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76th EAGE Conference and Exhibition - Workshops
- Conference date: 16 Jun 2014 - 19 Jun 2014
- Location: Amsterdam, Netherlands
- ISBN: 978-90-73834-90-3
- Published: 16 June 2014
121 - 140 of 142 results
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Upscaling in Vertically Heterogeneous TTI Models
Authors A. Stovas and Y. RoganovWe define the low-frequency upscaling of vertically heterogeneous transversely isotropic layers with a tilted symmetry axis. In order to be used for velocity model building, the seismic wavelet is used as a weighting function. For a VTI medium, the low-frequency upscaling gives more accurate effective anisotropy parameters comparing with the ones obtained from Backus averaging. We also show that upscaling in TTI media results in much smaller effective tilt angle comparing with intrinsic one.
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Practical Core Interpretation for Input to Deterministic Facies Modelling in Wave-dominated Deltaic Reservoirs
Authors R.J. Porter and B. BashokoohThe main purpose of this workshop is to highlight the significance of ‘traditional’ reservoir geology skills. Sedimentology, reservoir properties and log signatures will be combined in a practical approach to define reservoir genetic units (flow units), using a wave-dominated deltaic example. To emphasise the added value of this method, the results of a hands-on flow unit definition exercise using deltaic core material from the Book Cliffs, Utah, can be compared with a definitive answer. This is provided by a set of large-scale outcrop photo panels and Petrel static models which exactly define the sedimentary geometry and architecture of a field-scale exposure of fluvio-deltaic deposits. Participants can therefore judge the importance of the decision making processes such as deciding facies type, and the effect this could have on different reservoir geometries and architecture. Through a combination of lectures, correlation exercises and a hands-on core description/interpretation exercise, it will be shown that combining sedimentology and sequence stratigraphy with regional palaeogeographical knowledge, can provide a robust deterministic framework for 3D reservoir models, that accurately predict reservoir architecture and connectivity ahead of drilling.
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The Key to High Resolution Reservoir Characterization
Authors G. Burmester and K.A.T. MacPhersonThe core provides essential information on grain-size distributions, porosity and permeability variations as well as rock fabric and texture information, which are essential for facies and depositional environment interpretations. Extrapolation and reconciliation of these core lithofacies with open hole derived electrofacies is often problematic, due to the differences in resolutions between the two data types. Core facies are typically “lumped together” into units that can be segregated based upon their log responses. This up-scaling — often based upon log response cutoffs — can lead to differing rock “types” being lumped together because critical textural information related to sedimentary structures is omitted. As a consequence, stratigraphic correlations become based upon recognition of “log shapes,” rather than true reservoir properties, e.g., grain-size trends, bedding attitudes and facies contacts. Integration of core analysis and core descriptions with open hole logs and borehole image-based texture analysis prior to the stratigraphic interpretation can significantly enhance reservoir characterization and stratigraphic correlation. Key core derived information, e.g., grain-size trends, textures or spatial information, can be more readily extrapolated to high resolution borehole images, which in turn provide the essential intermediate link between the physical core and open hole log responses.
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Synthesis of Research and Education, Industry and Academia - A Case Study of 2-D Heterogeneities of Poroperm, Ultrasonic and Resistivity on Sub-meter
Authors M.C. Poppelreiter and J. HornungSpatial relationships of rock and petrophysical properties on a grid block scale (decimeter) are poorly known. These however are input to effective property models and near well-bore heterogeneities in geocellular models. To investigate and visualize such relationships slabs of typical clastic and carbonate reservoir rocks were analyzed. To this end rock properties such as grain size, sorting, pore types as well as petrophysical properties like porosity, permeability, ultrasonic speed and resistivity were systematically described. Results are displayed as property maps. Investigations will be used for training young petroleum engineers to link geology to petrophysical properties. Relationships are input to geological decisions such as geostatistics or geologically meaningful upscaling strategies.
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Multipulse Airborne TEM Technology and Test Results Over Oil-sands
Authors T. Chen, G. Hodges, A.N. Christensen and J. LemieuxThe MULTIPULSE™ technology enables a time-domain electromagnetic (TEM) system to transmit a high power pulse and one or multiple low power pulse(s) within a half-cycle. The high power pulse ensures good depth of exploration and the low power pulse allows a fast turn off and earlier off-time measurement as well to provide higher frequency information, thus allowing higher near surface resolution and better sensitivity to weak conductors. The MULTIPULSE technology can be applied to current airborne TEM systems such as the HELITEM® and GEOTEM® systems to increase their geobandwidth. The addition of the small pulse extends the range of the sensitivity tenfold toward the weak conductors and therefore expands the scope of applications of the TEM systems. We have field tested the HELITEM and GEOTEM MULTIPULSE systems in Fort McMurray, Alberta, Canada, over a typical oil sands geologic setting. The results demonstrate the effectiveness of the MULTIPULSE technology, showing comparable shallow geological resolution of the MULTIPULSE to that of the frequency-domain RESOLVE® system while maintaining superior depth of exploration.
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Tectonic Controlled of Cleats Development as Implication of Coal Bed Methane (CBM) Prospect in the Barito Basin, South B
Authors B. Sapiie, A. Rifiyanto and A. SuryanugrahaCleats are considered as one the important parameters in the CBM development particularly related to permeability. A complete characterization of cleat distributions and orientation may provide a better tool for indirectly estimating porosity and permeability in coal reservoirs as critical parameters for coalbed methane extraction. This paper is presented results of detail study cleats development within Miocene coal seams as part of CBM exploration and development. Most data were collected on mine walls (cross-section view measurement). Cleats data were collected for several coal seams from 60 scan lines and 39 windows measurement locations with total 20,000 cleats were measured from outcrops. Three major cleat orientations; WNW-ESE, NNW-SSE, and NE-SW. The relationship between cleat spacing and coal rank: bright coal (vitrain) generally have smaller cleat spacings than dull coal (durain). Coals with low ash content tend to have smaller cleat spacing than coals with high ash content. Relationship between coal density and calorific value shows high calorific value with low ash content tends to have large density. This suggests that coal composition related to cleats characteristics. This cleats origin might be subjected from several processes particularly superimposed by later processes such as hydrostatic pressure and tectonic stresses.
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Optical Multi-component Borehole Seismic Systems Continue to Deliver Unique Permanent Downhole Data
Authors T. Bostick and P. TravisFiber optic seismic sensors for permanent monitoring applications have continued to deliver unique, continuous multi-component seismic data from deep, high pressure/temperature wells for the last decade. Designed for long term deployment, these sensors optimize sensitivity, 3-component performance and reliability. The all-optical sensors achieve high fidelity borehole seismic sensing without the need for downhole electronics, and satisfy the requirement for ongoing monitoring for many years in hostile environments. First installed in 2002, applications have over the years included both VSP imaging and microseismic monitoring. The high sensitivity, multi-component sensors enable 3-C processing for imaging purposes and deliver directional fidelity for microseismic event location and characterization. Typically installed simultaneously in a well completion with other optical sensing technologies, such as pressure/temperature gauges and DTS, the all-optical, multi-parameter systems enable efficient integration of production and reservoir monitoring in the same well. Recent case studies demonstrate the robust nature of the technology to deliver high quality microseismic data in onshore HPHT gas storage and offshore injection wells.
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Fiber Optic Vector Sensors
Authors B.N.P. Paulsson, J.L. Toko, J.A. Thornburg and R. HeSeismic techniques dominate the characterization of subsurface structures, stratigraphy and reservoirs. They also dominate production monitoring processes. Borehole seismology, of all the seismic techniques, despite its current shortcomings, has been shown to provide the highest resolution characterization and most precise monitoring results because it generates higher signal to noise ratio and higher frequency data than surface seismic techniques. To address the critical site characterization and monitoring needs for EGS, CCUS and deep offshore reservoir programs Paulsson, Inc. has developed a fiber-optic based ultra-large bandwidth clamped borehole seismic vector array capable of deploying up to one thousand 3C sensor pods suitable for deployment into ultra-high temperature and high pressure boreholes. Tests of the new vector sensors have shown that the developed borehole fiber optic seismic sensor technology is capable of generating outstanding high vector fidelity data with extremely large bandwidth: 0.01 – 6,000 Hz. Field tests have shown that the system can record events at magnitudes much smaller than M-2.6 at frequencies up to 2,000 Hz. The sensors have also proved to be much more sensitive than regular coil geophones used in borehole seismic systems today. The fiber optic seismic sensors have furthermore been qualified to operate at temperatures over 300°C
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Distributed Acoustic Sensing for Borehole Seismic Applications
By T.R. ParkerDistributed acoustic sensing (DAS) technology enables the simultaneous collection of acoustic data at all points along a length of optical fibre. In this presentation, we look at the main options for the installation geometry (the cable deployed in the production tubing, clamped to the outside of the production tubing or cemented behind the casing) and discuss the effect of this geometry on the measured DAS signal. This comparison will examine the signal coupling from the formation to the fibre, and the resultant influence on the signal to noise ratio, and also look at the relative strength of the measured flow signal, in the case of a flowing well. Through this discussion, we will explain the important trade-off between the chosen DAS spatial resolution and the resultant signal-to-noise ratio. We will then extend the discussion to look at ways to tune the directionality of the DAS measurement and to tailor the DAS response to resemble the output from different standard geophysical sensor families. Through this presentation, we will aim to demonstrate the flexibility of the DAS sensing mechanism, and explain how this flexibility enables the dynamic optimisation of the system performance for various target measurements.
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Case Study of a Multi-Well 4D DAS-VSP
By D.J. HillSince the first DAS-VSP measurement was made in September 2009, there has been considerable progress in developing the technology and techniques to fully exploit the unique benefits of DAS for VSP. This technology is increasingly seen as an enabler for VSP measurements to be acquired in wells where it would be impracticable to run a conventional VSP with geophones. One particular use is in EOR applications where DAS-VSP is now being used to enable 4D VSP surveys to be taken in order to image the sub-surface changes to features, such as the growth of a steam chest. In this case study, we describe the setup and simultaneous acquisitions of a baseline 4D vibroseis survey using DAS-VSP deployed on eight vertical wells. We will explain how the eight systems were fully synchronised with vibroseis trucks and describe the process used to provide real-time, remotely viewable SEG-Y outputs from each well. Using DAS-VSP in EOR applications of this type, we will show how it is now possible to acquire low cost 4D imagery of the sub-surface across an entire field, which can be used to monitor the injection process, plan future pattern spacing and inform the infill strategy to increase the ultimate recovery.
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Wireline Deployment of Optical VSP in Vertical and Deviated Wells
Authors A. Hartog, B. Frignet, D. Mackie, M. Clarke, A. Constantinou, W. Allard and G. LeesThis workshop contribution will show comparisons of heterodyne distributed vibration sensing (hDVS) based fiber-optic borehole seismic surveys with those achieved near-simultaneously with conventional electrical tools; in all cases, the results are obtained with a hybrid wireline cable incorporating optical fibres as well as electrical conductors. Examples on vertical and offset wells are shown. We demonstrate that the improved vertical sampling resolution of the optical technique avoids spatial aliasing commonly encountered with the electrical results in spite of the superior signal to noise ratio of the latter. In recent field tests we achieved signal to noise ratios with the optical tool that are within a few dB of the comparable electrical results. Nonetheless, achieving good coupling between the sensing cable and the formation is essential to obtaining high quality results; the electrical tools are designed with clamping devices at each level, a feature that a standard wireline cable does not allow. We show examples of successful coupling and poor coupling in both vertical and deviated wells. Reliably providing good acoustic coupling between cable and formation is a critical step to rolling out a successful service using hDVS in exploration wells.
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Distributed Acoustic Borehole Seismic in Producing Offshore Wells
Authors K.N. Norgaard Madsen, M. Thompson, S. Dümmong, A. Kritski, Å.S. Petersen, D. Finfer and T. ParkerMany Statoil operated wells are completed with fibre optic cables, typically installed for transmitting data from pressure/temperature gauges in the wells. The use of fibre optic cables for Distributed Acoustic Sensing (DAS) to acquire borehole seismic data in producing wells has been tested in a cooperation project between Silixa, Weatherford and Statoil, supported by Technology Strategy Board UK. Offshore field trials have been successfully carried out by retrofitting Silixa iDAS units to fibre optic cables previously installed in producing wells. Seismic signals were generated by a towed source and recorded by iDAS using the fibres in the wells as distributed sensors. The iDAS measurements were carried out without disturbing the normal operation of the wells, which were all producing during the acquisition of down hole seismic data. The fibre optic cables used for the tests were installed strapped to tubing .i.e. without direct coupling to the formation. Even so, and in the presence of noise from production, it was possible to acquire seismic data with clear first arrivals from which travel times and interval velocities could reliably be obtained. Also reflected and refracted events are clearly visible. We will present results from DAS measurements in four producing offshore wells and discuss the potential of this exciting technology.
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Distributed Acoustic Sensing (DAS) for Reservoir Monitoring with VSP
Authors A. Mateeva, J. Lopez, R. Detomo, H. Potters, W. Berlang, S. Grandi, J. Mestayer, P. Wills, B. Cox and D. Kiyashchenko3D VSP has long been viewed as conceptually attractive for illuminating targets under complex overburden. However, the wide-spread use of 3D VSP has been hindered by the cost and risk of deploying geophones in a borehole, and by the limited availability of accessible wells. These hurdles are largely removed when acquiring downhole seismic with Distributed Acoustic Sensing (DAS) instead of geophones. Over the past several years Shell has acquired more than 20 DAS VSP-s around the world to test DAS performance and further its development. Early on we established the ability of DAS to provide fit-for-purpose VSP products such as checkshots, images, and time-lapse images in a variety of field situations. More recently, our focus has been on identifying VSP applications through which DAS can add most value. High on our list is reservoir monitoring for fields undergoing stimulation, such as water injection or Thermal EOR, particularly under complex overburden. In this talk we will show how DAS enables reservoir monitoring through VSP techniques that were unfeasible or cost-prohibitive with geophones. Those include frequent time-lapse monitoring onshore, in deepwater, in environmentally sensitive or congested areas, and simultaneously in many wells for full-field coverage with 3D VSP.
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Simultaneous Acquisition of DAS and Conventional Down-hole Geophone Array at Aqusitore, Canda
Authors J.D. Cocker, E.F. Herkenhoff, M.E. Craven, T. Nemeth, T.M. Daley, D. White and A. StrudleyA 3D VSP was acquired in Nov 2013 to quantify the sensitivity, directivity and coupling characteristics of Distributed Acoustic Sensing (DAS) data relative to conventional borehole geophones. This trial leveraged a collaborative research agreement between Chevron, Lawrence Berkeley National Labs and the Aquistore CO2 sequestration project in Saskatchewan run by the Petroleum Technology Research Centre (PTRC).
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DAS VSP Acquisition - Perspectives and Challenges
Authors V. Lesnikov and C. AllanicThe interest to the Distributed Acoustic Sensing (DAS) technology for borehole seismic data acquisitions is rapidly growing during the last several years. It opens up a lot of new opportunities of performing VSP acquisitions for time-lapse monitoring utilizing producer or injector wells. It can also be used in the high temperature, highly deviated or horizontal wells where deployment of conventional geophone tool arrays is always complicated. All of this could be done in a safe and cost effective manner with hundreds of downhole measurements recorded from the single shot at the surface. Meantime the current limitations of the DAS VSP are also well known. High level of the noise floor, directivity pattern, attenuation of the signal with the length of the fiber cable, uncertainty of the depth determination are among the observed problems. We discuss our current experience with DAS VSP recorded with the fiber cable deployed behind the production tubing and challenges for its widespread application, in particular deployment of the fiber cable and possible deepwater and subsea applications for which reliable underwater-mateable fiber-optic connectors and marinisation technology for DAS interrogators has yet to be developed.
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A Permanent Borehole Seismic Field Trial Comparing Fiber-optic Distributed Acoustic Sensing with Dedicated Geophones and Hydrophones
Authors B.E. Hornby, Q. Li, J. Konkler and S. SoulasWe show an analysis of data from a permanent borehole fiber-optic Distributed Acoustic Sensing (DAS) and dedicated receiver experiment in Milne Point, Alaska. The test well is 152m in depth and instrumentation consisted of fully instrumenting optical fiber in the well along with reference geophones and hydrophones placed in the well at 16 depth locations at 9.2m spacing, ranging from 15 to 150 m deep. Vibrators generated seismic signals with a 18.2m source point spacing. There are 8 sweeps at each source point. Each sweep time is 12s long and the receiver listening time is 16s. The correlated signal is 4s long and the DAS data have the same recording time as the geophones. The DAS implementation shown here treats each 1m of cable as an individual receiver resulting in a total number of DAS receivers equal to 143. Results detail direct comparison of data from both fiber-optic DAS receivers and the z-component of actual geophones, all permanently cemented in a borehole, with a surface vibroseis source. We examine data amplitude, frequency, phase, noise and other practical issues. We also present quantitative comparisons of signal/noise for both dedicated and virtual DAS receivers as well as some thoughts on the way forward for the DAS technology.
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Results of Field Testing of Simultaneous DAS and Geophone VSP
Authors T.M. Daley, D. Miller, B.M. Freifeld and K. DoddsAs part of a CO2 storage project at Citronelle, Alabama, VSP data was acquired with a short string of tubing-deployed, wall-locking, geophones (18 at 15 m spacing) and a long (3 km) fiber, also tubing-deployed. We will show data examples comparing geophone and DAS attributes such as spectral response, signal-to-noise ratio and ground motion sensitivity comparison.
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3D DAS-VSP Processing and Learning - Velocity Diagnosis and Update for Seismic Imaging Improvement
More LessIn 2012, Shell acquired its first dual-well 3D DAS-VSP (Distributed Acoustic Sensing - Vertical Seismic Profiling) data concurrently with an OBS survey in a deep water environment in the Gulf of Mexico. A work flow was developed to process the 3D DAS-VSP data and use the VSP first arrival times to diagnose the velocity models which were derived from previous surface seismic surveys for selecting a suitable initial velocity model to be updated with the travel time tomography inversion. The VSP diagnosis method was applied again to the updated VTI-inversion model to ensure the velocity updating effort is in the right track. Both DAS-VSP and OBS data were migrated with the initial VTI velocity model and the updated VTI-inversion model. It is found that both borehole and surface seismic images generated with the VTI-inversion model are significantly improved from those obtained with the initial model, especially for the seismic amplitudes at the target event. In this paper, we will share our processing procedure and some learning from our practices of processing marine 3D DAS-VSP data. Processing results from borehole seismic data acquired in Well 1 will be presented as examples.
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Integrating Multiscale Information when Using Seismic Information for Geological Modelling
By T. CadoretWith seismic quality improving every year, it is more and more frequent to use seismic information to help populating geological model. To achieve this, it is essential to handle efficiently the various scale changes it implies.
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Two Challenges in a Highly Heterogeneous Braided Fluvial Reservoir - Saturation Modelling in the Transition Zone and Dynamic Calibration
By P. CorbettBraided fluvial reservoirs are very heterogeneous (Coefficient of Variation greater than 1) with heterogeneity occurring at various scales (Corbett, 2012). High net-gross systems are interbedded and intercalated channel sands, overbank deposits, floodplain shales, soils, etc. Plant activity in warm arid climates also results in complicated diagenetic elements which can be present as primary characteristics of the sandstones (calcretes) or reworked as lag deposits in channel sandstones where they can be cemented. How might these characteristics affect the oil in place and the dynamic aspects of reservoir characterisation?
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