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First EAGE Workshop on Practical Reservoir Monitoring
- Conference date: 06 Mar 2017 - 09 Mar 2017
- Location: Amsterdam, Netherlands
- ISBN: 978-94-6282-206-1
- Published: 06 March 2017
40 results
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Valuation of Marine Seismic Monitoring Technologies
Authors J.L. Lopez, J.K. Przybysz-Jarnut, B.E. Cox and K. RattansinghWe present a method to assess the technical and economic pros and cons of various marine seismic monitoring techniques. The results are displayed in a Value vs. Cost diagram to guide business decisions on the type and frequency of seismic monitoring for the specifics of the reservoir and planned recovery method. The estimation of the economic benefit is the most useful part of the exercise, as it forces geophysicists and reservoir engineers to think about the uses of 4D seismic and the decisions that may be taken based on the data. We illustrate the methodology with an example inspired by the pre-salt carbonate fields offshore Brazil. We conclude that frequent seismic monitoring may deliver high value, such as 5% increase in recovery and large incremental NPV, so long as seismic costs are affordable (relative to alternative investments that may generate similar value). There is scope to reduce seismic monitoring costs by using new technologies or if the market grows in high cost locations.
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Extracting the Value from Non-repeat Seismic Surveys
Authors D. Eckert and E. SadikhovIn a low oil price environment, the choice of the 4D seismic technology needs to be adapted to tighter cost restrictions. Being able to reduce further the uncertainty related to specific technical needs will translate into better decision making. In this context we propose an approach which takes advantage of existing non-repeat 3D seismic surveys, in conjunction with production history, in order to steer the future 4D strategy. A North Sea example illustrates the flow and shows how a fit for purpose solution manages to extract valuable information from non-repeat surveys and eventually assess the need for a new repeat survey.
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Time-lapse Seismic Modeling on the Giant Johan Sverdrup Oil Field - A Feasibility Study
Authors A.O. Ndingwan, A. Jørstad, O. Kolbjørnsen, G.E. Berg and K. Eide-EngdahlJohan Sverdrup is one of the largest oil fields discovered on the Norwegian continental shelf and will be one of the most prominent projects in Norway. As a seismic monitoring strategy, large parts of the Johan Sverdrup field will be monitored with a permanent reservoir monitoring (PRM) system. This feasibility study, investigates the rock physics challenges, calibration and further tests the conceptual understanding of reservoir models. Fundamental time-lapse aspects of interest have been investigated such as the possibility of detecting 4D effects in the thin intra-Draupne Fm sandstones, robustness of the time-lapse signal, drainage detection, how early in the production cycle can 4D effects be observed and finally if 4D data can be used quantitatively to reduce uncertainty in reservoir evaluation.
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Small Airgun Sources for Frequent Low-Cost 4D Reservoir Surveillance
Authors D. Chalenski, K. Wang, M. Tatanova, J.L. Lopez, P. Hatchell and P. DuttaWe present the results of two Deepwater field trials to assess the feasibility of using smaller airgun sources for low-cost 4D imaging and reservoir surveillance. The first trial was conducted at a field instrumented with an Ocean Bottom Cable (OBC) Permanent Reservoir Monitoring system. Two nearly identical full shot-patch 4D surveys were acquired with different sized airguns, allowing side-by-side comparison of the resulting images. The second trial was conducted at a different field with Distributed Acoustic Sensing Vertical Seismic Profiles (DAS-VSP). A small shotbox was acquired over a period of 8 days with four different source sizes, one of which was repeated for zero-time 4D. Both field trials demonstrated that the small sources performed well, and may provide adequate data quality for monitoring large-scale changes in a reservoir. Smaller airgun sources may reduce costs of seismic surveys by allowing smaller vessels to be used, and could be a critical element of a frequent but minimal monitoring program at applicable fields. A valuation analysis is developed to understand the impact of the reduced cost and potentially reduced data quality when using smaller sources on the overall value to the reservoir surveillance program.
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Cost-effective 4D with Signal-apparition-enabled Sim Source Acquisition - Preliminary Results from an OBS Field Test
Authors K. Eggenberger, J.O.A. Robertsson, D.J. van Manen, F. Andersson, Å.S. Pedersen, M. Thompson and L. AmundsenSimultaneous source acquisition promises great efficiency gains but its suitability for reservoir monitoring applications remains contested. By utilizing an approach for simultaneous source acquisition, based on a novel view of seismic data sampling principles that is completely different to existing methods, we demonstrate that 4D-grade seismic data can be obtained from an OBS field data set acquired in the North Sea. Main drivers for developing this new simultaneous source technique are to create significant cost savings and increased flexibility in data acquisition for reservoir monitoring applications.
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Executing the Repeat Contract - a Case Study from Brazil
Authors P. Sack and F. GonzalezPRM and 4D surveys utilizing bottom equipment present a unique contracting challenge to the operator due to the very different installation and acquisition phases. The services of such a survey can be considered a commodity as opposed to the sensor equipment, and the equipment’s installation, which may hold a technological value. Therefore the services portion can be separated to attract market rates. To fully realize the gains and improvements of the repeat surveys, the collective survey timeline should be considered to check that the process is accommodated both during and between the interval surveys.
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Long Duration Time-lapse Experiment in Al Wasse, Saudi Arabia Using an Ultra-stable Seismic Source
Authors J. Kasahara, K. Al Damegh, G. Al-Anezi, F. Almalki, K. AlYousef, I. Alrougy, O. Alrougy, K. Murase, A. Kamimura, R. Kubota, Y. Hasada and O. FujimotoWe carried out a long-duration seismic time-lapse experiment consisting of two periods in 2012-2013 and 2015 in a water pumping field in the Kingdom of Saudi Arabia using an ultra-stable ACROSS seismic source and a geophone array. The comparison of travel times and amplitudes of P waves show quite small but distinct temporal variation with time. The maximum change is approximately 1.5 ms during two months both in the first and the second periods. Because the total travel time is 0.2 s, the change of 1.5 ms corresponds to 0.75%. The resolution of travel-time change is ~0.1 ms and it is good resolution to detect the change of subsurface caused by CO2 or high-temperature H2O injection to the heavy oil reservoir. We also discuss the NRMS repeatability of the observation system using the first arrivals at the stations within 700 m from the source and found that the NRMS repeatability was better than 5% during 2 month periods. The source itself might have roughly 2% NRMS repeatability. The NRMS repeatability is based on the waveform change. The present result supports that the ACROSS source has excellent repeatability well enough to discuss the time lapse of the subsurface.
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Incremental Gains from Revisiting 4D Timeshifts on Forties
Authors P.S. Rowbotham, E.C. Colledge, P.T. Rose, L.A. Singer and G.W. ByerleyThe Forties Field has a rich history of 4D seismic for selecting and de-risking infill drilling targets. Improvements in 4D acquisition and processing are leveraged by regularly reprocessing vintage seismic datasets. These improvements allow new target concepts to be developed, but also create new challenges in interpretation. Warping of time-lapse datasets prior to differencing can reduce 4D noise and enhance 4D amplitude signal for interpretation. However, warping can also damage 4D signal. An understanding of the behaviour of warping on the 4D data through numerical modelling and forward wedge modelling has helped to show why 4D warping can result in disagreement with the well production history. Parameterisation testing produces an improved differentiation between 4D noise and signal, and a better timeshift interpretation volume.
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4D Time Shift Interpretation and Pressure Calibration for the sub-salt Rotliegend Reservoirs of the Southern North Sea
Authors J.P. Brain and T. LassaigneTime lapse (4D) seismic in the Rotliegend reservoirs of the Southern North Sea is extremely challenging due to small 4D pressure depletion signals and complex overlying salt geometries. With gas production, pore pressure in the reservoir is reduced, stiffening the rock frame and inducing a velocity increase and reduction in travel time across the reservoir. In order to map depletion away from the producing wells and thereby identify potentially un-depleted areas, we are required to detect time shifts in the order of 1ms or less beneath the reservoir. Here, reflectivity can be variable and signal to noise poor, due to multiple contamination and complex imaging. In addition most baseline surveys in the area date from the late eighties and use two boat towing configurations, requiring additional acquisition effort and processing corrections. This paper describes the processing and interpretation workflows we have developed to measure reliable sub-salt time shifts, calibrate results for pressure prediction and estimate uncertainty. After a multi-field 4D seismic program, Nederlandse Aardolie Maatschappij (NAM) has drilled three wells to date based on 4D results and in all cases pressures were within the pre-drill predicted ranges.
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Modelling the Impact of Overburden Stress Arching on 4D Seismic Amplitude Changes
Authors A. Toomey, S. Fowler, J.P. van Gestel, T.G. Kristiansen, G. Brew, M. Horiuchi and R. LevineReservoir depletion can cause geomechanical changes in both the reservoir and in the overburden. When depletion pressures are large or when the reservoir rock is highly compressible, the increasing load on the reservoir rock during production may cause compaction. As the reservoir compacts and pulls away from the surface of the earth, a stress arch forms in the overburden. The stress arching reduces the load on the reservoir and results in a lower effective stress change in the reservoir than would be predicted from the reservoir pressures alone (shielding of the reservoir by the overburden). This effect is more pronounced for reservoirs with high aspect ratio (thickness to diameter ratio). These geomechanical changes result in both time-shift signals and impact on the amplitude changes between repeat seismic surveys. We show that it is important to include the geomechanical effects when modelling 4D seismic amplitude changes, as they can have a significant impact on the amplitudes observed. By incorporating these changes into a 4D simulation-to-seismic modelling workflow, we were able to explain an anomalous amplitude response observed in 4D seismic data acquired over the Atlantis field.
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Quantitative Interpretation of 4D-3C Seismic Data for an Oil-sands Reservoir
Authors C. Dumitrescu and G. LarsonQuantitative interpretation based on time-lapse joint PP-PS inversion and rock physics models were used to estimate the probabilities of three stages in the production cycle of an oil-sands reservoir located in the Athabasca Basin of Alberta, Canada. The ultimate goal of this work was to use seismically-derived elastic properties for imaging steam chamber extension, changes in fluid saturation within the reservoir, the extension of the warmed bitumen (future production zones), and temperature distribution inside the reservoir. A rock physics model was created to define three stages of production: “in situ”, “mobilized oil” and “displaced oil”. For each of the three stages, probability density functions (PDFs) were defined using the time-lapse elastic properties logs. Seismically-derived elastic properties, resulted from our deterministic time-lapse joint PP-PS prestack inversion, were matched to the rock physics model in the reservoir, and the clusters derived from crossploting time-lapse seismic data were projected in the 3D volume.
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Rock Physics and Time-lapse Seismic Analysis of Thermal Heavy Oil Production
Authors E.P. Mutual and D. ChoThis study outlines the workflow implemented to quantify changes in reservoir conditions due to steam injection and production of an Athabasca Oil Sands bitumen reservoir. A holistic approach to interpretation was implemented, encompassing unconsolidated rock physics modelling, seismic pre-conditioning, 4D low-frequency modelling, pre-stack 4D simultaneous AVO inversion, and rock physics driven probabilistic lithology classification to separate our elastic changes into steam or gas, water, and mobile oil. Ultimately, the identification of various production related effects such as steam chamber development and mobile oil leads to improved reservoir optimization opportunities, allowing for an increase in bitumen production.
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Integration of Continuous Time Lapse Seismic Data into Reservoir Models Using Onset Times
Authors G. Hetz, A. Datta-Gupta, J.K. Przybysz-Jarnut and J.L. LopezA permanent buried seismic monitoring system was deployed at Pad 31 in the Peace River Unit (Alberta, Canada) to understand the reservoir sweep during steam injection in the heavy oil field. Over 500 daily time lapse seismic surveys of the reservoir state (in terms of two-way travel time) are available throughout the monitoring period to study the changes propagation in the reservoir. We propose an efficient approach to integrate such frequent time lapse seismic data into reservoir models based on seismic onset times, the calendar time when the seismic attribute crosses a pre-specified threshold value at a given location. We demonstrate the power and utility of the proposed approach using time lapse data from a Cyclic Steam Stimulation (CSS) cycle in the pad with a total of 175 seismic surveys. The study shows the effectiveness of the method to handle large number of surveys by compressing them into a single map of onset times which clearly displays the changes propagation. Furthermore, the onset times can be used to efficiently update reservoir models through history matching of the time-lapse seismic data.
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Real Time Offshore Monitoring - Key Learnings - Pitfalls and Potentials
Authors E.V. Bergfjord, J.E. Lindgård, T. Thiem and L.W. BjerrumMicroseismic monitoring with ocean bottom data is still in its infancy compared to onshore microseismic. A compact PRM system was installed at the Oseberg field in order to monitor a shallow injection well, and in this presentation we have gathered some insights from this project. In addition we compare some properties of the P- and S-wave phases based on modelled microseismic events and we give practical recommendations which will benefit future applications of this technology.
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Geoguard - An Innovative Technology Based on Low-cost GNSS Receivers to Monitor Surface Deformations
Authors D. Sampietro, S. Caldera, M. Capponi and E. RealiniThe study of reservoir behaviour is an important topic when dealing with the removal or the injection of fluids into the underground (e.g. hydrocarbon production or natural gas storage). The monitoring of surface deformations provides a valid contribution to the analysis of the reservoir. Nowadays the InSar technique is one of the most commonly used, providing a spatial distributed information, but also GNSS geodetic receivers are able to provide continuously superficial displacements. Recent experiments have shown the possibility to obtain results similar to those of dual frequency receivers also with cheap single frequency receivers. In this work we present GeoGuard, an innovative end-to-end service, for the continuous geodetic monitoring of critical infrastructure and natural hazards based on GNSS single frequency receivers. This innovative solution would allow in principle to monitor with a moderate price a large number of points and to retrieve continuously 3D superficial deformations with millimetric accuracy. The terminal unit, called GeoGuard Monitoring Unit, has been specifically designed to operate in challenging environments, an ad-hoc processing software to deals with single frequency GNSS receivers observations has been designed and implemented too. Some results on a real experiment are reported to show the achievable accuracies of the whole system.
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Maximize Value with Efficient Next-generation Fiberoptic Monitoring Solutions
Authors A.V. Goertz, A. Smith and D. LecerfTime-lapse information can be used for different purposes, depending on whether it spans several years or only a few months between snapshots, or even reflects producton/injection-induced seismicity in real time. Synchronizing the availability of such 4D data with production-relevant decision gates, and ensuring sufficient resolution for these decisions, is the key to improve efficiency and optimize impact of 4D. PRM systems need to reliably function over the entire production lifetime of an asset and provide the sensitivity to both detect small 4D signals over short repeat intervals and continuously monitor tiny production-induced deformations. A fiberoptic solution is best capable of providing the required endurance in the seafloor environment over the entire asset lifetime. We present the next generation Optoseis pressure-balanced technology, and some novel procesing techniques that are very useful for PRM with sparse receiver sampling.
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Fibre Optic Sensor Arrays for Large Area Reservoir Monitoring
By P NashWe describe a fire optic sensor technology, originally developed for seabed permanent reservoir monitoring, which offers high channel counts and the ability to monitor large area reservoirs at high spatial density. We discuss how the technology can be adapted for the specific requirements of land use, and describe a sensor package developed for this application. We explain how the flexible nature of the technical approach allows integration of acceleration, pressure and EM sensors into a common architecture. We also describe how the same approach allows large area surface and downhole arrays to be interrogated simultaneously,
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Continuous Subsurface Monitoring by Passive Seismic with Distributed Acoustic Sensors - The “Stanford Array” Experiment
Authors E.R. Martin, B.L. Biondi, M. Karrenbach and S. ColeContinuous seismic monitoring can be a crucial tool to optimize hydrocarbon production as well as to provide early warning of potentially hazardous conditions developing in the subsurface. However, the cost of continuous monitoring is a significant obstacle to its widespread application. Distributed Acoustic Sensors (DAS) recording systems hold the promise to enable the recording of seismic data at much lower cost. We deployed a 2.45 km long DAS array with 610 virtual receivers under Stanford University campus and started to record passive seismic data continuously in September 2016. Preliminary analysis show that the data recorded by our DAS array can be used to monitor dynamic processes in the subsurface thanks to sufficient sensitivity to low-amplitude wavefields in the frequency band between .5 and 10 Hz. Our conclusion is supported by the coherency and the frequency content of recorded events corresponding to teleseismic and regional earthquakes as well as of the virtual sources synthesized by using interferometry.
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The Evolution of Life of Field Seismic Data on the Clair Field
Authors M. Ball, A. Mathieson and S. SoulasThe Clair field is the UK’s largest naturally fractured reservoir. The main development targets are Devonian in age with poor matrix properties. This makes Clair challenging territory for 4D Seismic surveillance, and heavily informs the choice of acquisition for the 4D programme. In 2006, a Permanent Reservoir Monitoring System was installed over Clair Phase 1. The five survey Life of Field Seismic (LoFS) programme has successfully informed Phase 1 depletion planning and well targeting, in addition to demonstrating the value of 4D for Clair Ridge. In 2017 the Clair JV will be acquiring the baseline for a new 4D seismic programme over Clair Ridge. Instead of selecting a permanent reservoir monitoring solution though, the Ridge 4D Programme will be executed using an ultra-high density Ocean Bottom Seismic (OBS) acquisition to suppress the 4D noise. This case study describes the factors that have led to the selection of a Re-deployable OBS solution for the future 4D programme on Clair, marking a departure from Permanent Reservoir Monitoring (PRM) on the field. Consideration is also made to emergent DAS (Distributed Acoustic Sensing) VSP technology, which may help to augment the future 4D programme through the provision of localised, on-demand 4D seismic surveillance.
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Practical Example of Data Integration in a PRM Environment, BC-10, Brazil
More LessThe BC-10 Argonauta field is located approximately 120 km (75 miles) southeast of the coastal city of Vitoria, in the state of Espírito Santo, Brazil in water depths ranging from 1,500 to 2,000 meters (4,920 - 6,562 ft.). Field production started in 2013, with a permanent reservoir monitoring (PRM) system put in place shortly after production start-up. With the PRM system installed, three monitor seismic surveys have been acquired providing high quality time-lapse observations for reservoir surveillance: With these repeat monitor surveys comes the challenge of abundant and frequent data requiring integration. Here, we suggest a solution for integrating all available reservoir data in a single interactive platform allowing all team members to benefit from rapid access to relevant datasets. Such an environment encourages the different scientific and engineering disciplines to challenge or confirm each other’s ideas, assumptions, and conclusions through direct qualitative and quantitative comparisons. This quickly generates the most possible value from the 4D seismic data, and hence the best reservoir surveillance decisions. The integration of all available data and models can have a direct impact on infill drilling, wells reservoir facility management (WRFM), future seismic activities, and overall cost reduction and revenue maximization
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Using PRM Data for Reservoir Management - An Interpreter’s View
Authors P. Sabel, T. Kindingstad, T.A. Melby and B. SatyavoluIn this study we will give an example from the user perspective on how PRM data are used in the daily work of the Snorre asset. The Snorre asset is organised teams assigned to particular fault blocks and reservoir management actions are discussed by these teams before actions are decided and taken. Together with downhole measurements, production and other field data, 4D data is regularly used in this context to complement the understanding we have of the reservoir. Time-lapse data acquisition with only a short time lag between the 4D surveys enables detailed correlation of actions taken for reservoir management with the 4D effects observed. Even small-scale actions like water or gas injection into particular stratigraphic zones can now be investigated. The values at stake when producing only one zone sub-optimally can be significant; and we will show an example for one well. Of course the same value potential cannot be assumed to be true for every well and every zone, but taking into account that the Snorre field has 66 active wells, each targeting several stratigraphic layers, this shows that the potential for value generation from PRM data is enormous.
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Permanent Reservoir Monitoring at Jubarte Field - 4D Results and Reservoir Characterization
Authors W.L. Ramos Filho, P. Dariva, C.C. Born, I.B. Zorzanelli, A. Goertz and A. SmithAt the end of 2012, Petrobras installed the first deep-water optical permanent reservoir monitoring (PRM) system over the Jubarte oilfield in the Campos basin offshore Brazil. The PRM pilot project covered approximately 9 sq. km with a fully fiberoptic 4-component (4C) sensor array. All topside optoeletronic equipment was installed on FPSO P-57. The primary objective was to validate the fiberoptic sensing technology to detect subtle impedance changes in the reservoir. This goal was achieved, allowing interpreters to apply an interpretation strategy to improve the understanding of flow patterns and to update the geological scenarios of the area based on very high quality 3D/4D images provided by the permanent system.
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Production-calibrated Interpretation of 4D Seismic Effects at Grane Field
Authors M. Ravasi, S.S. Roy, S. Agostini and M. AyzenbergGrane Permanent Reservoir Monitoring System has been installed in 2014 and five PRM surveys have been acquired till date. High quality 4D seismic is part of standard work process in Grane and ensures better well planning and optimization, production and injection well monitoring, and completion health check. Being able to identify relationships and trends between various types of dynamic data (e.g. 4D seismic and production) allows for better understanding of reservoir behaviour, which then translates into efficient actions with regard to well planning/optimization as well as model update for better predictions. In this work, we have identified a strong correlation between the liquid (cumulative oil plus water) production and a 4D seismic attribute sensitive to gas-oil contact movement for the Grane field, which has also helped to convert 4D responses into thickness changes and quantify the gas movement.
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Quantitative Seismic Reservoir Monitoring by Using a Wave-equation Based AVO Technology
Authors P. Haffinger, P. Doulgeris and A. GisolfThe authors describe a wave-equation based AVO technology with a specific focus on applications for reservoir monitoring. Introducing the wave-equation into the field of seismic reservoir characterisation allows derivation of quantitative reservoir models, including potential time-lapse changes, from band-limited seismic data. This is a consequence of properly modelling and utilising complex wave effects as internal multiple scattering, mode conversions and travel-time changes due to production effects. The scheme inverts for compressibility and shear compliance which are much more sensitive to changes in the reservoir fluids compared to conventional acoustic and shear impedances. While seismic angle/offset gathers in time are input to the method, the resulting reservoir models are directly in the depth domain. This intrinsic time-depth conversion is another benefit of using the wave-equation and simplifies integration of the reservoir model into reservoir modelling and simulation workflows.
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Simultaneous Joint Migration Inversion for Accurate Time-lapse Analysis of Sparse Monitor Surveys
Authors S. Qu and D.J. VerschuurWe propose that Simultaneous Joint Migration and Inversion (SJMI) as an effective time-lapse tool, does not require dense source/receiver sampling and is suitable for inexpensive sparse monitoring surveys, because of both the inversion process inside the imaging/inversion scheme and the extra illumination provided by multiples. Furthermore, with the help of SJMI, we design an interleaved survey by shooting the sparse surveys without exact acquisition repetition, which provides us further extra illumination of the subsurface to handle the geometry sparsity. With one complex synthetic example based on the Marmousi model, we demonstrate that the extra illumination provided by both imaging/inversion with multiples and changing the survey during monitoring can provide us better time-lapse results, if the proper method is applied to the datasets.
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Full Waveform Inversion for Reservoir Monitoring - Pushing the Limits of Subsurface Resolution
Authors M. Maharramov and B.L. BiondiFluid movement in the subsurface and the associated changes in saturation translate into changes of the subsurface elastic parameters. Stress changes, whether due to fluid extraction/injection or deformation such as slips on preexisting faults, affect the elastic parameters as well. Detecting and inverting the imprint of changing subsurface elastic parameters on seismic data lies at the heart of time-lapse seismic imaging for reservoir monitoring. In this work we demonstrate that the recently proposed technique of simultaneous time-lapse full-waveform inversion with a model-difference regularization can be used to extract high-resolution information on magnitude and location of subsurface velocity and stress anomalies, potentially providing valuable input for reservoir monitoring and assessment of geohazards.
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4D Full Waveform Inversion - A North Sea Case Study
Authors H. Hoeber, E. Hicks, M. Houbiers, S. Pannetier-Lescoffit, A. Ratcliffe and V. VinjeUsing highly repeatable permanent reservoir monitoring data from the Grane field in the Norwegian North Sea we show 4D FWI results using data with a seven-month acquisition interval between vintages. 4D FWI results show changes at the reservoir level that correlate with both injecting and producing wells. In addition, we find good agreement comparing the velocity differences from 4D FWI to 4D time-shifts and time-strains from fully processed and imaged seismic reflection data. We discuss the two methods used, potential limitations, and further work. Overall, this case study demonstrates the robustness of the seismic reflection processing as well as the potential of time-lapse FWI as a complementary reservoir monitoring tool.
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InSAR - Pro-active Remote Sensing for Reservoir Management and Monitoring Environmental Safety
Authors M.E. Allan, P.B. Leezenberg and R.F. HanssenInterferometric Synthetic Aperture Radar (InSAR) is a satellite-based technology that measures minute changes of surface elevation through time. These deformation changes, often less than 1 mm/month, may be caused by changes in the subsurface (e.g., imbalance between fluid withdrawal and injection, collapse of underground mines), or changes at the ground surface (e.g., surface blisters caused by shallow injection of steam or out-of-zone fluid movement, slope failures). Radar waves from successive passes of polar-orbiting satellites provide trillions of 3m by 3m pixels worldwide on a daily to monthly frequency. Using cloud computing and interferometry, the pixels over areas of interest can be used to monitor activities within oil and gas reservoirs, and also to give warnings of possible problems developing at the surface. Examples are shown for the Belridge giant oil field (California), Groningen giant gas field (the Netherlands), and the Peace River area (Alberta). In the three cases, surface deformation is used to monitor areal conformance in the reservoirs. Also, having satellite passes every 11 days means that reservoirs can be monitored proactively and the resultant datasets have the potential to replace traditional 4D seismic at a cost that is significantly less.
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How 4D Gravity and Subsidence Monitoring Provide Improved Decision Making at a Lower Cost
Authors M. Lien, R. Agersborg, L.T. Hille, J.E. Lindgård, H. Ruiz and M. VatshelleWhole-field subsidence and gravity monitoring is a well-proven, cost-efficient technology, with many field cases demonstrating both the high accuracies obtained and the value of the data for improved reservoir management. Seafloor subsidence and 4D gravimetric data are acquired with a small cost compared to seismic data. However, workflows for properly taking advantage of the information that lies in these data and their range of applicability are in general less widely known that for more conventional datasets. This abstract introduces first the principles behind offshore subsidence and 4D gravity monitoring. It then describes some field cases from the Norwegian Continental shelf (NCS) in which subsidence and 4D gravity data have been integrated into the field management workflow for production optimization and enhanced recovery. Finally, new developments towards making the technology even more cost efficient and the added value that can be expected as a consequence of these improvements are discussed.
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Four Decades of Gravity Monitoring of the Groningen Gas Field
Authors O. Eiken, M. Glegola, S. Liu and M.A. ZumbergeFirst, basics of modern microgravity monitoring and accuracies of alternative techniques are discussed. The history of gravity monitoring at the Groningen gas field is reviewed, with first survey aquired in 1978 and the most recent in 2015. The 2015-survey was aquired in a 24/7 operation, at a densified grid of 98 stations. Station uncertainties are estimated at 1.2 microGal (standard deviation). Gravity reductions of up to 84 microGal are estimated in the time-span 1978-2015, likely caused by the gas extraction. The most recent gravity survey on Groningen shows the feasibility of achieving 1-2 microGal in land surveys when using multiple relative meters, multiple visits, 24/7 operation, reference stations outside the reservoir and ties to absolute gravity stations.
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A Long-term Seafloor Deformation Monitoring Campaign at Ormen Lange Gas Field
Authors R. de Vries, T. Noble, P. Hatchell, S. Dunn, T. Frafjord and A. van den BeukelSeafloor deformation monitoring is a new technology concept for offshore oil and gas reservoir monitoring. It has the potential to cheaply and continuously monitor long term production induced changes in the reservoir and overburden and the data can also be used to spot any instantaneous events such as overburden instability or fault slip. At Ormen Lange, Norway´s second largest gas field, a small trial network was deployed on the seafloor in 2007, followed by a full-field network in 2010. The network was operational for 5½ years before being retrieved in 2016.
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The Impact of Environmental and Acquisition Variations for PRM 4D Processing - Snorre Case Study
Authors K. McCluskey, S. Buizard, M. McCluskey, R. Zietal and N. MoyleSince going live in 2014, five permanent reservoir monitoring (PRM) surveys have been acquired over the Snorre field at regular intervals. The PRM installation itself is currently the largest in the world consisting of 57 cables containing ~10,000 multi-component (4C) buried receivers and covering an area of around 200km2. The processing effort of the early PRM surveys was dedicated to establishing and optimising a robust, repeatable sequence with the objective of providing fast turnaround, high quality 4D seismic data. For key processing steps such as geophone reorientation and PZ summation the high degree of receiver repeatability allows us to apply operators derived on the base to subsequent monitor datasets. However, variations in environmental and acquisition conditions between surveys are observed and can impact the 4D response (generating so-called 4D noise). The purpose of this abstract is to highlight some of these issues and how they are dealt with in the context of fast delivery Snorre PRM data. The topics summarised are those which have been especially important to the Snorre dataset: source layback, water velocity and shot coverage harmonization.
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Very Sparse OBS Acquisition for 3D/4D Reservoir Imaging with High-order Multiples. Application to Jubarte PRM
Authors D. Lecerf, C. Barros, E. Hodges, A. Valenciano, N. Chemingui, S. Lu, P. Johann and E. ThedyA receiver’s decimation study has been performed, using the PRM Jubarte dataset acquired by Petrobras, for assessing the potential of very sparse seabed acquisitions in conjunction of a high-order multiple imaging techniques. This imaging process make use of the multiple reflections to increase significantly the fold, enabling therefore sparser seabed recording geometry without compromising the 3D or 4D image quality. The presented decimation test consists on taking out receiver included into circular patches within a diameter of 600 m. The number of sensor is then reduced by a factor two. The results demonstrate that it is possible the break some established limit in term of seabed sensor sparseness without compromising the resolution of 3D/4D imaging.
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Dip-angle Image Filtering for 4D Processing of Towed-streamer and OBN Datasets
Authors R.R. Haacke, L. Casasanta, S. Hou and J.R. HendersonOcean-bottom data are often acquired in the development and production stages of an oilfield’s lifecycle to guide well placement and water injection strategy. Although well suited to time-lapse monitoring, this type of ocean-bottom survey will miss the first time-step in which a field is explored, appraised, and undergoes initial fluid production. To capture this time step it is necessary to 4D co-process ocean-bottom data with the exploration dataset, usually surface towed streamer. Our example from the North Sea benefits from flexible trace pairing to produce high-fold subsets of the input data that generate more similar images than would otherwise be available. However, residual multiple generates significant 4D noise, as does un-cancelled migration operator from the very different, irregular, survey geometries. Migration to: (1) common-offset, (2) scattering-angle, and (3) dip-angle output domains provide opportunity to explore similarity-filtering strategies with the data. The scattering- and dip-angle gathers respond well to similarity filtering, but results show greater spatial resolution, signal continuity, and coherence when dip-angle gathers are used. Dip-angle is an intuitive domain in which to locate and attenuate un-cancelled migration operator in 4D, which is advantageous as migration noise is a major source of 4D noise in these data.
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DAS VSP in Deepwater GoM for Reservoir Monitoring - Lessons Learned
Authors M. Tatanova, D. Chalenski, A. Mateeva, P. Zwartjes, Z. Yang and J. LopezSeismic monitoring of Deepwater fields with ocean bottom nodes (OBN) has proven to deliver very high quality 4D data that impact field-development decisions and ensure the safety and efficiency of operations. However, the frequency of 4D OBN surveys is limited by the cost of acquisition, constraining its applicability to well and reservoir management (WRFM). A lower-cost 4D solution is needed for WRFM, such as Distributed Acoustic Sensing Vertical Seismic Profiles (DAS VSP). We proved the concept of reservoir monitoring with DAS 4D VSP in Deepwater GoM by achieving an NRMS of 7% and getting 4D VSP images comparable to those from the 4D OBN seismic in a wide range of depths. In addition to their monitoring value, recorded DAS VSP data have been used to explore the impact of various factors on DAS-VSP images, including fiber type and length, well flow conditions, and different airgun strengths. This paper will focus on lessons learned from the processing and acquisition of the DAS data, and the path forward on how to make the monitoring with DAS VSP even more affordable.
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Improving 4D Seismic Interpretation and Seismic History Matching Using the Well2seis Technique
Authors Z. Yin, M. Ayzenberg and C. MacBethA well2seis technique is proposed to incorporate available reservoir data from both 4D seismic and well production domains through cross-correlation, to prevent biased reservoir interpretation. The subsequent well2seis attribute shows the capacity to enhance dynamic reservoir interpretations by quantitatively integrating 4D seismic responses with their corresponding well behaviours. It reduces the interpretation workload by avoiding the need to work on many individual 4D differences separately. A joint workflow is then proposed to close the loop between the observed data and the predictions from the simulation model using the well2seis results. This workflow sequentially makes use of direct updating (for updating static models) and assisted history matching (for updating dynamic models) procedures. In the assisted history matching stage, the well2seis correlation attribute successfully acts as an alternative history matching attribute to the conventional production or 4D seismic data. The application of the proposed approach to a North Sea field shows that both the seismic and production history matching results are simultaneously improved to a satisfactory degree when minimising the misfit between the observed and simulated well2seis attributes.
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Automated Workflows Using 4D Seismic in History Matching
Authors T. Hance, S. Fowler, M. Riviere, B. Davies, M. Ball, J. Bradley and C. SelwoodTime-lapse seismic is a key surveillance tool, particularly for managing and maximising value from waterflood fields. To enable efficient integration of 4D results into the simulation model history match a 4D Assisted History Matching (4DAHM) tool has been developed. 4DAHM enables the calibration of dynamic models to 4D changes caused by water, gas and pressure changes. This allows simultaneous matching of reservoir simulation models to seismic and well data. For fields where it has been applied 4DAHM has delivered better-constrained models, better predictions for depletion planning and a time saving of 50% over previous approaches. This paper presents the 4DAHM workflow along with two case studies. 4D Assisted History Matching delivers a flexible and efficient means of incorporating 4D seismic data into an assisted history matching or 4D integration workflow - but as with any tool, informed use and good cross-discipline communication are key in maximizing value.
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Accommodating the V's. Rapid Quantitative Analysis in a Multidisciplinary 4D Environment
Authors B.J. Lynch, G. Brew and J. WheelwightRapid, easy access to a asset's multidisciplinary data coupled with time-lapse seismic should not be underestimated as a success factor in the 4D workflow. The frequent data acquisition, combined with economic pressures for return on investment, put considerable delivery pressures on asset teams. Once integrated, the availability of tools to quantitatively compare anomalies identified in the seismic data with the same areas in the dynamic flow models allow the provision of assisted history matching (AHM) workflows. Such robust and repeatable processes allow the reservoir model to be iteratively improved. Reducing uncertainty and leading to better reservoir management.
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4D Seismic History Matching of the Norne Field Model Using Ensemble-based Methods with Distance Parameterization
Authors Y. Zhang, O. Leeuwenburgh, S. Carpentier and P. SteeghsQuantitative use of 4D seismic data for history matching is still challenging. This is partly because of the high dimensionality and the large uncertainty involved in the seismic data. To circumvent these difficulties there have been some methods proposed with a focus on reparameterization of seismic attributes and reformulation of seismic objective functions so that the integration of 4D seismic data is more robust and efficient. A distance parameterization of seismic anomalies due to saturation effects was previously proposed to history match reservoir models in combination with the ensemble Kalman filter (EnKF). Because the parameterization reduces both nonlinearity and the effective number of data, an improved functioning of the EnKF can be achieved. In this paper, we further improve the distance parameterization by adopting a more robust measure of the distance between observed and simulated fronts. Numerical experiments with Norne field model are presented in which improved functioning of the proposed method is demonstrated.
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Large-scale Numerical Simulation of Reservoir Monitoring - SEAM Time Lapse
Authors D. Smit, S. Oppert, J. Stefani, V. Artus, J. Herwanger, P. Popov, A. Bottrill, L. Tan, W. Hu, J. Liu, W. Abriel, R. Detomo, W. Barkhouse and M.L. Oristaglioal oil fields. The reservoir modelling incorporated coupled effects of fluid flow and deformation during a simulated production scenario with 11 production wells and 6 water-injection wells penetrating the reservoir’s three compartments. Field-scale seismic, gravity and electromagnetic surveys were simulated before and after 2 years of production. This six-month project was designed as a pilot for a new multi-year collaborative research effort called SEAM Life of Field which is starting in 2017.
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