Seismic Exploration Methods Research Articles

The application of amplitude-preserved processing and migration for carbonate reservoir prediction in the Tarim Basin, China

Conventional seismic exploration method based on post-stack data usually fails to identify the distribution of fractured and caved carbonate reservoirs in the Tarim Basin, so the rich pre-stack information should be applied to the prediction of carbonate reservoirs. Amplitude-preserved seismic data processing is the foundation. In this paper, according to the feature of desert seismic data (including weak reflection, fast attenuation of high frequency components, strong coherent noises, low S/N and resolution), a set of amplitude-preserved processing techniques is applied and a reasonable processing flow is formed to obtain the high quality data. After implementing a set of pre-stack amplitude-preserved processing, we test and define the kernel parameters of amplitude-preserved Kirchhoff PSTM (pre-stack time migration) and subsequent gathers processing, in order to obtain the amplitude-preserved gathers used to the isotropic pre-stack inversion for the identification of caved reservoirs. The AVO characteristics of obtained gathers fit well with the synthetic gathers from logging data, and it proves that the processing above is amplitude-preserved. The azimuthal processing techniques, including azimuth division and binning enlargement, are implemented for amplitude-preserved azimuthal gathers with the uniform fold. They can be used in the anisotropic inversion to detect effective fractures. The processing techniques and flows are applied to the field seismic data, and are proved available for providing the amplitude-preserved gathers for carbonate reservoir prediction in the Tarim Basin.

Application of Comprehensive Geological Exploration for Engineering Site Option

In the process of engineering prospective design and constructing, it is necessary to avoid the adverse impact of geological phenomena, such as fault, karst and landslide. Therefore, it’s important to choose a favorable project address by scientific and effective detection with engineering geological conditions. The main exploration method for geological conditions is the geophysical exploration, including: high density electrical method, ground penetrating Radar, seismic exploration method and so on. The discrimination result with a single geological method changes much, and it is difficult to make an accurate analysis of the geological conditions. So we should composite a variety of exploration methods. In this paper, it expounds the fundamental, the working method, data explanations of the high density electrical method and ground penetrating Radar firstly. And then it takes exploration of candidate sites of an aluminum waste disposal plant for example, the geological conditions of candidate sites are analyzed under the two geophysical methods. The study results of engineering site option have a positive role in guiding the work.

Imaging the Nechako Basin, British Columbia, using ambient seismic noise1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.

The Nechako Basin in British Columbia, Canada is suspected to have hydrocarbon potential. However, it has been a difficult basin to explore because of the presence of Tertiary volcanic outcrop. The volcanic outcrop makes the use of conventional seismic exploration methods difficult owing to a strong velocity inversion at its base. An alternative is the passive source method known as ambient noise surface wave tomography. The method, which examines the high-frequency surface wave field that is obtained from noise analysis, is sensitive to large-scale crustal structure and has been successfully applied to measuring the depths of sedimentary basins. Station-to-station Green’s functions within the basin were estimated by cross-correlating the vertical components of the seismic noise data recorded by 12 POLARIS (Portable Observatories for Lithosphere Analysis and Research Investigating Seismicity) and CNSN (Canadian National Seismgraph Network) seismic stations between September 2006 and November 2007. The resulting Green’s functions were dominated by Rayleigh waves. The dispersion characteristics of the Rayleigh waveforms were measured within the microseismic band. Inversion of the dispersion curves produced 1-D and 2-D thickness models and 2-D group velocity models for the Nechako Basin and its surrounding region. The velocity models indicate two low group velocity structures within the basin that might represent sedimentary packages, and some pockets of high-velocity zones that show the presence of volcanic rocks within and on the basin. The thickness models indicated the presence of about six different velocity layers, in which the average thickness of the basin and the crust are ∼4.8 and 30–34 km, respectively.

Phase Velocity Variation at Periods of 0.5-3 Seconds in the Taipei Basin of Taiwan from Correlation of Ambient Seismic Noise

Improving seismic hazard mitigation of the densely populated metropol- itan area of and around the capital of Taiwan requires detailed knowledge of the 3D crustal structure of Taipei basin. The high levels of ambient noise and the low levels of regional seismicity of this region complicate investigations of crustal structure with traditional seismic exploration or earthquake tomography methods. We investigate the shallow crust in the metropolitan region using surface wave array tomography with time domain empirical Green's function (TDEGF) inferred from correlation of ambient seismic noise. Analysis of the TDEGF amplitudes suggests that the dominant sources of ambient seismic noise are the coastlines and shallow continental shelf of the Taiwan Strait, northwest of the study region. Our study demonstrates that ambient seismic noise tomography is feasible at periods of 0.5-3 s, which is much shorter than the 10-30 s used in most other studies, and which opens new opportunities for high resolution studies of near-surface heterogeneity. The lateral variation in Rayleigh wave phase velocity correlates well with surface geology and suggests that faults play an important role in the regional tectonic setting. High phase velocities mark the Tatun volcanic area, the Kuanyin Mountain dominated by Quaternary igneous rock, and the Miocene Western Foothills south of the Taipei fault. Low phase velocities characterize regions are along western and southeastern edges of the Taipei basin and the Pleis- tocene Linkou tableland. Main faults in the region are either marked by low phase velocities or define transitions between regions of high- and low-velocity anomalies.

Green’s theorem as a comprehensive framework for data reconstruction, regularization, wavefield separation, seismic interferometry, and wavelet estimation: A tutorial

Almost every link in the chain of exploration seismology methods used to process recorded data has been affected by Green’s theorem. Among the seismic processes that can be related to, and/or have benefited from, Green’s theorem are wavelet estimation, multiple elimination, regularization, redatuming, imaging, deghosting, and interferometry. This tutorial on various seismic exploration methods derived from Green’s theorem emphasizes seismic data reconstruction (including regularization and redatuming) and its relationship to interferometry as well as to wavelet estimation and wavefield separation. The last decade has witnessed ever-increasing attention within the energy industry and its concomitant representation in the published literature to methods dealing with wavefield reconstruction through in-terferometry or virtual-source techniques. The attention has re- newed interest in Green’s theorem because all different ap-proaches to interferometry can be derived from it. This tutorial provides a derivation and explication of the limitations of interferometric techniques (when interferometry is used to process measured data from marine surface seismic experiments with controlled sources) as approximations to Green’s theorem. This tutorial provides a definite statement of the comprehensive framework given by Green’s theorem to wavefield reconstruction and shows how different techniques are directly understood as specific mathematical forms and/or approximations to the theorem. The use of approximations can have shortcomings and create artifacts. These artifacts and errors are also analyzed and explained. All methods discussed in this tutorial recognize their foundation on Green’s theorem and have a secure mathematical-physics cornerstone to recognize the assumptions behind distinct approximate solutions and to guide the search for more accurate, effective techniques.

Seismic Exploration Method for Detecting Buried Fault and Its Upper Breakpoint in Quaternary Sediment Area—An Example of Yinchuan Buried Active Fault

AbstractSeismic exploration is an effective geophysical means for detecting buried faults. The spread geometries of seismic exploration are the main factors to affect the exploration results as well as the accuracy of fault location. Based on the shallow seismic exploration data from an active fault survey in Yinchuan city and in combination with the petroleum seismic exploration profiles and drilling data, this paper proposes an upward fault‐tracing method for determining the geometry of the target fault and its upper breakpoint in thick Quaternary sediments. The result shows that the combination of high resolution shallow seismic exploration and borehole geological section is an effective way for locating the buried fault and determining its activeness.

Method and apparatus for seismic data acquisition

A marine seismic exploration method and system comprised of continuous recording, self-contained ocean bottom pods characterized by low profile casings. An external bumper is provided to promote ocean bottom coupling and prevent fishing net entrapment. Pods are tethered together with flexible, non-rigid, non-conducting cable used to control pod deployment. Pods are deployed and retrieved from a boat deck configured to have a storage system and a handling system to attach pods to cable on-the-fly. The storage system is a juke box configuration of slots wherein individual pods are randomly stored in the slots to permit data extraction, charging, testing and synchronizing without opening the pods. A pod may include an inertial navigation system to determine ocean floor location and a rubidium clock for timing. The system includes mathematical gimballing. The cable may include shear couplings designed to automatically shear apart if a certain level of cable tension is reached.

Integrating seismic exploration methods into a geological sciences curriculum at Brigham Young Unversity

The continuing expansion in petroleum and other resource exploration and in geological hazard assessment for infrastructure development have combined to dramatically increase the need for training of university students in seismic imaging methods. This need is being met at Brigham Young University (BYU) by forming alliances or collaborations with private industry and government in order to provide financial support for research using seismic techniques, to obtain access to proprietary datasets, and to place students in the workplace as part of their university experience. Infrastructure support has been provided by BYU in the form of acquisition of seismic recording equipment, procuring of state‐of‐the‐art software for data processing and geologic mapping, and building of a dedicated 3D visualization lab. This infrastructure creates an environment that mimics research and exploration programs in private industry. Seismic geophysical research foci at BYU include (1) seismic characterization of deep reservoirs for carbon sequestration, (2) 3D seismic attribute analysis for petroleum prospecting, (3) high‐resolution seismic exploration applied to landslide and earthquake hazard assessments, (4) exploration of deep sedimentary basins that may be prospective for oil or gas, and (5) oilfield applications of seismic mapping in order to detect and map shallow faults that may function as leakage pathways.

Seismic acquisition in the beach of the Shengli oilfield

The beach of the Shengli oilfield, as the prospect for steady continuous development of the Shengli oilfield, has a large area, special geographic and geological conditions, and other technical difficulties so that exploration has been slow. Seismic acquisition methods in the beach area and very shallow water have been investigated and, with the introduction of new equipment, given rise to more sophisticated acquisition geometries. A series of improved seismic exploration methods in the beach area and very shallow water are established by analyzing different shot and receiver parameters. As a result, S/N ratio and resolution of seismic data have been improved significantly to identify subsurface structures, improve reservoir description, and increase reserves and production.

Method of high-density seismic imaging exploration and application samples

The paper introduces the method of high-density seismic imaging exploration, discusses its features different from conventional shallow seismic reflection wave technique, and illustrates the application effect of the method using three samples of engineering geological explorations on land and in water — exploration of underground cavity, location survey of sunk ship and investigation of channel silt depth.

Shallow crustal structure of Chicxulub impact crater imaged with seismic, gravity and magnetotelluric data: inferences about the central uplift

The structure of the onshore portion of the Chicxulub impact crater (Yucatan, Mexico) has been studied with seismic, gravity and magnetotelluric (MT) exploration methods. A dispersion analysis of Rayleigh waves along a 150-km long, east–west profile permitted the shallow Tertiary cover to be imaged to a depth of 400 m. Three layers were mapped. The thickness of the first two layers increase as we approach the sinkhole ring from the exterior of the crater (consistent with the existence of a central basin). Those thicknesses change from 100–150 m outside the crater rim to more than 200 m in the terrace zone. At the crater centre, the first layer is again approximately 100 m thick and has a low shear wave velocity (approximately 1 km s−1). Its velocity is slightly larger in the rest of the profile. Outside the central basin, we observed a third layer with a shear wave velocity larger than 1.8 km s−1, but its thickness could not be determined. The velocity distribution along our profile increases monotonously with depth, without low-velocity layers. The inferred inward slope of the two shallow layers immediately outside the central basin correlates well with a smooth gravity gradient. In addition, we present results of detailed gravity measurements along a profile that coincides (in part) with the line covered by the seismic experiment. These gravity measurements were inverted to obtain a density model. In this model (which is of course non-unique), the steep gravity gradients are explained by the faults along which the slumping of the terrace blocks took place. Two of these may correspond to the faults observed at radial distances of 85 and 96 km in offshore seismic data. Finally, we show results obtained using MT soundings. They provide additional, independent constraints on the structure of the Chicxulub crater. MT soundings at the centre of the crater show a sharper increase in resistivity than elsewhere in the impact structure. This sharper increase in resistivity may be related to the uplifted basement of the structural high at a depth of 4 km. Only the MT soundings located over the central gravity high display this feature. Our three different data sets are independently consistent with the existence of a central structural high in the crater and support a twin-peak shape for this high.

Application of a shallow seismic reflection method to the exploration of a gold deposit

The shallow seismic exploration method has been used extensively in petroleum exploration and geological engineering, but whether or not it is suitable for solid-ore exploration is still uncertain since solid ore deposits are usually irregularly shaped. The application of this shallow seismic exploration method to the Yangji-Shan gold deposit in south China is, however, an example of a successful attempt to determine subsurface structure and find potential orebodies using the technique. In combination with the study of regional metallogeneic characteristics, shallow seismic exploration can provide a potential approach to locating and exploring solid mineral resources. Industrial drilling has verified the interpreted results for the gold orebodies at Yangji-Shan.

CARNARVON BASIN ARCHITECTURE AND STRUCTURE DEFINED BY THE INTEGRATION OF MINERAL AND PETROLEUM EXPLORATION TOOLS AND TECHNIQUES

The Barrow and Dampier Sub-basins of the Northern Carnarvon Basin developed by repeated reactivation of long-lived basement structures during Palaeozoic and Mesozoic tectonism. Inherited basement fabric specific to the terranes and mobile belts in the region comprise northwest, northeast, and north–south-trending Archaean and Proterozoic structures. Reactivation of these structures controlled the shape of the sub-basin depocentres and basement topography, and determined the orientation and style of structures in the sediments.The Lewis Trough is localised over a reactivated NEtrending former strike-slip zone, the North West Shelf (NWS) Megashear. The inboard Dampier Sub-basin reflects the influence of the fabric of the underlying Pilbara Craton. Proterozoic mobile belts underlie the Barrow Sub-basin where basement fabric is dominated by two structural trends, NE-trending Megashear structures offset sinistrally by NS-trending Pinjarra structures.The present-day geometry and basement topography of the basins is the result of accumulated deformation produced by three main tectonic phases. Regional NESW extension in the Devonian produced sinistral strikeslip on NE-trending Megashear structures. Large Devonian-Carboniferous pull-apart basins were introduced in the Barrow Sub-basin where Megashear structures stepped to the left and are responsible for the major structural differences between the Barrow and Dampier Sub-basins. Northwest extension in the Late Carboniferous to Early Permian marks the main extensional phase with extreme crustal attenuation. The majority of the Northern Carnarvon basin sediments were deposited during this extensional basin phase and the subsequent Triassic sag phase. Jurassic extension reactivated Permian faults during renewed NW extension. A change in extension direction occurred prior to Cretaceous sea floor spreading, manifest in basement block rotation concentrated in the Tithonian. This event changed the shape and size of basin compartments and altered fluid migration pathways.The currently mapped structural trends, compartment size and shape of the Barrow and Dampier Sub-basins of the Northern Carnarvon Basin reflect the “character” of the basement beneath and surrounding each of the subbasins.Basement character is defined by the composition, lithology, structure, grain, fabric, rheology and regolith of each basement terrane beneath or surrounding the target basins. Basement character can be discriminated and mapped with mineral exploration methods that use non-seismic data such as gravity, magnetics and bathymetry, and then calibrated with available seismic and well datasets. A range of remote sensing and geophysical datasets were systematically calibrated, integrated and interpreted starting at a scale of about 1:1.5 million (covering much of Western Australia) and progressing to scales of about 1:250,000 in the sub-basins. The interpretation produced a new view of the basement geology of the region and its influence on basin architecture and fill history. The bottom-up or basement-first interpretation process complements the more traditional top-down seismic and well-driven exploration methods, providing a consistent map-based regional structural model that constrains structural interpretation of seismic data.The combination of non-seismic and seismic data provides a powerful tool for mapping basement architecture (SEEBASE™: Structurally Enhanced view of Economic Basement); basement-involved faults (trap type and size); intra-sedimentary geology (igneous bodies, basement-detached faults, basin floor fans); primary fluid focussing and migration pathways and paleo-river drainage patterns, sediment composition and lithology.

Exploration in the Shetland‐Faeroe Basin using densely spaced arrays of ocean‐bottom seismometers

Recent exploration activity in the peripheral regions of the Shetland‐Faeroe Basin, offshore northwest Scotland, has led to the discovery of some of the largest oil reserves on the United Kingdom (UK) continental shelf. We present results from two ocean‐bottom seismometer profiles acquired by Mobil North Sea Ltd. across the center of the Shetland‐Faeroe Basin. These data provide a powerful tool for delineating long‐wavelength velocity variations and thus have potential for reducing the nonuniqueness associated with conventional seismic exploration methods. Analysis of the first‐arrival traveltime data using both forward and inverse ray‐based techniques produces a well constrained velocity‐depth model of the basin fill. We estimate that the uncertainty in the velocity structure is ±5% from a series of trial and error perturbations applied to the final models. The velocity structure of the Faeroe Basin has three principal layers: (1) a near‐surface layer with velocities in the range 1.6 to 2.2 km/s, (2) a 3.0–3.2 km/s layer which is characterized by a northwards structural pinch out in the center of the basin, and (3) a deeper laterally heterogeneous layer with velocities in the range 3.8 to 4.2 km/s. In the northwestern portion of the basin, a high velocity (5.0 km/s) basaltic layer is imaged dipping toward the southeast at a depth of 2–3 km. The basement is mapped at a depth of 7–9 km in the center of the basin. Gravity modeling provides independent corroboration of our models through the application of a velocity‐density relationship obtained from a synthesis of physical property measurements. Reflections from the Moho indicate a crustal thickness of 18 ± 3 km, suggesting that the basin is underlain by highly attenuated continental crust, but the velocities in the basement are closer to those of the Faeroe Islands basalts than the expected Lewisian gneiss, suggesting that it may be highly intruded.

The CEC Geoscience programme - a multidisciplinary targeted programme in exploration R&D (1990-1993)

The integration of seismic exploration methods and geological understanding is a general theme of research in the geosciences. Several projects already proposed to the Commission of the European Communities (CEC) addressing this topic have been coordinated into a single programme-the GEOSCIENCE Programme. This coordination had several benefits and some costs. The interdisciplinary interaction of participants from different European nations is beneficial: it allows diffusion of scientific information and efficiency, and mutual control to avoid duplication of efforts; it also improves quality of research. However, contracts are more complex and the overheads for meetings and trips are higher. This first experience indicates that the benefits outweigh the costs.

Seismic exploration method and apparatus for cancelling nonuniformly distributed noise

First Page

Geophone apparatus and a seismic exploration method

First Page

Method and system for seismic exploration employing a dual‐dipole hydrophone streamer

A seismic exploration method and system employing a streamer that houses at least one pair of orthogonally mounted hydrophones. The streamer may be operated downhole in a well, or may be towed in a body of water by a marine vessel. In the downhole embodiment, the invention permits detection of seismic signals of interest with suppression of noise due to tube waves and (dipole and monopole) modal waves propagating in and along the well, and without the need for locking the seismic detectors to the wall of the well. In the marine embodiment, the invention permits selective detection of waves incident from any incidence direction of interest (including the horizontal and vertical directions). In all embodiments, the incidence angle of the detected seismic wave is determined. The amplitude of the detected wave may also be determined from the incidence angle and the amplitude components detected at each hydrophone.

Method of seismic exploration including processing and displaying shear seismic data

A method of seismic exploration including processing and displaying shear wave seismic data for identifying gaseous hydrocarbon-containing formations and for inferring changes in the geological character of subterranean formations. A measure of the shear wave reflection coefficient is obtained for selected seismic events in the shear wave seismic data. Measures of formation property contrasts represented by the selected seismic event are obtained from the shear wave reflection coefficients.

Seismic exploration using non‐impulsive vibratory sources activated by stationary, Gaussian codes, detecting vibrations via receivers within a wellbore and processing the results into distortion‐free final records

The disclosed invention is a method of seismic exploration using non-impulsive vibratory sources activated by stationary, Gaussian codes in a wellbore environment. The method adds a distortion-free quality to the full-waveform seismic records.