the basis of earthquake hypocenter temporal distribution.Bureau of Economic Geolog

Focused fluid flow along faults in the Monterey Formation, coastal California

ABSTRACT Fluid flow in fractured siliceous mudstone of the Miocene Monterey Formation of California is inferred to be highly focused toward map-scale faults that locally contain extensive amounts of carbonate and minor silica cement. The distance of crossstratigraphic flow, as inferred based on the strontium isotopic composition of carbonate fault cement, is close to the thickness of the Monterey Formation of 700 m in one of two study locations, Jalama Beach, and less than the formation thickness at another location, Arroyo Burro Beach. Fluid is thus derived from within the Monterey Formation rather than from underlying older units. Based on mass-balance estimates of the fluid volume required for fault cementation at Jalama Beach, the minimum distance of formation-parallel flow into the fault zone is 4 km and possibly Ͼ12 km. The inferred distance of flow parallel to the formation into this fault thus exceeds the distance of cross-formational upward flow along the fault by at least a factor of six. The mass-balance estimate requires that fluid flow along the fault is channeled into a pipe-shaped conduit rather than distributed along fault strike. Fluid flow from the surrounding formation into fault pipes is inferred to follow a radial rather than unior bilateral flow symmetry, using beddingconfined sets of extension fractures and stratabound breccia bodies. Radial fluid flow toward fault pipes requires fairly isotropic fracture permeability for flow along bedding and a low permeability across bed- ding. The inferred flow geometry illustrates the combined effect of fault permeability structure, permeability anisotropy of the surrounding formation, and hydraulic head distribution in controlling basinal fluid flow in faulted sequences

Supporting Information for: Occurrence and Origin of Nanoscale Grain Boundary Channels under Diagenetic Conditions

This supplementary information data set contains scanning electron microscopy (SEM) images and nanoscale grain boundary channel (NGBC) aperture data used in the main report, as well as EBSD misorientation plots.Natural fractures in shale and sandstone that formed under diagenetic and metamorphic conditions are frequently filled with mineral cement that lack residual fracture porosity visible under the petrographic microscope and that are generally interpreted to be impermeable. Scanning electron microscopy of calcite, dolomite, quartz, and barite fracture cement from low-permeability, diagenetically altered shale and sandstone formations provides evidence of open and variably connected elongate pores or gaps with apertures of 10-600 nm, referred to as nanoscale grain boundary channels (NGBC). Electron backscatter diffraction of samples prepared using broad ion-beam milling shows that NGBCs occur along grain boundaries of blocky or columnar fracture cement. Grain boundaries are either faceted or display undulation at the nanometer scale. NGBCs tend to increase in aperture with increasing maximum formation burial temperature, indicating dissolution-precipitation kinetics influences grain boundary structure. Transmission electron microscopy reveals heterogeneous crystallographic domains with possible amorphous regions bridging across grain boundary channels. We propose a model of dynamic concurrent dissolution-precipitation along grain boundaries that preserves NGBCs in carbonate and quartz fracture cements that have experienced diagenetic to low-grade metamorphic conditions. While partially healed, NGBCs may be sufficiently connected to increase permeability of low-permeability formations containing cemented fractures.Statoil Graduate Research Fellowship AAPG Foundation Geological Society of America Jackson School of Geosciences Fracture Research and Application ConsortiumBureau of Economic Geolog

Increasing of environmental safety in the underground mining of iron ores

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 21.06.01 – «Екологічна безпека». – Державний ВНЗ «Національний гірничий університет», Дніпропетровськ, 2014.Дисертація присвячена питанням підвищення екологічної безпеки видобутку залізних руд підземним способом для конкретних гірничо-геологічних умов Південно-Білозерського родовища. За результатами фізико-хімічного аналізу та біологічної оцінки стану атмосферного повітря на промисловому майданчику шахти та прилеглих до нього територій запропоновано розрахунок екологічної оцінки стану атмосферного повітря та технологічні рішення щодо технології відбивання запасів руди камер за допомогою емульсійних ВР. Надані технологічні рішення ведення очисних робіт при камерних системах розробки, впроваджені при видобуванні залізної руди на шахті «Експлуатаційна» ЗАТ «ЗЗРК». Ступінь екологічної небезпеки при впровадженні запропонованої технології знизиться в 2 рази, а собівартість видобутку 1 т руди зменшиться на 15%.В диссертационной работе решена актуальная научная задача в установлении закономерностей формирования загрязнения атмосферного воздуха от воздействия шахтных источников выброса. На основе результатов измерения концентрации экологически опасных веществ в исходящей струе воздуха, установлены закономерности изменения концентрации оксидов углерода, азота и серы от годового удельного расхода ВВ. Определение приземной концентрации суммарного воздействия опасных веществ позволило установить, что на их приземную концентрацию влияет расстояние от источника выброса и удельный годовой расход ВВ, что позволило выявить закономерности изменения приземной концентрации суммарного воздействия экологически опасных веществ с увеличением расстояния от каждого вентиляционного ствола шахты. Оценка общей токсико-мутагенной активности атмосферного воздуха позволила установить корреляционную зависимость изменения УПП от величины приземной концентрации суммарного воздействия. Исследования изменения биологических признаков озимой пшеницы, произрастающей на разном удалении от источника выброса, позволили установить, что их линейные размеры вблизи источника выброса увеличиваются, а с удалением от него уменьшаются, а весовые показатели, наоборот, вблизи – уменьшаются, а с увеличением расстояния – увеличиваются. По результатам исследования установлено корреляционную зависимость изменения биологической урожайности озимой пшеницы от величины приземной концентрации суммарного воздействия и расстояния до источника выброса. Определение последствий техногенеза в первом поколении, позволило установить, что токсичные газы, исходящие из вентиляционных стволов шахты оказывают существенное влияние на культуры в первом поколении, и способствует увеличению техногенеза при приближении к нему. Результатами исследования уста- новлены корреляционные зависимости изменения фитотоксического эффекта от величины приземной концентрации суммарного воздействия. На основании полученных результатов исследования разработан алгоритм расчета экологической оценки состояния атмосферного воздуха на промышленной площадке шахты и территории, прилегающих к ней и составлена оценочная шкала, с помощью которой определяются параметры экологической опасности выбросов железорудной шахты. Предложена технология отбойки руды при ведении очистных работ по отработке запасов камер с применением эмульсионного ВВ украинит-ПМ-2Б позволяющая повысить безопасность ведения взрывных работ, а также снизить загрязнения рудничной атмосферы продуктами взрыва до 50%, ингибирующее воздействие на состояние индикаторов по сравнению с применением тротилосодержащих ВВ до 13% и соответственно экологический риск в 2 раза, рассчитанный с учетом прогнозируемых концентраций загрязнителей в атмосфере и связанных с ними показателей индикаторов.The thesis is devoted to environmental safety improving of iron ore extraction by underground mining for specific geological conditions of South- Bilozerske field. As a result of physical and chemical analysis and biological assessment of air state in the mine industrial area and adjacent territories a calculation of the environmental assessment of air state and process solutions on the technology of reflection of ore cameras using emulsion explosives are proposed. Given technological solutions of extraction works in chamber system of mining are implemented in iron ore extraction of ”Ekspluatatsiina” mine of CJC “Zaporizhia Iron Ore Plant”. The degree of environmental hazards under the implementation of the proposed technology will decrease by 2 times, and the cost of production of 1 ton of ore will be reduced by 15%

Hydrogen Storage Assessment in Depleted Oil Reservoir and Saline Aquifer

Hydrogen (H2) is an attractive energy carrier to move, store, and deliver energy in a form that can be easily used. Field proven technology for underground hydrogen storage (UHS) is essential for a successful hydrogen economy. Options for this are manmade caverns, salt domes/caverns, saline aquifers, and depleted oil/gas fields, where large quantities of gaseous hydrogen have been stored in caverns for many years. The key requirements intrinsic of a porous rock formation for seasonal storage of hydrogen are: adequate capacity, ability to contain H2, capability to inject/extract high volumes of H2, and a reliable caprock to prevent leakage. We have carefully evaluated a commercial non-isothermal compositional gas reservoir simulator and its suitability for hydrogen storage and withdrawal from saline aquifers and depleted oil/gas reservoirs. We have successfully calibrated the gas equation of state model against published laboratory H2 density and viscosity data as a function of pressure and temperature. Comparisons between the H2, natural gas and CO2 storage in real field models were also performed. Our numerical models demonstrated more lateral spread of the H2 when compared to CO2 and natural gas with a need for special containment in H2 projects. It was also observed that the experience with CO2 and natural gas storage cannot be simply replicated with H2

Authigenic carbonate formation at hydrocarbon seeps in continental margin sediments: A comparative study

Authigenic carbonates from five continental margin locations, the Eel River Basin, Monterey Bay, Santa Barbara Basin, the Sea of Okhotsk, and the North Sea, exhibit a wide range of mineralogical and stable isotopic compositions. These precipitates include aragonite, low- and high-Mg calcite, and dolomite. The carbon isotopic composition of carbonates varies widely, ranging from −60‰ to +26‰, indicating complex carbon sources that include ^(13)C-depleted microbial and thermogenic methane and residual, 13C-enriched, bicarbonate. A similarly large variability of δ^(18)O values (−5.5‰ to +8.9‰) demonstrates the geochemical complexity of these sites, with some samples pointing toward an ^(18)O-enriched oxygen source possibly related to advection of ^(18)O-enriched formation water or to the decomposition of gas hydrate. Samples depleted in ^(18)O are consistent with formation deeper in the sediment or mixing of pore fluids with meteoric water during carbonate precipitation. A wide range of isotopic and mineralogical variation in authigenic carbonate composition within individual study areas but common trends across multiple geographic areas suggest that these parameters alone are not indicative for certain tectonic or geochemical settings. Rather, the observed variations probably reflect local controls on the flux of carbon and other reduced ions, such as faults, fluid conduits, the presence or absence of gas hydrate in the sediment, and the temporal evolution of the local carbon reservoir. Areas with seafloor carbonates that indicate formation at greater depth below the sediment–water interface must have undergone uplift and erosion in the past or are still being uplifted. Consequently, the occurrence of carbonate slabs on the seafloor in areas of active hydrocarbon seepage is commonly an indicator of exhumation following carbonate precipitation in the shallow subsurface. Therefore, careful petrographic and geochemical analyses are critical components necessary for the correct interpretation of processes related to hydrocarbon seepage in continental margin environments and elsewhere