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First EAGE Passive Seismic Workshop - Exploration and Monitoring Applications
- Conference date: 10 Dec 2006 - 13 Dec 2006
- Location: Dubai, United Arab Emirates
- ISBN: 978-90-73781-45-0
- Published: 10 December 2006
42 results
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Seven Microseismic Projects in Oman, What Have We Learned?
Authors F. H. Kindy, P. Engbers, A. Yahyai, P. Schoepfer and G. EngenSince 1999, a total of seven microseismic (MS) projects have been executed in PDO. These were deployed with a range of monitoring objectives including hydraulic fracturing, reservoir compaction and steam injection. In three of the cases, the projects have proved successful. For the rest of the projects however, they either failed or gave inconclusive results. The failures have been due to bad planning and management and/or equipment failure. But, in both successes and failures, PDO have gathered a wealth of knowledge and experience which are now being incorporated in the planning of upcoming MS projects. From these seven projects we share some of our key learnings with examples.
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Reservoir Monitoring Using Permanent In-Well Seismic
Authors B. E. Hornby, O. I. Barkved, O. J. Askim, S. Knudsen, F. X. Bostick III and B. A. WilliamsWe look at the benefits of placing permanent seismic sensors in a wellbore and recording data over time, either passively or with dedicated surface sources. Implementation involves placing an array of sensors permanently in a well along with the completion string. Challenges include recording data over fluid-flow noise in the well (production or injection) and reliability of the sensors and associated hardware. Applications include 4D imaging and monitoring of reservoir properties, both stand-alone and in conjunction with surface seismic, and mapping of faults and other features using micro-seismic events. Recently, a fibre-optic based system has been created for permanent emplacement in wellbores. This system has been tested with three field trials including a 2006 production well installation. Surveys have been conducted with simultaneous acquisition of permanent seabed and borehole arrays using both active surface sources and passive noise.
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Hydraulic Fracture Mapping in Treated Well – Channelized Reservoirs Development Optimization in Mexico
More LessThe fracture stimulation becoming of prime interest for waterflooding and Enhanced Oil Recovery (EOR), the orientation of the fractures is a key factor for the selection of optimum well locations. The microseismic monitoring of hydraulic fracturing treatment appears then as an helpful tool to map fractures. This paper presents the results obtained by PEMEX in channelized Chicontepec reservoirs (Mexico), where extensive fracturing jobs are largely carried out to stimulate the oil recovery of the turbidites reservoir complexes. The specificity of the presented monitoring surveys stands in the deployment of tools in the treatment well itself. The microseismicity recorded yields to provide consistent orientation of fractures. These results confirm the great potential of this unique approach, as it leads PEMEX to review the stimulation scheme for a cost-effective reservoir stimulation.
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Multi Channel – Multi Node Passive Microseismic Monitoring (PMM) Arrays – A Cost Effective Reservoir and Structural Moni
Authors I. Weir-Jones, S. A. Shore, S. M. J. Taylor, E. Stanley, R. H. Rasmusens and J. SeaphimThe authors discuss more than twenty years experience using passive microseismic monitoring techniques to monitor the behaviour of oil and gas reservoirs, underground openings (both mining and structural), and natural/artificial slopes. In the majority of these instances logistical and cost constraints have necessitated the dispersal of groups of sensors and their associated acquisition units. Under some circumstances this can give rise to complex problems when the data has to be recombined prior to processing. However, these problems are relatively minor when weighed against the cumulative benefits which accrue to the operations as a result of the utilization of high quality microseismic data acquired from an extensive sensor array operated for an extended period.
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Interpretation of Hydrocarbon Microtremors as Pore Fluid Oscillations Driven by Ambient Seismic Noise
Authors M. Frehner, S. M. Schmalholz, R. Holzner and Y. Y. PodladchikovOscillations of oil in a partially saturated porous reservoir are a possible mechanism for the observed spectral modification of ambient seismic background noise above hydrocarbon reservoirs. We couple a 1D wave equation to a linear oscillator equation, which represents the oscillations of the oil within the reservoir. The resulting system of equations is solved numerically with explicit finite differences on a staggered grid in both space and time. The ambient geoseismic noise is simulated by a source term in the equilibrium equations producing a Fourier spectrum of the solid velocity at the surface including all frequencies between 1 and 10 Hz. The numerical simulations show that the oil within the reservoir always oscillates with its eigenfrequency (given a small frictional damping). The corresponding resonance peak is clearly visible in the Fourier spectrum of the fluid velocity. First results show that a smaller Young’s modulus in the reservoir compared to the surrounding elastic material is necessary to transfer the oil oscillations from the fluid to the solid. For this case, the resonance frequency is also visible in the Fourier spectrum of the solid velocity at the Earth surface, because the fluid oscillations are transmitted by the elastic material to the Earth surface.
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Scientific Strategy to Explain Observed Spectral Anomalies over Hydrocarbon Reservoirs Generated by Microtremors
Authors S. M. Schmalholz, Y. Y. Podladchikov, R. Holzner and E. H. SaengerWorldwide one has observed narrow-band, low-frequency (1.5-4 Hz) tremor signals on the surface over hydrocarbon reservoirs (oil, gas and water multiphase fluid systems in porous media). These ‘hydrocarbon tremors’ possess remarkably similar spectral and signal structure characteristics, pointing to a common source mechanism, even though the depth (some hundreds to several thousands of meters), specific fluid content (oil, gas, gas condensate of different compositions and combinations) and reservoir rock type (such as sandstone, carbonates, etc.) for each of those sites are quite different. However, the physical mechanisms underlying these observations are presently not fully understood. Therefore we propose a scientific strategy for a better understanding of those phenomena. Using well-known rock physical relationships we have identified on macro-, meso- and microscale different mechanism which can induce anomalies in the low-frequency band. Using different numerical approaches we are able to compare these mechanisms with observations in the field.
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Spectral Anomalies in Microtremors Due to Subsurface Heterogeneities – 1D Numerical Simulations of Poroelastic Wave Propa
Authors S. M. Schmalholz, H. Steeb, Y. Y. Podladchikov and R. HolznerWe perform 1D numerical simulations of wave propagation in elastic and poroelastic media to investigate the Fourier spectra of the surface velocity-time signal for different material heterogeneities within the subsurface. The motivation of this study is to better understand the resonance effects in the low frequency band of observed ‘hydrocarbon tremors’. We use two systems of equations describing wave propagation in poroelastic media: one system based on the Biot theory and a second system based on the theory of porous media (TPM). The characteristic maxima in the Fourier spectra for low velocity surface layers, low velocity subsurface layers and attenuating subsurface layers can be predicted with analytical solutions for the standing wave resonance frequencies. Reflections from fluid-saturated layers generate Fourier spectra with amplitudes that depend on the layer thickness.
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Early Stress Experiments Using Microseismicity in Underground Coals Mines
Authors B. J. Evans, P. Hatherly and X. LuoThe use of seismicity for understanding the dynamics of fracturing during changes in the rock stress state has been ongoing for over 20 years in the mining industry. In particular for the last 15 years, seismicity data has been used in coal mining as a hazard or rock fall indicator during underground mining. This paper highlights the first trial of the use of seismicity in an underground coal mine in Australia and the first indicator that dynamic seismicity data can be used to track the onset of fracturing which may then be used to determine the rock stress state during dynamic loading and unloading conditions in an underground long-wall mine. The results of this case history assists the understanding of how seismicity can be used during production.
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Time Reversal for Source Imaging
Authors D. J. Gajewski, E. Tessmer, B. Kashtan and C. VanelleThe passive seismic method for reservoir monitoring and characterisation and monitoring of hydraulically induced fractures is developing into a main stream technology in the oil business. Current techniques rely on the fact that the recorded event is detectable at most of the stations of the recording array. Weak events, not visible in the individual seismogram of the array, are missed out. We present an approach based on reversed modeling (time reversal), where no picking of events in the seismograms of the recording array is required. Assuming the correct velocity model, the reversely modelled wavefield focuses at the hypocenter of the seismic event. The origin time of the event is given by the time where maximum focusing is observed. Limitations in aperture lead to location and timing errors even for the correct velocity model.
These errors are below the prevailing wavelength and the signal length.
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Soft Soil Amplification of Ambient Seismic Noise – Field Measurements and Numerical Modeling of H/V Ratios
Authors M. Lambert, B. Steiner, S. M. Schmalholz, R. Holzner and E. H. SaengerModifications of the seismic background noise spectrum were observed above hydrocarbon reservoirs (‘hydrocarbon tremors’). Other effects, such as for example the presence of soft soil layers, can also amplify the background noise at certain frequencies. The effect of soft soil amplification is widely used to derive resonance frequencies of the site as well as the S-wave velocity and thickness of the soil layer. One of the most popular techniques to determine those values is the so called Nakamura’s H/V spectral ratio technique. We observe soil related modifications in our measured data and we are able to reproduce those effects with a 2D finite difference wave propagation model. The synthetic results match very well the analytical predictions. Such simulations help to clean measured data from soft soil related effects and thus to improve the identification of hydrocarbon related information in the microtremor spectra.
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Estimation of S-Wave Velocity in Bam Region (Iran) Using Microtremors and SPAC Method
Authors A. Fereydouni and M. R. GhayamghamianThe accuracy of Vs profiles, the ability to reach large penetration depths in urban and industrial areas and its low cost make array observation of microtremors very popular for site effect studies. The major objectives of the present study is to describe the SPAC method and an example of its application for the site characterization in Bam. Comparison the results with existing geotechnical data proved the reliablity of the SPAc method.
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Simultaneous Inversion for Velocity and Passive Microseismic Event Locations – A Particle Swarm Optimization Approach
Authors T. I. Urbancic, S. Zantout and P. McGillivraying place within the reservoir as steam is introduced. The introduction of fluid and varying temperatures during cyclical steaming cycles have direct influence on the pre-existing physical properties of the rock and as a result, the velocity model in use needs to be calibrated accordingly. Since passive source waveforms are influenced by the dynamic nature of the reservoir properties it is sufficient to say that their associated event locations need to account for these changes. To this end, we employ a Particle Swarm Optimization (PSO) approach to invert for both the velocity model and the spatial locations of the events. Based on this approach, we observed P-wave velocity reductions up to 16% at the reservoir level for any given cycle. The re-located microseismic events appear ‘well behaved’ in the context of reservoir processes, and the location uncertainty of the re-located events dropped by approximately 21%. The approach further opens opportunities to examine the anisotropic conditions in the reservoir and assist in re-defining velocity derived lithologic boundaries.
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Feedbacks on Passive Seismic Monitoring Experiments
More LessThe paper gives some feedbacks on a series of field experiments dealing with Hydraulic fracture mapping, CO2 injection associated with EOR and gas storage. The aim is to share experience and to discuss about location uncertainty, nature of phenomena that induce the seismicity, scale effects and how to proceed to perform a survey depending on field objectives and site properties.
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Induced Seismicity from from 15 Years of Injection at the World’s Deepest, Continuous Injection Well, Paradox, Colorado,
More LessIn southwestern Colorado, USA, the USA Bureau of Reclamation high-pressure injects waste water at between ~800 and ~1,300 l/min, 4.3 to 4.8 km below the surface. The injection has induced more than 4,400, surface-recorded seismic events (i.e., magnitude ≥ M0). The event locations group into two distinct zones: a principle zone (>95% of the events) asymmetrically surrounding the injection well to a maximum distance of ~3+ km and a secondary, ellipsoidal zone, displaced ~8 km northwest of the injection well. Within the principal zone, the events align into groups distinctly showing at-depth stratigraphy and the local fracture and fault system. The fractures mapped by seismic locations align with the fault planes determined from the seismic waveforms. The major faults of the system are aseismic, running parallel to the principal stress direction (determine from seismic waveforms), which agrees with the direction between the secondary seismic zone and the injection well. This shows that the main faults act as long, fluid conduits from injection well to the displaced secondary seismic zone. Since 1996, when continuous injection began, Reclamation has altered injection 3 times to control the seismicity while maintaining acceptable brine injection volume.
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Monitoring of an Uncontrolled Gas Flow by Sea Bottom Seismic Instruments – A North Sea Case Study
Authors K. A. Berteussen, K. Kolbjørnsen, D. O. Larsen and P. KristiansenWhile drilling a deep target Saga Petroleum had an uncontrolled situation were gas from the target were injected into sandlayers above through a leak in the casing. Over a period of approximately two weeks seismic data were registered from a small array of geophones located on the sea-bottom close to the platform.
Several periods of high underground seismic activity were identified. These are most likely induced small earthquakes. With such a sea bottom seismic it is possible to determine the direction to the underground acoustic source, but one has only limited control on the distance from the receivers, and thereby also limited control on the source depth. It is, however, possible to discriminate between activity close to the surface and genuine underground seismic events. The observed events are not located to the well path. Almost all of the major events taking place in the recording period are located west of a line going South-southeast to North-¬northwest. There is possibly a tendency for the events to move outward with time. The events could basically be explained as being caused by the moving front of hydrocarbons into shallow sandlayers. Systematically repeated phenomena not hitherto understood are, however, also observed.
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Simultaneous Treatment and Remote Well Monitoring of Microseismicity from a Hydraulic Fracture
Authors K. D. Mahrer, R. J. Zinno, J. R. Bailey, M. DiPippo and S. ZantoutIn June 2006, in a sandstone-shale sequence in the western USA, two borehole seismic arrays were deployed to record and map the source locations of the microseismicity created by a hydraulic fracture treatment. The intent was to use the microseismic locations from each array as an overlay to map the hydraulic fracture network and compare the maps from the two deployments. The first array was in a remote well ~210 m from the treatment well and at the treatment depth. This array was ~150 m long, self-locking, contained 15 levels of 3-component sensors, and required external sources to orient the sensors. The second array, the “TABS” or TriAxial Borehole Seismic array, was deployed in the treatment well during and following the proppant-baring treatment. TABS is ~23 m long, contains 3, 3-component sensors, is self-locking, and includes a sensor orientation package. During the operation, a 45-minute injection followed by a 1-1/2-hour post treatment monitoring, the offset array failed to detect any discernable, useful signals – subsequent processing may pull signals from the noise. Comparatively, TABS, which monitored only during the post-treatment, recorded ~400 events without subsequent processing.
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Microseismic Feasibility Study - Monitoring Gas Injection in Middle East Field
Authors R. Alfaro, F. Cerda, J. L. Lesueur and B. TournemineA microseismic feasibility study is presented to monitor the injection of gas in the Arab-D reservoir of an offshore Middle East field. Full waveform modeling and detection sensitivity analysis have shown that the proposed network of installing sensors at reservoir depth in observation wells has high detection capabilities. However the modeling results reveal that interferences would exist between direct and refracted/reflected waves making it difficult to identify first P-wave and S-wave arrivals from microseismic events. Large location uncertainties are also expected with the proposed network. As a result the feasibility study recommends placing in each observation well some additional shallower sensors ~400 meters above the reservoir. Based on these feasibility results a decision will be made whether to proceed with a field trial survey.
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Microseismic Spot Study in Heavy Oil Field
More LessThis paper describes a microseismic spot study that was carried out using 397 buried sensors on a steam injecting heavy oil field in Alberta, Canada. 4 microseismic events from 2301 possible candidates were located on the surface even after improvement of the signal through deconvolution and filtering of human activity. No microseismic events originating from the reservoir were detected. However a possible correlation has been observed between coherent noise and steam injection processes.
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Design of a Low Power, Wireless, Passive Seismic Monitoring Instrument
Authors H. C. Bland, M. B. Bertram and R. R. StewartRural and remote passive seismic monitoring sites are often challenged by the lack of power and communication utilities. Sites without power lines require costly on-site generation (from diesel, gasoline, propane) or self-sustaining power sources (solar, wind). In all cases, electrical power is a key component in the capital and operating cost of surface-based monitoring systems.
An instrument was designed for environmental and oilfield passive seismic monitoring with very low power consumption. The device was designed to use either a wired or wireless network link for data communication. Designed for sample rates up to 4 KHz, the instrument is ideally suited for connection to seismic-band sensors such as geophones or accelerometers. A low-noise, high-gain, programmable gain preamplifier provides the necessary amplification for the A/D converter.
Several of these instruments have been installed at two remote sites using wireless data transmission. Running on solar power alone, the instruments have operated very successfully over the past two years. Reliability and the availability of remote diagnostic facilities are found to be key components in a successful remote passive seismic monitoring program.
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The Place of Passive Seismic in E & P
Authors S. Kapotas, N. Martakis and A. TselentisThe increase on the demand for Passive Seismic especially in the domains of exploration and production has most recently become a challenging field of opportunity. The method based on uncontrolled sources, requires an understanding and analysis of what we call passive events in a careful manner, so as not to be misinterpreted leading to a possible damage of its credibility. The objective of this presentation is to look at one of the methodologies that benefit from passive sources, and justify its use with case studies. Integrated Passive Seismic using P and S-wave travel times from natural micro-earthquakes can accurately estimate 3D Vp (structural) and Vp/Vs (lithologic) information of the subsurface. and reservoir related parameters.
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Frontier Exploration Using Passive Seismic
Authors P. Duncan and J. LakingsWe present a case history of 3-D seismic imaging in the Uinta Basin of Utah using passive seismic as an example of how passive techniques can aid exploration efforts in frontier areas. The area is topographically rugged making conventional seismic exploration expensive. Additionally, surface access is controlled by federal authorities and subject to stringent regulations which make permitting of conventional seismic almost impossible. The survey began in June, 2005. Over 12 months of passive data have been acquired. The catalogue of located events exceeds 6000 events. Tomographic inversion to a velocity model has shown structures of exploration interest.
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Virtual Surface Seismic Data from Downhole Passive Arrays
More LessMonitoring oilfield reservoirs by downhole seismic arrays typically consists of picking traveltimes of direct arrivals and locating the hypocenter of the fracturing rock. The 3-component array typically has no more than a handful of geophones located in one or more wells. To broaden the use of this downhole recording array I propose that it can, in principle, also be used to record 3D VSP data from controlled surface sources. These VSP data with free surface multiples can then be interferometrically transformed into virtual surface seismic reflection data, so that the subsurface reflection coverage is almost the same as a surface seismic experiment. To support this proposal, I present interferometric imaging results from 2D and 3D VSP data. Images from free surface related multiples show that the subsurface reflection illumination is almost as wide as that of a surface seismic experiment and is much larger than that from a conventional VSP image.
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Passive Infra-Frequency Microseismic Technology – Experience and Problems of Practical Use
Authors B. Y. Meltchouk, A. E. Suntsov, S. L. Aroutunov and A. M. MekhninInfra-frequency microseismic technology ANCHAR is based on the analysis of microseismic background of the Earth and is designed for prediction of oil bearing of formation rocks. Based on the 15-year experience of applying the microseismic technology to prediction of oil and gas, authors analyze the problems arising in microseismic technologies based on the use of amplitude characteristics (AC) of microseismic. Proposed is a new criterion based on the statistical analysis of displacement vector of the microseismic background considered as random time series (EC). Demonstrated is its benefits, particularly, better daily reproducibility as compared to approaches based on amplitude characteristics. Presented are case studies of applying the infra-frequency microseismic technology in hard-to-access areas of West Siberia in Russia and examples of ANCHAR applications in other world regions.
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A Remote, Wireless Microeismic Monitoring System
Authors R. R. Stewart, D. C. Lawton, H. Bland and Z. ChenThis paper discusses the design, installation, and performance of a remote microseismic monitoring system in a mountainous terrain. The system was designed to detect local seismic events that could be precursors of a landslide or indicators of seismic activity related to hydrocarbon production in the area. Six 3-component seismic stations were installed on Turtle Mtn., Alberta, Canada - site of North America's most fatal landslide in 1903. The area is also host to considerable natural gas production. We discuss the sensors used, recording apparatus, data transmission, marshalling, and storage. Event detection algorithms have been developed and hypocentre determination codes emplaced. We provide an overview of recent results.
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Surface Passive Seismic in Kuwait
By G. R. RachedSurface passive seismic is a direct hydrocarbon saturation indicator technique. It detects the presence of subsurface hydrocarbons by recording and spectroscopically analyzing the low-frequency acoustic/seismic background noise (between 0.5- 10 Hz) which is actively emitted by the earth. The measurements after filtering and analysis can be calibrated with well data and integrated with other geophysical data to provide information which can lower the uncertainty level for drilling and field development decisions. Measurements were carried out in Kuwait to evaluate their suitability to map the extent of hydrocarbon occurrences. The main concern being the suitability of the technology to differentiate between various reservoirs in stacked-reservoir environment. The level of certainty in the resulting map could not be accessed as there is a possibility that some deep reservoirs have not penetrated by the wells in the area of the experiment. It was concluded that the technology (at this point) cannot indicate the distribution of the occurrence among the stacked reservoirs since the measured indicators are the summation of the response of all the underlying reservoir layers. Nevertheless, the areas with highest hydrocarbon potential indication will normally be the most interesting ones.
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Application of Passive Seismic (IPDS) Surveys in Arabian Peninsula
More LessInfrasonic Passive Differential Spectroscopy (IPDS), called also as Passive seismic, is relatively a new technology for hydrocarbon reservoir (oil and gas) detection and monitoring. Application of this technology was utilized in several countries worldwide since 1996.
The Passive Seismic (IPDS) technique is based on the principles of non-linear behavior of multiphase fluid systems in porous reservoirs. Hydrocarbons in the pore system can be detected at surface as a characteristic deformation caused by ambient vibration of the normal signature of the natural earth’s noise signal in the low frequency range between 1 Hz and 10 Hz.
The technology is to becoming the leader in the development and application of passive low frequency acoustic and electromagnetic technologies for the detection of hydrocarbons and oil reservoirs monitoring – from the surface.
The main objective of the Passive seismic IPDS survey campaigns in the Arabian Peninsula in Oil and Gas fields (UAE, Kuwait, & Jordan) was to run such surveys as an exploration, delineation, reservoir monitoring and time laps monitoring tool under sand dunes-desert conditions.
The secondary objective was to provide information concerning detailed aerial hydrocarbon and vertical distributions. Up to date; run surveys in 15 exploration, appraisal and development areas.
Over 1,000 measurements were acquired from several exploration and development areas in Middle-East and 15,000 worldwide. The profiles pass through over hundreds of exploration, dry, appraisal, producer, and injector wells. The correlation with known data from these wells result in a correlation coefficient better than 80%, and the correlation between hydrocarbon net pay zone and Geospectra IPDS data related to several wells were excellent.
Based on the results of these surveys several new exploration areas were identified and additional hydrocarbon pools were found as an extension of existing fields under development and avoided a lot of dry holes. More than 13 wells drilled in B & Q fields based on the passive seismic (IPDS) direct hydrocarbon indication maps, most well results came exactly as predicated.
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Microseismic Monitoring with a Surface Array
Authors P. Duncan and J. LakingsWe propose an alternative to down hole microseismic monitoring that uses large arrays of surface geophones. The method presents several logistical and technical advantages over more common down hole techniques, but has its drawbacks as well. We have employed the technique in more than 16 projects to date and present here some of the results and observations on that work.
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Passive Seismic and Surface Deformation Monitoring of Steam Injection
More LessIn this paper, we present two case studies demonstrating the use of passive seismic and surface deformation of steam injections. The first example is of a cyclic steam injection, and the second a SAGD injection. The paper also highlights the geomechanical integration of passive seismic data and strains inverted from surface deformation.
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How Microseismic Data Monitored from Treatment Well Can Lead to Fracture Imaging – Feedback from Field Experiments
Authors C. Maisons, E. Gaucher, E. Fortier and P. KaiserFor any oil company, the knowledge of fluid paths within its reservoir is key information for production optimizing. Hence the ever growing interest of understanding any seismic activity induced by stimulation operations such as fracturation jobs. Indeed, microseismic monitoring of such experiments can lead to fracture mapping – usually, it is carried out from a distant observation well. The originality of our field feedback relies on a monitoring from the treatment well itself. Over the last years, we have collected a significant catalogue of multiple frac jobs experiments (beyond 20 jobs, within various overburdens types, using different probes in various survey geometries). The variety of configurations yet leads to very consistent conclusions as to the fracture characterization, by taking advantage of both types of waves - and validates our treatment well approach.
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Field Monitoring Using a Large Passive Seismic Array in Saudi Arabia – Field Pilot Study
Authors M. Jervis and S. DasguptaA large passive seismic array has been installed over a field in Saudi Arabia. This array comprises both downhole and surface 3C sensors and is designed to record microseismic events from the reservoir zone about 2km deep over an area of about 9 sq km. The main objective is to demonstrate that microseismic events which occur in the reservoir are detectable and that they can be used for mapping fluid flow and fracture pathways.
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Same Data, Different Results – The Apples and Oranges of Microseismic Data Processing
Authors F. H. Kindy, P. Engbers, A. Yahyai, P. Schoepfer, G. Engen and C. Van EdenHaving had a total of seven microseismic projects to date, PDO are in the unique situation were they have microseismic data acquired from a given field independently analyzed or processed by more than one party. For one field, identical data processed by two vendors gave very different results, both in number of events and their locations for the same recording period. For another field, the scattered data is believed to be correct whereby the nicely aligned data was found to be unreliable after a quality check. These differences raise many questions regarding MS data processing: why are these results different and are the differences a result of bad processing or different methodology used? We find that there are several factors for the differences including the processing methodology, the input data and the MS event screening and characterizing process used by the different vendors. Specific input and direction from the client are useful to ensure such discrepancies are reduced.
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Microseismic Monitoring of a Petroleum Field in Oman
Authors S. Sarkar, E. Sze and M. N. ToksozA case study of microseismic monitoring using extensive data from two different seismic networks in a petroleum field in Oman is presented. Spatial-temporal analysis of these microearthquake locations reveals fault structures, identifies causes of induced seismicity and fault reactivation. Shear-wave splitting analyis is used to map anisotropy and the stress direction in the reservoir.
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Induced Seismicity in the Oil & Gas Reservoirs of the South & South Western Iran
Authors M. Jalali, H. Memarian and M. ZareZagros Basin, extending from south to south west of Iran, is one of those large sedimentary basins of the world that shows high seismicity rate. The purpose of this research is to model and acquire the induced seismicity in the oil and gas reservoirs of this basin, resulted from extraction or injection of fluids in the reservoirs.
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Oil Reservoir Monitoring in Middle East Carbonates – Passive Seismic as an Alternative Approach to 4D Seismic
More LessMany of the supergiant oil fields in the Middle East produce from prolific carbonate reservoirs. Collectively these carbonate rock reservoirs hold over 50% of the proven world oil reserves (Nurmi, 1997). The ultimate oil recovery from these reservoirs could be optimized by monitoring the water flood areal sweep efficiency and by monitoring the changes in the remaining oil saturation between the wells, as the reservoir is produced. The sparse well spacing and large drainage areas for producing wells in these fields along with the rock physics properties of the reservoir matrix and fluids, however, make such monitoring a technical challenge.
The limestone-dolomite reservoir rock matrix has high rigidity modulus and the reservoir pore fluids show only a small elasticity contrast, as the oil is replaced by aquifer water. This is primarily due to relatively low gas-oil-ratio (GOR) in these undersaturated oil reservoirs, absence of a gas cap and mixed salinity water due to the injection of lower salinity brine in the reservoir. The combination of these reservoir properties produces a weak 4D seismic or time-lapse seismic effect from oil production in these reservoirs. For fluid monitoring in such reservoirs an alternative to time-lapse or 4D seismic technique is needed.
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Seismic Monitoring of Underground Storage in Salt Cavity in a Seismo-Tectonic Context
Authors E. Fortier, P. R. Renoux and C. M. MaisonsCaverns stability is monitored using a permanent seismic surveillance network operating since 1992. This paper summarized the results concerning underground storage monitoring in a seismo-tectonic context. Over the last 14 years, the seismic network has recorded 1800 internal micro-seismic events (magnitude < 0.5), and 500 external seismic events located close to the site. The objective is to show whether the seismicity is associated to exploitation activities (leaching) or to the local geological tectonic activity.
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Passive Seismic Imaging of Deformation Induced by Hydraulic Fracture Complexity in the Naturally Fractured Barnett Shale
Authors S. C. Maxwell, C. K. Waltman, N. R. Warpinski, M. J. Mayerhofer and N. BoroumandMicroseismic mapping is extensively utilized in the Barnett Shale, to map hydraulic fracture complexity associated with interactions of the stimulation with pre-existing fractures. Previous studies have indicated a fair correlation between the well performance and extent of the seismically active volume. However, in addition to this measure of the extent of the stimulated fracture network, the characteristics of this fracture network is also expected to impact the well performance. In particular, the fracture spacing is believed to be important factor controlling the potential gas flow. In this paper, we utilize the density of the total seismic moment release (a robust measure of the microseism strength) as an indication of the seismic deformation that may correlate to the fracture density. The study uses a set of microseismic maps of hydraulic fracture stimulations, including cases where the stimulated reservoir volume measured by the extent of the seismically active region poorly correlated with the well performance. Incorporating the seismic moment density to assess the fracture density with the network extent, an improved correlation with the well performance was observed.
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Passive Seismic Monitoring at a CO2 Injection Site, Violet Grove, Alberta, Canada
Authors H. C. Bland, R. Chalaturnyk, H. Soderberg and D. C. LawtonAt the Penn West pilot project, 100 km southwest of Edmonton, Alberta, Canada, CO2 is being injected into the Cretaceous Cardium Formation in the Pembina Oil Field for enhanced recovery and carbon sequestration purposes. The reservoir is being monitored using passive seismic borehole array. Additional active seismic surveys are periodically performed to obtain time-lapse seismic images. A passive seismic array was installed on production tubing, along with fluid samples ports and pressure temperature sensors. Borehole geophones are used in combination surface three-component geophones to obtain sparse, 4D, multicomponent surveys of the study area. To date, the repeat active seismic surveys show indication of reservoir changes as a result of the CO2 injection. Passive seismic monitoring is ongoing, but has yet to yield any measurable levels of seismicity generated by the CO2 flood.
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Recent Experience of System Optimization for Wide Area PMM Installations
Authors I. Weir-Jones, P. M. Duncan, Ph. D., S. A. Shore and S. M. J. TaylorBased upon current experience with large PMM systems being deployed in North America, North Africa and the Gulf the authors review the factors which should be considered when designing PMM systems for various types of reservoir monitoring applications. Using specific examples of PMM systems designed to monitor heavy oil production is North America, CO2 sequestration in North Africa, and production optimization in Saudi Arabia the key factors influencing the design and operational characteristics of cost effective PMM systems are reviewed. The paper concludes with a review of the features which will be incorporated in different types of PMM systems in the near future.
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Data Acquisition, Transfer and Processing for Multi Channel Permanent PMM Systems
Authors I. Weir-Jones, P. M. Duncan, Ph. D., S. A. Shore and S. M. J. TaylorThis paper discusses the acquisition, transfer and subsequent processing/presentation of data from four different permanent PMM installations. The installations differ in both size, location, data processing procedures and ultimate function.
In terms of complexity, capability and addressability this new Aramco PMM system probably represents the current state of the art in permanents deployed, unmanned passive microseismic monitoring systems. The paper concludes with a review of system data handling capabilities as they currently, or will soon, exist using the characteristics of this new system for illustration purposes.
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Design Considerations for Cost Effective PMM Systems
Authors I. Weir-Jone, P. M. Duncan, S. A. Shore and S. M. J. TaylorThis paper provides potential users of passive microseismic monitoring data with an outline of the decisions which need to be made prior to deciding whether or not to deploy a PMM system, defining the system’s specifications and issuing the statement of work to potential suppliers. It is also intended to summarize the issues and functional parameters which must be defined in order to ensure that the installed system will be useful for all stakeholders and that the actual installation process will be as stress free as possible.
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Seismic Interferometry Applied to Passive Data
Authors K. Wapenaar, D. Draganov, W. Mulder, J. Singer and A. VerdelOne of the applications of Seismic Interferometry (SI) is the reconstruction of the Earth’s reflection response from the crosscorrelation of seismic background noise recorded at the surface. In recent years, several authors have derived the relations that govern this process. The quality of the reconstruction has been extensively examined with numerical modeling results.
We applied SI to background-noise field data recorded in a desert area. The reconstructed results show several coherent events which align well with reflections from an active survey along the same line.
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