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73rd EAGE Conference and Exhibition - Workshops 2011
- Conference date: 23 May 2011 - 27 May 2011
- Location: Vienna, Austria
- ISBN: 978-90-73834-13-2
- Published: 27 May 2011
41 - 60 of 129 results
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Effective Petrophysics models leading to Business Decisions
By John OwensThe business decision for this exercise is “Where to drill an infill well?”. It is proposed that the key petrophysical consideration involves the evolution of subsurface realisations combined with lessons learned during the production life of the field as shared between the subsurface team. Attention is paid to three key learning points: • What did the team “know” prior to first production and how has subsequent drilling and production changed the understanding of the reservoir? • How does the current understanding influence the decision for the infill well location? • How to react to the unexpected during drilling of the infill well?
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Effective Reservoir Management models leading to Business Decisions
By Mike KingReservoir management can be thought of as a sequence of activities in which we: 1) Build a model, or class of models, that embodies our understanding of the reservoir description and reservoir processes to obtain predictions of how the field will perform 2) Use these models to make a business decision, e.g., the placement of an infill well 3) Measure the reservoir performance after the action is taken, and either revise or validate the models being used for subsequent predictions Each step of this process can be enhanced through the use of multiple models. When we work with more than a single model we’re better able to represent our uncertainty in performance prediction and to expose the risk associated with the business decision. We are also better able to design a surveillance program by attempting to distinguish between different subsurface models. Examples will be drawn from North Sea experience with mature assets on the success (or failure) of these strategies.
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Interactive Exercise on a Field Data Set
Authors Patrick Corbett, Glynn Williams, Olivier Gosselin, Thierry Coleau and Mike ChristieThis interactive seminar will provide a field data set for working in small teams. The work will build on the morning workshop presentations from experts in their respective fields – geological modelling, petrophysics, geophysics and petroleum engineering. These experts together with the above convenors will endeavour to lead the participants through the exercise – doubtless ensuring that each team will lead to different outcomes. The teams will compare the results with previously worked up models. In this way, insights into the various interpretations and various interpretation methods can be made. The objective of the work will be to focus on a typical oil field business decision - e.g. to identify the optimum infill well drilling location(s). A presentation on some of the real challenges within the field will be presented at the conclusion of the workshop. Through this session and the contributions of the morning sessions – it is intended that the cross-disciplinary understanding of all participants will benefit from the workshop. The EAGE/SPE AGORA principles are that all technical voices are heard democratically – much in the spirit of the original Athens AGORA – before reaching the appropriate decisions.
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Towards Joint Inversion of Electromagnetic, Seismic, and Production Data for Reservoir Characterization and Monitoring
Authors Aria Abubakar, Tarek M. Habashy, Lin Liang, Guozhong Gao, Jianguo Liu, Maokun Li and Guangdong PanThere are variety of measurements that may illuminate the reservoir with varying coverage and resolution such as: Electromagnetic (EM) (controlled-source EM (CSEM), magnetotelluric (MT), surface to borehole (STB), and cross-well EM), Seismic (surface seismic, cross-well seismic and vertical seismic profiling (VSP)), gravity (surface and borehole), and production history/well testing data. Each measurement on its own will provide incomplete information due to the non-uniqueness and limited spatial resolution associated with their interpretations. However, when they are integrated together and combined with other measurements such as near-wellbore data, they may provide considerable values: to enable inference of pertinent reservoir properties, to enhance the predictive capacity of a reservoir model, and to help us in making appropriate field management decisions with reduced uncertainty. In this presentation, we will present an overview of joint inversion approaches for integrating EM, seismic, and production data. For reservoir characterization applications, we will present both joint structural and petrophysical algorithms for integrating EM and seismic data (CSEM & surface seismic and cross-well EM & cross-well seismic). For reservoir monitoring applications we will present EM data (both for cross-well and STB) inversion algorithms constrained by the fluid-flow simulator (ECLIPSE). In the inversion for both EM and seismic we employ full nonlinear approach (or the so-called full-waveform inversion) so that we can utilize all the information from the data. We will also discuss challenges, advantages, and disadvantages of these approaches by using some test cases.
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Integrating Crosswell Electromagnetic Imaging and Reservoir Data for Dynamic Modeling of Water Injection in Carbonate Reservoir
More LessCrosswell Electromagnetic (EM) tomography is a recently developed technology to estimate the formation resistivity distribution in the interwell volume. The data are acquired by fixing receivers in one well, and measuring the magnetic field as a solenoid source broadcasts a continuous sinusoidal signal as it moves up the well in a second well some distance. The resistivity distribution is then estimated through non-linear inversion of the data with respect to an initial resistivity model. In this project time-lapse crosswell EM images are used to monitor apparent saturation changes in a water injection pilot in basal low-reservoir quality units of a giant carbonate field in the Middle East. The evolution of water saturation is deduced from the inverted resistivity distributions. Note that to obtain a detailed image of apparent saturation changes, the initial model incorporates realistic representations of the small-scale heterogeneities common to carbonate reservoirs. These include detailed thickness variations and thin dense layers interbedded in some reservoir units. The highly constrained images are then compared to dynamic reservoir simulation results derived from models of various levels of complexity. Simulations show that if flow barriers are not included between various reservoir units, the injected water will move upward across the reservoir units which is inconsistent with the EM. Successive adjustments were therefore applied on the dynamic model to honor the EM images as well as the injection pressure results. Properly constrained with seismic geologic and flow data the EM results provide useful information about the location and behavior of the fluid front in the formation and allow identifying the adequate level of geological details that needs to be preserved in a dynamic model.
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Feasibility Analysis of Surface-to-reservoir Electromagnetics for Waterflood Monitoring
Authors Daniele Colombo, Mike Jervis and Thierry TonellotWe analyze, by means of a synthetic model, the feasibility of detecting the electromagnetic (EM) field variations related to waterflood in a large Saudi Arabian Jurassic reservoir. We utilize a 3D structural reservoir model and derive the geoelectric parameters from careful analysis of well logs acquired at the Saudi Aramco Technology Test Site. The resistivity variations as a result of water flooding are derived using characteristic parameters and injection water salinity of the field. We model a geometry consisting of a radial surface galvanic source and four EM receivers located at the reservoir level. The full EM field is modeled in the time domain and the horizontal and vertical electric field (Ex and Ez) and horizontal crossline magnetic field (dBy/dt) components are interpreted and analyzed. Results indicate that all the modeled fields show substantial variations as a result of water saturation changes with field strength values above the noise level expected for EM sensors. The results will be validated next by modeling more complex and realistic 3D patterns of water saturation in the reservoir, as derived directly from reservoir simulation. Given that one of the modeled components is the vertical electric field, the electrical anisotropy of the overburden is expected to play a significant role in the response and will be taken into consideration in the next round of modeling. Modeling results also suggest that the type of borehole EM sensors currently available in the industry may not be adequate for surface-to-reservoir EM applications.
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Stochastic Inversion of CSEM and Seismic Data for Reservoir Properties with the Neighbourhood Algorithm
Authors M. Fliedner and S. TreitelStochastic (“Monte Carlo”) methods like the Genetic Algorithm (GA) and Simulated Annealing (SA) have become increasingly popular for the inversion of geophysical data. Only forward modelling is needed to evaluate the objective function. In addition to a “best” model, some stochastic methods yield statistical information about the range of acceptable models for a given error tolerance by estimating Bayesian integrals of the posterior probability density distribution (PPD). Having a statistically significant sampling of the model space and the associated error surfaces (PPDs) rather than a single “best” model allows us to assess the reliability and resolution power of different inversions given the available data and prior knowledge of geologically reasonable constraints on the expected solution. This is particularly important when we try to combine different types of data, e.g. seismic and electromagnetic measurements. Such joint inversions are particularly useful for reservoir characterization as a single type of measurement is not sensitive to all the parameters of interest. Seismic data provide a high resolution view of the subsurface and are sensitive to rock porosity, they are usually insensitive to the different fluids in a reservoir. Electromagnetic data, on the other hand suffer from low resolution, but are very sensitive to changes in saturation due to the high resistivity of hydrocarbons compared to brine (Hoversten et al. 2006). Through appropriate rock physics transforms, CSEM data can help to constrain the low-frequency trend of the seismic properties (Mukerji et al. 2009).
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Capacitive Electric Field Measurements for Geophysics
Authors A.D. Hibbs, Dickey R.P., Derby K., Petrov T., Lathrop D., Rusakov N., Krupka M.A. and and Markel J.Over the last ten years Quasar Federal Systems (QFS) has developed capacitive electric field sensors for use on land, airborne, and underwater. Airborne, these sensors have enabled the first measurement of the E-field in air at the μV/m level and the first three-axis measurement of the electric field. Underwater the sensors have produced the lowest reported voltage noise while exhibiting exceptional stability and robustness over time. On land, highly accurate measurements of the electric field can be made in dry sand without the addition of water or electrolytes to increase the local ground conductivity. QFS has created a division, Quasar Geophysical Technologies to commercialize its technology for geophysical science applications. The fundamental features, present performance and projected limits of capacitive E-field sensing will be reviewed. The benefit for specific problems in practical E-field measurements will be discussed and examples from recent field tests presented.
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Stochastic Inversion of Seismic and Electromagnetic Data for CO2 Saturation Prediction
More LessStochastic inversion of seismic (AVA) and electromagnetic (CSEM) data are used to predict reservoir porosity and CO2 saturation. The inversion uses Markov Chain Monte Carlo (MCMC) sampling techniques coupled with statistical rock-physics models. The parameters estimated are, Vp/Vs, acoustic impedance, density, porosity, water saturation and a Lithology indicator. Smoothing is achieved by use of a spatial correlation length in a Markov Random Field representation of the Lithology indicator. The algorithm is demonstrated using a detailed 2D synthetic model constructed for benchmarking avo inversion algorithms that has been adapted to replace hydrocarbon with CO2 in the reservoir sands. Synthetic seismic and CSEM data are used to test the resolution of porosity and CO2 saturation predictions under a range of experimental variables. Three types of rock-physics models are considered; 1) linear regressions between variables, 2) Gaussian distribution fits to clusters of variables in two dimensions, and 3) N dimensional multivariate covariance distributions, where N is the total number of inversion parameters. The choice of rock physics model, the proximity of wells used for rock physics, and data noise levels all effect the quality of the porosity and CO2 saturation prediction. Predictions of porosity and CO2 saturation are better when the porosity and saturation are included in the inversion (1 step inversion) compared to inverting only for geophysical parameters followed by a stochastic estimation of porosity and CO2 saturation given the geophysical parameters (2 step inversion).
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3D Reservoir Model and Resource Estimation for a North Sea Oil Field from Quantitative Seismic and CSEM Interpretation
Understanding reservoir properties and fluid distribution is the aim of petroleum geophysics, in particular in the field appraisal and development phases. The ultimate goal is not only to identify and delineate hydrocarbon charged reservoirs, but to quantitatively determine the volume and distribution of oil and gas contained. Since no single measurement has the required response properties to achieve this, it is now recognized that integration of different types of data with complimentary sensitivity will be essential. In this study, we describe a quantitative, joint interpretation of 3D seismic and 3D controlled source electromagnetic (CSEM) data from the Troll western oil province (TWOP), an oil and gas field in the Norwegian North Sea.
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Strategies for Reservoir Characterization and Production Monitoring using Controlled Source Electromagnetic Data
Authors Evert Slob, Marwan Wirianto, Jürg Hunziker and and Wim MulderExploiting the fact that in a marine environment the source is continuously in action while towed behind a boat has improved CSEM capability as a direct resistor indicator. We have taken this synthetic source aperture concept one step further to show on numerically modeled data that uncertainties in source location and orientation are eliminated using a processing procedure called interferometry by multi-dimensional deconvolution. This procedure also eliminates the effects of the sea-surface. This procedure could work well for acquisition according to the present industry practice, under realistic uncertainties in receiver location and orientation, and realistic levels of noise. This is a data-driven procedure that requires properly recorded data. In case some data are not properly recorded due to receiver clipping, a hybrid model-driven data-driven approach must be used. We show some simple 2D examples to illustrate the concept of this procedure, including its drawbacks and advantages for characterization and monitoring purposes.
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3D Inversion of Time-lapse CSEM Data from Dynamic Reservoir Simulations of the Harding field, North Sea
Authors Michael S. Zhdanov, Noel Black, Alexander V. Gribenko, Glenn A. Wilson and Ed MorrisRecent studies have inferred the feasibility of time-lapse controlled-source electromagnetic (CSEM) methods for the monitoring of offshore oil and gas fields. The time-lapse CSEM inverse problem is highly constrained though inherently 3D since the geometry of the reservoir is established prior to production from high resolution seismic surveys; rock and fluid properties are measured from well logs; and multiple history matched production scenarios are contained in dynamic reservoir models. Using Archie’s Law, rock and fluid properties from dynamic reservoir simulations of the Harding field in the North Sea were converted to resistivity, from pre-production in 1996 to decommissioning in 2016. CSEM data were simulated for each state. We demonstrate how 3D inversion can be used for monitoring the oil-water contact from pre-production to end of oil production in 2011, and for monitoring of the gas-water contact 2011 to 2016 during gas production. In particular, we show that focusing regularization is able to recover sharp resistivity contrasts across the oil-water and gas-water boundaries, whereas smooth regularization fails to recover an adequate resistivity contrast.
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SAR Interferometry Applications: the Outlook for Sub Millimeter Measurements
By F. RoccaOptical leveling campaigns, tiltmeters, GPS and InSAR are geodetic techniques used to detect and monitor surface deformation phenomena. In particular, InSAR data from satellite radar sensors are gaining increasing attention for their cost-effectiveness and unique technical features, making it possible the monitoring of large areas, even revisiting the past. Moreover, more advanced InSAR techniques (PSInSARTM, SqueeSARTM) developed in the last decade are capable of providing millimeter precision, comparable to optical leveling, and a high spatial density of displacement measurements, over long periods of time without need of installing equipment or otherwise accessing the study area. Thanks to the high density and quality of the measurements the PSInSAR data can be successfully used in geophysical inversion, to measure the permeability of oil reservoirs and/or to evaluate the possibilities and risks due to seismic faulting in the sequestration of CO2. In these cases, the precision, the sub weekly frequency of the measurements and the time required for the data to be available are the most important aspects, more relevant than the spatial resolution.
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Stereo Satellite Elevation Mapping Accuracy and Application
More LessThe new generation of 50cm resolution stereo satellite photos are demonstrated to have relative horizontal accuracies in the range of 10cm in 10km. Using sophisticated image matching, signal enhancement and noise attenuation methods “borrowed” from the field of oil and gas exploration seismic processing, elevation maps with better than 50cm vertical accuracy, on 1m centers, can be produced from these 50cm stereo satellite photos. We call our processing of Digital Elevation Models (DEMs) from stereo satellite photos “geophysical processing” to differentiate it from the conventional photogrammetric stereo photo elevation mapping methods. This new geophysical stereo satellite elevation processing method produces stereo satellite DEMs with significantly better horizontal resolutions and vertical accuracies then the conventional photogrammetric processes. The resolution and accuracy of these high resolution geophysical stereo satellite DEMs has been demonstrated with thousands of ground survey points and by direct comparison with LiDAR DEMs. In areas of sparse vegetation the 1m posted DEMs produced from 50cm stereo satellite photos have demonstrated elevation accuracies of better than 50cm RMSE. These stereo satellite DEMs have resolutions and accuracies similar to high quality LiDAR DEMs.
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Monitoring Oil and Gas Facilities: Use of Natural Reflectors and Artificial Corners Reflectors
Authors M. de Farago, G. Cooksley, M. de Faragó and J. Garcia RoblesInSAR based ground motion monitoring of oil and gas facilities, including pipelines, plants and LNG terminals, contributes to production planning and the safety of operations. Factors such as seismicity, landslides, coastal erosion or anthropogenic effects such as the oil and gas activities themselves may cause infrastructure to be affected by ground motion, which may in turn pose a threat to the surrounding population and wildlife, or the efficiency of the infrastructure itself. The PSI technique is an efficient tool for assessing and monitoring the effects of the aforementioned on the infrastructure and the surrounding area.
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SqueeSAR Surface Displacement Measurements for Reservoir Monitoring and Modelling in the InSalah Project
Authors A. Ferretti, A. Fumagalli, F. Novali, C. Prati, F. Rocca and A. RucciKnowledge of the structure controlling the fluid/gas flow at the reservoir layer is critical in many activities, such as petroleum/gas extraction and carbon capture sequestration (CCS). To this end, timelapse geophysical observations are considered as an important instrument to better understand the fluid flow in the subsurface. In the last decade, a new remote-sensing technology called PSInSAR™ - based on the use of satellite radar data - is receiving an increasing attention, thanks to its capability to provide accurate, large-scale surface deformation measurements with millimetric precision. The utility of such data for reservoir monitoring and modeling, has been proved in the InSalah project, one of the three most famous CCS project. SAR data has been used to track the injected CO2 [1], to monitor possible fault reactivation and to estimate the effective permeability of a producing gas reservoir.
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Multitemporal Lidar Monitoring of Landslides
By Franco CorenThis paper’s aim is to demonstrate the possibility to successful apply high resolution multitemporal LiDAR to landslide monitoring in the special case of an active, large earthflow characterised by rapid to moderate rate of movement (the Valoria landslide, Northern Apennines, Italy). The Valoria landslide is a large, active earthflow which mostly involves low-plasticity scaly clays (Manzi et al., 2004; Corsini et al., 2006). It has been completely reactivated in 2001, and since then it has been intermittently active with displacements that in one season could be in the order of hundreds of meters. This recent evolution has caused a significant modification in the slope morphology, with quite distinct depletion and accumulation zones. Landslide occurrence is related to a variety of factors such as underlying geology, mechanical properties of soil and rocks, degree of weathering, groundwater conditions, and the presence (or absence) of geological structures such as joints, faults, and shear zones (Fell et al., 2000). Because of this complexity, landslide monitoring is commonly adopted both in the early detection of risk factors and as an effective tool for landslide hazard management and analysis (Sassa & Canuti, 2008).
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The Role of Gravity Gradiometry in the Rremote Sensing Tool Kit
By Duncan BateThe natural variations in Earth’s gravitational field can provide the explorationist with information on the density variations in the subsurface. With careful consideration, and often integration with other data, this can in turn be used to improve our understanding of the geological setting and where valuable resources may be found. The use of gravity measurements has long been present in exploration geophysics. Originally this involved the field geophysicist walking the ground with the instrumentation to record the data. However, advances were made allowing the measurements to be taken from a moving platform far above the surface (sea, air, or satellite). As the gravity technique is passive, recording only the natural properties of Earth it is well suited to a remote sensing deployment. This reduces cost and allows large areas to be covered quickly, safely and with no direct contact with the ground.
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Cross-validation and Integration with Ground Based Geophysical Data
Authors A. Laake, C. Strobbia, A. Cutts, L. Velasco and M. SheneshenReservoir mapping in the Gulf of Suez petroleum system is challenging because rifting fragmented the reservoirs by rift-parallel and transfer faults leaving the reservoirs confined to stratigraphic, structural, and combined traps. We have developed a technique to address this challenge that integrates fault outcrop mapping using satellite image interpretation, seismic near-surface characterization techniques such as Rayleigh wave velocity mapping and ray parameter interferometry, as well as ant tracking of faults and geobody delineation on a prestack time-migrated (PSTM) cube. The technique utilizes a combination of geographic information system (GIS) and geological modelling software for surface/subsurface integration. The joint analysis of Rayleigh wave data with satellite imagery provides a nearsurface structural geological model. The suite of near-surface geological products is enabled by the acquisition, processing, and interpretation of point-receiver seismic data. Detailed shallow structural geology could be imaged in the near surface, a data regime that is conventionally masked by the acquisition noise from the seismic acquisition. The shallow geological model comprises shallow lithological horizons as well as fault zones, the mapping of which may assist the mitigation of shallow drilling risks. The integration of surface and subsurface structural mapping provides the tectonic framework for delineation of the reservoirs in the rift-faulted environment of the Gulf of Suez.
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An Overview of Numerical Methods Suitable for Geophysical Imaging
Authors J. Virieux, R. Brossier H. Calandra, V. Etienne, S. Operto, A. Ribodetti and R-E PlessixModelling methods are nowadays at the heart of any geophysical interpretation approach. These are heavily relied upon by imaging techniques in elastodynamics and electromagnetism, where they are crucial for the extraction of subsurface characteristics from ever larger and denser datasets. While highfrequency or one-way approximations are very powerful and efficient, they reach their limits when complex geological settings and solutions of full equations are required for high resolution imaging. A review of three important formulations will be carried out during this presentation: the spectral method, which is very efficient and accurate but generally restricted to simple earth structures, and often layered earth structures; the pseudo-spectral, finite-difference and finite-volume methods based on strong formulation of the partial differential equations, which are easy to implement and currently represent a good compromise between accuracy, efficiency and flexibility; and the continuous or discontinuous Galerkin finite-element methods that are based on the weak formulation, which lead to more accurate earth representations and therefore to more accurate solutions, although with higher computational costs and more complex use. The choice between these different approaches is still difficult and depends on the applications. Guidelines are given here through discussion of the requirements for imaging/ inversion.
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