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Second EAGE Passive Seismic Workshop - Exploration and Monitoring Applications 2009
- Conference date: 22 Mar 2009 - 25 Mar 2009
- Location: Limassol, Cyprus
- ISBN: 978-90-73781-59-7
- Published: 22 March 2009
1 - 20 of 35 results
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Improved Event Location with Single Well Monitoring – A Case Study from Ekofisk
Authors G.A. Jones, D.G. Raymer and J.M. KendallWe relocate microseismic events from the Ekofisk reservoir in the North Sea that were recorded over an 18-day period in April 1997. A array of six 6-component sensors deployed in a vertical borehole with a 20 m spacing detected nearly 4500 events. Events are located using P- and S-wave travel times and azimuthal particle directions, which are calculated using a recently developed noise-weighted analytical-signal singular-value-decomposition method. A inherent 180 degree ambiguity in event locations exists with data recorded by sensors in a signal borehole and 1D velocity model. We remove this ambiguity using dip information estimated as part of the particle motion analysis. The relocation yields 1333 events, which are primarily concentrated in the producing part of the reservoir. In general, our location accuracy is 15m, but most events locate to within 10m. In comparison to the original event locations, the new locations show less scatter and cluster into more linear patterns, we interpret as fault structure.
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Non-linear Calibration of Complex Velocity Models in Microseismic Jobs
Authors T. Bardainne and E. GaucherThe calibration of the velocity model in microseismic jobs is critical to achieve statistically reliable microseismic locations. Indeed, the lack of knowledge of the wave propagation medium is the main source of location inaccuracy. This paper presents a non-linear calibration method of velocity models for passive, microseismic surveys. This method analyzes multiple time and polarization arrivals and uses a non-linear inversion, simulated annealing algorithm, which prevents the velocity solution from converging to a local minimum, to minimize the residuals and the location error measurements. This method calibrates complex velocity models which can be described, by velocities (P&S), velocity gradients, dip of layers or 3d surface layers. We present an example that demonstrates a significant decrease in location errors of microseisms as compared to typical methods.
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Passive Seismic Monitoring of a Heavy Oil Field
Authors A.C. Rosca, R.T. Langan, A.J. Jupe, S.C. Maxwell and P. DillettA pilot project was designed to monitor induced seismic activity in a relatively shallow heavy oil reservoir located in a low permeability, high porosity, silicious shale. Several hundred microseismic events have been located over the past two years using data recorded at two borehole seismic arrays. Microseismic activity occurs predominantly in two separate depth zones: one within the reservoir and one in the shallow overburden. Larger events are located at the top of the reservoir close to the injection well; shallow clusters of smaller events could identify fluid migration pathways in the overburden.
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Automatic Determination of Full Moment Tensor Solutions from P-wave First Motion Amplitudes
Authors D. Kuehn, H.N. Gharti, V. Oye and M. RothStandard microseismic monitoring nowadays focuses on event locations, but information on detailed source parameters is rarely extracted. The estimation of full moment tensor solutions of microearthquakes may provide valuable information on presence and geometry of faults as well as stress fields and changes thereof. Therefore, we included a full moment tensor inversion using automatically picked P-wave first motion amplitudes in addition to the computations of source spectra and related source parameters. We tested the routine using synthetic polarities and synthetic waveforms computed in a complex 3-D velocity model. In a first application, we investigated mining-induced seismicity in the Pyhäsalmi ore mine, Finland. Approximately 50% of the events show strong non-double couple components. Known explosions could be retrieved, being used as quality control of the method.
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Microseismic Measurements and Results in a Flowing Well During Well Stimulation
Authors U.G. Rinck, L.B. Barzaghi, L.V. Vetri, F.F. Ferulano, A.S.B. Boivineau and M.D. DibitettoThe measurement of low magnitude microseismic signals is a challenge inside a producing or injecting well with the high amplitude level of flow noise. We will present a recent deployment of the PS3-FW sensor tool technology for flowing wells and the results from the monitoring of a stimulation operation together with the reservoir understanding derived from it.
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Fracture Characterisation Using Estimates of Shear-wave Splitting from Microseismic Data
Authors J-M. Kendall, O. Al-Harrasi, J.P. Verdon, A. Wuestefeld and A. Al-AnbooriWe summarize observations of shear-wave splitting from passive seismic monitoring in a range of petroleum settings. Such measurements are relatively rare, but the emerging picture is one of fracture-induced anisotropy where a number of factors control both spatial and temporal variations. These observations offer insights into the state of stress in a reservoir and can serve as a ground-truth for geomechanical models.
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Reservoir Monitoring Using Induced Seismicity Magnitude – A Case Study from Oman
Authors S. Sarkar, M.N. Toksöz, H. Zhang, F. Al-Kindy, H.J. Lewandowski and N. Al-TouqiWe present a case history of passive seismic monitoring with location and characterization of seismic events induced by oil and gas production and water injection at a petroleum field in Oman. Two different monitoring networks have recorded thousands of microseismic events in the field over the last 9 years. We used data from both networks to locate the events and to analyze the patterns and causes of induced seismicity in the field. Locations of these events correlate with preexisting fault maps derived from surface seismic, and delineate structures that were previously unmapped by the same. Spatial and temporal analyses of event locations indicate large scale fault reactivation in the field. Comparisons between induced seismicity and production/injection data in the field suggest gas production as the primary cause of inducing seismicity in the field. The use of passive seismic technology in this field has been very effective in the characterization and surveillance of the reservoir.
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A Review of Crosscorrelation and Multidimensional Deconvolution Seismic Interferometry for Passive Data
Authors E.N. Ruigrok, K. Wapenaar, J.R. van der Neut and D.S. DraganovIn the search for new hydrocarbon reservoirs a number of sedimentary basins have so far been underexplored due to exploration challenges, like, e.g., difficult terrains to employ vibrator sources. Instead of conducting an active seismic survey, the first exploration data could be delivered by using natural seismicity and seismic interferometry (SI). For this purpose, arrays with continuously recording receivers would need to be installed in the exploration area. With SI, seismicity due to natural sources in the subsurface can be remapped to receiver positions on the Earth’s surface. The remapped responses can subsequently be used to create a (low-frequency) reflectivity image of the subsurface. Initially, SI was proposed as a crosscorrelation (CC) of responses. Recently, an alternative remapping procedure for passive data was proposed, by performing a multidimensional deconvolution (MDD). We evaluate both methods. We show that with both methods physical events can be retrieved correctly, also when there are moderate losses in the medium. In realistic situations, for both methods, additionally, specific artifacts are created, so-called internal events. We show how these artifacts could be recognized and removed.
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Recent Microseismic Monitoring Results from VSP and Permanent Sensor Deployments in Saudi Arabia
Authors M. Jervis and S.N. DasguptaA large surface and downhole microseismic network is complemented with a temporary VSP tool deployment to investigate water flooding in Ghawar. Water injector rates are varied to induced microseismicity in the Arab-D reservoir to map possible fracture zones and flood front variations.
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Focal Mechanism Determination from Few Sensors – Application to the Arkema-Vauvert Site, France
Authors M Godano, A. Pussacq, T. Bardainne, E. Gaucher and M. ValetteWe developed a method that enables computing focal mechanisms with only a few sensors. This method is based on a non-linear inversion of the P, SV and SH amplitudes of microseisms recorded on a set of sensors. Information brought by the focal mechanism enables determining the direction of the mechanism and the associated geological structure. Moreover, the computation of the mechanism enables a better estimate of the conventional source parameters. This full analysis has been performed on two microseismic clusters in the Arkema-Vauvert site in the south-East of France. Results of the focal mechanism study highlight that the two clusters are totally different in terms of source behaviour: one is characterized by the occurrence of the seismicity along an important identified thrust fault; the other is characterized by the reactivation of a well-known listric fault.
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Detection of Micro-seismic Events Using a Surface Receiver Network
Authors E. Schisselé and J. MeunierA new micro-seismic detection method is presented. It uses the redundancy offered by large horizontal arrays of geophones to automatically detect micro-seismic events without any time picking and this, even in poor signal-to-noise ratio conditions. The various performances of this method (precision versus computational time, signal-to-noise ratio, source grid parameters,) will be discussed and compared with those of the full semblance method on numerical signals. Results obtained using a real data set will be shown.
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Dual Treatment Monitoring with a Horizontal Receiver Array
Authors G.C. Michaud, W.S. Leaney, L. Bennett, M. McClay, K. Ainsworth, M. Kaiser and B. McPhersonMicroseismic monitoring from a horizontal well poses some challenges in terms of accurately determining the depth of the microseismic events. To handle data recorded by receivers distributed generally in deviated or horizontal wells, the full polarization vector in addition to event times must be included in the location algorithm. A 3D waveform-based grid search method is described and is applied to a dataset recorded with a horizontal receiver array to monitor a simultaneous dual well treatment. The results of the data processing workflow show a good estimation of the fracturing positions and growth on both sides of the receiver array.
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Microseismic Estimation of Permeabilities of Tight-gas Sands
Authors V. Grechka and S.A. ShapiroThe objective of hydraulic well stimulation is creating a network of fractures in a tight rock that enhance its natural permeability and make hydrocarbon production economic. As both the geometry of fractures and the permeability of treated formation influence the subsequent production, their assessment is important for development of tight-gas fields. While the fracture shapes and orientations are conventionally inferred from microseismic data acquired in the process of stimulation, here we demonstrate that the same data also allow quantifying the formation permeability. We discuss the permeability-estimation technique that utilizes the dynamics of microseismic clouds and apply it to data recoded during hydraulic fracturing of two wells drilled in the Pinedale Field, Wyoming, USA. The obtained permeabilities are then used to predict the gas rates.
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Microseismic and 3D Seismic Anisotropy Fracture Mapping – A North America Tight Gas Case History
By J.E. WolfeA tight gas case history from the North America Rocky Mountains shows the capability of borehole microseismic and 3D seismic anisotropy to delineate fracture systems induced in a clastic reservoir by hydraulic fracturing of a horizontal well. Dual monitoring of the horizontal well completion indicates improvements in fracture mapping by compressing hypocenters of the microseisms to more linear features that are corroborated by production logging flowmeter. Fracture half-lengths and vertical heights of fractures are indicated for reservoir modelling. Advanced processing of the microseismic 3-component geophone first motions indicates fracture azimuth and dips from a moment tensor inversion and suggests a conjugate set of orthogonal fractures in the reservoir. 3D seismic anisotropy results, using a fast and slow velocity direction calculated from the data, suggest inherent microfractures present in the rock prior to completion. Surface fault mapping in the field supports fractures mapped by both the microseismic and the 3D seismic anisotropy. Multiple regression analysis of drilling, completion and 3D seismic anisotropy parameters versus initial production for 30, 90 and 180 days results show independent contributions to production. A predictive production model based on the multiple regression analysis allows for future well planning and completions to optimise well performance.
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Understanding Hydraulic Fracture Growth by Mapping Source Failure Mechanisms
Authors T.I. Urbancic, T. Morrish and V. ShumilaDeveloping a model of hydraulic fracture development to characterize the effective fracture volume and identify potential means for re-stimulation of previously treated wells by utilizing seismic moment tensor inversion techniques
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Location Uncertainties in Passive Seismic Monitoring
Authors L. Eisner, W. Heigl and P.M. DuncanIn this study we shall address the effects of the receiver geometry, arrival time uncertainty and velocity model errors on location uncertainties. The effect of the velocity model error will be limited to a consideration of homogeneous media, although heterogeneity may have as profound effect on location accuracy as receiver distribution. Although many different sensor distributions are conceivable, we will focus on those that are most commonly applied in practice to include a 2-D grid of receivers on the earth’s surface and linear arrays of receivers in vertical boreholes.
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Microseismic Deformation Rate Monitoring
Authors S.C. Maxwell, J. Shemeta, E. Campbell and D. QuirkMicroseismic monitoring of hydraulic fractures is an important tool for imaging fracture networks and optimizing the reservoir engineering of the stimulation. The range of magnitudes of the recorded microseisms depends at the lower limit on the array sensitivity; while the upper limit varies significantly from site to site. In this paper the variation in the microseismic magnitude range is examined and compared with the injection and site characteristics. Although there are numerous potential factors effecting the seismic deformation, the energy of the pumping and state of stress appear to be the two dominant factors. However, interaction with pre-existing faults also results in increased deformation. In this paper these factors are examined using the seismic injection efficiency, defined as the ratio of seismic energy release to the hydraulic energy expended during the injection. Ultimately, this can potentially be used to design the stimulation to maximize the deformation. Characterization of the seismogenic potential is also important for seismic hazard assessment, as well as the design of passive monitoring.
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Goodbye Noise, Hello Signal! Improving Microseismic Monitoring in Noisy Environments
Authors F.H. Kindy, G. Engen, I. Ismaily, N. Touqi and A. YahyaiOver the last decade, Petroleum Development of Oman have deployed several microseismic monitoring systems. Due to the maturity of many of the oilfields in Oman, anthropogenic noise is in abundance. Given that the magnitude of some of the microseismic events can be as low as M = -3, noise can seriously hamper the detection and/or processing of such events. This paper describes PDO's experiments on new hardware and software to increase S/N. We show some examples of how our implementaion techniques improved event detection thresholds. In addition, we propose simple solutions that are not only more effective at noise reduction, but are also cheaper both in implementation and in reducing the subsequent cost of data processing.
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Predicting Microseismicity from Coupled Fluid-flow and Geomechanical Simulation
Authors D.A. Angus, J.M. Kendall, J.S. Segura, Q.J. Fisher and M. DutkoIn this paper, we predict microseismicity for a series of simple rectangular reservoir geometries using results from coupled fluid-flow and geomechanical simulation. The results are analysed in terms of their spatial and temporal variations in distribution. We also evaluate the associated failure mechanisms to characterise the type of brittle failure. We find that microseismicity is sensitive to reservoir size. In the small reservoir microseismicity is confined to the edges and in the larger models, where stress arching is significant, microseismicity extends further from the edges as well as up into the overburden. We observe also a transition in the style of faulting, from normal to oblique strike-slip, as well as variation in magnitude of failure of up to 5 orders of magnitude. This work represents some of the research being conducted for the IPEGG (Integrated Petroleum Engineering, Geomechanics and Geophysics) consortium, an industry sponsored research partnership between the University of Bristol, University of Leeds and Rockfield Software Ltd.
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3D Integration of Active and Passive Seismic for Reservoir Monitoring
Authors A.L. Vesnaver, L. Lovisa and G. BöhmIn this paper, we present an integrated procedure for estimating hypocentres and complex 3D velocity models by the joint traveltime inversion of micro-earthquakes and active surface seismic data. Reflection tomography can reconstruct the major formation interfaces along extended areas, but its vertical velocity resolution between interfaces is low. Micro-earthquakes may improve the ray illumination at the reservoir, so improving in sequence the 3D velocity model and their location precision. This data integration improves also the time origin estimation of micro-earthquakes.
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