Field Data Acquisition Research Articles

Hydraulic-Fracture-Width Inversion Using Low-Frequency Distributed-Acoustic-Sensing Strain Data Part II: Extension for Multifracture and Field Application

Summary Low-frequency distributed-acoustic-sensing (LF-DAS) strain data are direct measurements of in-situ rock deformation during hydraulic-fracturing treatments. In addition to monitoring fracture propagation and identifying fracture hits, quantitative strain measurements of LF-DAS provide opportunities to quantify fracture geometries. Recently, we proposed a Green’s function–based algorithm for the inversion of LF-DAS strain data (Liu et al. 2020b) that shows an accurate estimation of fracture width near the monitor well with single-cluster completions. However, multicluster completions with tighter cluster spacings are more commonly adopted in recent completion designs. One main challenge in the inversion of LF-DAS strain data under such circumstances is that strain measurements at fracture-hit locations by LF-DAS are not reliable, which makes the individual contribution of each fracture to the measured strain data indistinguishable. In this study, we first extended the inversion algorithm to handle multiple fractures, investigated the uncertainties of the inversion results, and proposed possible mitigation to the challenges raised by completion designs and field data acquisition through a synthetic case study. Ideally, there are available data on both sides of each fracture so that the inverted width of each fracture can be obtained with a negligible error. In reality, the strain data are usually limited, providing less constraint on the width of individual fracture. Nevertheless, the inversion results provide an accurate estimation of the width summation of all fractures. To evaluate the individual fracture width, a time-dependent constraint is added to the inversion algorithm. We assume that the width at the current timestep is dependent on the width at the previous step and the width variation between the two timesteps. The width variation can be roughly estimated from LF-DAS strain-rate data at the fracture-hit location. This extra constraint helps to improve the inversion performance. Finally, a field example is presented. We show the width summation of all fractures and the width of each individual fracture as a function of treatment time. The time-dependent width profiles show consistent trends with the LF-DAS strain-rate data. The calculated strains from the inverted model match well with the LF-DAS measured strain data. The findings demonstrate the potential of LF-DAS data for quantitative hydraulic-fracture characterization and provide insights on better use of LF-DAS data. The direct information on fracture width helps to calibrate fracturing models and optimize the completion designs.

Participatory Mapping as a Didactic and Auxiliary Tool for Learning Community Integration, Technology Transference, and Natural Resource Management

Participatory mapping is a tool for community work linked to natural resource management. It is an auxiliary for diagnosis and data acquisition from communities and their natural resources. In Baja California, there are several indigenous communities, some close to urban areas but still unknown to most people in cities as well as visitors. These communities are fighting to restore and maintain their language, tradition, territory, biological, and cultural diversity. This work was carried out by linking members of the indigenous community of San Jose de la Zorra with bachelor’s and graduate degree students, to obtain information on the biological, cultural, and economic activities of the community through participatory mapping. The learning experience was significant for all participants; although it was not the intention in this study, students had the unique opportunity to exchange information and learn culture and biodiversity from indigenous people. The indigenous community was involved in field data acquisition and the use of some information and communication technology resources developed for this approach, and used it for natural resource management and decision making. The main results of this experience were wide format printed maps that were placed on several sites inside and outside the community, digital mapping that gave information about natural, cultural, and economic resources of the community for local and foreign visitors, and technology transference to solve problems identified by the community.

The development and application of China national landslide database and information system

Landslide caused significant damage to people and economical properties. Establishing a comprehensive landslide database is a fundamental task to support landslide mitigation. However, numerous challenges such as non-standardized data collection, inefficient data maintenance, discontinuous data update, and insufficient data service have become the major problems to establish a reliable, dynamic, and comprehensive landslide database. After two decades of development, more than 322,000 landslide events have been collected through professional field surveys, routine field inspections, and public reporting into the China national landslide database. Also, an information system, which was primarily built for data dynamic management, field data acquisition and integration, classified data storage, efficient data processing, real-time statistics, and information services have been achieved. In this paper, the China national landslide database and information system, including the development progress, database architecture, data services, and future developments, are introduced in details. The key considerations and experiences obtained through the development of China national landslide database and information system such as the establishment of massive landslide inventory data acquisition standardization process, comprehensive mechanism of data quality control and dynamic maintenance, services of landslide information system could be helpful for any other countries or regions that also greatly suffering from landslides, and contribute to the improvement of landslide risk reduction in the world.

Geohazards Inventory in Central Asia Using the Geohazard Mapping Module of the FAO Collect Earth and Earth Map Tools

Different national agencies in Central Asia assess and conduct long-term observations of dangerous geomorphological processes (geohazards) in their countries. However, these surveys are being conducted predominantly on those sites where direct threats and risks to the population or to critical infrastructure are observed. Neither field data acquisition nor regular remote sensing based observations cover the entire territory of Central Asia countries. With the recent developments in Earth Observation and cloud technologies, these observations and monitoring easily cover entire countries or regions. In this case study, the authors demonstrate the benefit of using the FAO Collect Earth and Earth Map tools for monitoring of geohazards in the Uzgen region of Kyrgyzstan.It is argued that by integrating the knowledge, skills and experience of local experts with the latest developments in EO and cloud computing, geohazards mapping will be carried out with high accuracy and without big financial investment. This study aims to outline good practice for data management that will ensure the required quality of information produced within this study. The successful result of this case study will be a starting point for broad use of this approach for observation and monitoring of geohazards, and for developing a Geohazards Inventory in Kyrgyz Republic and further in Central Asia.

Advances in perimetry for glaucoma.

Perimetry remains important for the diagnosis and management of glaucoma despite advances in imaging technology. The purpose of this review is to describe advances in the acquisition and analysis of visual field data and highlight novel techniques for performing perimetry. Studies have focused on improving the detection of patients at highest risk of severe vision loss and the development of innovative testing strategies that allow for more frequent testing. Artificial intelligence has been utilized in research settings to improve detection and characterization of glaucomatous field damage. Furthermore, tablet-based strategies and virtual reality headsets show promise for glaucoma screening and remote monitoring of patients with glaucoma. New testing strategies and research findings have improved our ability to identify patients with both paracentral and mid-peripheral visual field progression. New strategies have the potential to make visual field testing more efficient, reliable and accessible for patients with glaucoma.

Rapid mapping technique for data acquisition: The case of a summer school in the Banjarnegara district, Indonesia

Global environmental change makes us aware of the impact of natural hazards. Natural hazards are phenomena with large spatial dimensions and impacts but whose mapping and monitoring data can be recorded only by using satellite or aerial remote-imaging platforms (Poursanidis & Chrysoulakis, 2017). Given that Southeast Asia is the region in the world that is most vulnerable to disasters, it is necessary to implement capacity building for the young scientists in this region so that integrated disaster communities can be developed in their respective countries and possibly in the whole of Southeast Asia. This can be done through summer school, one of the best ways to transfer knowledge. The purpose of this article is twofold: (1) to explain the use of summer school to improve young scientists’ knowledge and understanding of rapid-mapping techniques; and (2) to perform a qualitative assessment of a summer school for rapid-mapping projects. The results of this project showed an increase in the basic science knowledge of the summer school participants (representatives of eight Southeast Asian countries) in terms of initial disaster data provision, field data acquisition using unmanned aerial vehicles, and the rapid-mapping system development design.

ASSESSING THE PRECURSORS OF POVERTY AMONG FAMERS IN THE SAVANNA ZONE OF CROSS RIVER STATE BEING TETFUND RESEARCH GRANT STUDY

Precursors of poverty relate to inherent factors that determine economic and social development of persons. This paper devotes attention to the investigation of these causes in a typical poverty of ravaged region of Nigeria in the Sub-Saharan belt of Africa. Here predominantly, over 80% of the populations are peasant farmers whose livelihood sustainability are constrained by social and ecological parameters. The paper adopted the approach by isolating the key elements of the social and ecological variable that may contribute to retardation of progress. Following field data acquisition, the data were tested statistically using the chi-square (x2) technique of analysis. The results of the two parameters were separately evaluated following the decision rates. From the findings, based on hypothesis I using socio-cultural variables the null hypothesis was rejected and the alternative accepted. Hence there is significant difference in the sociocultural precursor in poverty incidence in the area. Again for hypothesis, II, based on ecological parameters. The null hypothesis was also rejected indicating that there is a significant variable in causing poverty in the area.

Constructing vertical measurement logs using UAV-based photogrammetry: Applications for multiscale high-resolution analysis of coarse-grained volcaniclastic stratigraphy

Volcaniclastic stratigraphy can be difficult to map and describe due to its complex nature. However, such stratigraphy preserves information about fluctuations in volcanic activity and sedimentation and is vital to understanding volcanic systems. Uncrewed aerial vehicle (UAV) based analysis of volcanic stratigraphy can enhance mapping and analysis, especially on vertical surfaces where outcrop exposure is greatest. Here we present a method for using small UAVs to produce vertical grain size and bedding measurement logs, or quantitative stratigraphic columns, of vertical volcaniclastic stratigraphy. We demonstrate the range of high-accuracy measurements and parameters that can be collected for building measurement logs using consumer grade UAVs through a case study in the Marysvale volcanic field where we collected 34,422 grain measurements from 21 individual units. The purpose of producing such measurement logs is to enhance lithofacies analysis through the use of large quantitative datasets and improve the reproducibility of data reporting. Whereas descriptions of volcaniclastic units such as those describing grading are often reported qualitatively, we describe methods for calculating numerical parameters for enhanced lithologic analysis including grain size, grading, clast to matrix ratios, and shape characteristics. The methods described in this paper can enhance field data acquisition, mapping, and quantitative analysis of volcaniclastic deposits and are applicable to a wide range of other geologic settings where coarse-grained clastic sedimentary deposits exist.

Inversion of rayleigh waves dispersion using quantum-behaved PSO to characterize the embankment of mud flow Dam in Sidoarjo (LUSI)

The characterization of the embankment can be done by constructing the shear wave velocity in subsurface. The investigation of near surface wave velocity using Rayleigh wave dispersion analysis is popular. This method is very fast and effective to construct the vertical wave velocity, but has no unique solution. As a result, the inverse modelling is often trapped in local optimums. Therefore, we used Quantum-behaved PSO to get the best solution (global optimum). Inversion method using Quantum-behaved PSO was performed on synthetic and field measurement data. Field data acquisition was executed at P80-81 using both active and passive surface waves methods. The inversion result of Rayleigh wave dispersion is shear wave velocity structure. Shear wave velocity imaging resulted by this method was used to characterize the embankment of mud flow dam in Sidoarjo (LUSI) and be compared to the resistivity measurement data. The subsurface structure which is constructed from the inversion of Rayleigh wave gives the same result as the resistivity.

The Scientific Operations of Snow Eagle 601 in Antarctica in the Past Five Austral Seasons

The Antarctic ice sheet and the continent both play critical roles in global sea level rise and climate change but they remain poorly understood because data collection is greatly limited by the remote location and hostile conditions there. Airborne platforms have been extensively used in Antarctica due to their capabilities and flexibility and have contributed a great deal of knowledge to both the ice sheet and the continent. The Snow Eagle 601 fixed-wing airborne platform has been deployed by China for Antarctic expeditions since 2015. Scientific instruments on the airplane include an ice-penetrating radar, a gravimeter, a magnetometer, a laser altimeter, a camera and a Global Navigation Satellite System (GNSS). In the past five austral seasons, the airborne platform has been used to survey Princess Elizabeth Land, the largest data gap in Antarctica, as well as other critical areas. This paper reviews the scientific operations of Snow Eagle 601 including airborne and ground-based scientific instrumentation, aviation logistics, field data acquisition and processing and data quality control. We summarize the progress of airborne surveys to date, focusing on scientific motivations, data coverage and national and international collaborations. Finally, we discuss potential regions for applications of the airborne platform in Antarctica and developments of the airborne scientific system for future work.

Magnetotelluric transect across the São Luís cratonic fragment, the Gurupi belt and the Parnaíba basin, N-NE Brazil

The study area is located in the N-NE region of Brazil where Precambrian rocks of the São Luís Cratonic Fragment and the Gurupi belt are overlain by Phanerozoic sediments of the Parnaíba and São Luís basins, making the assessment of the extents of these geotectonic domains difficult. One of the main objectives of the present study was to elaborate a NNW-SSE-trending, 180-km long magnetotelluric transect, aiming to identify the geotectonic domains of the study area by means of their geoelectric characteristics. The magnetotelluric (MT) technique is a geophysical method that detects the natural variations of the terrestrial electric and magnetic fields so as to investigate the geoelectric characteristics of the subsurface. By means of a MT survey for field data acquisition, calculation of impedance tensors and 2D inversion modeling, the geophysical transect and additionally an interpretive geological model were elaborated for the study area. The combined transverse electric (TE) and transverse magnetic (TM) geophysical model revealed superficial conductive (Parnaíba and São Luís basins and sedimentary coverings), resistive (São Luís Cratonic Fragment) and very resistive (Gurupi mobile belt) portions up to depths of the order of 15 km. These results attested for correlations between the São Luís Craton (South American Plate) and the West African Craton (African Plate), especially regarding the Gurupi Belt (in Brazil) and the Rokelide Belt (in Liberia), which are considered to be the boundaries of a triple junction related to the supercontinent Rodinia taphrogenesis. Besides presenting an unprecedented geophysical investigation along the São Luís Cratonic Fragment and the Gurupi Belt, this study promotes the discussion on the correlations between the Brazilian Gurupi and the African Rokelide belts for metallogenetic purposes.

Magnetic anomalies of the NW Iberian continental margin and the adjacent abyssal plains

ABSTRACT The NW Iberian margin is a hyperextended continental margin, formed during the opening of the North Atlantic Ocean, where a subsequent partial tectonic inversion has undergone during the Alpine Orogeny. This succession of tectonic episodes determines the magnetic signature of the margin. The Spanish Exclusive Economic Zone Project has carried out seven one-month cruises between 2001 and 2009. To extend and densify the spatial coverage, we have used data from the World Digital Magnetic Anomaly Map. Here, we describe the methodology used for the acquisition and data processing of the magnetic field data. The use of diverse instrumentation, a non-complete external field’s cancelation, and the use of different magnetic core field models, contributed to the total error budget. To reduce it, we have used a leveling algorithm which minimizes all these contributions. Finally, a statistical analysis was applied using crossover residuals, showing a resolution better than 28 nT.

Single Scanner BLS System for Forest Plot Mapping

The 3-D information collected from sample plots is significant for forest inventories. Terrestrial laser scanning (TLS) has been demonstrated to be an effective device in data acquisition of forest plots. Although TLS is able to achieve precise measurements, multiple scans are usually necessary to collect more detailed data, which generally requires more time in scan preparation and field data acquisition. In contrast, mobile laser scanning (MLS) is being increasingly utilized in mapping due to its mobility. However, the geometrical peculiarity of forests introduces challenges. In this article, a test backpack-based MLS system, i.e., backpack laser scanning (BLS), is designed for forest plot mapping without a global navigation satellite system/inertial measurement unit (GNSS-IMU) system. To achieve accurate matching, this article proposes to combine the line and point features for calculating transformation, in which the line feature is derived from trunk skeletons. Then, a scan-to-map matching strategy is proposed for correcting positional drift. Finally, this article evaluates the effectiveness and the mapping accuracy of the proposed method in forest sample plots. The experimental results indicate that the proposed method achieves accurate forest plot mapping using the BLS; meanwhile, compared to the existing methods, the proposed method utilizes the geometric attributes of the trees and reaches a lower mapping error, in which the mean errors and the root square mean errors for the horizontal/vertical direction in plots are less than 3 cm.

Analysis of gravity anomaly for groundwater basin in Bandar Lampung city based on 2D gravity modeling

The research aims to delineate the groundwater basin in Bandar Lampung from gravity anomaly. Field data acquisition was carried out at 403 points with a spacing of 2-3 km, covering the Bandar Lampung and surrounding areas. Data processing through gravity data corrections, namely drift, tide, Free Air, Bouguer and Terrain using Geosoft Oasis Montaj 8.3. The Bouguer density used is 2.67 gr/cm3. For the anomaly separation, spectrum analysis and regional and residual anomaly separation were carried out, whereas 2D modeling was carried out by forward modeling. This basin boundary analysis is based on gravity residual anomaly patterns, gravity Second Vertical Derivative (SVD) analysis, and 2D gravity modeling. There are two low residual anomaly patterns (-22 to -5 mGal), where the boundaries of the basin can be clearly delineated from SVD analysis. This 2D model shows layers with a density of 2.3 gr/cm3 which are the Young Volcano Formation (Qhv) and the Lampung Formation (QTl) which have depths of up to 1.0-1.5 km. This Groundwater Basin correlates well with the hydrological pattern with a water discharge of 5 to 100 l/sec.

A compact ocean bottom electromagnetic receiver and seismometer

Abstract. Joint marine electromagnetic (EM) and seismic interpretations are widely used for offshore gas hydrate and petroleum exploration to produce improved estimates of lithology and fluids and to decrease the risk of low gas saturation. However, joint data acquisition is not commonly employed. Current marine EM data acquisition depends on an ocean bottom electromagnetic receiver (OBEM), and current seismic exploration methods use seismometers. Joint simultaneous data acquisition can decrease costs and improve efficiency, but conventional independent data receivers have several drawbacks, including a large size, high costs, position errors, and low operational efficiencies. To address these limitations, we developed a compact ocean bottom electromagnetic receiver and seismometer (OBEMS). Based on existing ocean bottom E-field receiver (OBE) specifications, including low noise levels, low power consumption, and low time drift errors, we integrated two induction coils for the magnetic sensor and a three-axis omnidirectional geophone for the seismic sensor to assemble an ultra-short baseline (USBL) transponder as the position sensor, which improved position accuracy and operational efficiency while reducing field data acquisition costs. The resulting OBEMS has a noise level of 0.1 nV m−1 rt−1 (Hz) at 1 Hz in the E-field, 0.1 pT rt−1 (Hz) at 1 Hz in the B-field, and a 30 d battery lifetime. This device also supports a Wi-Fi interface for the configuration of data acquisition parameters and data download. Offshore acquisition was performed to evaluate the system's field performance during offshore gas hydrate exploration. The OBEMS operated effectively throughout the operation and field testing. Therefore, the OBEMS can function as a low-cost, compact, and highly efficient joint data acquisition method.

An experimental study on terahertz light field data acquisition and digital refocusing

In recent years, terahertz imaging has attracted great attention due to its advantages including penetrability and nondestructive property. The field imaging technology within the terahertz range is expected to enhance the terahertz image quality and improve its application effect. In this paper, an experiment on the data acquisition and digital refocusing of the terahertz light field was conducted. Firstly, the basic principle, system structure, and the method of reconstructing light field imaging were analyzed. Secondly, the terahertz focal plane array camera was used to collect the data about light field and digital refocusing was used to get the computed imaging. Finally, the reconstructed image was enhanced to obtain higher depth resolution, angle resolution, and object contour resolution. Experimental results showed the feasibility and ability of terahertz light field imaging to improve image quality and enrich retrieval effects.

Negative apparent resistivities in surface resistivity measurements

Apparent resistivity is traditionally defined as the resistivity of a hypothetical homogeneous half-space that would yield the same response as that measured over the real earth with the same acquisition parameters. Negative apparent resistivity contradicts this definition of apparent resistivity as we cannot physically attain a homogeneous medium with negative resistivity. However, we often encounter negative apparent resistivity in field data acquisition; it is regarded as the effect of measurement error or noise. In this paper, we re-investigated the idea that negative apparent resistivity, especially in the dipole-dipole measurement, can be caused by a natural geological structure even when the earth is isotropic and flat, and the survey line is straight. The results from 3D numerical modelling revealed that negative apparent resistivity in the dipole-dipole measurement can be encountered particularly when the resistivity contrast between the conductive body and background medium is extraordinarily high. Moreover, negative apparent resistivity can occur only when the current source is very close to one side of the conductive body, like in the mise-ả-la-masse case, and the potential dipole is placed at the opposite side of the body.

Practical configured microtremor array measurements (MAMs) for the geological investigation of underground space

Underground space utilization is becoming increasingly essential for modern metropolitan cities such as Singapore. Mapping a soil/rock interface using traditional borehole investigation methods is expensive and difficult, owing to the numerous physical constraints within a built-up city. Boreholes are often far apart, resulting in many unforeseen ground conditions during subsequent excavation. Geophysical methods are sometimes employed as possible alternatives for fast, economical, and efficient bedrock surveys. The goal of this study is to investigate the practical details of applying microtremor array measurement (MAM) as a non-invasive surface wave survey for mapping soil/rock interfaces in Singapore. Critical configurations in field data acquisition are examined, and practical recommendations for array construction are provided. In addition, 30 in situ MAM tests are carried out for two major geological formations in Singapore. From the results, a standard shear wave velocity (Vs) of 500 m/s is found to be suitable for interpreting the soil/rock interface, for the Bukit Timah Granite and Jurong formations. However, the method does not predict well when soft Kallang formation deposits are present. Other limitations are also discussed in the later parts of this paper. Conclusions and practical recommendations are discussed, providing constructive guidance to the industry. The proposed Vs-based method and associated guidelines and limitations can be used to create a digital geological database and are especially useful for rock profiling in an urban environment.

Modeling strawberry biomass and leaf area using object-based analysis of high-resolution images

Quantifying canopy biophysical parameters is critical to agricultural research and farm management. In this study, strawberry dry biomass and leaf area were modeled statistically using high spatial and temporal resolution imagery. A mobile field data acquisition system was used to acquire thousands of very high resolution (~0.5 mm) close-range images seven times throughout the strawberry growing season. Ortho-mosaics and dense point clouds were generated through Structure from Motion (SfM) and used in Object-Based Image Analysis (OBIA) at the sub-leaf level to extract canopy structure variables such as planimetric canopy area, canopy average height, and canopy smoothness metric. Regression analysis was carried out using these image-derived canopy variables as predictors to model leaf area (R2 = 0.79; ten-fold cross-validation RMSE = 0.056 m2) and dry biomass (R2 = 0.84; ten-fold cross-validation RMSE = 7.72 g) obtained through destructive measurements. Results indicate consistent predictive power through the season and across 17 strawberry genotypes. The study showed that the canopy smoothness metric developed in this study as an indicator of canopy density could complement other variables (planimetric canopy area, canopy average height) that describe canopy geometric properties.

Identifikasi Lapisan Pembawa Mineral Emas dengan Metode Resistivitas dan Induksi Polarisasi di Desa Paningkaban Kecamatan Gumelar Kabupaten Banyumas Jawa Tengah

The research has been done in the Paningkaban village, Gumelar District, Banyumas Regency, Central Java Province. This research aims to identify technically the presence of gold mineral distribution using the method of geoelectricity-resistivity and induced polarization (IP), to interpret the obtained resistivity and chargeability data from the research area, to determine the subsurface structure model in the reasearch area, and find out the potential of gold in the research area i.e Paningkaban. The method in this research includes field data acquisition, data processing, and data interpretation. The acquisition uses a syscal resistivitymeter tools by stretching 200 meters of cable on each track that has been connected to the electrode and porous pot. The results obtained from the acquisition are primary data which are still in the form of voltages, currents, and apparent chargeability values. Based on this data, the processing is carried out to obtain the resistivity and chargeability profiles so that can be interpreted and correlated. The correlation between the resistivity and chargeability data was carried out to identify the gold mineralization zone in two dimensions. The presence of gold mineralization is characterized by the emergence of rocks with a low resistivity value and high chargeability because mineralization in the geological area is seen in quartz veins. Quartz veins are common features of many deposits and are indicative of the presence of mineralization, especially gold. Based on the results of the interpretation, the subsurface rock which contain gold minerals are found on each line, with resistivity values ranging from 4,25 – 17,3 Ωm and the chargeability value ranges from 26,4 – 226 msec. These rocks which are estimated to contain gold minerals are the sandy clay.