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- Volume 33, Issue 5, 2015
First Break - Volume 33, Issue 5, 2015
Volume 33, Issue 5, 2015
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Surface time-lapse multi-component seismology – a new technology for hydraulic fracture monitoring? A Montney Shale gas case study
Authors I. Viñal and Thomas DavisSeveral technologies have been traditionally used to monitor hydraulic fractures. Microseismic methods and the use of tiltmeters have provided satisfactory results. These methods estimate the vertical location of the failure events due to the stimulations with adequate accuracy. This study aims to evaluate the value that 4D surface seismic can add as a complementary method for hydraulic fracturing monitoring. Seen initially as a purely qualitative tool, its effectiveness as a powerful quantitative technique is being established among the scientific community. The present work provides evidence that time-lapse multi-component seismic data can monitor the hydraulic stimulations of two horizontal wells in the Montney Shale. The methodology focuses on the detection of time-lapse time shifts using both compressional and mode-converted wave data. The results prove the detectability of the changes in the stress field using this technique. Changes are observed not only within the reservoir but also in the overburden and the variations above the reservoir constitute the main focus of the interpretation. Results suggest that 4D seismic can be of great help in building accurate models of the reservoirs and their surroundings, which in turn will allow for prediction of the stimulation performance and optimization of recovery.
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Direct measurement of water velocity and tidal variations for improved 4D repeatability in marine seismic acquisition
Authors Kanglin Wang, Shaun Dunn, Jacob Ward and Paul HatchellGeophysicists concur that the quality of marine seismic data is often constrained by geometric variation in source and receiver locations, as well as water velocity uncertainty, caused by the multitude of environmental effects that prevail at offshore field locations. Such uncertainties make significant contributions to the nonrepeatability of marine time-lapse seismic data, and affect the quality of 4D data processing and interpretation. In order to reduce some of these uncertainties we have developed a seafloor instrument called a Pressure Inverted Echo Sounder (PIES). This instrument measures tidal variation and average water velocity at regular intervals. When placed at multiple locations across the survey area the instrument enables determination of the spatial and temporal variations in water velocity throughout each seismic survey and across multiple surveys as necessary. The resulting data can be used to reduce the seismic direct arrival inversion process to a very accurate positioning and timing exercise. In this article, the authors aim to describe the process of measuring tidal variation and water velocity including a description of the instruments used, an examination of the data processing steps required, and an analysis of the results provided by various deployments at Shell-operated fields.
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Calibration of Vp/Vs ratio in isotropic layered model using passive seismic data
Authors Dawid Szafranski and Iga PawelecA realistic velocity model is the basis for good interpretation of seismic data. Usually the main challenge is deriving the S-wave velocity model because P-wave velocities can be constrained from active seismic (e.g., check shots). Without reliable information about propagation of P- and S-waves we are not able to correctly locate hypocentres of earthquakes even with very well-picked arrival times. In the oil and gas industry, we usually have much better knowledge about P-waves than about S-waves. Information about P-wave velocities is often derived from an active seismic survey and sonic logs. Information about only P-wave velocities is sufficient when we want to use a dense network of receivers (usually 100 and more) for earthquake location (e.g., Duncan and Eisner, 2010). However, it is much more expensive than monitoring with a sparse network. Hence, there is a need to acquire information about S-wave velocity distribution in the subsurface.
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Modern coastal systems of Qatar as analogues for arid climate carbonate reservoirs: improving geological and reservoir modelling
Authors C.J. Strohmenger and Jeremy JamesonMaximizing recovery in oil and gas fields relies on geological models that realistically portray the spatial complexity, composition, and properties of reservoir units. Present day arid climate coastal systems, like the coastline of Qatar provide analogues for depositional and diagenetic processes that control reservoir quality in ancient reservoirs. Many major reservoirs in Qatar and the Middle East formed under conditions that are remarkably similar to those shaping the Qatari coastlines of today. Major controls on coastal sedimentation patterns are: 1) coastline orientation, 2) wind, wave and tidal energy, 3) climate, 4) relative sea level, 5) depositional relief, and 6) sediment sources. Strong NW prevailing winds (Shamal winds) drive shallow marine circulation patterns, creating four very distinct depositional profiles: windward, leeward, oblique, and protected. Windward coastlines are marked by reef development and intertidal sheet and beach sands. The leeward coastal profile is dominated by an eolian sediment supply, as sand dunes are blown into the sea. Along windward and oblique coastlines, hardgrounds (beachrock) stabilize circulation patterns, creating mud-prone back beach areas of micobial mats and mangroves. Protected coastlines are characterized by finer-grained peneroplid sands and low-relief beaches. Grain size, composition, and dimensions of coastal sands vary due to wave energy. Coastal deposits are equally affected by high-frequency oscillations in sea level. Approximately 6000 years ago, sea level was about 2 to 4 metres higher than it is currently and the Qatari coastline was up to 10 km inland. Most coastal deposits and sabkhas are relics of this ancient highstand in sea level. Punctuated sea-level drops to present-day level have led to the formation of seaward-stepping beach spit systems. Sedimentation patterns and their diagenetic overprint were studied in detail at the coastal sabkha of Mesaieed, which represents an oblique coastal system relatively to the predominant wind direction. Detailed field mapping, radiocarbon age dating analyses, and the integration of geotechnical borehole data, as well as data from numerous shallow pits allowed reconstructing the thickness of the Holocene, the dating and spatial reconstruction of the progradational pattern of the beach spits relative to the varying sea level, and the mapping of the amount and distribution of porosity destroying gypsum. The observed spatial complexity and heterogeneity of modern coastal systems are important aspects to be considered for conditioning three-dimensional geological models. Modern depositional systems along the Qatar coastline, like the one studied at the Mesaieed sabkha, are particularly useful as analogs for conditioning subsurface data sets in geologic (static) and reservoir (dynamic) models.
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Automated seismic facies for data integration: an example from Fort Worth Basin, Texas (USA)
More LessThe benefits associated with the integration of independent seismic attributes that are influenced by the same geological phenomenon in a qualitative analysis of reservoir physical properties or distribution of geologic features is well recognized. A new data integration approach which combines automated seismic facies with a visual-based framework is proposed in the present work. Automated seismic facies is the mechanism for integrating multi-seismic attributes. The output is a collection of seismic facies which reveals significant geologic patterns in the input seismic attribute data. The visual-based framework allows the direct involvement of interpreters’ expertise to steer the seismic facies creation and select the seismic facies scheme providing the best data integration solution. The illustrative example shown in the paper demonstrates the usefulness and capability of the proposed approach for data integration analysis.
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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)