Mapping of the Maastrichtian-Danian boundary in the coastal area of Køge Bugt by gamma- and resistivity logging

1998 ◽  
Vol 44 ◽  
pp. 101-113
Author(s):  
Ole Larsen
Keyword(s):  
Water Supply ◽  
Coastal Area ◽  
Apparent Resistivity ◽  
Boundary Surface ◽  
Contour Map ◽  
Geophysical Logging ◽  
Resistivity Logs ◽  
Vertical Displacements ◽  
Resistivity Logging ◽  
Two Peaks

The Maastrichtian-Danian boundary surface has been mapped by geophysical logging of water supply borewells in the coastal area of Koge Bugt south of København. The transition from bryozoan limestone of Danian (earliest Palaeogene) age with a variable apparent resistivity between 100 and 250 Ohmm to chalk of Maastrichtian (latest Cretaceous) age with a relatively stable apparent resistivity in the range 60-80 Ohmm is easily detected on most resistivity logs. Gamma logs show a characteristic anomaly with two peaks in the uppermost Maastrichtian chalk approximately 8-10 meters below the Maastrichtian-Danian boundary. This gamma anomaly is caused by a layer of marl, which is found persistently in the whole area between Kobenhavn and Koge. The marl is probably equivalent to the Kj~lby Gaard Marl, known from outcrops of uppermost Maastrichtian chalk in northwest Jylland. A preliminary contour map has been prepared displaying the elevation of the boundary surface between the Danian limestone and Maastrichtian chalk below. This map shows that the limestones are weakly folded with structures very similar to those observed in the outcrops of Stevns Klint and also detected by recent seismic studies of the limestone basement in 0resund. The structures can be interpreted without introducing major vertical displacements along faults.

SALT BED IDENTIFICATION FROM UNFOCUSED RESISTIVITY LOGS

Geophysics ◽  
1961 ◽  
Vol 26 (3) ◽  
pp. 320-341
Author(s):  
J. R. Lishman
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Borehole Diameter ◽  
Drilling Fluids ◽  
Characteristic Shape ◽  
Resistivity Logs

Salt beds have almost infinite electrical resistivity. They differ from other infinitely resistive beds in that they are usually soluble in drilling fluids, and give rise to enlarged boreholes. An infinitely resistive bed lying between shales may be recognized from the characteristic shape of the electric log resistivity curves, and the ratios of their readings. Any one of the curves may then be used to compute the borehole diameter, and hence decide whether the bed is salt. Where a washed out salt bed is adjacent to another infinitely resistive bed in which the borehole is to gauge, the configuration of the curves is very characteristic. Apparent resistivity ratios again help to identify the salt.

Inversion of borehole normal resistivity logs

Geophysics ◽  
1984 ◽  
Vol 49 (9) ◽  
pp. 1541-1548 ◽  
Author(s):  
Fang‐Wei Yang ◽  
Stanley H. Ward
Keyword(s):  
Theoretical Model ◽  
Ridge Regression ◽  
Arbitrary Number ◽  
Inverse Method ◽  
Apparent Resistivity ◽  
Random Noise ◽  
High Resistivity ◽  
Number Of Layers ◽  
Boundary Position ◽  
Resistivity Logs

This paper reports on an investigation of the inversion of borehole normal resistivity data via ridge regression. Interpretation is afforded of individual thin beds and of complicated layered structures. A theoretical solution is given for a layered model containing an arbitrary number of layers in the forward problem. Two forward model results for resistive and conductive thin beds indicate that for high‐resistivity contrasts, the departure between true and apparent resistivity may be more important than the effects caused by the variations in borehole diameter and mud resistivity. Four normal resistivity logs were chosen to test the inversion scheme. Two of the logs were theoretical logs with and without random noise added, and the remaining two were field examples. Theoretical model results and field examples indicate that the inverse method can be used to obtain the resistivity for each layer when the boundary position is known, but it also can be used to obtain the thickness and resistivity for each layer simultaneously.

Evaluation of risk communication for rural water supply management: a case study of a coastal area of Bangladesh

2011 ◽  
Vol 14 (10) ◽  
pp. 1237-1262 ◽  
Author(s):  
Md. Atikul Islam ◽  
Hiroyuki Sakakibara ◽  
Md. Rezaul Karim ◽  
Masahiko Sekine
Keyword(s):  
Water Supply ◽  
Risk Communication ◽  
Coastal Area ◽  
Supply Management ◽  
Rural Water Supply ◽  
Water Supply Management ◽  
Rural Water

Effectiveness of solar disinfection (SODIS) in rural coastal Bangladesh

2015 ◽  
Vol 13 (4) ◽  
pp. 1113-1122 ◽  
Author(s):  
Md. Atikul Islam ◽  
Abul Kalam Azad ◽  
Md. Ali Akber ◽  
Masudur Rahman ◽  
Indrojit Sadhu
Keyword(s):  
Drinking Water ◽  
Water Supply ◽  
Coastal Area ◽  
Rainwater Harvesting ◽  
Low Cost ◽  
Treatment Technology ◽  
Solar Disinfection ◽  
E Coli ◽  
Alternative Water ◽  
Alternative Water Supply

Scarcity of drinking water in the coastal area of Bangladesh compels the inhabitants to be highly dependent on alternative water supply options like rainwater harvesting system (RWHS), pond sand filter (PSF), and rain-feed ponds. Susceptibility of these alternative water supply options to microbial contamination demands a low-cost water treatment technology. This study evaluates the effectiveness of solar disinfection (SODIS) to treat drinking water from available sources in the southwest coastal area of Bangladesh. A total of 50 households from Dacope upazila in Khulna district were selected to investigate the performance of SODIS. Data were collected in two rounds to examine fecal coliform (FC) and Escherichia coli (E. coli) contamination of drinking water at the household water storage containers and SODIS bottles, and thereby determined the effectiveness of SODIS in reducing fecal contamination. All water samples were analyzed for pH, electrical conductivity, turbidity and salinity. SODIS significantly reduced FC and E. coli contamination under household conditions. The median health risk reduction by SODIS was more than 96 and 90% for pond and RWHS, respectively. Besides, turbidity of the treated water was found to be less than 5 NTU, except pond water. Only 34% of the participating households routinely adopted SODIS during the study.

scholarly journals Simulation of DC dual-laterolog measurements in complex formations: A Fourier-series approach with nonorthogonal coordinates and self-adapting finite elements

Geophysics ◽  
2009 ◽  
Vol 74 (1) ◽  
pp. E31-E43 ◽  
Author(s):  
Myung Jin Nam ◽  
David Pardo ◽  
Carlos Torres-Verdín
Keyword(s):  
Fourier Series ◽  
Apparent Resistivity ◽  
Adaptive Finite Element Method ◽  
Fourier Series Expansion ◽  
Electrical Anisotropy ◽  
Rock Formations ◽  
Resistivity Logs ◽  
Dip Angle ◽  
Dual Laterolog ◽  
Deviated Wells

Dual laterolog (DLL) makes use of a galvanic conduction principle to focus electrical currents into rock formations, thereby minimizing shoulder and borehole effects in the measurement of formation resistivity. The tool includes two separate focusing systems: deep-sensing (LLd) and shallow-sensing modes (LLs). Laterolog current-focusing systems were designed for operation primarily in vertical boreholes penetrating horizontal layers; only recently their design has been revised for operation in deviated wells in the presence of electrical anisotropy. We simulated three-dimensional (3D) DLL measurements in dipping, invaded, and electrically anisotropic formations and appraised the corresponding effects on apparent resistivity logs. Simulations were performed by combining the use of a Fourier-series expansion in a nonorthogonal system of coordinates with an existing 2D goal-oriented, higher-order, and self-adaptive finite-element method. This numerical algorithm yields accurate solutions in limited CPU time because only a few Fourier modes are needed to simulate practical applications. For the calculation of focused currents, we introduced an embedded postprocessing method that incorporates a synthetic focusing principle to compute current intensities at each iterative step of optimal mesh refinements. Our numerical method accurately simulates 3D DLL measurements in rock formations that exhibit extreme contrasts of electrical resistivity. Simulations indicate that LLs resistivity logs are more sensitive to both invaded and anisotropic layers than LLd resistivity logs. In deviated wells, shoulder-bed effects on apparent resistivity logs increase with an increase of dip angle, and are emphasized across thin conductive layers. Electrical anisotropy effects on apparent resistivity logs increase substantially with dip angle.

scholarly journals On coincident loop transient electromagnetic induction logging

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. E211-E220 ◽  
Author(s):  
Andrei Swidinsky ◽  
Chester J. Weiss
Keyword(s):  
Apparent Resistivity ◽  
Earth Model ◽  
Late Time ◽  
Concentric Cylinder ◽  
Transient Electromagnetic ◽  
Water Based ◽  
Resistivity Logs ◽  
Invasion Models ◽  
Whole Space ◽  
Formation Resistivity

Coincident loop transient induction wireline logging is examined as the borehole analog of the well-known land and airborne time-domain electromagnetic (EM) method. The concept of whole-space late-time apparent resistivity is modified from the half-space version commonly used in land and airborne geophysics and applied to the coincident loop voltages produced from various formation, borehole, and invasion models. Given typical tool diameters, off-time measurements with such an instrument must be made on the order of nanoseconds to microseconds — much more rapidly than for surface methods. Departure curves of the apparent resistivity for thin beds, calculated using an algorithm developed to model the transient response of a loop in a multilayered earth, indicate that the depth of investigation scales with the bed thickness. Modeled resistivity logs are comparable in accuracy and resolution with standard frequency-domain focused induction logs. However, if measurement times are longer than a few microseconds, the thicknesses of conductors can be overestimated, whereas resistors are underestimated. Thin-bed resolution characteristics are explained by visualizing snapshots of the EM fields in the formation, where a conductor traps the electric field while two current maxima are produced in the shoulder beds surrounding a resistor. Radial profiling is studied using a concentric cylinder earth model. Results found that true formation resistivity can be determined in the presence of either oil- or water-based mud, although in the latter case, measurements must be taken several orders of magnitude later in time. The ability to determine true formation resistivity is governed by the degree that the EM field heals after being distorted by borehole fluid and invasion, a process visualized and particularly evident in the case of conductive water-based mud.

Distortion in resistivity logging at shallow depth

Geophysics ◽  
1995 ◽  
Vol 60 (4) ◽  
pp. 1058-1069 ◽  
Author(s):  
Tien‐Chang Lee ◽  
Brian N. Damiata
Keyword(s):  
Point Source ◽  
Line Source ◽  
Apparent Resistivity ◽  
Homogeneous Medium ◽  
Radial Distance ◽  
Ground Surface ◽  
Current Electrode ◽  
Potential Electrode ◽  
Resistivity Logging ◽  
Source Array

Owing to the proximity of an insulating ground surface, normal resistivity logging at shallow depths (less than 30 m) can yield an apparent resistivity that exceeds 200% of the formation resistivity for a homogeneous medium. The distortion is more acute for long‐normal than for short‐normal logging. Three examples from a landfill site in southern California are presented to show such distortion. The patterns of distortion are similar for logging devices consisting of either two point‐source electrodes or one point‐source and one finite length, line‐source electrode. The former electrode array is a generally accepted approximation of the latter. However, the simulated apparent resistivity for the line‐source array is greater than that for the point‐source array at any given depth. A resistivity contrast between the formation and the borehole fluid can shift the magnitude of the background apparent resistivity but does not significantly alter the pattern of distortion. The magnitude of the distortion can be reduced by placing the reference‐ground potential electrode at a radial distance that is about equal to the spacing between the downhole upper potential electrode and the upper current electrode. It can also be removed by including the radial distance in an array‐dependent geometric factor that accounts for the resistivity of the borehole fluid and the proximity of the logging device to the ground surface.

scholarly journals KEBUTUHAN AIR BERSIH MASYARAKAT DI DAERAH PERDESAAN NELAYAN Di Wilayah Pesisir Kabupaten Pasir, Kalimantan Timur

2018 ◽  
Vol 2 (2) ◽  
Author(s):  
Satmoko Yudo ◽  
Taty Hernaningsih
Keyword(s):  
Local Government ◽  
Water Supply ◽  
Coastal Area ◽  
Social Economy ◽  
Coastal Region ◽  
Public Facility ◽  
East Kalimantan ◽  
Sea Transportation ◽  
Food Fish ◽  
Potential Area

Coastal region is very potential area for developing in  sectors of fish, low and middle business from domestic industrial such as: food and husbandary food, fish net and shipping, services, trasnportation and travel. Concerning to high conomical potency in this coastal area is expected to be supporting area for central activities.  For this supporting in public facility  require elictricity, road and sea transportation, telecommunication, housing, health and the important is water supply.  In providing water supply infrastructure is needed good planning so that the result outcomes in right purpose and  beneficial for certain community. One of the supporting  in planning is to know social-economical condition of this community. This paper will show in general the result of coastal community social economy in Local Government, Pasir, East Kalimantan.  Kata kunci : Masyarakat nelayan, perencanaan penyediaan air bersih, kondisi sosial-ekonomi penduduk pesisir.

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