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- Volume 33, Issue 7, 2015
First Break - Volume 33, Issue 7, 2015
Volume 33, Issue 7, 2015
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Enhanced downhole microseismic processing using matched filtering analysis (MFA)
Authors D.W. Eaton and E. CaffagniP assive-seismic methods provide an effective surveillance technology for monitoring the growth and activation of fracture networks during hydraulic-fracture (HF) stimulation of unconventional reservoirs, since microseismic events occur as localized brittle-failure processes that accompany tensile fracture growth (Warpinski, 2009; Maxwell, 2010). A number of acquisition geometries are used for microseismic monitoring (e.g., Eisner et al., 2010), including downhole geophone arrays installed in a deep wellbore close to the injection zone as well as deployment of surface and/or near-surface arrays. Downhole acquisition within a single monitor well is a commonly used configuration; although it is subject to a number of limitations that stem from limited observational apertures (Eaton and Forouhideh, 2011), this approach provides some distinct advantages by virtue of proximity of the sensors to the treatment zone (Maxwell et al., 2010). This paper introduces a novel correlation-based method for detection, location and analysis of microseismic events, tailored for a downhole recording geometry.
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Utilizing source mechanism and microseismic event location to identify faults in real-time using wireless seismic recording systems – an Eagle Ford case study
Authors Karl Harris and Robert BaconIn a time when every penny counts it is critical for operators to become more efficient in all activities. This includes determining the best approach for microseismic monitoring during hydraulic fracturing. Surface microseismic monitoring measurements are particularly suited for determining rock failure mechanisms, such as dip-slip or strike slip failures. Coupled with the ability to acquire these measurements and determine the failure mechanisms in real time during fracturing operations, allows operators to take actions to deal with costly geohazards. In this case study, the methodology related to data acquisition methods, and analysis and interpretation from microseismic monitoring to determine possible fault locations will be explained.
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Using induced polarization measurements to derisk hydrocarbon exploration in the Fingerdjupet-Hoop area, Barents Sea, Norway
Authors Kim Maver, Phillip Hargreaves, Andrea Klubika and Sergey A. IvanovExploration for hydrocarbons has been ongoing in the Barents Sea since the 1980s. Until now, ten wells have been drilled within the Fingerdjupet-Hoop area with variable success, but with an overall disappointing outcome. Alternative technologies are now being employed by the oil exploration industry in an attempt to discover the hidden secrets of this promising region. The Norwegian 23rd Licensing Round includes 14 blocks in the Fingerdjupet-Hoop area. As part of the prospect evaluation of the area and derisking of future wells, recently acquired induced polarization (IP) measurements, supported by 2D broadband-processed seismic, can provide valuable insight (Maver et al, 2015). This paper will describe the use of IP and its application as an exploration de-risking tool in general, and in the Barents Sea specifically.
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To frac or not to frac: assessing potential damage as related to hydraulic fracture induced seismicity
Authors Adam Baig, Gisela Viegas, Ted Urbancic, Eric von Lunen and Jason HendrickConcerns about seismic hazards during hydraulic fracturing, and other stimulation and injection practices in the petroleum industry has reached a crossroads in the last few years. Incidents in Blackpool, England, Fox Creek, Alberta, the general increase in seismicity in areas such as Oklahoma and Kansas, to name a few, have shined a light on the potential of hydrocarbon field operations to generate seismicity at levels that are of public concern. In general, to address these concerns, a number of jurisdictions have instituted various ‘traffic-light’ systems to govern the response of the industry to the potential occurrence of significant magnitude events. Generally, these protocols dictate that below a certain magnitude threshold, no response is necessary; once an event is in the ‘amber’ magnitude range, reporting to the regulator may entail more frequency and/or injections that need to be moderated. Finally, once an event is in the ‘red’ magnitude range, the injection in some jurisdictions could be halted. The exact application of these protocols, due to the nature of this approach, varies from jurisdiction to jurisdiction. Further, there has been poor time correlation between injection periods and the occurrence of induced seismic events with many occurring outside time periods we would commonly associate with fluid injection. Magnitude is the most ubiquitously reported parameter about an earthquake. The Richter Scale is probably seismology’s biggest contribution to the public consciousness motivated by a desire to quickly describe how an earthquake ranks with size with respect to others. However, reducing the nuances of an earthquake to a single magnitude number ignores many of the factors that control how the earthquake is perceived. For the example of seismic hazard, the effect of a potential earthquake is not quantified in terms of magnitudes but in probabilities in exceeding certain ground motion thresholds. The utility of this quantification is that it immediately can be related to building codes and the designs for different structures, which are all built to withstand shaking to various thresholds. Determining the magnitude is only part of the equation. Numerous other parameters impact the shaking felt on the surface, including (but not limited to) the depth of the event, the radiation patterns of the seismicity, and the stress release of the events. Considering an approach based on measured ground motion potentially removes the vagueness and ambiguity associated with the traffic light system often suggested by regulatory agents.
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Time-lapse characterization of the Niobrara reservoir from multi-component seismic data, Wattenberg Field, Colorado
Authors Taraneh Motamedi and Thomas L. DavisMulti-component time-lapse data were acquired by RCP and Anadarko Petroleum Corp over a section of land within the Wattenberg Field to monitor hydraulic stimulation of 11 horizontal wells drilled in mid-2013, targeting the Niobrara and Codell Formations (Figure 1). Multiple methodologies were utilized to extract azimuthal anisotropy signatures from pure mode seismic volumes in order to characterize the in-situ and induced fractures within the reservoir. The amplitude and traveltime analysis of poststack fast and slow shear wave data provided an estimated volume which is believed to relate to the stimulated rock volume; the azimuthal amplitude analysis of prestack fast and slow shear wave data proved to be a higher resolution fracture characterization tool providing measures of fracture orientation and density; and the azimuthal traveltime analysis of prestack compressional wave data is believed to provide measures of the reservoir stress state.
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Strain localization in sandstone and its implications for CO2 storage
Geological storage of CO2 is a key technical solution to the climate-energy challenge, but it has a number of technological constraints (Baines and Worden 2004; Halland et al., 2011), broadly under the themes of assuring adequate storage capacity and long-term storage integrity. A suitable CO2-storage reservoir should consist of rock formations with sufficient porosity, permeability and connectivity in order to provide an adequate storage volume. The role of faults and their associated deformation structures (such as deformation bands and fractures) in controlling both storage capacity and long-term storage integrity is thus a key factor in achieving globally significant CO2 storage (Figure 1). Although some sedimentary basins on the Norwegian continental shelf already harbour operational CO2- injection and storage projects such as Sleipner (Zweigel et al., 2004) and Snøhvit (Hansen et al., 2013), our understanding of reservoir fluid communication due to compartmentalization is far from complete and will be important for further use of the offshore basins for CO2 storage. In addition to the inherited structural features, elevated injection pressures may cause hydraulic fractures or stimulate fault reactivation which both point to the need to characterize the geomechanical response of the rock system to CO2 injection (Rutqvist, 2012; Iding and Ringrose, 2010). In the present work, we investigate the effects of faults and their related structures on the geomechanical and petrophysical properties of sandstone reservoirs. Important components of fault systems include fractures and deformation bands in the damage zone and fault core (Caine et al., 1996; Shipton and Cowie, 2003; Fossen et al., 2007). Fault systems may enhance or suppress fluid communication, which in turn may affect the storage capacity and conductivity of the candidate reservoirs (Figure 1). As a case study, a reservoir model of the Tubåen Formation at the Snøhvit CO2 injection site in the Barents Sea (Grude et al., 2013; Hansen et al., 2013) was investigated using 4D seismic data and fault attribute analysis. The characteristics of deformation structures (e.g. sub-seismic faults, deformation bands and fractures) were investigated by field studies of outcrop analogues and by triaxial laboratory experiments to provide a basis for numerical modelling. Fault architecture within reactivated fault systems was studied by the use of analogue modelling. Key questions addressed in the work include: a) Where and when might strain localize in the reservoir? b) How does rock strain influence fluid communication? c) How might structural architecture affect CO2 storage effectiveness?
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The brain behind the scenes − Neurobiological background of exploration geophysics
More LessIn this paper, I introduce the neurobiological background of four crucial aspects of human cognition linked with geophysics:imaging, integration, pattern recognition and exploration. Following the most recent results obtained in neurobiological research, I will try to bridge the activity of our geoscientists with fundamental concepts of cognitive sciences. These are the ability of the human brain to produce mental images, perform selection and pattern recognition and integrate multi-sensory information. Moreover, I suggest that geophysics is not exclusively a rational activity. In fact, following the most advanced neurobiological theories, I suppose that exploration geophysics istriggered by specific neural systems located in primordial areas of the subcortical brain. These areas are responsible for the basic emotions of all mammalians, such as those driving the exploration of their environment. Finally, I suggest possible research directions for improving brain performances in the practice of geosciences. My approach is supported by the modern concept of ‘neuroplasticity’. This idea assumes that, even into adulthood, experience can significantly change both the brain’s physical structure (anatomy) and functional organization (physiology). I introduce the work hypothesis that the idea of brain empowerment can be applied in the geophysical and geological work, with many practical implications.
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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)