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- Volume 38, Issue 1, 2020
First Break - Volume 38, Issue 1, 2020
Volume 38, Issue 1, 2020
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Step-out well positioning using hydrocarbon indicators from seismic inversion: a case study
Authors Taner Arpacı and Hüseyin ÖzdemirAbstractAVO attributes and especially absolute rock properties from prestack seismic inversion after calibrating to existing production wells are demonstrated to reduce the risk of drilling dry wells. At a mature onshore gas field, step-out well position optimization using inverted rock and reservoir properties to identify sweet spots has been successful. Initial prestack inversion used empirically generated shear sonic logs in the background model. The inversion results indicated a possible commercial gas accumulation in bypassed pay zones, and this was proven by drilling. Log data from this new well, including the shear sonic measurement, was incorporated into the background model. The prestack inversion was rerun and the improved inversion results indicated a new prospect. This has recently been drilled and the well found a 10-m thick gas sand reservoir.
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Quality control of land nodal seismic recording systems
Authors Tim Dean, Matt Grant and Hoang NguyenThe 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.
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The operational impact of nodes on large-scale seismic operations
By Jason CrissThe global acceptance of recording nodes in seismic operations is gradually increasing. Many regions of the world have either switched or are in the process of transitioning to nodal operations. Several factors have encouraged this transition among seismic contractors and their respective clients. High among these factors are cost of operations, flexibility of operations in a variety of terrain types, higher HSE requirements of field personnel, changes in the methods of acquisition and the demand for higher density shooting and single sensor recording. In Canada and the United States, the transition to nodal operations for seismic data recording is nearly complete. Whereas, adoption of nodes on the very large-scale projects of the Middle East and North Africa is in its infancy. This is partially due to the existence of enormous volumes of cable equipment in the inventories of seismic contractors but is also due in part to the fact that these projects span many years of continuous operations. The motivation to increase the recorded trace density while decreasing HSE exposure, cost of operations and environmental impact is driving new interest in nodal operations on large-scale projects. Nodes promise to positively impact many if not all of these motivational factors during this transition.
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WSGF — Time for a change part 1: Damped Harmonic Oscillators and the Vibrator/Ground model
Authors Spencer L. Rowse and Robert G. HeathIn land seismic exploration a vibrator is used to generate a controlled wave-train of seismic energy into the earth by the forced oscillations of the ground surface over several seconds in what is known as a vibroseis sweep. Usually, these oscillations are sinusoidal in character and are generated by a hydraulic force acting on two masses, a baseplate (BP) that is in firm contact with the ground and a reaction mass (RM) positioned above the baseplate via a hydraulic actuator connecting both masses. The oscillations generated by the vibrator mechanism propagate away from the vibrator location through the subsurface in the form of seismic waves and are reflected/refracted back to the surface and recorded electronically by multiple sensors laid out on the surface or in a borehole. The energy received at each sensor is the result of the seismic signal generated by the vibrator (its signature) modified by the earth’s geology and the travel paths taken by the propagating wave. In mathematical terms, the signal received at the sensor is the seismic signal convolved by the earth. Unlike impulsive seismic sources, such as dynamite, the raw vibroseis field records are generally uninterpretable because of the relatively low energy output of the source and the multiple overlapping seismic signals that are reflected and refracted during the transmission of the sweep. In addition, the vibroseis signal is contaminated with undesirable environmental and source-generated noise and must be ‘deconvolved’ with the sweep signal to produce an interpretable record that resembles the wavelet generated by an impulsive source. Obviously, the more accurate the deconvolution operator is in replicating the source signature, the greater the resolution obtained in the processing of the seismic data.
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Potential stratigraphic fans and fan deltas in the Older Cambay Shale — an emerging play type in the Northern Cambay Basin
Authors Sreedurga Somasundaram, Singh Rahul, B.N.S. Naidu and Neeraj KumarCambay Basin is one of the most prolific proven petroliferous basins in India, located in Gujarat state. It has more than 60 years of hydrocarbon exploration history with an average success rate of about 40%. Almost all the major structural traps in the basin have already been drilled for easy oil. Consequently, exploration has shifted to identify undrilled strati-structural/stratigraphic traps.
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Where next for Land Nodal systems?
By Steve WilcoxAn article from Dean, Tulett and Barnwell entitled Nodal land seismic acquisition: the next generation was published in First Break in January 2018, and described the evolution of wireless land seismic acquisition systems from their early origins in the 1970s to the current generation of nodal products. It went on to describe how these nodal products are used in acquisition projects and the various logistical benefits and challenges.
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Volumes & issues
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Volume 42 (2024)
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Volume 41 (2023)
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Volume 40 (2022)
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Volume 39 (2021)
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Volume 38 (2020)
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Volume 37 (2019)
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Volume 36 (2018)
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Volume 35 (2017)
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Volume 34 (2016)
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Volume 33 (2015)
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Volume 32 (2014)
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Volume 31 (2013)
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Volume 30 (2012)
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Volume 29 (2011)
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Volume 28 (2010)
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Volume 27 (2009)
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Volume 26 (2008)
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Volume 25 (2007)
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Volume 24 (2006)
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Volume 23 (2005)
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Volume 22 (2004)
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Volume 21 (2003)
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Volume 20 (2002)
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Volume 19 (2001)
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Volume 18 (2000)
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Volume 17 (1999)
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Volume 16 (1998)
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Volume 15 (1997)
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Volume 14 (1996)
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Volume 13 (1995)
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Volume 12 (1994)
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Volume 11 (1993)
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Volume 10 (1992)
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Volume 9 (1991)
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Volume 8 (1990)
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Volume 7 (1989)
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Volume 6 (1988)
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Volume 5 (1987)
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Volume 4 (1986)
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Volume 3 (1985)
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Volume 2 (1984)
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Volume 1 (1983)