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- Volume 34, Issue 7, 2016
First Break - Volume 34, Issue 7, 2016
Volume 34, Issue 7, 2016
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Shear-wave splitting analysis of downhole microseismic data for reservoir characterization of the Montney Formation, Pouce Coupe, Alberta
Authors Ben P. Andrews and Thomas L. DavisFollowing the symbiotic emergence of hydraulic fracture stimulation and microseismic monitoring, the phenomenon of shear-wave splitting is now being measured from completions operations. This study focuses on the downhole microseismic survey acquired at Pouce Coupe during the hydraulic fracture treatment of three horizontal wells. Microseismic shear-wave splitting analysis was performed to better constrain the physical rock properties of the Montney Formation. A strong temporal correlation was also observed between shear-wave splitting measurements and completion data providing insight into the response of the reservoir during hydraulic stimulation. In recent years, significant strides have been made to improve and semi-automate a workflow to measure shearwave splitting from microseismic data. Multiple studies have previously exploited this approach to model seismic anisotropy and infer the strength and orientation of aligned fracture sets and sedimentary fabrics within producing reservoirs (Verdon et al., 2011).
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Towards an improved understanding of induced seismicity associated with hydraulic fracturing
Authors Katherine Bosman, Adam Baig, Gisela Viegas and Ted UrbancicSparked by a number of recent high-profile incidents of seismic events felt on the surface near petroleum field operations, there has been growing concern over seismic hazards associated with hydraulic fracture stimulation and injection programmes. In response, several jurisdictions have enacted regulations requiring modification or temporary shut-down of operations in treatment wells close to earthquakes which exceed certain magnitude thresholds. These recently proposed magnitude-based ‘traffic light’ systems that break from existing standards and regulations related to seismic hazard, which are typically based on measured ground shaking (velocity and acceleration). Observed shaking, and the associated risk of damage or injury, is determined by several factors including both earthquake source characteristics and site- and raypath-specific conditions. Additionally, the ground motion, and associated hazard, produced by injection-induced seismicity is variable for events of the same magnitude, owing to differences in stress release behaviour and source depth. Ground shaking is directly measured by seismic instruments and directly related to building codes and structural design specifications. To achieve a more consistent and reliable regulatory standard, we suggest that regulations be based on ground motion, rather than magnitude, for the evaluation of seismic hazards associated with injection-induced seismicity.
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Offshore injection and overburden surveillance using real-time passive seismic
Authors S. Bussat, L.W. Bjerrum, B.D.E. Dando, E.V. Bergfjord, K. Iranpour and V. OyeIn 2013 a seismic caprock monitoring system with 172 nodes was installed on the Oseberg oil and gas field in the Norwegian North Sea. It was specifically designed for active and passive seismic monitoring of a disposal injection well. The aim of the monitoring is for a safer operation with avoidance of leakages to the sea, and increased injection. Despite installation and yearly maintenance costs but owing to benefits in the operation of the injector, the system provides yearly savings of around $1.2 million. Currently, the system does most of the passive seismic analysis – microseismic and interferometry – in real time, and we present data examples from the last two years. Typical noise in the data (seismic shooting, platform generated noise and marine traffic) are removed and the signal-to-noise ratio is significantly improved, resulting in better detections and event location, especially for small microseismic events. Seismic interferometry is used to observe/detect changes in the water column and the shallow subsurface down to several hundred metres. Several offshore hydrocarbon-bearing fields have experienced fractures in the overburden from injection into disposal wells, including leakage to the surface. Although injection procedures to avoid this are effective, they significantly limit the rates and pressures of the injection. To overcome this, a permanent offshore seismic monitoring system using both active and passive seismic methods has been developed. It was installed at the seabed of the North Sea Oseberg field in 2013 with the main aim to control caprock integrity and ensure safe injection, which makes the system unique.
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Automatic passive seismic data processing with no prior information: the contribution of Surface Wave Tomography
Passive Seismic Tomography (PST) has been successfully applied for years in solving difficult exploration and production problems. Using local microearthquakes as seismic sources and dense microseismic networks as receivers, this methodology exploits significant numbers of continuous records that have to be thoroughly examined, in order to extract all useful information. In such applications, the greatest possible number of microseismic events is required in order to increase our knowledge of the subsurface. Although processing and analysis of microseismic data has been traditionally carried out manually by expert analysts, automation of these procedures has become mandatory. The vast volume of continuous data to be processed, as well as the subjective factor that is unavoidably introduced by the involvement of different analysts in the phase picking process, leads to the need for automation of the specific procedures (Leontarakis et al., 2015). Regardless of the way that processing and analysis of passive seismic data is carried out, the choice of the appropriate initial 1D velocity model is of primary importance, especially in the case of the PST method, where the sources (local earthquakes) are unknown and hypocentres should be accurately defined. The 1D velocity model, as well as the mean Vp/Vs ratio, are important prerequisites for a reliable initial event location.
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Separating weak surface microseismic events from noise
Authors Ted Shuck, David E. Diller, Barry Fish and Rob KowalskyMicroseismic events that are detected at the surface are often very weak, with moment magnitudes as low as -2. Such weak events present a difficult analysis problem to ensure that they are ‘real’ events that originate from microseismic activity near the reservoir zone. There are many sources of noise that can give the appearance of genuine microseismic events, including reflected noise from the frac operation, reflected noise from vehicles, and spatially isolated but persistent noise that causes interference patterns that may be erroneously interpreted as evidence of geologic anomalies. Signal-to-noise enhancement methods can help to discriminate between valid events and noise propagating near the surface. Reflected noise from surface sources may have a similar apparent velocity and depth as valid events but can be recognized by its pulsating nature. Source mechanisms provide information about the fractures, but also give us a tool to help determine whether weak events are real or the result of noise sources. We present a classification scheme that incorporates these methods and observations.
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Best students papers in Vienna showcase young talent coming through
Three student papers have been chosen as the best submissions for the EAGE Annual Conference in Vienna. The work – covering pore scale visualization of polymer viscoelasticity, process-based modelling of sediment distribution in fluvial crevasse splays, and using effective medium theory to better constrain full wave inversion – is a testament to the great young talent coming through in the world of geoscience.
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Quantitative 4D analysis using business analytics techniques
Authors Mark Thompson, Marianne Houbiers, Jane McConnell and Duncan IrvingA Reservoir Data Warehouse was successfully created where key subsurface information used for geophysical reservoir monitoring has been transformed, integrated, and stored into a geospatially registered relational database. Quantitative 4D analysis was performed on the data, utilising the power of the parallel processing architecture of the high-performance analytical database, and combining traditional 4D analysis and business analytics tools. The 4D analysis successfully demonstrated quantitative relationships between the different data. At its simplest the Reservoir Data Warehouse enables a more sustainable and easily accessible solution for data integration and co-visualization, and simplification in the data management realm. At its most powerful the Reservoir Data Warehouse will enable the creation of new subsurface workflows where large amounts of data from disparate origins can be analysed jointly and presented in existing software solutions, or in newly developed cross-disciplinary software solutions.
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Importance of conceptual geological models in 3D reservoir modelling
Authors J. Cavero, N.H. Orellana, I. Yemez, V. Singh and E. IzaguirreConceptual Geological Models (CGM’s) represent geological knowledge and are traditionally visualized by 2D geologic crosssections. Construction of CGMs is a non-linear and complex process which involves application of geological rules and experience. These models describe essential features of geological situations, illustrate the principal processes of the petroleum system, and provide important information about reservoir characteristics, pressure and fluid flow of the field under study. The CGMs are being extensively used as the key input for 3D reservoir modelling and simulation at different stages of E&P projects. A fully integrated CGM building process consists of at least four stages: construction of one or more structural models, identification of depositional models, construction of sedimentary facies models and finally building of diagenetic facies models. This process requires integration of geological, geochemical, geophysical, and petrophysical data along with information from well testing and production into a comprehensive model describing the physical features of the geologic system. This paper briefly describes the different components of CGM and the model building process. The importance of integrating CGM in the 3D reservoir models has been demonstrated through an example of siliciclastic reservoir. This reservoir has complex internal sedimentary distribution and stratigraphy which leads to high subsurface uncertainties. The study shows that different possible conceptual geologic scenarios provide significantly different Hydrocarbon-In-Place, recoverable resources and production forecasts. Therefore, the successful application of appropriate CGM’s is critical for better 3D reservoir characterization and modelling which enables us to identify and rank the key reservoir uncertainties and assess their impact, establish interdependency of spatial property distribution, make volumetric assessments, plan the number and location of wells including their drainage area, optimize recovery efficiency and obtain reliable production forecasts.
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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)