Search

Land seismic surveys acquired in anything but the barest landscapes encounter obstacles that cause the planned survey points to be either shifted or skipped. Besides these forced changes, an increased awareness of the environmental impact of seismic surveys, coupled with a general lack of trust and even opposition to the traditional energy industry, has resulted in a demand to minimize the impacts of the clearing that is necessary to allow access to the survey lines. We present a method to reduce the environmental impact of seismic surveys without compromising seismic imaging. The process is straightforward and can be applied automatically using standard mathematical software (in this case, MATLAB). For the example shown here, where the line spacing was particularly dense, the impact on vegetation greater than 2 m in height was reduced by 55%. For less dense geometries, where there is more opportunity to offset points, the impact is likely to be larger.

Within the coal industry, there is a rich history of the use of the surface seismic method, principally for exploration and employing sparse 2D lines for broad resource delineation and structural modeling. However, the acquisition of 3D seismic surveys adjacent to open-cut mines (from which the majority of coal is extracted) for superior resource definition ahead of their expansion has been explored only recently. Although the reflection results are extremely useful and enable the mapping of faults with sub-5 m throws, there is still interest in determining if the seismic data can be used to image both structures and rock properties in the near surface. In addition to mapping near-surface structures that have geotechnical implications, the ability to map the overburden properties (which can be quite heterogeneous) is desired. Before mining activities can take place, the overburden needs to be removed. The cost of the removal method employed is directly affected by the depth of the weathered layer and rock properties. In particular, hardness can vary significantly. In this paper, we demonstrate how high-density seismic data originally acquired for reflection processing can be processed to generate high-resolution velocity (both VS and VP) depth volumes, which enable the successful identification of shallow structures and the creation of highly detailed near-surface rock-property volumes.

This essay considers the “descriptive turn” in literary studies from the vantage point of poetics, arguing that the history of Western poetry, from the Greeks to the present, offers through the category of epideixis a theory and practice of description that illuminates some of the methodological impasses of contemporary literary studies. Epideixis, a basic mode of pointing or linguistic ostension, confers value, often by way of praise or blame, without trying to persuade its audience with the practical immediacy of political or forensic rhetoric. Drawing on the ordinary language philosophy of Ludwig Wittgenstein and Stanley Cavell, the essay suggests that praise constitutes a philosophically rigorous alternative to critique. This argument is exemplified via the work of Mark Doty, a contemporary poet of description-as-praise.

The results of an experiment aimed at identifying the nature of major noise sources within an urban area are described. We found the strongest noise source to be an irrigation pump located adjacent to the geophones. The noise from the pump had a narrow bandwidth centered at 75 Hz with a duration of 5 minutes every 17 and 34 minutes during the day and night, respectively. Traffic noise was mainly restricted to between 10 and 25 Hz, with its strength decreasing between 9 p.m. and 6 a.m. Passing aircraft resulted in noise between 30 and 200 Hz lasting about 1 minute. Electrical noise was observed at the supply frequency of 50 Hz, although additional noise at 45 Hz also was observed. Given these results we recommended that acquisition within the area should be restricted to late evening or early morning, receiver locations should be selected to avoid strong localized sources of electrical and/or mechanical noise, and any cables associated with the recording system should be as short as possible (although nodal systems are preferable). If nodal systems are deployed for logistical reasons, real-time noise monitoring should be deployed to identify and avoid bursts of high-amplitude, short-duration noise.

The move from cable-based telemetry seismic acquisition systems with strings of wire-connected geophones to independent nodal, single sensor recording has been dramatic and is reflected by the plethora of nodal systems on offer and their increased use globally. With this shift in technology there has been some change in field methodologies. However, opportunity exists to be more creative in the approaches taken in acquisition and quality control of surface seismic nodal data and subsequent data processing. The use of automation is discussed along with challenging the linear approach typically taken in project execution, to the movement of some field-based support tasks to the town office and a new look at how to implement field quality control measures along with their related specifications. This paper therefore explores the seismic process from the planning stages, to the setting of quality control specifications and how automation can be implemented in field activities with examples given. The objective of this new collective approach is to reduce field exposure (personnel and time), to create a clear focus on critical field quality control parameters, and to ultimately drive down costs., Open-Access Online Publication: March 01, 2023

The vast majority of land seismic data has been recorded using systems where the sensors are connected to the recording truck by cables. This has allowed the quality of the recording system, and the data it collected, to be assessed in real-time. The emergence of nodal acquisition systems (Dean et al., 2018), in particular ‘blind’ systems where the data is not recovered until the node has been collected and downloaded, however, has refocused attention on just what level of QC is required.

In a previous paper, we described how a small electromagnetic vibrator could be manufactured using commercially available components for less than US$2,000. The basis of the unit was a set of four ...

Buckland Hill, near Fremantle in Western Australia, was the site of a costal defence battery from 1942 until 1963. After the army left the site in the mid-1980s, it was developed for housing, but t...

Early on in the history of seismic acquisition the advantages of being able to acquire data without the impediment of cables was identified. Despite the introduction of numerous systems since the 1...

Numerous new nodal seismic acquisition systems have been recently introduced that are significantly more advanced than those previously available (Dean et al. 2018). These new generation nodes are not only lightweight (the lightest currently commercially available is the Inova Quantum, being only 650 g) but also have significant battery lives, with 50 days not being unusual. Other than the Geometrics Atom, they have mostly been developed for large channel count surveys — thousands to tens of thousands. Often, however, surveys are acquired on a reduced scale, i.e. employing relatively small channel counts (from 24 to several hundred) and/or having a limited duration (four weeks or less). Examples of such ‘limited-scale’ surveys involve geotechnical work (refraction, Multi-Channel Analysis of Surface Wave (MASW), etc.), passive monitoring, and reflection surveys over small areas, such as mine sites. In this paper, we will look at the suitability of these recently introduced nodal systems for use in such limited-scale surveys. We begin by describing the acquisition systems that are currently used for such surveys before addressing positioning, an essential part of any survey. We then look at the influence of geophone selection, including 3-component recording and other recording parameters. We will then address the operational use of nodal systems and seismic sources. We finish with a brief data example followed by a discussion.

A vertical seismic profile (VSP) survey involves placing sensors in a borehole to record the passage of energy transmitted using a source of seismic energy placed on the surface. The sensors are usually contained within sondes that are coupled to the borehole wall using mechanical clamps. Existing VSP acquisition systems are generally unsuitable for acquisition using the wireline units typically used for minerals logging. In this paper we describe a new multis-sonde VSP acquisition system specifically designed for acquiring high-resolution VSP surveys in hard-rock environments.

Passive seismic surveys are becoming of increasing interest for characterising the near surface, in particular the depth of cover. For passive seismic acquisition ambient noise is both signal and n...

Rain has long been a problem for land seismic surveys, in terms of its effect on the condition of the surface and near surface, and also due to the seismic noise it creates when raindrops hit the ground. I measured the seismic signature of rainfall using water dripped from height using a pipette and natural rain in Winchester, England, over a three-month period. My results indicated that rain noise is concentrated at frequencies of greater than 80 Hz with a detectable range of less than 1 m. Drops of water landing directly on a geophone result in events with amplitudes nearly 30 times larger than those landing next to the geophone. Items placed on the surface of the ground, such as cables, absorb the energy of the impact and reduce the level of the resulting seismic noise. Burying geophones results in attenuation of rain noise by between 7.7 and [Formula: see text]. But, given the effort required to bury geophones, it is likely that data processing algorithms, or the placement of vibration-absorbent matting, are likely to be the preferred strategies for dealing with the noise.

Land seismic surveys are most often acquired in remote areas, thus the predominant noise source is often the wind. In urban areas, however, noise sources abound, including electrical cables, mechanical equipment, aircraft, and traffic. We recorded seismic data continuously over three days at a test site located in suburban Perth, Western Australia (32° 0’ 40”S, 115° 53’ 22”E). and found that the highest amplitude noise was mechanical (centred on 75 Hz), but the most consistent noise was traffic related (10-25 Hz). Electrical noise was identified but given its moderate amplitude and relatively consistent frequency it should be easily removed in processing. Aircraft flying over the test site resulted in moderately high level of noise with a wide bandwidth (30-200 Hz) but the noise generally lasted only a minute. Based on these results we recommend that: acquisition should be carried out during the late night/early morning; receiver locations should be chosen with care to avoid sources of noise; analogue cabling should be as short as possible to avoid electrical noise; real-time QC should be in place to identify short-duration high-amplitude noise periods during which acquisition should cease.

The construction of geological and geotechnical models in typical Pilbara iron ore environments is vital to enable an optimized mine design for the life of the asset, while maintaining pit wall integrity and overall mine safety. Geotechnical assessments require the measurement of geomechanical properties, such as the triaxial shear, direct shear and unconfined compressive strength tests and pressure and shear wave velocities on diamond core samples. Ideally, these velocities would be measured in Reverse Circulation (RC) boreholes as their spatial density is far higher than diamond drilled holes. Unfortunately, despite its value, such data is seldom collected as a large proportion of the holes are above the water table, limiting the use of sonic-logging tools. Even if measurements are possible, damage to the borehole caused by drilling biases the resulting velocity measurements. This paper details the results of a trial using the vertical seismic profile method to directly measure in-situ seismic velocities in RC boreholes. The method was successful in determining the velocities of the formations through the entire length of the holes. The data in several boreholes was of sufficient quality for the application of more advanced processing methods, important for geological mapping and the processing and interpretation of surface seismic data. The success of this first trial has implications for future iron-ore developments in the Pilbara. The widespread acquisition of accurate seismic velocity data is likely to enable the creation of more accurate geotechnical models and could improve future development decisions.

Since its introduction in the late 1950s, hydraulic vibrators have become the dominant source for land seismic surveys. The hydraulic vibrators typically used for commer-cial land seismic acquisition, however, are large, costly to operate and expensive to purchase. This inhibits their use for small-scale and short-duration surveys as well as Vibroseis research. In this paper we describe, in detail, the construction of a portable vibrator from commercially available components for a cost of less than $US2,000. Data shows that the vibrator is able to successfully transmit sweeps from 15 to 180 Hz with different spectral contents. The vibrator produces a stronger signal than a sledge-hammer and we estimate its output to be around 1 kN. The frequency content of the data was concentrated at lower frequencies (

Within the last two years six new land seismic nodal acquisition systems have been launched, a pace unmatched even during the oil boom of the late 2000s/early 2010s. Any acquisition system that utilizes recording instrumentation that does not incorporate cables is often referred to as a nodal system. Some instruments, however, are beginning to blur what initially appears to be a clear boundary. For example, the U-Node system from Seismic Instruments utilizes a node that records data from up to 24 different channels that can then be stored locally or transmitted via Wi-Fi to a central system. The reduction in cabling, which is usually cited as the core advantage of nodal recording, is therefore limited to the backbone connecting the central recording system to the field recording units. In this paper we will concentrate on nodes that are designed to record data from a single point and are thus typically limited to six or fewer channels. Over the history of nodes there have been six major categories developed (listed roughly in the order of their introduction): 1. Delayed data – Data is stored on the node and then transmitted after each shot, or stacked series of shots, is completed. 2. Remote-controlled – data is recorded internally but recording is initiated via radio messages. 3. Remote-synchronized – data is recorded continuously but the timing signal is issued via radio. 4. Real-time data – Data is transmitted in real-time. 5. Real-time QC – Status and or quality control data is transmitted in real-time. 6. Blind – the node records data internally and does not provide status or QC information in real-time. In this article we look at how nodal systems have evolved over the last 50 years. We begin with a historical overview starting from the early 1970s finishing in 2015. We then introduce the latest nodal systems and look at the implications of their use for seismic survey acquisition logistics. Finally, we will discuss the implications of these new systems and make some suggestions about where future developments should lie.

(2016). High Productivity Vibroseis Techniques: a Review. Preview: Vol. 2016, No. 184, pp. 36-40.

There is currently much work being done to improve the low-frequency content of land vibroseis data. Although techniques exist for designing sweeps that can extend the bandwidth down to as low as 1 Hz, the inclusion of these frequencies comes at considerable cost, either in the time taken to acquire a sweep or in the reduction of the total sweep energy. We describe the limitations on vibrator performance and how those limitations can be overcome using specialized sweep-design techniques. Perhaps more importantly, we describe how such sweeps can be optimized in terms of maximizing their energy content and verifying their performance.

Distributed vibration sensing, also known as distributed acoustic sensing, is a relatively new method for recording vertical seismic profile data using a fibre optic cable as the sensor. The signal obtained from such systems is a distributed measurement over a length of fibre referred to as the gauge length. In this paper, we show that gauge length selection is one of the most important acquisition parameters for a distributed vibration sensing survey. If the gauge length is too small, then the signal-to-noise ratio will be poor. If the gauge length is too large, resolution will be reduced and the shape of the wavelet will be distorted. The optimum gauge length, as derived here, is a function of the velocity and frequencies of the seismic waves being measured. If these attributes vary considerably over the depth of a survey, then the use of different gauge lengths is recommended. The significant increases in data quality resulting from the use of multiple gauge length values are demonstrated using field data.

Distributed vibration sensing (DVS), also known as distributed acoustic sensing (DAS), is a relatively new method for recording seismic data using a standard fiber-optic cable as the sensor. Although the dynamic range and noise floor of DVS systems are currently below those of industry-standard seismic sensors, usable seismic data can be obtained in downhole configurations, as this is the source and receiver configuration at which DVS is most sensitive. The use of DVS for more conventional land and marine seismic acquisition is still some way off. However, the potential benefits of simple, lightweight fiber-optic cables, with fine spatial sampling and the ability to instrument all offsets of any spread, suggest it is worth pursuing these new applications. Permanent reservoir monitoring, particularly for marine environments, represents another application where the simplicity of fiber-optic sensors is attractive. Advances in laser interrogation techniques and signal processing continue to improve the quality of DVS data, increasing its potential applications across the seismic industry.

The output from the hydraulic vibrators typically used for land seismic surveys is controlled by monitoring the acceleration measured by accelerometers mounted on the reaction mass and baseplate. The considerable energy output by such vibrators, which are coupled with the sensitivity of the accelerometers used, results in crosstalk if more than one vibrator is being used. In this paper, we present the results of a field experiment in which we measured the crosstalk between two adjacent vibrators. We found that the level of crosstalk was approximately ‐20 dB when the vibrators were adjacent but decreased with increasing frequency and separation. This result has implications for measurements of vibrator performance, source‐signature deconvolution, and in particular, estimates of the total energy output by a fleet of vibrators.