scholarly journals IDENTIFIKASI CEKUNGAN HIDROKARBON “RAE” BERDASARKAN DATA MAGNETOTELURIK DI DAERAH BULA, MALUKU

2020 ◽  
Vol 4 (3) ◽  
pp. 41-57
Author(s):  
Gita Purna Rae Wanudya ◽  
Syamsurijal Rasimeng ◽  
Rustadi Rustadi ◽  
Noor Muhammad Indragiri
Keyword(s):  
Oil Sands ◽  
High Resistivity ◽  
Second Step ◽  
Rock Formations ◽  
Formation Zone ◽  
Resistivity Model ◽  
Hydrocarbon Formation ◽  
Robust Process ◽  
Clay Cap ◽  
Data Processing Methods

The research had been performed using Magnetotelluric to get a 2D model based on variations in resistivity of the subsurface rock. The purpose of this study was to determine the hydrocarbon formation zone. The research method to achieve the research objectives, among others, the first filtering performed on the data with a robust process. This process consists of Robust No Weight, Robust Rho Variance and Ordinary Cohenerency. The second step is done to change the format Selection XPR And Edi. A third inversion resistivity model for the review get a 2D cross section. Based on the findings of the eight data processing methods of measurement points obtained information Magnetotelluric rock formations. Formation hidrokrabon What are the areas is research a reservoir and caprock. The layer in 1600 m – 2700 m depth from the surface which resisvity 12 -33 m assumpted as clay cap. While the layer in 2700 m – 5000 m depth from the surface with high resistivity 41- 250 m is assumpted as oil sands (reservoir). The trap zone of this hidrocarbon formation categorized into structural trap which is the trap of anticline.

BAYESIAN MAGNETOTELLURIC INVERSION USING METHYLENE BLUE STRUCTURAL PRIORS FOR IMAGING SHALLOW CONDUCTORS IN GEOTHERMAL FIELDS

Geophysics ◽  
2021 ◽  
pp. 1-66
Author(s):  
Alberto Ardid ◽  
David Dempsey ◽  
Edward Bertrand ◽  
Fabian Sepulveda ◽  
Flora Solon ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Clay Content ◽  
3D Models ◽  
Bayesian Inversion ◽  
Inversion Method ◽  
Geothermal Fields ◽  
Geological Information ◽  
Resistivity Model ◽  
Irreducible Uncertainty ◽  
Clay Cap

In geothermal exploration, magnetotelluric (MT) data and inversion models are commonly used to image shallow conductors typically associated with the presence of an electrically conductive clay cap that overlies the main reservoir. However, these inversion models suffer from non-uniqueness and uncertainty, and the inclusion of useful geological information is still limited. We develop a Bayesian inversion method that integrates the electrical resistivity distribution from MT surveys with borehole methylene blue data (MeB), an indicator of conductive clay content. MeB data is used to inform structural priors for the MT Bayesian inversion that focus on inferring with uncertainty the shallow conductor boundary in geothermal fields. By incorporating borehole information, our inversion reduces non-uniqueness and then explicitly represents the irreducible uncertainty as estimated depth intervals for the conductor boundary. We use Markov chain Monte Carlo (McMC) and a one-dimensional three-layer resistivity model to accelerate the Bayesian inversion of the MT signal beneath each station. Then, inferred conductor boundary distributions are interpolated to construct pseudo-2D/3D models of the uncertain conductor geometry. We compared our approach against a deterministic MT inversion software on synthetic and field examples and showed good performance in estimating the depth to the bottom of the conductor, a valuable target in geothermal reservoir exploration.

Confidence in Solutions of Flow Through Stochastically Generated Hard Rock Formations

1985 ◽  
Vol 50 ◽  
Author(s):  
Carol Braester ◽  
Roger Thunvik
Keyword(s):  
Hard Rock ◽  
A Priori ◽  
Fracture Network ◽  
Measurement Model ◽  
Second Step ◽  
Limited Data ◽  
Data Set ◽  
Geometrical Properties ◽  
Rock Formations ◽  
Flow Through

AbstractConfidence in solutions of flow through stochastically generated hard rock formations was studied with the aid of a simplified synthetic model. The formation is conceptualized as a fracture network intersecting an impervious rock mass. The geometrical properties of the fracture network were assumed to be known while fracture transmissivities were considered a stochastic process.First, network fracture transmissivities were generated using a given probability distribution function. This a priori model was considered the “true formation”. In a second step, only a limited amount of information, similar to that obtained in reality from boreholes, was used to construct a conditioned-by-measurement model.Identical flow tests were performed on a formation constructed with limited data and on the “true formation”. The ratio of the rates of flow resulting from these tests was considered a measure of confidence in the stochastically generated formation. The results, with this model and a particular data set, show uncertainty values between 47% to 63%, corresponding to fracture sample sizes of 11% and 2% respectively, from the total number in the network.

scholarly journals Electrical resistivity tomography applied to geologic, hydrogeologic, and engineering investigations at a former waste-disposal site

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. B231-B239 ◽  
Author(s):  
Jonathan E. Chambers ◽  
Oliver Kuras ◽  
Philip I. Meldrum ◽  
Richard D. Ogilvy ◽  
Jonathan Hollands
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Site Investigation ◽  
High Resistivity ◽  
Potential Zone ◽  
Resistivity Tomography ◽  
L2 Norm ◽  
Resistivity Model ◽  
2D And 3D ◽  
2D Resistivity

A former dolerite quarry and landfill site was investigated using 2D and 3D electrical resistivity tomography (ERT), with the aims of determining buried quarry geometry, mapping bedrock contamination arising from the landfill, and characterizing site geology. Resistivity data were collected from a network of intersecting survey lines using a Wenner-based array configuration. Inversion of the data was carried out using 2D and 3D regularized least-squares optimization methods with robust (L1-norm) model constraints. For this site, where high resistivity contrasts were present, robust model constraints produced a more accurate recovery of subsurface structures when compared to the use of smooth (L2-norm) constraints. Integrated 3D spatial analysis of the ERT and conventional site investigation data proved in this case a highly effective means of characterizing the landfill and its environs. The 3D resistivity model was successfully used to confirm the position of the landfill boundaries, which appeared as electrically well-defined features that corresponded extremely closely to both historic maps and intrusive site investigation data. A potential zone of leachate migration from the landfill was identified from the electrical models; the location of this zone was consistent with the predicted direction of groundwater flow across the site. Unquarried areas of a dolerite sill were imaged as a resistive sheet-like feature, while the fault zone appeared in the 2D resistivity model as a dipping structure defined by contrasting bedrock resistivities.

scholarly journals Large-scale 3-D modeling by integration of resistivity models and borehole data through inversion

2014 ◽  
Vol 18 (11) ◽  
pp. 4349-4362 ◽  
Author(s):  
N. Foged ◽  
P. A. Marker ◽  
A. V. Christansen ◽  
P. Bauer-Gottwein ◽  
F. Jørgensen ◽  
...  
Keyword(s):  
Large Scale ◽  
Clay Fraction ◽  
Relative Length ◽  
High Resistivity ◽  
Depth Interval ◽  
Borehole Data ◽  
Data Set ◽  
Resistivity Data ◽  
Resistivity Model ◽  
D Model

Abstract. We present an automatic method for parameterization of a 3-D model of the subsurface, integrating lithological information from boreholes with resistivity models through an inverse optimization, with the objective of further detailing of geological models, or as direct input into groundwater models. The parameter of interest is the clay fraction, expressed as the relative length of clay units in a depth interval. The clay fraction is obtained from lithological logs and the clay fraction from the resistivity is obtained by establishing a simple petrophysical relationship, a translator function, between resistivity and the clay fraction. Through inversion we use the lithological data and the resistivity data to determine the optimum spatially distributed translator function. Applying the translator function we get a 3-D clay fraction model, which holds information from the resistivity data set and the borehole data set in one variable. Finally, we use k-means clustering to generate a 3-D model of the subsurface structures. We apply the procedure to the Norsminde survey in Denmark, integrating approximately 700 boreholes and more than 100 000 resistivity models from an airborne survey in the parameterization of the 3-D model covering 156 km2. The final five-cluster 3-D model differentiates between clay materials and different high-resistivity materials from information held in the resistivity model and borehole observations, respectively.

Revisiting Toba Caldera: an insight from regional magnetotelluric data

2020 ◽  
Author(s):  
Lukman Sutrisno ◽  
Fred Beekman ◽  
Yunus Daud ◽  
Jan Diederik Van Wees
Keyword(s):  
Fault System ◽  
High Resistivity ◽  
Magnetotelluric Data ◽  
Recording Time ◽  
Magma Plumbing System ◽  
Basement Structures ◽  
Clay Cap ◽  
Surface Geology ◽  
Toba Caldera ◽  
Sumatran Fault

<p>Regional magnetotelluric (MT) survey had been conducted to image resistivity structures beneath Toba Caldera, Indonesia. A crustal-scale 2D inversion model is generated from ten MT stations with extended recording time, deployed along NE-SW regional line to cross perpendicularly both the Caldera and the nearby regional strike-slip fault system, the Sumatran Fault. High resistivity background is likely related to Palaeozoic rocks which is basement of the Tertiary sediments and the Quaternary volcanics. The most noticeable conductive anomaly is located between 10-20 km deep, interpreted as the main magma reservoir beneath the region. An intermediate, less than 10 km-deep, less conductive anomaly beneath the Caldera is interpreted as shallow magma chamber affected by the last major eruption. Shallow, less than 2 km-deep conductive layers are associated either with hydrothermal clay cap beneath the Caldera, or sedimentary formations of the nearby basins. Other conductive anomaly is spatially associated with the Sumatran Fault which located 15 km away from the Caldera. Parameter plots of some stations are consistent with the orientation of basement structures, while the others may be affected by more complex caldera structures. A conceptual model of magma plumbing system beneath the Caldera is then interpreted from the combination of regional resistivity structures, surface geology, and available seismic tomography.</p>

scholarly journals Magnetotelluric investigation in the High Agri Valley (southern Apennine, Italy)

2015 ◽  
Vol 15 (4) ◽  
pp. 843-852 ◽  
Author(s):  
M. Balasco ◽  
A. Giocoli ◽  
S. Piscitelli ◽  
G. Romano ◽  
A. Siniscalchi ◽  
...  
Keyword(s):  
Seismic Data ◽  
Southern Italy ◽  
High Resistivity ◽  
Normal Faulting ◽  
Quaternary Deposits ◽  
Valuable Data ◽  
Marine Deposits ◽  
Resistivity Model ◽  
Different Thickness ◽  
Apulia Platform

Abstract. In this paper we present the result of a magnetotelluric (MT) investigation carried out across the High Agri Valley (HAV), southern Italy. Several MT soundings were carried out in order to obtain a ~15 km long 2-D resistivity model with an investigation depth of ~10 km. The main aim was to provide valuable data on the geological and structural setting of the HAV. The MT model was compared with pre-existing geological, geophysical and seismic data. The MT model can be schematized as a superposition of three stack lateral varying layers with different thickness and resistivity values: a surficial low–medium resistivity layer associated with the Quaternary deposits and to the allochthonous units; and a deeper high resistivity layer related to the Apulia Platform, separated by a thin layer connected to the mélange zone and to the Pliocene terrigenous marine deposits. Sharp lateral resistivity variations are interpreted as faults that, on the basis of accurate focal mechanism computations, display normal-faulting kinematics.

Predicting controlled-source electromagnetic responses from seismic velocities

2014 ◽  
Vol 2 (3) ◽  
pp. SH115-SH131 ◽  
Author(s):  
Dieter Werthmüller ◽  
Anton Ziolkowski ◽  
David Wright
Keyword(s):  
Standard Deviation ◽  
Feasibility Studies ◽  
Real Data ◽  
Second Step ◽  
Seismic Velocities ◽  
Well Control ◽  
Controlled Source ◽  
Electromagnetic Responses ◽  
Resistivity Model ◽  
Electric Anisotropy

We created a workflow to predict controlled-source electromagnetic (CSEM) responses from seismic velocities and compared the predicted responses with CSEM data. The first step was to calculate a resistivity model from seismic velocities in a Bayesian framework to account for the uncertainties. The second step was to estimate the electric anisotropy and improve the resistivity model for the depths at which there was no well control. The last step was to use this updated resistivity model to forward-model CSEM responses and compare the result with CSEM data. The comparison with real data revealed that the measured CSEM responses were generally within plus and minus one standard deviation of the predicted responses. This workflow was able to predict CSEM responses, which can prove very useful for feasibility studies before acquisition and interpretation after acquisition of CSEM data.

scholarly journals Electrical resistivity modeling around the Hidaka collision zone, northern Japan: regional structural background of the 2018 Hokkaido Eastern Iburi earthquake (Mw 6.6)

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Hiroshi Ichihara ◽  
Toru Mogi ◽  
Hideyuki Satoh ◽  
Yusuke Yamaya
Keyword(s):  
Three Dimensional ◽  
High Resistivity ◽  
Reverse Fault ◽  
Magnetotelluric Data ◽  
Epicentral Area ◽  
Collision Zone ◽  
Conductive Zone ◽  
Significant Area ◽  
Resistivity Model ◽  
Hidaka Collision Zone

Abstract The Hidaka collision zone, the collision boundary between the NE Japan and Kurile arcs, is known to be an ideal region to study the evolution of island arcs. The hypocenter of the 2018 Hokkaido Eastern Iburi earthquake (Mw 6.6) in the western part of the Hidaka collision zone was unusually deep for an inland earthquake, and the reverse fault that caused the earthquake has an uncharacteristically steep dip. In this study, we used three-dimensional inversion to reanalyze broadband magnetotelluric data acquired in the collision zone. The inverted resistivity model showed a significant area of high resistivity around the center of the collision boundary. We also identified a conductive zone beneath an area of serpentinite mélange in a zone of high P–T metamorphic rocks west of the high-resistivity zone. The conductive zone possibly reflects areas rich in pore fluids related to the formation and elevation of the serpentinites. Sensitivity tests indicated the need for additional magnetotelluric survey data to delineate the resistivity distribution around the epicentral area of the 2018 earthquake although the resistivity model showed a conductive zone in this area.

scholarly journals Anatomy of active volcanic edifice at the Kusatsu–Shirane volcano, Japan, by magnetotellurics: hydrothermal implications for volcanic unrests

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Kuo Hsuan Tseng ◽  
Yasuo Ogawa ◽  
Nurhasan ◽  
Sabri Bülent Tank ◽  
Naoto Ujihara ◽  
...  
Keyword(s):  
Transfer Functions ◽  
Three Dimensional ◽  
Geothermal System ◽  
Near Surface ◽  
Final Model ◽  
Brittle Ductile Transition ◽  
Seismicity Distribution ◽  
Resistivity Model ◽  
Geothermal Model ◽  
Clay Cap

Abstract We aimed to perform three-dimensional imaging of the underlying geothermal system to a depth of 2 km using magnetotellurics (MT) at around the Yugama crater, the Kusatsu–Shirane Volcano, Japan, which is known to have frequent phreatic eruptions. We deployed 91 MT sites focusing around the peak area of 2 km × 2 km with typical spacings of 200 m. The full tensor impedances and the magnetic transfer functions were inverted, using an unstructured tetrahedral finite element code to include the topographic effect. The final model showed (1) low-permeability bell-shaped clay cap (C1) as the near-surface conductor, (2) brine reservoir as a deep conductor (C3) at a depth of 1.5 km from the surface, and (3) a vertical conductor (C2) connecting the deep conductor to the clay cap which implies an established fluid path. The columnar high-seismicity distribution to the east of the C2 conductor implies that the flushed vapor and magmatic gas was released from the brine reservoir by breaking the silica cap at the brittle–ductile transition. The past magnetization/demagnetization sources and the inflation source of the 2014 unrest are located just below the clay cap, consistent with the clay capped geothermal model underlain by brine reservoir. The resistivity model showed the architecture of the magmatic–hydrothermal system, which can explain the episodic volcanic unrest.

Internal structure and conditions of permafrost mounds at Umiujaq in Nunavik, Canada, inferred from field investigation and electrical resistivity tomography

2008 ◽  
Vol 45 (3) ◽  
pp. 367-387 ◽  
Author(s):  
Richard Fortier ◽  
Anne-Marie LeBlanc ◽  
Michel Allard ◽  
Sylvie Buteau ◽  
Fabrice Calmels
Keyword(s):  
Electrical Resistivity ◽  
Internal Structure ◽  
Prior Information ◽  
Electrical Resistivity Tomography ◽  
Reference Model ◽  
High Resistivity ◽  
Unfrozen Water ◽  
Resistivity Tomography ◽  
Unfrozen Water Content ◽  
Resistivity Model

A systematic approach was used for the interpretation of the electrical resistivity tomography carried out on two permafrost mounds at Umiujaq in Nunavik, Canada, to assess their internal structure and conditions. Prior information under the form of a geocryologic model of the permafrost mounds was integrated in the inversion of the pseudo-section of apparent electrical resistivity. The geocryologic model was developed from the synthesis of previous field investigations, including shallow and deep sampling, temperature and electrical resistivity logging, and cone penetration tests performed in the permafrost mounds. Values of electrical resistivity were ascribed to the different layers making of the geocryologic model to define a synthetic resistivity model of the permafrost mounds used as a reference model to constrain the inversion. The constrained resistivity model clearly show the presence of ice-rich cores in the permafrost mounds underscored by high resistivity values in excess of 30 000 Ωm, while the unfrozen zones surrounding the permafrost mounds are characterized by resistivity values lower than 1000 Ωm. The spatial distribution of unfrozen water and ice contents in the permafrost mounds were also assessed according to empirical relationships between the electrical resistivity and water contents. The ice content is highly variable and can be as high as 80% in the ice-rich cores, while the unfrozen water content varies between 2% and 5%. The integration of prior information in the inversion process leads to a more realistic constrained resistivity model showing sharp resistivity contrasts expected at the boundaries such as the permafrost table and base.

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