Fifty years of case histories

The aim of this study is to review the geophysical investigations in civil engineering and urban planning by some case histories in Turkey. Geophysics deals with a wide array of earth phenomena, including the temperature distribution of the earth's interior (the source, configuration and variations of the geomagnetic field) and the large-scale features of the terrestrial crust, such as rifts, continental sutures and mid-oceanic ridges. From the geophysical point of view, civil engineering and urban planning includes several geophysical topics used to investigate the physical properties, the physical techniques for regional and local land use planning or micro-zonation, the natural disaster risk estimation studies, etc. In this study, the geophysical approach, regarding civil engineering and urban planning against the natural or artificial disaster risk in macro (human/nature) and micro (society/earth) scales, is given. Geophysical methods provide solutions to a wide range of geotechnical problems: Slope stability, soil liquefaction and amplification studies, site investigations and testing, water works, subways, etc. In this study, an evaluation of the geophysical methods applied to geotechnical problems related to the soils is presented. Soils consist of the products of physical and chemical weathering of the rocks of the earth’s crust. As a part of the engineering design, the aim of a site/soil investigation is to provide the basic data to evaluate the interaction of the natural environment with the proposed structure. As it is known, using physical measurements in geophysics, it is studied as the natural and artificially generated physical fields of the earth. Key words: Geotechnical engineering, geophysics, earthquake engineering, soils, soil dynamics.

The art of exploration geophysics is reviewed with reference to classical and current literature. Its main features are described, the state of instrumentation and theory in it is discussed, and the problems it has yet to solve are examined. Exploration geophysics is both a science and an industry. As a science it draws on its parent sciences of physics and geology, and it has a reciprocal relationship with its sister disciplines of seismology and geodesy. Since its predictions often cannot be verified, it lacks one indispensable ingredient of science—the power of self criticism. It also suffers because its discoveries are proprietary and therefore often not published to be built on or challenged. In spite of these handicaps, its scientific status is rising. More trained workers than ever before are in the field, and their publications are of better quality. As an industry, exploration geophysics has long had the financial support that public funding has only recently given to science in general. It has served the demand for mineral discoveries well, but has sometimes failed to give the best possible support to its clients through lack of rapport between those who study problems and those who make decisions about them. The instruments and devices used by exploration geophysics have in general surpassed its fundamental needs. In 1930 the reflection seismograph was untested, and the field gravity meter was not invented, although they were clearly needed, and their prototypes, the refraction seismograph and the torsion balance, were plainly inadequate. Now it is possible to take almost any geophysical measurements found desirable, and the instrumental problem is usually to take them faster and with lighter and more dependable gear. The present frontiers of the art are not in the observing of data but in their interpretation and application to the search for minerals. The interpretation of seismic records is still in a relatively primitive form. How far it will be developed in the future depends on how acutely it is needed, but it is not easy to see the end of the data-processing techniques that are now being studied. The interpretation of gravimetric, magnetic, electrical, and radioactivity observations still requires personal skill, although automatic computing techniques have been applied to the first two types.

Undercompaction anomalies are known to be related to abnormal pressure conditions and can be detected from seismic velocities. The case history presented here deals with another type of anomalous zone that has been encountered below an undercompacted section and which is believed to be due to an open fracture system under high fluid pressure conditions. After a short presentation of some geomechanical concepts and the geological context, this paper focuses on three aspects: the identification of the anomalous zone using drilling, log and seisrnic velocity data; the understanding of the mechanisms involved in the initiation and development of the anomalous zone; and the main consequences for petroleum exploration.

This article presents a tutorial of the bases for, and problems encountered with, the resistivity and induced polarization methods in geotechnical and environmental applications. It commences with a discussion of aqueous electrolytic conduction in rocks including consideration of the effects of temperature, rock texture, rock type, geological processes, and of the presence of clay minerals. Both electrode and membrane polarization in soils and rocks are described. The elementary theory for the resistivity and induced polarization methods is introduced via formulas for electrodes on homogeneous and layered half-spaces. The notion of apparent resistivity is presented. Vertical electric sounding is described in relation to curve types, inversion, equivalence, anisotropy, and correlation. Profiling with resistivity is briefly treated while combined sounding-profiling is treated in more detail for both the resistivity and induced polarization methods. The parameters used to describe the induced polarization phenomena are introduced. A brief discourse follows on data acquisition and processing, including design considerations for transmitters and receivers, electrodes, and wire logistics. A section on arrays and the factors involved in selecting an array provokes the disclosure that while their application in geotechnical and environmental studies usually is straightforward much remains to be learned about the resistivity and induced polarization methods in general. Specific topics requiring study are comparative studies of various arrays in (a) depth of exploration in sounding and in profiling, (b) resolution of horizontal structures, (c) sensitivity to depth, (d) sensitivity to lateral effects, (e) sensitivity to buried and surface topography, and (f) the effectiveness of focused arrays. References to recent significant publications on one-, two-, and three-dimensional forward and inverse interpretation procedures follow. Problems encountered with these methods are initially treated under the section on arrays and are expanded with specific reference to geologic noise and negative induced polarization effects. The advantages of focused arrays are illustrated. The paper concludes with nine representative examples of applications.

Geological information can be interpreted from data collected from drill holes and geophysical method surveys. Limited number of expensive drill holes cannot provide enough information for the vast interest area, but geophysical methods can tell the soil properties through physical parameters as resistivity or inverse of conductivity and seismic velocity if their measurement stations can be sufficiently located. Useful prior geophysical parameter models play a vital role in directing their inversion flow and recovering the good, predicted earth model. Geophysical parameters and chemical elements have strong correlations. This inspires 3D electrical resistivity model building from existences of data collected from drill holes in the Kevitsa Ni‐Cu‐PGE mineral deposit, Northern Finland. In our work, shallow neural network is applied to predict conductivity value from available mineral chemical elements for each drill hole. Then, 3D interpolation can build 3D conductivity model from all the conductivity values as being measured or predicted. The processed 3D geophysical parameter model can show great match with seismic data and other drill hole information. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Cross-disciplinary education: The use of interactive case studies to teach geophysical exploration

Agricultural Geophysics in South Korea: Case Histories and Future Advancements

Landslide is one of the most serious natural geological disasters. Its production condition is complicated, and it is influenced by various natural geological factors. For its evaluation of stability and selection of treatment scheme, the geophysical exploration method is often used to get the related geological information. In recent years, more and more engineering practices indicate that the single geophysical exploration method has the limitations such as inaccurate and intuitive information. The comprehensive geophysical prospecting method is widely used for its characteristics of comprehensive, rapid and rich information, and it is of great significance to selection of treatment scheme for the landslide. Based on Gaijiayin Mountain landslide on Lanzhou-Chongqing and combined with the landslide survey data, using the high-density resistivity method and the integrated geophysical exploration of the Rayleigh surface wave method the parameters such as velocity and resistivity are obtained, and the scope of the landslide slip surface, depth and sliding are further determined. The deformation, failure, development process and the relevant laws are understood so as to provide powerful evidence for the scheme determination of landslide governance. ©, 2015, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved.

Multi-component seismic surveying for near surface investigations: examples from central Wyoming and southern England

Crossed dipole sonic logging data has traditionally been used in the openhole environment to:identify natural fracture systems and their orientation,evaluate far field stress data for 3D stimulation modeling, andseismic correlations and synthetic modeling. Materials presented inthis paper will show open hole and cased hole comparisons of flexural/shearwave slowness data and the anisotropy analysis in both fast and slowformations. The paper will show through-casing fracture identification examplesfrom the Cretaceous-Jurassic formations in Southern Mexico that have beenconfirmed with inflow analysis. The paper will also show applications ofthrough-casing anisotropy analysis combined with oriented perforating in theBurgos Basin in North Eastern Mexico. These techniques have resulted in lowerbreakdown pressures on stimulation treatments due to minimizing near wellboretortuosity. 2D and 3D analytical and finite-difference wave propagationsimulators have been developed to verify the open-hole and cased-holescenarios. The finite-difference simulations are used as a predictive tool toidentify cased-hole conditions that are either favorable, or unfavorable forcased-hole dipole acquisition. Introduction Dipole logging requires the propagation of a low frequency out-of-phaseflexural wave that is detected by the acoustic receivers on opposite sides ofthe logging tool. To accomplish this symmetry is required. The wireline dipolesonic tool must be centralized in a near round borehole. For through casingdipole logging, the casing should also be centralized, and the material in thecasing-formation annulus must be radially uniform. The effects of boreholeovality, tool centralization, or casing centralization on waveform propagationare illustrated in Fig. 1 for a 1.5 kHz center frequency flexural wave. Lowerfrequency flexural/dipole transmitted pulses have longer wave lengths, thanhigher frequency flexural wave propagation, thereby slightly reducing the phaseshift due to borehole geometry effects. An elliptical borehole is common indeviated wells due to eccentralization of the drill string and bottom holeassembly. Acquiring crossed dipole sonic data at low frequency and in two axes(X and Y) often minimize these environmentally induced effects. The crossed dipole sonic logging tool is frequently run open hole in what isreferred to as a "quad-combo" (natural gamma ray, eccentered dual spacedneutron, density, dual induction, or dual lateralog with appropriate standoffs, centralized dipole sonic, and navigation tool). One such logging toolstring is configured such that the X-dipole measurement is aligned with thedensity pad, which due to gravity effects will seek the low side of theborehole in deviated well conditions. Therefore, the X dipole measurement maybe affected by tool positioning effects in the angle build sections of deviatedwellbore. The Y-dipole measurement is orthogonal to the density pad and in poorborehole conditions often provides quality shear wave slowness data. Aspreviously discussed, centralization is required, but in certain bore holeconditions this may not be operationally possible. Acquiring crossed dipoledata through casing is a viable option, provided the borehole conditions arefavorable. Unfavorable conditions for through casing dipole logging areexcessive washouts, poor radial placement of cement, lack of casingcentralization, and poorly consolidated formations. Advanced waveformprocessing, such as slowness anisotropy analysis, which is used to determinethe fast and slow shear wave travel times and their corresponding orientationrequires that a navigation device be run simultaneously with the dipole sonictool.1 In open hole logging conditions magnetometers andaccelerometers are utilized. In deviated cased hole logging conditionsmulti-axes accelerometers can be used. In near vertical cased hole loggingconditions a gyroscope is required. Anisotropy analysis can be performedwithout tool navigation data, to determine the magnitude of the anisotropy, butthe orientation of the fast and slow shear waves is referenced to the toolface, which can rotate while logging. This is frequently done in geologicconditions where the anisotropy is know to be a result of natural fracturing, and fracture orientation is not desired.

The principal objective of seismic exploration is to determine three geologic parameters, the structural top, the bottom, and the lateral extent of an oil and gas reservoir. Conventional (100%) data is very efficient in locating the structural top and bottom of reservoirs. Two-dimensional (2D) common depth point (CDP) seismic data provides an immense improvement in seismic data quality over conventional (100%) data. This improvement enables the explorer to better visualize and map the reservoir in each direction of the seismic line. Three-dimensional (3D) seismic technology provides even more mappable data and capability. The explorer may visualize every imaginable direction and subtlety of a reservoir. This talk compares conventional (100%), two-dimensional (2D), and three-dimensional (3D) seismic data from the Midcontinent. Case histories of the Douglass (Upper Pennsylvanian) in Texas, the Morrow (Lower Pennsylvanian) in Colorado, the {open_quotes}Chat{close_quotes} (Mississippian) and the Hunton (Silurian-Devonian) in Oklahoma, and the Simpson (Ordovician) in Kansas will be discussed. Major and independent operators can maximize their exploration efforts by integrating existing data with three-dimensional (3D) technology and a solid geologic interpretation.

Over the past two decades, the use of larger, deeper draft container ships has resulted in a need to provide deeper channels and berths to accommodate these larger vessels. In January 1998, the Port of Los Angeles (POLA) approved the Main Channel Deepening Program to deepen the Main Channel and associated channels and turning basins from the existing Elevation (El.) -45 feet MLLW (mean lower low water) to El. –50 feet MLLW. Since approval of that project, new vessels in the world container fleet and ship orders indicated that container vessels with a draft of 52 feet were being planned. In order to meet the need for deeper-draft vessels and in cooperation with the United States Army Corps of Engineers, POLA examined the feasibility of dredging the navigational channels within the Port of Los Angeles to as deep as El. –55 feet MLLW. The dredged materials from the new Channel Deepening Project will allow POLA to pursue future expansion and terminal development. A case history is presented herein that demonstrates integration of geophysical survey and geotechnical exploration data that was utilized to characterize dredge material, interpret subsurface stratigraphy, and determine the extent of structurally unsuitable fine-grained deposits. This integration was implemented by entering subsurface geophysical survey and geotechnical exploration data into a Geographic Information System (GIS) database. In addition to assisting in the site characterization, the GIS database has been used to determine limits of dredge units, create stratigraphic surfaces and subsurface cross sections, and to provide an estimate of the quantities of suitable material for strategic placement within the fill areas.

Although the High Folded Zone in the Kurdistan Region of Iraq forms part of the Zagros-Taurus Folds and Thrust belt considered one of the potential hydrocarbon provinces, the oil fields within the zone are still lacking in geophysical exploration and scientific research. So, the rationale behind this study is the prospecting and evaluation of one of the Tertiary carbonate reservoirs at the “WN” oil field in the Duhok area by integrating the 3D seismic and well-log data. The methodology covered seismic interpretation, well logs and their relevant petrophysical analysis, attribute computation, and 3D static property modeling. The constructed reservoir maps revealed a double-plunging rollover anticlinal structure trending in the East-West direction parallel to the Taurus Mountain series. A total of nineteen minor reversal faults trending E-W to ENE-WSW dissecting the northern limb of the anticline were manually interpreted. The isopach map shows various thicknesses ranging from 160 to 330 m, averaging 245 m. The property models show the limited values of their parameters as the effective porosity is limited (0.97-23%), the secondary porosity (0.43-11.7%), permeability (0.00-238.8 mD), the water saturation (12.44-99.8%), and the clay volume (0.00-9.8%). The results of this research indicate that the horizon is a promising reservoir characteristic.

Well based modeling and seismic data analysis were used to investigate the potential of Amplitude Variation with Angle (AVA) for fluid discrimination in a high porosity carbonate reservoir in a producing UAE oil field. Gassmann fluid substitution was used to model well log data, which included compressional and shear sonic logs and density logs to produce synthetic well logs representing the reservoir at 100% fluid saturations of brine, oil and gas at reservoir pressure and temperature conditions. The average VP/VS ratio for brine saturated reservoir (~2.0) was observed to be higher than both the oil (~1.7) and gas (~1.6) saturated reservoir cases. The modeled brine, oil and gas logs were used to calculate the AVA responses at the top and base of a thick, 25–35 % porosity reservoir layer using the Zoeppritz equations. The responses for all three fluids were found to be a Class-IV type AVO anomaly. Seismic amplitude variation on the synthetic CDP gathers was successful at discriminating brine from hydrocarbon but could not differentiate oil from gas. These encouraging results on synthetic data suggest that with good quality seismic data it can be possible to see a difference in AVA responses between brine and hydrocarbon filled porous reservoirs. An AVA study was performed using available relative amplitude CDP gathers along a 2D seismic line extracted from a 3D seismic volume. The results were able to discriminate between areas saturated with brine from those with hydrocarbon. The real seismic results were in good agreement with synthetic model results. The angle stack analysis was successful at improving the signal-to-noise ratio in lower fold seismic data and reduced the input data size requirement when dealing with larger CMP gathers. The effects of varying key reservoir and seismic properties on AVA response were examined to help understand the potential for misinterpretation. Introduction Seismic amplitude responses are affected by the types of rock present, the degree of consolidation, the saturating fluids plus rock properties such as porosity of the reservoir and the encasing layers. Gassmann fluid substitution is used to produce log data, which are representative of porous carbonate reservoirs filled with 100% brine, oil and gas. The fluid properties represent typical reservoir fluids under typical reservoir pressure and temperature conditions. The average VP/V S ratio for a brine saturated reservoir is approximately 2.0, for an oil saturated reservoir around 1.7 and for the gas saturated case around 1.6. Synthetic CMP gathers were created from the brine, oil and gas log data. The synthetic CMP gathers were put through an amplitude analysis at the top and base interfaces of the reservoir layer and found to be AVO class-IV anomaly and were successful at discriminating brine from hydrocarbon but could not differentiate oil from gas. These encouraging results on synthetic data suggest that with good quality seismic data, it should be possible to see a difference in AVA response between brine and hydrocarbon filled porous reservoir. Modeling from the available well log data is used to calibrate the observed seismic AVA responses. AVA analysis was performed on real seismic along a 2D seismic line extracted from a 3D seismic volume over a carbonate reservoir in U.A.E. This case history over a known hydrocarbon occurance was used to confirm that different fluid types can be detect ed and agreed with the modeled results. The AVA responses were validated using the reservoir saturation information from the reservoir model and simulation modeling.

In January 2010 BP Exploration Jordan Ltd signed an agreement with the Hashemite Kingdom of Jordan and the National Petroleum Company (NPC) to explore and appraise the 7,200 sq km Risha Concession. The concession, in the desert of Eastern Jordan, bordering Iraq, Syria and Saudi Arabia contains the partially developed Risha Gas Field. This has historically been a poor seismic data quality area, mostly due to a complex and variably karstified near-surface. There was a sparse coverage of heritage 2D lines and two 3D surveys covering just 5% of the concession and a strong need for a large areal coverage of improved quality 3D seismic data. New and cost-effective techniques in acquisition and processing have been deployed to address the seismic coverage and quality issues, and during 2010 to 2012, a ~5000 sq km Simultaneous Source Seismic (DS3) survey was acquired and processed. The high-density wide-azimuth acquisition was carried out in a time and cost-efficient way. Following innovative acquisition and processing techniques to address the extreme scattered noise problem, high quality seismic attribute products have allowed insights into lithology and potential fracture distribution for the first time in the area. In this paper we discuss the acquisition, processing and analysis that have allowed the data quality improvement and the impact on reservoir interpretation.