Borehole breakout analysis: results from the AND-2A Well

To define the present-day stress field in the upper crust and to understand the recent tectonic activity in Antarctica, a study of breakout measurements along AND-2A well was performed. The borehole breakout is an important indicator of horizontal stress orientation and occurs when the stresses around the borehole exceed that required to cause compressive failure of the borehole wall (Bell and Gough, 1979; Zoback et al., 1985, Bell, 1990). The enlargement of the wellbore is caused by the development of intersecting conjugate shear planes that cause pieces of the borehole wall to spall off. Around a vertical borehole, stress concentration is greatest in the direction of the minimum horizontal stress (Shmin), hence, the long axes of borehole breakouts are oriented approximately perpendicular to the maximum horizontal stress orientation (SHmax). The orientation of breakouts along the AND-2A well was measured using acoustic (BHTV) and mechanical (Four-Arm Caliper) tools. Borehole televiewer (BHTV) provides an acoustic "image" of the borehole wall (360 degree coverage) and gives detailed information for investigation of fractures and stress analysis. The four-arm caliper is the oldest technique for borehole breakout identification and it is included in routine dipmeter logs. A quality value has been assigned to the well results in agreement with the World Stress Map quality ranking scheme (Zoback, 1992; Heidback et al., 2010) based mainly on the number, accuracy, and length of breakout measurements. The result is presented as rose diagram of the breakout directions where the length of each peak is proportional to the frequency and the width to the variance of its gaussian curve. We have analyzed the following curves to recognize the breakout: the azimuth of Pad 1 (P1az), the drift azimuth (HAZI), the two calipers with respect to the bit size (BZ) curve and the curve relative to the deviation of the well. The AND-2A Four-Arm Caliper data cover a depth interval between 637 down to 997 mbsl, that corresponds to 360 m of logged interval. We have distinguished breakouts and some washouts only in the interval from 753 to 825 mbsl. From borehole televiewer images, we have data from 398 mbsl down to 1136 mbsl. The BHTV worked well showing a lot of interesting features such as many bedding, lamination and fractures (natural and induced) but poor breakouts. The rare breakouts have also a small size (called protobreakouts) but they are consistent with induced features. Considering the breakout result from caliper and BHTV, the AND-2A borehole is unfortunately classified as D quality. This means that to obtain a reliable active stress field of the area it is necessary to compare this result with other available data

Optimal control of a step-by-step transmission of vehicles

Рассматривается актуальная задача оптимального выбора передаточных чисел трансмиссии транспортных средств (ТС), оснащенных двигателями внутреннего сгорания (ДВС) со ступенчатой коробкой передач, по критерию минимального расхода топлива. Анализ научно-технической литературы показал отсутствие простых и достаточно обоснованных алгоритмов управления энергоустановкой автомобиля, представляющей собой систему, состоящую из ДВС и регулируемой трансмиссии. Целью настоящей работы является теоретическое обоснование закона переключения передаточных чисел ступенчатой трансмиссии, обеспечивающего максимальную топливную экономичность для любого мощного и скоростного режима ТС. В основу предлагаемого метода положено однопараметрическое множество линейных преобразований, связывающих момент двигателя и его частоту вращения с тяговым усилием и скоростью ТС. Множеству передаточных чисел трансмиссии соответствует множество одноэкстремальных функций удельных расходов топлива. Множество точек линий равных уровней расходов топлива, соответствующих двум соседним значениям передаточных чисел трансмиссии, образует линию переключения передач. Предложен соответствующий алгоритм переключения передаточных чисел, обеспечивающий наиболее экономичное функционирование энергоустановки ТС в условиях переменных силовых и скоростных режимов.The actual problem of optimal selection of means of transport (MT) gear ratios, equipped with internal combustion engines (ICE) with a step-by-step gearbox according to the criterion of minimum fuel consumption is considered in the article. An analysis of the scientific and technical literature has showed the absence of simple and sufficiently justified algorithms for controlling the vehicle’s power plant, which is a system that consists of an ICE and an adjustable transmission. The aim of this work is the theoretical justification of the law of gear ratios shifting of a step-by-step transmission, ensuring maximum fuel efficiency for any power and speed mode of MT. The proposed method is based on set of linear transformations that connect the engine moment and engine speed with a traction force and a speed of MT. The set of gear ratios correspond to the set of one-extremal functions of specific fuel consumptions. The set of points of equal levels lines corresponding to two neighboring values of the gear ratios of the transmission forms a gear shift line. An appropriate algorithm for switching gear ratios is proposed, which ensures the most efficient operation of a power plant of MT in conditions of variable power and speed modes

Age–depth model of the past 630 kyr for Lake Ohrid (FYROM/Albania) based on cyclostratigraphic analysis of downhole gamma ray data

Gamma ray (GR) fluctuations and potassium (K) values from downhole logging data obtained in the sediments of Lake Ohrid from 0 to 240 m below lake floor (b.l.f). correlate with fluctuations in δ18O values from the global benthic isotope stack LR04 (Lisiecki and Raymo, 2005). GR and K values are considered a reliable proxy to depict glacial-interglacial cycles, with high clastic input during cold and/or drier periods and high carbonate precipitation during warm and/or humid periods at Lake Ohrid. Spectral analysis was applied to investigate the climate signal and evolution over the length of the borehole. Linking downhole logging data with orbital cycles was used to estimate sedimentation rates and the effect of compaction was compensated for. Sedimentation rates increase on average by 14 % after decompaction of the sediment layers and the mean sedimentation rates shift from 45 cm kyr-1 between 0 and 110 m to 30 cm kyr-1 from 110 to 240 m b.l.f. Tuning of minima and maxima of gamma ray and potassium values versus LR04 extrema, in combination with eight independent tephrostratigraphical tie points, allows establishing of a robust age model for the downhole logging data over the past 630 kyr. © Author(s) 2015

Downhole Measurements in the AND-2A Borehole, ANDRILL Southern McMurdo Sound Project, Antarctica

Under the framework of the ANDRILL Southern McMurdo Sound (SMS) Project successful downhole experiments were conducted in the 1138.54 metre (m)-deep AND-2A borehole. Wireline logs successfully recorded were: magnetic susceptibility, spectral gamma ray, sonic velocity, borehole televiewer, neutron porosity, density, calliper, geochemistry, temperature and dipmeter. A resistivity tool and its backup both failed to operate, thus resistivity data were not collected. Due to hole conditions, logs were collected in several passes from the total depth at ~1138 metres below sea floor (mbsf) to ~230 mbsf, except for some intervals that were either inaccessible due to bridging or were shielded by the drill string. Furthermore, a Vertical Seismic Profile (VSP) was created from ~1000 mbsf up to the sea floor. The first hydraulic fracturing stress measurements in Antarctica were conducted in the interval 1000-1138 mbsf. This extensive data set will allow the SMS Science Team to reach some of the ambitious objectives of the SMS Project. Valuable contributions can be expected for the following topics: cyclicity and climate change, heat flux and fluid flow, seismic stratigraphy in the Victoria Land Basin, and structure and state of the modern crustal stress field.Published57-683.2. Tettonica attivaN/A or not JCRrestricte

The Wunstorf Drilling Project: Coring a Global Stratigraphic Reference Section of the Oceanic Anoxic Event 2

No abstract available. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.4.05.2007" target="_blank">10.2204/iodp.sd.4.05.2007</a

Sedimentological processes and environmental variability at Lake Ohrid (Macedonia, Albania) between 640 ka and present day

Lake Ohrid (FYROM, Albania) is thought to be more than 1.2 million years old and hosts more than 200 endemic species. As a target of the International Continental Scientific Drilling Program (ICDP), a successful deep drilling campaign was carried out within the scope of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project in 2013. Here, we present lithological, sedimentological, and (bio-)geochemical data from the upper 247.8 m of the overall 569 m long DEEP site sediment succession from the central part of the lake. According to an age model, which is based on nine tephra layers (1st order tie points), and on tuning of biogeochemical proxy data to orbital parameters (2nd order tie points) and to the global benthic isotope stack LR04 (3rd order tie points), respectively, the analyzed sediment sequence covers the last 640 ka

The SCOPSCO drilling project recovers more than 1.2 million years of history from Lake Ohrid

The Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project is an international research initiative to study the influence of major geological and environmental events on the biological evolution of lake taxa. SCOPSCO drilling campaigns were carried out in 2011 and 2013. In 2011 we used gravity and piston coring at one of the five proposed drill sites, and in 2013 we undertook deep drilling with the Deep Lake Drilling System (DLDS) of Drilling, Observation and Sampling of the Earth's Continental Crust (DOSECC). In April and May 2013, a total of 2100 m sediments were recovered from four drill sites with water depths ranging from 125 to 260 m. The maximum drill depth was 569 m below the lake floor in the centre of the lake. By retrieving overlapping sediment sequences, 95% of the sediment succession was recovered. Initial data from borehole logging, core logging and geochemical measurements indicate that the sediment succession covers >1.2 million years (Ma) in a quasi-continuous sequence. These early findings suggest that the record from Lake Ohrid will substantially improve the knowledge of long-term environmental change and short-term geological events in the northeastern Mediterranean region, which forms the basis for improving understanding of the influence of major geological and environmental events on the biological evolution of endemic species

500,000 Years of Environmental History in Eastern Anatolia: The PALEOVAN Drilling Project

International Continental Scientific Drilling Program (ICDP) drilled a complete succession of the lacustrine sediment sequence deposited during the last ~500,000 years in Lake Van, Eastern Anatolia (Turkey). Based on a detailed seismic site survey, two sites at a water depth of up to 360 m were drilled in summer 2010, and cores were retrieved from sub-lake-floor depths of 140 m (Northern Basin) and 220 m (Ahlat Ridge). To obtain a complete sedimentary section, the two sites were multiple-cored in order to investigate the paleoclimate history of a sensitive semi-arid region between the Black, Caspian, and Mediterranean seas. Further scientific goals of the PALEOVAN project are the reconstruction of earthquake activity, as well as the temporal, spatial, and compositional evolution of volcanism as reflected in the deposition of tephra layers. The sediments host organic matter from different sources and hence composition, which will be unravelled using biomarkers. Pathways for migration of continental and mantle-derived noble gases will be analyzed in pore waters. Preliminary 40Ar/39Ar single crystal dating of tephra layers and pollen analyses suggest that the Ahlat Ridge record encompasses more than half a million years of paleoclimate and volcanic/geodynamic history, providing the longest continental record in the entire Near East to date

Scientific drilling of Lake Chalco, Basin of Mexico (MexiDrill)

The primary scientific objective of MexiDrill, the Basin of Mexico Drilling Program, is development of a continuous, high-resolution ∼400 kyr lacustrine record of tropical North American environmental change. The field location, in the densely populated, water-stressed Mexico City region gives this record particular societal relevance. A detailed paleoclimate reconstruction from central Mexico will enhance our understanding of long-term natural climate variability in the North American tropics and its relationship with changes at higher latitudes. The site lies at the northern margin of the Intertropical Convergence Zone (ITCZ), where modern precipitation amounts are influenced by sea surface temperatures in the Pacific and Atlantic basins. During the Last Glacial Maximum (LGM), more winter precipitation at the site is hypothesized to have been a consequence of a southward displacement of the mid-latitude westerlies. It thus represents a key spatial node for understanding large-scale hydrological variability of tropical and subtropical North America and is at an altitude (2240 m a.s.l.), typical of much of western North America. In addition, its sediments contain a rich record of pre-Holocene volcanic history; knowledge of the magnitude and frequency relationships of the area's explosive volcanic eruptions will improve capacity for risk assessment of future activity. Explosive eruption deposits will also be used to provide the backbone of a robust chronology necessary for full exploitation of the paleoclimate record. Here we report initial results from, and outreach activities of, the 2016 coring campaign

Extending the tephra and palaeoenvironmental record of the Central Mediterranean back to 430 ka: A new core from Fucino Basin, central Italy

Here we present the first tephrostratigraphic, palaeomagnetic, and multiproxy data from a new ∼98 m-deep sediment core retrieved from the Fucino Basin, central Italy, spanning the last ∼430 kyr. Palaeoenvironmental proxy data (Ca-XRF, gamma ray and magnetic susceptibility) show a cyclical variability related to interglacial-glacial cycles since the Marine Isotope Stage (MIS) 12-MIS 11 transition. More than 130 tephra layers are visible to the naked eye, 11 of which were analysed (glass-WDS) and successfully correlated to known eruptions and/or other equivalent tephra. In addition to tephra already recognised in the previously investigated cores spanning the last 190 kyr, we identified for the first time tephra from the eruptions of: Tufo Giallo di Sacrofano, Sabatini (288.0 ± 2.0 ka); Villa Senni, Colli Albani (367.5 ± 1.6 ka); Pozzolane Nere and its precursor, Colli Albani (405.0 ± 2.0 ka, and 407.1 ± 4.2 ka, respectively) and Castel Broco, Vulsini (419–490 ka). The latter occurs at the bottom of the core and has been 40Ar/39Ar dated at 424.3 ± 3.2 ka, thus providing a robust chronological constrain for both the eruption itself and the base of the investigated succession. Direct 40Ar/39Ar dating and tephra geochemical fingerprinting provide a preliminary radioisotopic-based chronological framework for the MIS 11-MIS 7 interval, which represent a foundation for the forthcoming multiproxy studies and for investigating the remaining ∼110 tephra layers that are recorded within this interval. Such future developments will contribute towards an improved MIS 11-MIS 7 Mediterranean tephrostratigraphy, which is still poorly explored and exploited