Triaxial Measurements Research Articles

Application of W/O Drilling Fluid in Horizontal Well with Long Horizontal Sections in Oil Shale Formations

To address the challenges of oil shale formation well wall instability,micro and nano pore blocking, long horizontal section well friction and borehole purification.We have analysed the nature of formation lithology,matrix pore size and specific surface by using linear expansion method,rolling recovery method and nuclear magnetic resonance method,and developed a white W/O drilling fluid system with an oil-to-water ratio of 70:30 by developing emulsifiers,tackifying and shear strength-improving agents,plugging agents and preferably filter loss agents,and wetting agents.The system was evaluated by using the breakthrough pressure test triaxial compression test and relaxation measurement method in the laboratory. The evaluation results showed that the system could not only maintain the strength of the rock sample but also improve the plasticity of the rock sample after the drilling fluid soaked with the breakthrough pressure of 6.5MPa,and it had good suspension capacity after the relaxation value reached 60s.The field test results show that the system has stable rheological properties and solves the problems of well wall instability and borehole purification,with the well diameter expansion rate of only 3.8% and the mechanical drilling speed of up to 10.85m/h.The SY-1 well has set a record for the longest horizontal section of 1800m in the Liaohe River oil area.

Triaxial detection of the neuromagnetic field using optically-pumped magnetometry: feasibility and application in children

Optically-pumped magnetometers (OPMs) are an established alternative to superconducting sensors for magnetoencephalography (MEG), offering significant advantages including flexibility to accommodate any head size, uniform coverage, free movement during scanning, better data quality and lower cost. However, OPM sensor technology remains under development; there is flexibility regarding OPM design and it is not yet clear which variant will prove most effective for MEG. Most OPM-MEG implementations have either used single-axis (equivalent to conventional MEG) or dual-axis magnetic field measurements. Here we demonstrate use of a triaxial OPM formulation, able to characterise the full 3D neuromagnetic field vector. We show that this novel sensor is able to characterise magnetic fields with high accuracy and sensitivity that matches conventional (dual-axis) OPMs. We show practicality via measurement of biomagnetic fields from both the heart and the brain. Using simulations, we demonstrate how triaxial measurement offers improved cortical coverage, especially in infants. Finally, we introduce a new 3D-printed child-friendly OPM-helmet and demonstrate feasibility of triaxial measurement in a five-year-old. In sum, the data presented demonstrate that triaxial OPMs offer a significant improvement over dual-axis variants and are likely to become the sensor of choice for future MEG systems, particularly for deployment in paediatric populations.

Development and preliminary application of a minimum axle-distance triaxial measurement system for the acoustic characteristics of marine sediments

The seabed sediments have different original stress states. It is of great significance to study the acoustic characteristics of sediments in different stress states. By adding an acoustic device into the geotechnical Global Digital Systems (GDS) stress path triaxial system, a minimum axle-distance triaxial measurement system for the acoustic properties of seabed sediments is developed. The GDS triaxial system is used to simulate the in-situ stress state of sediments, and the acoustic measurement system is used to measure the sound attenuation and sound velocity of them. The reliability of the developed measurement system is verified by the pure water calibration test. Then, the sound attenuation and sound velocity of triaxial specimens of the sandy sediments in Hangzhou Bay, China, are tested with different effective stresses and excitation frequencies. Test results are consistent with the existing acoustic theory of marine sediments, which verifies the effectiveness of the developed measurement system. It indicates that the developed measurement system can be applied to study the acoustic properties of seabed sediments in different original seabed stress states.

Tutorial: Petrophysics of Thinly Bedded Formations

This paper was written in response to a personal request from the Editor to contribute a “tutorial” on thin-bed petrophysics. The paper is not intended to be an exhaustive review of all the work that has been done regarding thin-bed petrophysics. Instead, it is an introduction to the different types of methods available, with some discussion on the strengths and weaknesses of each. Thin beds have posed problems for petrophysicists for many decades, mostly because conventional interpretation techniques in thin beds tend to overestimate water saturation, owing to the very low resistivities often seen in hydrocarbon-bearing intervals. There are a number of different techniques available to the petrophysicist for evaluating thin beds, including conventional “bulk volume” techniques, various types of high-resolution modeling, and different low-resolution modeling techniques, both with and without triaxial resistivity measurements. There is no single best technique to use. Instead, the most appropriate method is dependent on the formation complexity and the types of data available. Generally, it is very useful to have triaxial resistivity measurements to understand the formation anisotropy better. However, in some cases, simple “triple-combo” logging suites may be sufficient, provided the interpretation can be improved and verified with core data. In other cases, complex formation modeling is required to provide the best results with low uncertainty. If using either low- or high-resolution modeling, the reporting of evaluation results is not straightforward. Net reservoir and net pay cutoffs require special consideration, and the results are specific to the formation components rather than the bulk volume formation, as they are with conventional reservoir summaries. Furthermore, the quantification of petrophysical uncertainties in formation modeling of thinly bedded formations is better done using scenario modeling rather than Monte Carlo processing, which is commonly applied with bulk volume techniques.

First LWD Co-Located Antenna Sensors for Real-Time Anisotropy and Dip Angle Determination, Yielding Better Look-Ahead Detection

Electromagnetic (EM) resistivity tools measure the electrical properties of downhole formations that are critical in determining the hydrocarbon saturation of a reservoir. In complex and heterogeneous reservoirs, both horizontal and vertical formation resistivities are required to obtain an accurate hydrocarbon saturation. For decades, wireline multicomponent induction type measurements have provided reliable determination of formation anisotropy, structural dip, and dip azimuth in wells with any orientation relative to the bedding planes. Logging-while-drilling (LWD) multi-array propagation resistivity tools have also demonstrated similar capability in deviated wells where the relative dip angle is between 45° and 90°. However, measuring anisotropy and dip in wells with a low relative dip angle still poses difficulties for LWD propagation resistivity systems because of the antenna structures employed. This paper describes the development of a new LWD EM sensor equipped with an innovative, co-located, tilted antenna structure. The tool, along with a unique processing scheme, enables the determination of horizontal and vertical resistivity as well as the dip angle and the azimuth of the formation based on an assumption of transversely isotropic (TI) formation models (Graciet and Shen, 1998) while drilling in real time. The co-located sensor design is capable of acquiring multicomponent signals that are sensitive to formation anisotropy and structural dip in wells at any orientation. Modeling studies and several field trials have proven that the design concept can detect these formation properties at any arbitrary wellbore deviation. This paper presents test results from the new technology, together with reference measurements from azimuthally compensated LWD and fully triaxial wireline resistivity measurements. A good comparison is observed in these trials, providing an independent verification of the tool performance. The azimuthal measurements of the new sensors allow for determining formation anisotropy and dip at any wellbore deviation (Bittar et al., 2011b; Bittar et al., 2012), as well as providing 360° azimuthal resistivity and geosignals and allowing a three-dimensional (3D) resistivity mapping technique for real-time decisions. Integrating the co-located antennas with deep-reading antennas in a near-bit collar further provides both anisotropy measurements and ultradeep signals very close to the bit and enhances look-ahead detection ranges for LWD applications.

Gastrointestinal nematode infection affects overall activity in young sheep monitored with tri-axial accelerometers

Animals suffering from parasitism typically display altered grazing behaviour and a voluntary reduction in feed intake. These changes are potentially important as indicators of disease. Recent advances in sensor technologies provide the opportunity to objectively measure animal activity while on pasture. Tri-axial accelerometers measure body movement in terms of acceleration, which can then be used to estimate physical activity over time. This study investigated if tri-axial measures of overall activity can be used to assess the impact of gastrointestinal nematode (GIN) infection in young sheep. To address this, the overall activity, faecal nematode egg count (FEC) and body weight of two treatment groups of Romney X Suffolk ram lambs were compared. Animals were monitored for four days using tri-axial accelerometer sensors mounted on a ram mating harness after 42-days grazing on contaminated pasture. On Day 0, all lambs were given anthelmintics. Subsequently, a Suppressive Treatment Group (n = 12) was treated with anthelmintics every two weeks. An Untreated Group (n = 12) did not receive further anthelmintics. Overall activity levels were monitored from Day 42 – 46. Activity level was calculated as vectorial dynamic body acceleration (VeDBA). Anthelmintic treatment had a significant effect on FEC but there was no evidence found for a treatment effect on body weight growth over the 42-day period. An effect of treatment and lamb starting weight on overall activity was found (beta = –0.74, 95 % CI –1.17 to –0.30, p = 0.002), identifying a negative impact of parasitism on activity in heavier animals. These results highlight the usefulness of this approach in assessing the effect of GIN parasitism on sheep monitored remotely. If a threshold value of activity could be determined, it could provide a useful tool for farmers and managers that serves as an early indicator of parasitism in sheep.

Second-order effects in parametric-resonance magnetometers based on atomic alignment

Optically-pumped magnetometers (OPM) based on parametric resonance allow real-time tri-axial measurement of very small magnetic fields with a single optical access to the gas cell. Most of these magnetometers rely on circularly polarized pumping light. We focus here on the ones relying on linearly polarized light, yielding atomic alignment. For these magnetometers we investigate three second order effects which appear in the usual regimes of operation, so to clarify if they translate to metrological problems like systematic errors or increased noise. The first of these effects is the breakdown of the three-step approach when the optical beam has a large intensity. The second one is the breakdown of the rotating wave approximation when the frequencies of the RF fields are not much larger than the rates of other atomic processes. The third one is the tensor light-shift which appears when the light is slightly detuned from resonance. This work should help to clarify the accuracy reachable with OPM, which is an important question notably for medical imaging applications.

An Investigation on Failure Behaviour of a Porous Sandstone Using Single-Stage and Multi-stage True Triaxial Stress Tests

The deformational characteristics of a set of synthetic sandstones when subjected to true triaxial stress conditions were investigated in this study. The experimental results showed that the lateral stress anisotropy (σ2 ≠ σ3) significantly affected the rock’s compressive strength, elastic modulus, inelastic deformation, dilatancy and failure mode. By increasing the intermediate principal stress (σ2) over quasi-isotropic conditions (σ2 = σ3), the measured compressive strength increased more than twice in some cases, and the onset of dilatancy was suppressed to more than 80% of the peak stress. The obtained failure stresses were examined against a Mogi-type true triaxial criterion and indicated a good fit to the empirical model. Furthermore, multistage-true triaxial tests were carried out on the sandstones, and their results were compared against the single-stage test data to examine the suitability of this testing method for evaluation of the σ2 impact on the rock’s mechanical properties. Over the course of each multistage-true triaxial test, a sample was loaded to several levels of intermediate principal stress, while the minimum stress was held constant. Comparing the results of the multistage-true triaxial tests on the synthetic sandstones with the equivalent single-stage true triaxial measurements revealed noticeable differences between the resultant rock strengths and elastic properties. The findings of these tests are discussed and the potential mechanisms responsible for the observed disagreements are explained in this paper.

Development and evaluation of automated ultrasonographic detection of bladder diameter for estimation of bladder urine volume.

Bladder urine volume has been estimated using an ellipsoid method based on triaxial measurements of the bladder extrapolated from two-dimensional ultrasound images. This study aimed to automate this process and to determine the accuracy of the automated estimation method for normal and small amounts of urine. A training set of 81 pairs of transverse and longitudinal ultrasound images were collected from healthy volunteers on a tablet-type ultrasound device, and an automatic detection tool was developed using them. The tool was evaluated using paired transverse/longitudinal ultrasound images from 27 other healthy volunteers. After imaging, the participants voided and their urine volume was measured. For determining accuracy, regression coefficients were calculated between estimated bladder volume and urine volume. Further, sensitivity and specificity for 50 and 100 ml bladder volume thresholds were evaluated. Data from 50 procedures were included. The regression coefficient was very similar between the automatic estimation (β = 0.99, R2 = 0.96) and manual estimation (β = 1.05, R2 = 0.97) methods. The sensitivity and specificity of the automatic estimation method were 88.5% and 100.0%, respectively, for 100 ml and were 94.1% and 100.0%, respectively, for 50 ml. The newly-developed automated tool accurately and reliably estimated bladder volume at two different volume thresholds of approximately 50 ml and 100 ml.

Signal interference of non-uniform tire load on stress-in-motion sensing element

ABSTRACT Sensing elements in Stress-In-Motion (SIM) system were designed to measure vertical and tangential tire-pavement contact forces under uniform loading conditions. However, in reality, the contact forces are not uniformly distributed. Compared with tangential shear force, non-uniform vertical contact force causes a bending moment which may take significant errors to tri-axial contact stress measurements. In the research, three tire thread-sensing element contact conditions (uniform, non-uniform and point load) were applied and influences of the non-uniformity on vertical and tangential stress signals were determined by finite element method. It was found that significant errors may occur as a result of the contact force non-uniformity. The error of the vertical contact force measurement was up to 65% (non-uniform load). In extreme situation with point load, the error would be greater. The errors caused by vertical contact force non-uniformity to the tangential contact stress measuring signals were 15% (non-uniform force) and 60% (point load). So designing of the SIM sensing element and decoupling method between measuring signals should be carefully reconsidered.

三轴力解耦测量的高灵敏触觉传感器

三轴力解耦测量的高灵敏触觉传感器

Void growth and coalescence in hexagonal close packed crystals

Crystal plasticity finite element analyses are carried out in three dimensions to investigate void evolution in hexagonal close packed single crystals. Two crystallographic orientations are considered favoring either slip or twinning, which are both accounted for in the formulation. The effect of stress state is analyzed by varying some nominal measure of overall triaxiality. The orientation and stress state dependence of the effective response, including void evolution, are characterized in some detail, as driven by the micromechanics of plastic deformation. Particular emphasis is laid on crystallographic aspects, such as the emergence of deformation sectors, the influence of the polar character of twinning, and directional void growth. In addition, all analyses were conducted up to strain localization so as to uncover orientation and crystallographic aspects of void coalescence. The potential implications of slip and twinning mechanisms on ultimate failure in hexagonal close packed materials are discussed.

Uni- and triaxial accelerometric signals agree during daily routine, but show differences between sports

Accelerometers objectively monitor physical activity, and ongoing research suggests they can also detect patterns of body movement. However, different types of signal (uniaxial, captured by older studies, vs. the newer triaxial) and or/device (validated Actigraph used by older studies, vs. others) may lead to incomparability of results from different time periods. Standardization is desirable. We establish whether uniaxial signals adequately monitor routine activity, and whether triaxial accelerometry can detect sport-specific variations in movement pattern. 1402 adolescents wore triaxial Actigraphs (GT3X) for one week and diaried sport. Uni- and triaxial counts per minute were compared across the week and between over 30 different sports. Across the whole recording period 95% of variance in triaxial counts was explained by the vertical axis (5th percentile for R2, 91%). Sport made up a small fraction of daily routine, but differences were visible: even when total acceleration was comparable, little was vertical in horizontal movements, such as ice skating (uniaxial counts 41% of triaxial) compared to complex movements (taekwondo, 55%) or ambulation (soccer, 69%). Triaxial accelerometry captured differences in movement pattern between sports, but so little time was spent in sport that, across the whole day, uni- and triaxial signals correlated closely. This indicates that, with certain limitations, uniaxial accelerometric measures of routine activity from older studies can be feasibly compared to triaxial measures from newer studies. Comparison of new studies based on raw accelerations to older studies based on proprietary devices and measures (epochs, counts) will require additional efforts which are not addressed in this paper.

LSS-RM: Using Multi-Mounted Devices to Construct a Lightweight Site-Survey Radio Map for WiFi Positioning.

A WiFi-received signal strength index (RSSI) fingerprinting-based indoor positioning system (WiFi-RSSI IPS) is widely studied due to advantages of low cost and high accuracy, especially in a complex indoor environment where performance of the ranging method is limited. The key drawback that limits the large-scale deployment of WiFi-RSSI IPS is time-consuming offline site surveys. To solve this problem, we developed a method using multi-mounted devices to construct a lightweight site-survey radio map (LSS-RM) for WiFi positioning. A smartphone was mounted on the foot (Phone-F) and another on the waist (Phone-W) to scan WiFi-RSSI and simultaneously sample microelectromechanical system inertial measurement-unit (MEMS-IMU) readings, including triaxial accelerometer, gyroscope, and magnetometer measurements. The offline site-survey phase in LSS-RM is a client–server model of a data collection and preprocessing process, and a post calibration process. Reference-point (RP) coordinates were estimated using the pedestrian dead-reckoning algorithm. The heading was calculated with a corner detected by Phone-W and the preassigned site-survey trajectory. Step number and stride length were estimated using Phone-F based on the stance-phase detection algorithm. Finally, the WiFi-RSSI radio map was constructed with the RP coordinates and timestamps of each stance phase. Experimental results show that our LSS-RM method can reduce the time consumption of constructing a WiFi-RSSI radio map from 54 min to 7.6 min compared with the manual site-survey method. The average positioning error was below 2.5 m with three rounds along the preassigned site-survey trajectory. LSS-RM aims to reduce offline site-survey time consumption, which would cut down on manpower. It can be used in the large-scale implementation of WiFi-RSSI IPS, such as shopping malls, hospitals, and parking lots.

Evaluating Micro-Seismic Events Triggered by Reservoir Operations at the Geothermal Site of Groß Schönebeck (Germany)

This study aims at evaluating the spatial and temporal distribution of 26 micro-seismic events which were triggered by hydraulic stimulation at the geothermal site of Gros Schonebeck (Germany). For this purpose, the alteration of the in-situ stress state and the related change of slip tendency for existing fault zones due to stimulation treatments and reservoir operations is numerical simulated. Changes in slip tendency can potentially lead to reactivation of fault zones, the related movement can lead to the occurrence of seismic events. In the current numerical study, results obtained based on the thermal–hydraulic–mechanical coupled simulation are compared to field observations. In particular, the study focuses on describing the fault reactivation potential: (1) under in-situ stress conditions; (2) during a waterfrac stimulation treatment; and (3) during a projected 30 years production and injection period at the in-situ geothermal test-site Gros Schonebeck. The in-situ stress state indicates no potential for fault reactivation. During a waterfrac stimulation treatment, micro-seismic events were recorded. Our current evaluation shows an increase of slip tendency during the treatment above the failure level in the direct vicinity of the micro-seismic events. During the projected production and injection period, despite increased thermal stress, the values for slip tendency are below the threshold for fault reactivation. Based on these results, and to prove the applied method to evaluate the observed micro-seismic events, a final discussion is opened. This includes the in-situ stress state, the role of pre-existing fault zones, the adopted criterion for fault reactivation, and a 3D rock failure criterion based on true triaxial measurements.

Influence of footwear comfort on the variability of running kinematics

Footwear comfort is an important factor in design, purchase and use of running shoes but current measures require multiple subjective assessments. Therefore, an objective and more reliable surrogate measure of footwear comfort would be of high relevance. In other research fields, perceived comfort was found to influence the variability of movement execution. Consequently, the purpose of this study was to investigate the influence of perceived footwear comfort on the variability of running kinematics as a potential surrogate measure of comfort. Thirty-six recreational athletes ran in five different running shoes on an indoor track while their running kinematics were recorded using a foot-mounted tri-axial inertial measurement unit (IMU). Footwear comfort was measured through multiple subjective assessments. The relative variability of IMU data was determined across the swing phase of 45 gait cycles and compared between the most and least comfortable shoes. Lower footwear comfort was associated with lower kinematic variability especially in the second half of the swing phase but only for variables that are not directly linked to the forward propulsion during running and mainly describe frontal and transverse joint rotations. The constraints of an uncomfortable shoe may lead to the adaptation of a more monotonous running style with the goal to stay in the least uncomfortable movement path. This finding may partially explain a previously described higher injury risk when exercising in footwear of lower comfort, as more repetitive forces could increase the risk of overuse injury. The results of this study implicate the possible use of IMU-based kinematic variability as a surrogate measure of footwear comfort, which could complement subjective measures.

Investigation of Stress Status in the Micro-Space of Surface and Subsurface Layer

One of main issues when evaluating or analysing quality and functional properties of work-piece is identification of status of residual stress. Every treatment or machining process generates residual stress in the surface and subsurface layers of the material structure. The residual stress has a large influence on the functional properties of the components. The article is focused on the method of triaxial measurement of residual stress after machining the surface of sample by high feed milling technology. Significance of triaxial measuring is the capability of measuring in different angles so it is possible to acquire stress tensor containing normal and shear stress components acting in the spot of measuring, using a Cartesian coordinate system.

Triaxial Measurement of Residual Stress After High Feed Milling Using X-ray Diffraction

Surface integrity has been an important research topic in the last decades. Machining generates residual stresses in the surface and subsurface layers of the structural elements. The residual stress has a large influence on the functional properties of the components. X-ray diffractometry is a non-destructive method applicable for the measurement of residual stresses in surface and subsurface layers of components. The article deals with the method of triaxial measurement of residual stress after machining the surface of sample by high feed milling technology. Significance of triaxial measuring is the capability of measuring in different angles so it is possible to acquire stress tensor containing normal and shear stress components acting in the spot of measuring, using a Cartesian coordinate system. For comparison, a simple measurement of residual stresses in the point indicates the stress direction only in normal direction of the measured surface.

Operational and Safety Performance Investigation of Skew Superelevation Runoff

Hydroplaning and the corresponding hydroplaning speed of a vehicle are critical road safety concerns. To avoid hydroplaning, nine technical measures are available. One of the most effective is the construction of skew superelevation runoff at the critical pavement section of a highway, especially in highway rehabilitation and reconstruction projects. The concept was introduced in the German RAS-L design guide of 1984; its implementation is found mainly in central European countries. Skew superelevation runoff was adopted in recent freeway projects, some of which are reconstructions of existing two-lane highways into freeways to address identified sections with high potential for hydroplaning. Its use under normal traffic has resulted in concerns about its safety and comfort effectiveness. To investigate the operational and safety performance of the constructed skew superelevation runoffs, accurate triaxial acceleration measurements were carried out on the Korinthos-Patra freeway in Greece for a combination of vehicles and speeds along these skew superelevation runoff sections. Resulting limitational thresholds were shown to be adequate for safe operation of the skew superelevation runoff. Vehicle occupant comfort thresholds, however, are narrow and require specific additional construction improvements when design values are not observed.

Triaxial Measurement Method for Analysis of Residual Stress after High Feed Milling by X-Ray Diffraction

Abstract Surface integrity is a broad term which includes various quality factors affecting the functional properties of parts. Residual stress is one of these factors. Machining generates residual stresses in the surface and subsurface layers of the structural elements. X-ray diffractometry is a non-destructive method applicable for the measurement of residual stresses in surface and subsurface layers of components. The article is focused on the non-destructive progressive method of triaxial measurement of residual stress after machining the surface of sample by high feed milling technology. Significance of triaxial measuring is the capability of measuring in different angles so it is possible to acquire stress tensor containing normal and shear stress components acting in the spot of measuring, using a Cartesian coordinate system.