Offset Field Research Articles

Present-day stress control on fluid migration pathways: Case study of the Zechstein fractured carbonates, NW-Germany

Abstract Understanding the orientation and connectivity of fracture systems in tight reservoirs is essential to reduce uncertainties in reservoir development and production. However, the actual flow potential of the fractures can be controlled by the present-day stress field. Dilation- and slip tendency analyses can improve fracture permeability evaluations and thus, aid in estimating the hydrocarbon recovery of a field. This study focuses on a naturally-fractured, relatively tight (matrix permeabilities of 0.01–1 mD) and gas-producing Late Permian (Zechstein) reservoir in the Southern Permian Basin, northern Germany. Fracture data are obtained from resistivity image log data of a 775 m long horizontal well, and show principal NE – SW orientation with main dip angles steeper than 70°. To quantify the potential of those fractures that contribute to the flow within the reservoir, dilation (Td)- and slip (Ts) tendencies are calculated. Two different stress scenarios are defined based on known variations in the orientation of the horizontal stresses between formations below and above the Zechstein salt in an offset field approximately 5 km away. Results of Td and Ts strongly depend on the strike and dip angle of the fractures, with sub-vertical fractures showing highest potential to dilate while fractures with dip angles of 60° are favorably oriented for slip. Fractures with orientations parallel to the principal horizontal stress have highest slip- and dilation tendencies. Adding this information to the calculation of fracture permeability results in a significant reduction of the calculated flow potential due to the influence of the stress field. Thus, incorporating stress field data helps reducing risks in field development planning.

Optical Sensing of Broadband RF Magnetic Field Using a Micrometer-Sized Diamond

High-resolution field imaging with minimized invasiveness is of growing interest with the development of radio frequency (RF) integrated circuits and planar antenna characterization. In this paper, we propose an optical broadband sensor with static offset magnetic field using a diamond crystal that contains an ensemble of nitrogen-vacancy (NV) centers. The spatial resolution of micrometer scale is demonstrated by using a diamond crystal of this size. This technique is based on the modulation of fluorescence emitting by NV center under green laser excitation, by an off-axis magnetic field at radio frequencies. We demonstrate experimentally the detection of an RF magnetic field, with minimum measurable amplitude on the order of 0.1 Gauss, which is limited by the noise floor of the avalanche photodetector. The sensitivity can be further improved by noise suppression in optics. The bandwidth of the sensor is measured to be 15 MHz.

In situ XRD analyses for asymmetric responses of poled PLZT ceramics during electric fatigue

Electric fatigue behaviors of the poled lanthanum-doped lead zirconate titanate (PLZT) ceramics were investigated using a home-made electric loading apparatus in conjunction with a conventional X-ray diffractometer. The XRD data were measured under actions of the applied direct current electric fields on the as-received poled PLZT specimens being experienced various cycles (10N) of alternating current (AC) electric fields. Experimental data showed that in addition to apparent degradation in remnant polarization, asymmetries in hysteresis loops and fraction of 90° domain switching curves were observed. It was found that an offset electrical field (\(\Delta {{\text{E}}_N}\)) was induced in the poled specimen by polarization with its direction against the direction of the polarization. Furthermore, the magnitude of \(\Delta {{\text{E}}_N}\) and the degree of asymmetry (δN) decreased as the number of AC electric fatigue cycles (10N) varied from 100 to 106. In situ XRD data suggested that the poled specimen exhibited different abilities to reorient a-domains into c-domains when the applied electric fields were opposite. The δN not only depended linearly on \(\Delta {{\text{E}}_N}\), but also on abilities of the poled specimen to reorient a-domains into c-domains.

Segmentation of the Wear Area of Planar Shoeprint Using Mean Shift

In the field of forensic science, the wear area of planar shoeprint is a useful information for analysis of criminal suspects. However, the identification of shoeprint wear areas is often subjective to the expert’s personal experience. In this paper, considering the characteristics of planar shoeprint images, a segmentation algorithm based on mean-shift is proposed to process planar shoeprint image to get the wear area. Firstly, the multiplicative intrinsic component optimization method(MICO) is employed to pre-segment the image. This method combines the level set with the offset field correction method to segment the outline of the unevenly printed shoeprint image. Secondly, we use mean shift to segment the image. Finally, we compare the actual wear area with the segmented wear area. It is found that the segmentation effect is good. By pattern recognition method, the wear area of the shoeprint is segmented to provide more objective technical support for detecting cases.

Fabrication and ferromagnetic resonance study of BZT-BCT/LSMO heterostructure films on LAO and Pt

Abstract In this article, dynamic magnetic properties of La0.7Sr0.3MnO3 (LSMO) thin film capped with a Pb-free ferroelectric BZT-BCT layer deposited on two different substrates, i.e. lanthanum aluminate (LAO) and Platinum (Pt), by pulsed laser deposition (PLD) have been investigated using ferromagnetic resonance (FMR) spectroscopy. The heterostructures of BZT-BCT/LSMO on LAO substrate were highly (0 0 l)-oriented whereas these were randomly oriented on Pt substrate. The well-behaved M-H hysteresis loops were observed at room temperature for both heterostructures indicating the ferromagnetic behavior of LSMO. The right shift of the hysteresis loop of the heterostructure was observed due to the magnetoelectric coupling between ferroelectric and ferromagnetic layers. The FMR measurements yield optimum values of different important parameters such as the linewidth offset, Gilbert damping, gyromagnetic ratio, and in-plane uniaxial anisotropy field of the thin films, which are essential to design spin valve and magnetic tunneling based devices. We found the lowest Gilbert damping parameter of ∼0.03 for the BZT-BCT/LSMO/LAO heterostructure due to spin orbit coupling. In addition, the gyromagnetic ratio was also obtained to be small (0.002 GHz/Oe) in the same film. These results open new possibilities to use BZT-BCT/LSMO heterostructure for future spintronic device applications.

Mercury\u2019s anomalous magnetic field caused by a symmetry-breaking self-regulating dynamo

The discovery of Mercury’s unusually axisymmetric, anomalously axially offset dipolar magnetic field reveals a new regime of planetary magnetic fields. The cause of the offset dipole remains to be resolved, although some exotic models have been proposed. Deciphering why Mercury has such an anomalous field is crucial not only for understanding the internal dynamics, evolutionary history and origin of the planet, but also for establishing the general dynamo theory. Here we present numerical dynamo models, where core convection is driven as thermo-compositional, double-diffusive convection surrounded by a thermally stably stratified layer. We show that the present models produce magnetic fields similar in morphology and strength to that of Mercury. The dynamo-generated fields act on the flow to force interaction between equatorially symmetric and antisymmetric components that results in north-south asymmetric helicity. This symmetry-breaking magnetic feedback causes the flow to generate and maintain Mercury’s axially offset dipolar field.

A Block Ramp Errors Correction Method of Planet Subpixel Offset: Application to the 2018 Mw 7.5 Palu Earthquake, Indonesia

Planet optical images have a short revisit period and high spatial resolution, so they have great potential in surface offset monitoring. However, few studies have focused on the error source analysis and accuracy improvement in the offset field of Planet images. In this study, we investigate the optimal band selection of the Planet images and the error sources for subpixel offset monitoring, using the 28 Sept. 2018 Mw7.5 Palu earthquake as an example. The results show that Band 2 is the optimal band for surface offset monitoring and ramp errors are the dominating error source in the offset field. Considering the imaging characteristics of Planet satellites, we propose a block ramp errors correction method. Our proposed method can improve the accuracy of the Planet subpixel offset by 25% in comparison with the traditional method. We also compare the Planet images subpixel offset result with the Sentinel-2 subpixel offset result and find they are in good consistency. We combine the corrected Planet images offset and SAR images offset to solve the complete 3D deformation field of the Palu earthquake, which shows that the ruptured fault is a left-lateral strike-slip fault accommodated with normal component in the Palu-Koro fault. The earthquake was dominated by south-north and vertical deformation, with the maximum deformation of 6 m and 4 m in the horizontal and vertical directions, respectively. This study also has set a good example for using the Planet images for natural hazards monitoring (such as earthquakes and landslides).

Exploration of an unconventional petroleum resource through extensive core analysis and basin geology interpretation utilising play element methodology: the Lower Goldwyer Formation, onshore Canning Basin, Western Australia

Theia Energy Pty Ltd1 (Theia Energy) discovered a potential unconventional hydrocarbon resource in the Ordovician Lower Goldwyer (GIII) Formation shale located on the Broome Platform of the onshore Canning Basin. The collation, processing, analysis and interpretation of all available regional data culminated in a successful exploration well, Theia-1 (drilled in 2015), which, based upon petrophysical and core analyses, intersected a 70 m gross oil column at 1500–1570 m depth. Theia-1 recovered essential core and wireline log data required to analyse and assess the play elements and reservoir properties necessary for a viable shale oil and gas development. Utilisation of an ‘Unconventional Play Element’ methodology has proven the unconventional hydrocarbon potential of the GIII Formation, and preliminary modelling indicates that economic stimulated flow rates may be achieved. Further operations (a test well with multi-stage hydraulic fracture stimulation) are scheduled in the coming permit year to further quantify the presence of extractable organic matter in the GIII Formation, assess hydrocarbon flow rates, determine fluid composition and appraise commercial viability. This paper will discuss Theia Energy’s exploration campaign in the onshore Canning Basin starting with the regional evaluation, which encompassed all available geoscience data (offset wells, pre-existing seismic and potential analogue fields) and modern specialised shale analysis (sequence stratigraphy, paleogeography, geochemistry, unconventional petrophysics and petroleum systems modelling), to develop a robust regional geological model for the GIII Formation. Pre-drill analysis reduced exploration risk and successfully identified the key geological play elements essential for the successful Theia-1 exploration evaluation program.

Energy condition of isothermal magnetoelectric switching of perpendicular exchange bias in Pt/Co/Au/Cr2O3/Pt stacked film

Energy condition for isothermal reversible magnetoelectric switching of exchange bias was investigated using Pt/Co/Au/Cr2O3/Pt stacked films with different thicknesses of the antiferromagnetic layer (tAFM). We discussed the effective magnetic anisotropy energy of the antiferromagnetic layer (KAFMeff), the interface exchange coupling energy (JINT), and the offset electric field (E0). The dependence of KAFMeff on tAFM suggested that the magnetic domain wall motion significantly influenced the switching of the electric-field-induced magnetization similar to an ordinal ferromagnet. Below 0.025 mJ/m2, JINT was equal to the exchange anisotropy energy (JK), and above 0.025 mJ/m2, JINT exceeded JK, suggesting that JK is restricted by the magnetic domain wall energy. The dependence of E0 on tAFM revealed that E0 mainly arose from the interfacial uncompensated antiferromagnetic moment. The obtained results suggest that the energetic interpretation of static switching of electric-field-induced magnetization in Cr2O3 was similar to that of the ordinary ferromagnetic materials.

An optimised Hydraulic Fracturing Treatment on Challenging Rizq Field

Hydrocarbon production from unconventional reservoirs is often associated with hydraulic fracturing operations. In many cases however, the high in-situ stresses and complex natural fracture network hinder an effective stimulation process. Therefore, different strategies are adopted to increase the success chance of stimulation. These strategies are in many cases field dependent and thus cannot be extended to other fields. In this study, we demonstrate a new work flow to ensure a successful stimulation process in an unconventional gas field in Pakistan. Well Rizq-01 was drilled as an exploration into challenging PAB formation which is tight sandstone with 0.3mD permeability but highly fractured. Exploration wells in offset fields were drilled and stimulated in the same formation and resulted in screening-out and inability to place enough proppant due to fracture complexity and high in-situ-stresses. To overcome these challenges, extensive petrophysical and geomechanical analysis were performed to introduce a new workflow for stimulation of the formations with similar characteristics. The workflow includes a) Extract extensivewell log information for better understanding of stress barriers, stress magnitude and orientation, Young’s Modulus, formation fluid information, other essential petrophysical properties, b) Sensitivity analysis on the hydraulic fracturing treatment including the proppant size, type and volume, and fluid systeme.g. the design was based upon geomechanical and petrophysical interpretations of the openhole log data, and c) Redesign of fracturing treatment process utilizing a first-of-its-kind onsite pre-frac test results, showing its helpfulness in the absence of bottom-hole gauge. The study therefore summarizes the challenges, the work flow implemented, and the lesson learnt for successful stimulation job in Rizq Field.

Rock-Strength Analysis and Integrated FEA Modeling Optimize Bit Selection

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 186264, “Rock-Strength Analysis and Integrated FEA Modeling Optimize Bit Selection for Deepwater Exploration Drilling,” by M.R. Yoan Mardiana and Bonar Noviasta, SPE, Schlumberger, prepared for the 2017 SPE/IATMI Asia Pacific Oil and Gas Conference and Exhibition, Bali, Indonesia, 17–19 October. The paper has not been peer reviewed. Well X is a deepwater exploration well with a carbonate primary target. Traditionally, bit records from offset wells or fields have been the only main source of data for bit selection. Often, bit selection has been trial-and-error because of limited data availability. Now, however, rock-strength-analysis (RSA) software is a requirement for prejob planning to select a bit. Using log data from offset wells, a bit-selection software based on unconfined compressive strength (UCMPS) calculations has been used to optimize the bit selection for Well X. Comprehensive RSA for Bit Selection RSA software generated a comprehensive formation-evaluation and bit-selection analysis for a drilling application. Mud logs from offset wells were used to interpret the rock type. Some electronic logs that have petrographic analysis capability, such as gamma-ray, compressional sonic, density, neutron, and resistivity analysis, quantified the rock appearance and percentage depth-by-depth. The RSA software provided 18 rock types to be analyzed, from sedimentary rocks, such as sandstone, claystone, and limestone, to hard igneous and volcanic rocks. Bits were selected on the basis of their capability to drill a formation with a certain hardness. On the basis of that study, compressional sonic logs converted to shear sonic, combined with the formation type, can be used to calculate the UCMPS of the formation. Apart from drilling parameters, UCMPS is the main contributor to rate of penetration (ROP). UCMPS is also used to calculate abrasion and impact index of the formation. On the basis of the lithology to be drilled, rock UCMPS, formation abrasion, and impact index, the RSA application uses offset-well data from more than 12,500 wells to choose a fixed or roller-cone drill bit with an appropriate combination of cutting structure, gauge protection, hydraulic configuration, and other critical characteristics. With the RSA software, formation characteristics from offset wells can be analyzed. To expand the scope of the formation analysis, several wells from surrounding fields in the same region-al geology also have been correlated and analyzed. A polycrystalline-diamond-compact (PDC) -bit selector in the RSA software considers the blade count of the bit, the cutter size, and the blade profile on the basis of the compressive strength, formation abrasion, and formation impact. The harder the formation is, the software will recommend fewer blades and smaller cutter sizes for the bit to improve durability. If the formation consists mostly of shale and claystone, bit-balling flags will be generated and the bit should have better hydraulic optimization to improve bit cleaning. To reduce the risk of having an under-gauge bit because of abrasion, proper gauge protection should be added to the bit.

The Construction of a Graphene Hall Effect Magnetometer

This paper deals with design and fabrication of graphene micro-Hall devices along with driving and processing electronics to construct a highly sensitive graphene magnetometer system. Graphene micro-Hall elements were fabricated by implementing microfabrication techniques. Custom driving and processing circuitry was designed and built on a printed circuit board and integrated with fabricated graphene Hall devices; reducing the offset equivalent magnetic field and greatly improving the sensitivity. The performance parameters were quantitatively analyzed for characterizing the sensitivity in terms of linearity, current-related sensitivity, and magnetic field resolution. The potential of graphene magnetometers for detection capability of low fields has been demonstrated with a current related sensitivity of 2540 V/AT and magnetic field resolution of 162 nT/ $\surd $ Hz.

Coseismic displacements on Ischia island, real-time GPS positioning constraints on earthquake source location

We use GNSS data to simulate the early seismic source location of a M 4 event occurred in the island of Ischia, Italy. The study suggests that real-time GNSS data can support the seismic location system in the early stage of the emergency phase. We demonstrate that this very shallow earthquake, triggered significant displacements at a few stations in less than half an hour. Using exclusively GPS data, the first location of the hypocenter was possible with a latency of only 20 minutes. Early upgrades of the offset field in the first two hours confirm the source location confined within 1-2 km in the horizontal plane and less than 1 km depth.

Observation of proximities between spin-1/2 and quadrupolar nuclei in solids: Improved robustness to chemical shielding using adiabatic symmetry-based recoupling

We introduce a novel heteronuclear dipolar recoupling based on the R21−1 symmetry, which uses the tanh/tan (tt) shaped pulse as a basic inversion element and is denoted R21−1(tt). Using first-order average Hamiltonian theory, we show that this sequence is non-γ-encoded and that it reintroduces the |m| = 1 spatial component of the Chemical Shift Anisotropy (CSA) of the irradiated isotope and its heteronuclear dipolar interactions. Using numerical simulations and one-dimensional (1D) 27Al-{31P} through-space D-HMQC (Dipolar Heteronuclear Multiple-Quantum Correlation) experiments on VPI-5, we compare the performances of this recoupling to those of other non-γ-encoded |m| = 1 heteronuclear recoupling schemes: REDOR (Rotational-Echo DOuble Resonance), SFAM (Simultaneous Frequency and Amplitude Modulation) and R42−1(tt). Such comparison indicates that the R21−1(tt) scheme is more robust to CSA, offset and radiofrequency field inhomogeneities than the other schemes. We take advantage of the high robustness of R21−1(tt) to CSA and offset to demonstrate the possibility to correlate the signals of 207Pb isotope with those of neighboring half-integer spin quadrupolar nuclei. Such approach is demonstrated experimentally by acquiring 11B-{207Pb} D-HMQC 2D spectra of Pb4O(BO3)2 crystalline powder.

Simulation of high efficiency silicon heterojunction solar cells with molybdenum oxide carrier selective layer

A silicon heterojunction solar cell constructed with sub-stoichiometric molybdenum oxide (MoOx) carrier-selective layer and crystalline silicon substrate, which possesses a potential to achieve high power conversion efficiency, is investigated by numerical simulation tool AFORS-HET. In this work, MoOx is chosen as the emitter layer of the silicon heterojunction solar cell to mitigate parasitic light absorption losses. The influences of MoOx and p-a-Si:H layers with different thicknesses on the performances of the heterojunction solar cells are compared. The surface effect passivation is then used to explain the behavior of open circuit voltage increased with thickness variation, which physical mechanism is characterized by introducing the built-in electric field and minority carrier lifetime. Furthermore, we use the carrier recombination rate, band offset, and built-in electric field to investigate the effect of defect density states in the MoOx hole selective layer. In this paper, the highest power conversion efficiency of 27.27% is obtained by optimizing the thickness and defect density states of MoOx layer.

Sensitive and stable vector magnetometer for operation in zero and finite fields.

We report on an optically pumped magnetometer that uses multiple laser beams to pump and probe spin-polarized Cs atoms. The selected sensor geometry allows for operation in finite magnetic fields as well as close to zero field. In finite fields the magnetometer employs free spin precession signals to determine the field modulus and direction as described in a separate publication. This publication focuses on the magnetometer operation close to zero field, which is based on a ground state Hanle resonance. The four laser beams permit the simultaneous measurement of two orthogonal magnetic field components in a differential detection scheme that greatly suppresses technical laser power noise. Sensitivities better than 54 fT/Hz1/2 could be demonstrated simultaneously for both measurement channels in a well shielded environment. A minimum Allan deviation, limited by residual field fluctuations, of better than 40 fT was observed for integration times of 2s. The magnetometer achieves high sensitivity and stability in offset fields as well as close to zero field and is, thus, a universal tool for low frequency magnetic field measurements.

Stability analysis of a magnetic waveguide with self-generated offset field

The unexpected emerging stability of a time-modulated magnetic guide, realized without external offset fields, is demonstrated. We found a steady periodic solution around which the nonlinear dynamics is linearized. To investigate the orbital stability of the guiding, a formal criterion based on the analysis of the eigenvalues of the monodromy matrix of the system dynamics is used. To circumvent the difficulty in finding an analytical expression for these eigenvalues, a Lyapunov transformation of the system variables is proposed. From this transformation, an equation of state for the system parameters is derived, and it allows one to estimate an upper bound for the computed stability domains. In particular, we found a general expression for the threshold modulation frequency below which the guiding is unstable. Using experimentally accessible parameters, the stable guiding of 87Rb atoms is investigated.

An ultrashort throw ratio projection lens design based on a catadioptric structure

In this paper, we present a rotational symmetry for an ultrashort throw (UST) lens with offset field. The UST lens has a throw ratio of 0.23 and a total track of 195 mm. The optical elements of the UST lens are comprised of two parts. First, a catadioptric projection lens where the catadioptric function permits reaching an ultrashort throw ratio, short total track, while at the same time requiring fewer lens elements. The second part is a collimating lens which takes advantage of the telecentric condition to generate uniform total internal reflection (TIR) in the TIR prism. With this design, an effective focal length of -1.96 mm and a f-number of 2.4 can be obtained. The root mean square spot size and lateral colour of all fields are smaller than one pixel in size. The maximum optical distortion of −0.97% and TV distortion of 0.2% are acceptable. In terms of image quality, the modulation transfer function (MTF) values for all fields are above 0.65 at 0.245 line pairs/mm. Even when the tolerance error is considered, the MTF values for all fields are still above 0.3. The suitability of the novel UST lens design for projection applications is discussed.

MnNi-based spin valve sensors combining high thermal stability, small footprint and pTesla detectivities

Magnetoresistive sensors with high thermal robustness, low noise and high spatial resolution are the answer to a number of challenging applications. Spin valve sensors including MnNi as antiferromagnet layer provide higher exchange bias field and improved thermal stability. In this work, the influence of the buffer layer type (Ta, NiFeCr) and thickness on key sensor parameters (e.g. offset field, Hf) is investigated. A Ta buffer layer promotes a strong (111) texture which leads to a higher value of MR. In contrast, Hf is lower for NiFeCr buffer. Micrometric sensors display thermal noise levels of 1 nT/Hz1/2 and 571 pT/Hz1/2 for a sensor height (h) of 2 and 4 μm, respectively. The temperature dependence of MR and sensitivity is also addressed and compared with MnIr based spin valves. In this case, MR abruptly decreases after heating at 160°C (without magnetic field), contrary to MnNi-based spin valves, where only a 10% MR decrease (relative to the initial value) is seen at 275°C. Finally, to further decrease the noise levels and improve detectivity, MnNi spin-valves are deposited vertically, and connected in parallel and series (in-plane) to create a device with low resistance and high sensitivity. A field detection at thermal level of 346 pT/Hz1/2 is achieved for a device with a total of 300 SVs (4 vertical, 15 in series, 5 in parallel).

Estimation of gradients in quantum metrology

We develop a general theory to estimate magnetic field gradients in quantum metrology. We consider a system of $N$ particles distributed on a line whose internal degrees of freedom interact with a magnetic field. Usually gradient estimation is based on precise measurements of the magnetic field at two different locations, performed with two independent groups of particles. This approach, however, is sensitive to fluctuations of the off-set field determining the level-splitting of the particles and results in collective dephasing. In this work we use the framework of quantum metrology to assess the maximal accuracy for gradient estimation. For arbitrary positioning of particles, we identify optimal entangled and separable states allowing the estimation of gradients with the maximal accuracy, quantified by the quantum Fisher information. We also analyze the performance of states from the decoherence-free subspace (DFS), which are insensitive to the fluctuations of the magnetic offset field. We find that these states allow to measure a gradient directly, without the necessity of estimating the magnetic offset field. Moreover, we show that DFS states attain a precision for gradient estimation comparable to the optimal entangled states. Finally, for the above classes of states we find simple and feasible measurements saturating the quantum Cram\'er-Rao bound.