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Wei Z.,INOVA Geophysical Equipment Ltd. | Phillips T.F.,INOVA Geophysical Equipment Ltd.
75th EAGE Conference and Exhibition Incorporating SPE EUROPEC 2013 | Year: 2013

Extending the frequency bandwidth towards low frequencies using the Vibroseis method has gained a lot of attenation recently. The source (vibrators) becomes one of the obtacles in the success of recording low frequency seismic signals. How do we increase the vibrator ground force at low frequencies (< 10 Hz)? Can the vibrator control electronics effectively supress harmonic distortion at low frequencies? This paper attempts to provide a fresh look at these questions.

Liu Z.,China National Petroleum Corporation | Sa L.,China National Petroleum Corporation | Dong S.,China National Petroleum Corporation | Han X.,INOVA Geophysical Equipment Ltd
Shiyou Diqiu Wuli Kantan/Oil Geophysical Prospecting | Year: 2013

Kernel seismic acquisition equipment is one of the key factors in geophysical exploration technology applications. The equipment development is the motive power to promote seismic exploration technology development. Some of new acquisition approaches such as high density, wide azimuth, and full wave, turn into the key technologies to solve more and more complex geology problems in oil and gas exploration. Over ten-thousand-channel acquisition systems, high-fidelity and broadband digital sensors, and new featured vibrators for high production acquisition are foundations of the technology application. This article introduces development of the kernel seismic acquisition equipment in the world and analyzes its current status in China. According to the authors, the equipment development direction will be hybrid data recording systems with wireless and wire data transmission, digital sensors, high-efficient and broadband vibrators in order to meet future geophysical development requirements in China.

Wei Z.,INOVA Geophysical Equipment Ltd | Phillips T.F.,INOVA Geophysical Equipment Ltd
Geophysics | Year: 2013

Acquiring low-frequency seismic data using Vibroseis techniques has gained attention in recent years. Successful application of low-frequency Vibroseis acquisition requires evaluating each element of the data acquisition system and ensuring that each part of the system contributes to the success of the method. We focus on generating low frequencies with Vibroseis sources rather than recording and preserving them. To generate the low-frequency signals using seismic vibrators, it is better to know (1) the hydraulic and mechanical system of the vibrator; (2) the design of a low-frequency sweep that can deliver the vibrator ground force maximally; and (3) the vibrator control system that can minimize the harmonic distortion of the vibrator ground force output at low frequencies. Field tests show that hydraulic pump flow is not a limiting factor for the generation of the low frequencies for most modern seismic vibrators. In addition, with harmonic distortion reduction control, the vibrator performance at low frequencies is improved. © 2013 Society of Exploration Geophysicists.

Spiewak S.,University of Calgary | Selvakumar A.,INOVA Geophysical Equipment Ltd. | Arjmand M.T.,University of Calgary | Lawrence E.,Polytec Inc.
ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) | Year: 2010

Microsystems Technology based inertial sensors offer important advantages in low-invasive measurement of spatial motion with sub-micron accuracy. Their successful implementation hinges upon achieving very low distortion and noise at the low end of the frequency spectrum. Of particular importance is the Vibration Rectification Error (VRE) - An apparent shift in the signal bias that occurs when inertial sensors are subjected to vibration. A common approach to the reduction of VRE is assuring a highly symmetrical mechanical structure of sensors. Furthermore, a low cross-Axis sensitivity is desirable. In accelerometers these properties are achieved by employing multiple flexures supporting the seismic mass. However, this may lead to mechanical over-constraining and multiple local equilibria rather than a single global one. Multiple equilibria combined with the nonlinearity of flexures create conditions for chaotic behavior, which can greatly degrade the sensors' performance. We investigate representative architectures of high performance servo accelerometers, study the impact of over-constraining, and develop comprehensive dynamic models accounting for the presence of this condition. Given the complexity of spatial motion of the proof mass and resulting deformations in the flexures, we employ computer aided generation of constitutive, symbolic and scaleable models of the investigated sensors. We illustrate analytical investigations with numerical simulations and experimental results. Copyright © 2010 by ASME.

Wei Z.,INOVA Geophysical Equipment Ltd | Phillips T.F.,INOVA Geophysical Equipment Ltd | Hall M.A.,INOVA Geophysical Equipment Ltd
Geophysics | Year: 2010

Vibrators are the most widely used sources in land seismic exploration. Successful application of vibroseis technology requires evaluating each element in the vibrator system and ensuring that each part of the system contributes to the success of the method. To obtain a high-quality image of the subsurface using the vibroseis method, it is beneficial to know: the frequency bandwidth the vibrator and its control system can deliver; the outgoing signal from the vibrator and the repeatability of the source signature; and the harmonic distortion level on the vibrator force output and the limits the vibrator is subject to. Fundamental discussions on the vibrator system that have been forgotten over time are presented. © 2010 Society of Exploration Geophysicists.

Wei Z.,INOVA Geophysical Equipment Ltd | Phillips T.F.,Dawson Geophysical
Geophysics | Year: 2013

Extending the vibroseis bandwidth toward low frequencies (below 10 Hz) can bring many benefits for land seismic exploration such as deeper signal penetration and for nearsurface inversion techniques. Due to physical limitations in vibrator mechanical and hydraulic systems, the ground force output from a vibrator at low frequencies is limited. This limited ground force output is severely distorted by harmonic distortion such that the ground force in fundamental frequencies is reduced. We focused on reducing harmonic distortion through vibrator control algorithms to improve vibrator performance at low frequencies. The purpose was to show that with only vibrator control algorithms, the fundamental ground force from a vibrator can be noticeably improved at low frequencies. In addition, we demonstrated a synthetic case using the weighted-sum ground force to simulate slip-sweep acquisition. Presumably, reducing source generated harmonic distortion can help decrease the slip time in slip-sweep operations thereby increasing productivity rates. © 2013 Society of Exploration Geophysicists.

Wei Z.,INOVA Geophysical Equipment Ltd | Hall M.A.,Geokinetics
Leading Edge (Tulsa, OK) | Year: 2011

The vibroseis method has, for half a century, achieved great success in land seismic exploration. However, some practical issues still arise that have remained theoretically unexplained. For example, on soft ground, the vibrator produces subharmonics and ultra-subharmonics in addition to main harmonics; whereas on hard ground, the vibrator generates harmonics only. Geophones on soft ground also behave abnormally while geophones on hard ground behave normally. This paper analyzes these phenomena and demonstrates that the softness of the ground's top layer is responsible for subharmonics and ultra-subharmonics. This soft ground layer causes the geophone abnormality as well. Unfortunately, quantification for this behavior has not been achieved. © 2011 Society of Exploration Geophysicists.

Wei Z.,INOVA Geophysical Equipment Ltd | Hall M.A.,Geokinetics | Phillips T.F.,INOVA Geophysical Equipment Ltd
Geophysical Prospecting | Year: 2012

The seismic vibrator has become a very important source for land data acquisition and there have been dramatic improvements in recent times in the application of the vibroseis technique. These improvements have led to much increased productivity and in many cases much denser source sampling. At the same time, the vibrator itself has seen little improvement over the last couple of decades. There are needs in a few areas where an improvement in the vibrator itself can bring benefits to the quality of the seismic data acquired. This paper describes progress in four such areas, low-frequency performance, high-frequency performance, an improved estimate of the vibrator groundforce and source signature consistency over variable ground conditions. Each of these vibrator characteristics will be discussed in turn. Meanwhile, two field test results in which the performance of two different vibrators in these four areas are compared. © 2011 European Association of Geoscientists & Engineers.

Wei Z.,INOVA Geophysical Equipment Ltd | Phillips T.F.,INOVA Geophysical Equipment Ltd
Geophysical Prospecting | Year: 2012

The vibroseis method has become the principal data acquisition method in land seismic exploration. It seems that this method has been extended to its limits as the search for energy resources continues. Many practical issues arising from field operations have remained theoretically unexplained, for example, variations in wavelet arrival time, inaccurate wavelet estimation and harmonics in the wavelet itself. The focus of this paper is the proposal of a new model, which is referred to as the vibrator-coupled ground model, to simulate the filtering effects of a complex coupling system consisting of the coupling between the baseplate and the ground as well as the coupling between the captured ground mass near the vibrator baseplate and the surrounding earth. With this vibrator-coupled ground model many of the practical issues mentioned above were reasonably addressed. Furthermore, it was demonstrated from experimental tests that both the pilot sweep and the weighted-sum groundforce, when filtered by the vibrator-coupled ground model, are proportional to the far-field particle velocity whereas the unfiltered signals are not. The harmonics on the filtered weighted-sum groundforce successfully maintain a proportional relationship with the harmonics seen in the far-field signal. © 2011 European Association of Geoscientists & Engineers.

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