Subsurface Distribution Research Articles

ANALISIS SEBARAN PENCEMARAN LINDI (LEACHATE) BERDASARKAN SIFAT KELISTRIKAN BATUAN MENGGUNAKAN METODE GEOLISTRIK

Tempat Pembuangan Akhir (TPA) Jeruklegi memiliki sistem pengelolaan lindi yang masih berpotensi adanya resapan air lindi di bawah permukaan. Pencemaran lindi dapat terjadi jika aktivitas TPA yang berlangsung terus-menerus dan berdampak pada masyarakat sekitar. Pencemaran lindi merupakan polusi lingkungan yang termasuk salah satu bencana buatan manusia minor. Penelitian ini merupakan langkah awal pencegahan bencana yang dilakukan dengan identifikasi sumber bencana. Identifikasi dilakukan dengan menganalisis sebaran lindi sekitar TPA di bawah permukaan dengan metode geolistrik dengan konfigurasi Wenner-Schlumberger. Hasil akuisisi data berupa resistivitas batuan yang diolah menjadi resistivitas semu untuk selanjutnya dimodelkan. Pemodelan inversi bawah permukaan pada beberapa titik dekat permukaan tanah yang menunjukkan adanya kontaminasi lindi ditunjukkan dengan nilai resistivitas kurang dari 1 ohm.m. Kontaminasi lindi pada kedalaman lebih dari 20 m tidak terlihat karena tidak adanya perbedaan resistivitas. Hal tersebut terkonfirmasi dengan uji kimia air sumur bor warga sekitar dengan hasil bahwa air tersebut sesuai dengan standar higiene sanitasi.
 Kata kunci: lindi, resistivitas, geolistrik, Wenner-Schlumberger.

Influence of dual Ge/C pre-amorphization implantation on the Ni1−xPtxSi phase nucleation and growth mechanisms

The impact of dual Ge/C pre-amorphization implantation (PAI) processes on the Ni0.9Pt0.1(7 nm)/Si system phase sequence has been investigated by advanced X-ray diffraction techniques and transmission electron microscopy (TEM). Using a high carbon implantation dose, it is found that the expected development of Ni-rich phases is not observed: a thick amorphous Ni1−xPtxSi layer developed until Ni0.9Pt0.1 full consumption, followed by the development of a thin crystalline Ni1−xPtxSi layer along the TiN interface. By increasing the temperature further, this last one abruptly thicken, creating the final silicide layer. An alternative model to grain boundary diffusion is discussed, accounting for the final distribution of the foreign species within the silicide layer. The use of Ge in dual Ge/C PAI processes is proposed to impact the growing mechanisms by alloying to fine-tune the carbon distribution in the substrate sub-surface.

Structural mapping and gold mineralisation potential evaluation from airborne time – domain electromagnetic (TDEM) data of Ilesha Schist Belt, southwestern Nigeria

The airborne Time-domain electromagnetic data acquired over the Ilesha Schist Belt in southwestern Nigeria were filtered, enhanced and analysed to generate ground conductivity responses at different time gates and employed to characterise the subsurface in terms of rock distribution, structural framework as well as evaluate the gold and base metal mineralisation potential of the region. The near-surface sensitive early time gate conductivity responses (EMZ1 – EMZ3) indicate relatively high subsurface conductivity distribution (60–120 mS/m) in amphibole schist and pegmatite terrain in the west while medium to low-conductivity (<5 mS/m) values were recorded in the east underlain by granitic rocks. Major and minor linear/sub-linear conductive features having conductivity in excess of 2 mS/m and trending NE-SW, NNE-SSW, NNW-SSE and ENE-WSW directions were delineated on the mid conductivity time gate responses (EMZ3 – EMZ5). One of which presents geometry and pattern consistent with the well-reported Ifewara – Iwaraja fault system that runs through the entire Ilesha Schist Belt. Very high anomalous conductivity (160–300 mS/m) responses at late conductivity time gates (EMZ10 – EMZ13) with characteristic long decay curves were obtained over isolated zones, especially along fractures and veins suggesting the occurrence of structurally controlled gold and base metal mineralisation.

PROFIL VERTIKAL HANTARAN PANAS BAWAH PERMUKAAN MANIFESTASI PANAS BUMI DI BAGIAN BARAT GUNUNG TAMPUSU

Indonesia is an area that has enormous geothermal potential. In North Sulawesi itself, there are three geothermal locations, including Lahendong, which is the first geothermal field in Eastern Indonesia to produce electricity, then other locations, namely in Tompaso and Kotamobagu. Strategically, Tampusu Mount is located between Tondano Lake and Linow Lake where the two lakes are the largest types of manifestation in North Sulawesi. This manifestation occurs due to the conduction of heat transfer from subsurface rock to surface rock. This study aims to analyze the distribution of temperature at shallow depths to predict the vertical profile of the thermal conductivity of geothermal manifestations in the western part of Tampusu Mount. By using surfur 11 software, it was found that the subsurface temperature distribution at shallow depths was dominated by high temperatures ranging from 30ºC - 43ºC. The lowest temperature ranges from 20ºC - 23ºC and the vertical profile of subsurface heat conduction in the western part of Tampusu Mount is not evenly distributed in each soil layer, because the temperature data obtained varies.

Molecular Dynamic Simulation of Micro-Structured Diamond Tool in Silicon Carbide Cutting

Abstract Silicon carbide (SiC) is an important material in many industrial applications. However, due to the hardness and brittleness nature, achieving ultra-precision machining of SiC is still challenging. In recent years, function surface with micro-structures has been introduced in cutting tool to suppress wear process. But the wear mechanism of the structured tool has not been revealed completely. Therefore, in present research, molecular dynamic simulations were conducted to investigate the cutting performance of the micro-structure on the nano scale cutting process of 3C-SiC. The simulation results showed that the dislocation propagation in workpiece can be suppressed with a structured tool. The micro-structures have a significant influence on the stress distribution in the workpiece subsurface. Furthermore, the abrasive wear of the structured tool is obvious smaller since the edges of the tool became blunt and the contact face between tool and workpiece changed to the close-packed plane of diamond. Moreover, the amorphization of the structured tool is effectively suppressed. This study contributes to the understanding of the material behavior involved in the ultra-precision cutting of SiC.

Experimental investigation on the subsurface stress distributions in specimens with different strengths after ultrasonic impact treatment

Experimental investigation on the subsurface stress distributions in specimens with different strengths after ultrasonic impact treatment

Rock abundance and evolution of the shallow stratum on Chang'e-4 landing site unveiled by lunar penetrating radar data

The Yutu-2 rover, part of the Chang'e-4 (CE-4) mission to the lunar farside, has been exploring the Von Kármán crater (VK) within the South Pole-Aitken (SPA) gathering data on its geology. The Lunar Penetrating Radar's (LPR) 500 MHz antenna reveals the subsurface structure up to 40 m in depth, which helps to construct models on the evolution of the shallow stratum. This work presents the analysis and interpretation of the data collected during the first twenty lunar days, from January 2019 to July 2020. Below an 11±4-meter surface regolith layer, the radar image reveals well-defined reflectors that are interpreted as discrete depositional layers. These marked density boundaries could indicate a geologically brief time interval between each arrival, which prevented the materials to undergo a deeper homogenization through space weathering. To investigate further, we generated a subsurface rock distribution map using the correlation of dual-channel antennas data from the same channel. Clusters of rocks located at the bottom of each ejecta stratum are revealed, probably sorted by size due to the statistically less frequent occurrence of larger impact events admixing the deeper-seated materials. The bowl-shaped outline discovered in both rock and LPR energy distribution maps is interpreted to represent a 150±30 m wide and 10±5 m deep paleo-crater that was excavated within three thin ejecta layers. The CE-4 LPR reveals a complex geological history within the Von Kármán crater with no fewer than four impact events delivering meters thick ejecta at the CE-4 landing area following the end of the infilling phase.

Perhitungan Cadangan Batupasir di Derah Perencanaan Tambang Desa Pegongsoran, Kecamatan Pemalang, Kabupaten Pemalang, Jawa Tengah

Indonesia has large number of sandstone reserves throughout the region. One of the potential reserves of Sandstones located in Pegongsoran, Pemalang. The purpose of the study is to know subsurface rock distribution so amount of Sandstones reserves can be determined for mining. The method used is Schlumberger arrays configuration geoelectrical method. Geoelectric measurements carried out at four points, geological mapping also conducted to know geological conditions and surface geomorphology.. From data processing in the field lithology found in the field are volcanic breccia, sandstones, and tuff. To figure out the subsurface conditions and rock layer distribution is performed correlation with three sections A-A’ section consist of GL-04, GL-03, GL-01. The B-B’ section consist of GL-04, GL-02, GL-01 C-C’ section consisting of the geoelectrical points GL-03 and GL-02. Based on volumetric calculation result with model block method using Rockworks software sandstones volume is 2,030,000 m3 while Calculation results using Cross-section method is 1,788,845m3

Seismic expression of miocene carbonate platform and reservoir characterization through geophysical approach: application in central Luconia, offshore Malaysia

A substantial proportion of proven oil and gas reserves of the world is contained in the carbonate reservoir. It is estimated that about 60% of the world’s oil and 40% of gas reserves are confined in carbonate reservoirs. Exploration and development of hydrocarbons in carbonate reservoirs are much more challenging due to poor seismic imaging and reservoir heterogeneity caused by diagenetic changes. Evaluation of carbonate reservoirs has been a high priority for researchers and geoscientists working in the petroleum industry mainly due to the challenges presented by these highly heterogeneous reservoir rocks. It is essential for geoscientists, petrophysicists, and engineers to work together from initial phases of exploration and delineation of the pool through mature stages of production, to extract as much information as possible to produce maximum hydrocarbons from the field for the commercial viability of the project. In the absence of the well-log data, the properties are inferred from the inversion of seismic data alone. In oil and gas exploration and production industries, seismic inversion is proven as a tool for tracing the subsurface reservoir facies and their fluid contents. In this paper, seismic inversion demonstrates the understanding of lithology and includes the full band of frequency in our initial model to incorporate the detailed study about the basin for prospect evaluation. 3D seismic data along with the geological & petrophysical information and electrologs acquired from drilled wells are used for interpretation and inversion of seismic data to understand the reservoir geometry and facies variation including the distribution of intervening tight layers within the Miocene carbonate reservoir in the study area of Central Luconia. The out-come of the seismic post-stack inversion technique shows a better subsurface lithofacies and fluid distribution for delineation and detailed study of the reservoir.

Application of particle swarm optimization to 3D Euler deconvolution and 3D modeling of gravity data—a case study from Biga and Çan towns, NW Turkey

The subsurface density distribution in the NW Turkey, between Biga and Can towns, is interpreted using 3D Euler deconvolution and 3D modeling methods. Particle swarm optimization is used for the both methods to show its ability to solve a wide range of geophysical gravity problems with minor changes. During 3D modeling, the desired level of smoothness is forced using a smoothing filter, and a penalty is added to the cost function to prevent artifacts. Using these measures, the method is found to be able to recover models from gravity data successfully. 3D Euler solutions revealed possible branches of the known faults. 3D modeling suggests densities up to ρ =2.9 g/cm3 for the basement rocks and ≤2.6 g/cm3 for the sedimentary cover. According to the recovered model, 3D Euler solutions for structural index value of 0 has a better fit to the sedimentary thicknesses. The study area is placed in the Intra-Pontide suture zone, formed by the collision of the Sakarya continent with the Istanbul Zone, and the recovered model indicates that the Can-Biga Fault Zone may correspond to the Intra-Pontide suture in the region. The model also shows that the earthquakes in the region are mostly occurring near the boundaries of the low- and high-density areas. Even though the previous studies have shown this relation using conductivity models, the results indicate that the same relation can also be inferred from gravity data.

Integrated Subsurface Analysis of Thickness and Density for Liquefaction Hazard: Case Study of South Cilacap Region, Indonesia.

The thickness of the liquefable layer can be the factor inducing liquefaction hazard, apart from seismicity. Several studies have been conducted to predict the possibility of the liquefable layer based on the filed sampling. However, a detailed investigation of the subsurface interpretation has not been defined, in particular the thickness estimation of the liquefable layer. This study is carried out in south Cilacap area where potential liquefaction is exists due to the earthquake history data and near surface condition. The aim of this study is to investigate the physical properties and thickness distribution using GGMplus gravity data and resistivity data. This research is conducted by spectrum analysis of gravity model and 2D resistivity model . This study’s main results is by performing the residual gravity anomaly with the associated SRTM/DEM data to define the subsurface physical distribution and structural orientation of the area. Residual gravity anomaly is also separated through the low pass filter in order to have robust interpretation. The residual anomaly indicates that the area has identical structural pattern with geological and SRTM map. The results show a pattern of high gravity index in the northeast area of ​​the study having range of 70 – 115 MGal gravity index, associated with the volcanic breccia, and a low gravity profile with less than 65 in the southwest, associated with the alluvial and water table dominated distribution. The thickness of Alluvial is determined by resistivity model with H1 at a range of 3 meters and H2 at a range of 4 m. This research is included in the potential liquefaction category with the potential for a large earthquake.

Modeling the effects of individual layer thickness and orientation on the tribocorrosion behavior of Al/Cu nanostructured metallic multilayers

Nanostructured metallic multilayers (NMMs) are emerging materials with excellent mechanical, tribological, and corrosion properties, making them ideal candidates to be used under extremely conditions. The high wear and corrosion resistance lead to enhanced tribocorrosion resistance of NMMs compared to many traditional metals and alloys. In this work, a multiphysics finite element model was developed to study the material deformation and degradation during tribocorrosion from wear, corrosion, as well as their synergy. Specifically, this model accounts for elastic-plastic mechanical deformation during wear and galvanic corrosion between exposed inner layers after wear. The effects of individual layer thickness (from 10 to 100 nm) and layer orientation (horizontally and vertically aligned) on the tribocorrosion behavior of Al/Cu NMMs was studied. Both factors were found to affect the subsurface stress and plastic strain distribution and localized surface corrosion kinetics, hence affecting the overall tribocorrosion rate. This model and the obtained understanding could shed light on future design and optimization strategies of NMMs against tribocorrosion.

Analysis of heat extraction performance and long-term sustainability for multiple deep borehole heat exchanger array: A project-based study

In the context of reducing carbon emission, Deep Borehole Heat Exchanger (DBHE) array has a large potential in extracting geothermal energy to provide building heating in densely populated urban areas. To investigate the thermal interaction among the DBHE, a comprehensive numerical model has been built with the OpenGeoSys software, and it is validated by monitoring data from a pilot project in Xi’an, China. The long-term simulations manifest that the outlet temperature of the DBHE array has a noticeable draw-down of 4.70°C over 20 years in comparison to the single borehole setup. The maximum difference of outlet temperature among individual DBHE can reach up to 0.88°C over 20 years, which will lead to a shifted thermal load of 23.35kW (12.25% of the designed average value). Based on the predicted subsurface temperature distribution, a non-linear correlation can be established between the drawdown in working fluid temperature and the accumulated amount of extracted heat. The finding of work implies that the thermal interaction among individual DBHE is of significance for the sustainability of the system, and comprehensive numerical modeling should be considered in the designing procedure.

Fault-controlled carbonate cementation: A case study from Eocene turbidite-delta sandstones (Dongying Depression) and implication for hydrocarbon migration

The subsurface distribution of carbonate cements in sandstones is cornerstone in understanding the fluid regime and origin of cements to shed the light on hydrocarbon migration. Petrography, cuttings, cores, well logs, and seismic data were integrated to better understand the distribution of carbonate cements in the Eocene turbidite-delta sandstones of the Dongying Depression. Petrographic examinations (including cathodoluminescence, CL) reveal that the carbonate cements are mainly calcite with minor ankerite that precipitated in deep burial settings. The significant abundance of carbonate cements near fault zones implies migration of fluids from deep settings through late fractures developed by compaction under deep burial conditions. The extent of carbonate-cemented zones may reach hundreds of meters away from the faults, while scatter carbonate cements are much more extensive. The relationship of pervasive and scattered calcites with oil-bearing sandstones suggests that the pervasive calcite cementation started as soon as the hydrocarbon and brine mixed fluid were displaced while the scatter calcite cements came after. The occurrence of abundant carbonate-cemented zones in the delta front oil-free sandstone intervals suggests possible hydrocarbon migration to the overlying sandstone units.

Characterization of the basement aquifers over Edéa-Kribi corridor using remote sensing and electrical resistivity method—a case study from Central Africa

The access of safe groundwater in the regions made up of crystalline basement terrains, as it is the case along the Edea-Kribi corridor (Central Africa), is a challenge. The study of fracture networks is fundamental for groundwater research. This paper aims to (1) map structural lineaments that could develop underground aquifers in metamorphic rocks and (2) characterize the structure and geometry of these aquifers using remote sensing, drilling, geology and geophysical data in this region. Geo-structural method based on photo-interpretation of topographic data was used in the structural mapping of the lineament features that were validated by geological fracture map. Vertical electrical sounding (VES) and horizontal electrical profile (HEP) techniques were used to highlight the subsurface resistivity distribution and identify the geometry of the groundwater potential areas. This geometry was validated by lithological and depth drilling cuts. The results show that the tectonic control of the underground flow is supported by the fracture networks N10-55, N45, E-W, N80-100, N110, N145, N170 and N310. Also, three conductive zones corresponding to three anomaly forms (U, V and H) are distinguished. The fracture networks contain deep basement aquifers from 19 to 55 m with hydraulic flows varying between 2 and 10 m3/h and characterized by U and V electrical anomaly forms. They are covered by a layer of overburden (clay-sandy or clayey lateritic) deep of 9 to 20 m allowing the storage and filtering of infiltration water. Furthermore, the aquifers identified in the H anomaly form are located in the depth higher than 40 m and have hydraulic flows ranging from 1 to 5m3/h. Finally, the aquifers with higher productivity (between 4 and 10 m3/h) are obtained in the N10-55 directed fractures and related to the presence of electrical anomalies of types U and V at those locations.

Conceptual interpretation seismic 3d using rms amplitude and dip-azimuth attribute analysis for identification structure and facies model in physical geographic

Interpretation of seismic 3D data using attributes analysis to determine the condition of the subsurface geology and distribution facies as physical geography study. The results of interpretation formed surface horizon analysis of structures located in the southwest (SW) is the high of the continuous anticline to the northeast (NE) and the structure of the valley are in the south (S) continuously until the northeast (NE). From the results of the RMS amplitude attribute map shows that high amplitude anomalies uneven section southwest (SW). Show areas indicated as coal facies deployment area and assuming a low impedance possibility for the existence of coal facies. The map dip, azimuth, dip-azimuth can be analyzed map depicts stance or azimuth direction and dip (slope) time domain structure with angle pattern shown seismic trace with section 4501 and the arbitrary line a - b and line c - d clarify seen a pattern of fractures (faults) on a small scale where the direction nearly perpendicular to the strike of major fault.

Subsurface structure investigation of the United Arab Emirates using gravity data

AbstractThe crustal structure beneath the United Arab Emirates (UAE) is still relatively unknown. Here, we use regional gravity data to constrain the subsurface density distribution and structure of the crust of the UAE by applying diverse gravity derivatives methods such as horizontal derivative (HDR), analytic signal (AS), and tilt angle (TA) to analyze the subsurface structure and perform three-dimensional (3D) gravity inversion for imaging crustal structure from the surface down to 35 km depth. The results are compared with known geological regional structures and the location of the petroleum fields.The Bouguer anomalies range from −100.8 to 113.5 mGal. The 3D gravity inversion results and the maximum Bouguer values coincide with the ophiolitic Hajar mountains in the east and the successive anticlines (uplifted basement rocks) and synclines in different parts of UAE, which could be promising sites for future mining and petroleum exploration. Also, the 3D density model results and the minimum Bouguer anomalies are located over the Aruma Basin, eastern UAE Platform, and Low Central UAE Platform, which can be the places for deep groundwater aquifers. These new results from HDR, AS, and TA successfully identify known geological structures, especially in the eastern part of UAE.

Upgraded GROWTH 3.0 software for structural gravity inversion and application to El Hierro (Canary Islands)

GROWTH 3.0 is a software package to determine the subsurface 3D density distribution that adjust discrete gravity anomaly values determined from gravity observations. The software uses very general assumptions and quite automatically determines the 3D density structures described by the aggregation of thousands of small rectangular prisms. A previous version of the software was published in 2011. However, methodological developments and computational technical evolution made it necessary to upgrade the software to include new advances and recent improvements in the inversion methodology (automatic determination of density contrasts, background medium with downward density increase, etc.), and a change in the computer operating system (from Windows XP, which was compatible with the 2011 version, to Windows 10 Pro for the current version). Here we describe the new upgraded version of the software package (which can be downloaded free), its use and application, using the study of El Hierro (Canary Islands) as a test case from which to obtain a 3D density model of its crustal structure. We also give a brief geological and volcanological interpretation.

Subsurface geoelectrical structure from 3-d inversion of magnetotelluric data of Gisenyi geothermal field, western part of Rwanda

In this paper, a set of Magnetotelluric (MT) data collected from 69 stations at the Gisenyi geothermal field in the western part of Rwanda were used to derive a 3D electrical resistivity distribution model to investigate deep geologic structures related to the geothermal resources. The MT method is a geophysical technique commonly used in geothermal exploration projects. The aim of this study is to investigate subsurface electrical resistivity distribution in the Gisenyi geothermal area to gain an understanding of the process related to geothermal activities and to model deep crustal structures. MT data analysis using phase tensors revealed the nature of the subsurface structures of the geothermal area prior to performing a 3D MT inversion. The dimensionality analysis results revealed a 3D conductivity structure in the deeper portion. The ModEM 3D MT inversion code was used to infer the subsurface electrical distribution from the MT responses. The recovered 3D resistivity distribution model showed a conductive region (<10 Ω.m) at deeper depths beneath a thick high-resistivity zone with a resistivity more than 100 Ω.m. The 3D model indicates patches of high and low resistivity at shallow depths related the presence of recent volcanic lavas and basement rocks from the surface to depths of a few hundred meters. The MT model revels important subsurface structures that can be related to the geothermal resource in the area. The deep-seated conductive body is presumably associated to the heat source of the Gisenyi geothermal system.

Modeling In-situ tectonic stress state and maximum horizontal stress azimuth in the Central Algerian Sahara – A geomechanical study from El Agreb, El Gassi and Hassi Messaoud fields

Central Algerian Sahara hosts many prolific hydrocarbon accumulations in the Paleozoic successions. In this work a contemporary stress field of the Saharan platform has been evaluated using the dataset from recently drilled wells in El Agreb, El Gassi and Hassi Messaoud fields. A pore fluid pressure gradient of 0.56 PSI/feet is interpreted from the in-situ measurements in the Paleozoic reservoir units. Vertical stress (Sv) modeled from the bulk-density data indicates an average of 1.02 PSI/feet gradient. Rock elastic property-based approach is employed to model the magnitudes of minimum (Shmin) and maximum horizontal stress (SHmax) components, which were calibrated with leak off test/minifrac and breakout widths, respectively. Paleozoic stress profiles reveal Shmin/Sv range of 0.74–0.84, while SHmax/Sv varies between 1.1 and 1.33. Subsurface stress distribution indicates that the present-day stress field in the Saharan platform is principally strike-slip faulting (SHmax > Sv > Shmin). A cumulative 1490 m of B-D quality wellbore breakouts, inferred from the acoustic image logs, suggest a NW-SE/WNW-ESE SHmax orientation, which is parallel to the absolute African plate motion and Africa-Eurasia plate convergence direction, implying ridge push force to be the dominant contributor to the tectonic stress field. Mean SHmax orientation shows slightly anticlockwise rotation (126°N to 144°N) from south (El Agreb) to north (Hassi Messaoud field). Inferences are discussed regarding the fault slip potential and hydrocarbon reservoir development.