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Seventh EAGE Workshop on Passive Seismic 2018
- Conference date: March 26-29, 2018
- Location: Krakow, Poland
- Published: 26 March 2018
25 results
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Experiment Investigation On The Formation Of Hydro-Fracture System By Fracturing The Large Scale Coal-Rock Combination
More LessSummaryTaking the efficient exploitation of coalbed methane resources as the object in the soft coal strata, experiments on the formation of crack system were investigated by fracturing large-size coal-rock combination specimens. The results shows that due to the differences in mechanical properties and characteristics between coals and sandy mudstone, In the process of hydraulic fracturing from the hard sandy mudstone into the coal mass, the complex fracture system was formed on the coal-rock combination. The penetration, diversion or offset occur at the interface between the coal and the rock under the influence of the interfacial cohesive force. The diversion or offset leading to the fracture patterns complex, which will improve the fracture system.
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Microseismic Full Waveform Modeling And Location Uncertainty In Anisotropic Media
By P. ShiSummaryFull waveform modeling is a powerful tool to understand elastic wave phenomena in complex media and is widely used in exploration geophysics. Among many full waveform modeling methods, the finite-difference method is widely used. This study is focused on developing an efficient finite-difference forward modeling tool, which is suitable for modeling wave propagation in anisotropic media for microseismic monitoring. As both dislocation and non-double-couple source are observed in microseismic monitoring, an arbitrary moment tensor source is implemented in the forward modeling tool. We equally distribute the increments of shear stress on the staggered-grid to obtain an accurate and symmetric moment tensor source. Our modeling tool provides an efficient way to obtain the Green's function of basic moment tensor component in anisotropic media, which is the key of moment tensor inversion and source mechanism characterization in microseismic monitoring.
Seismic anisotropy will make the recorded wavefield much more complex, thus making microseismic imaging difficult. In our research, wavefields in anisotropic media have been carefully simulated and analysed for further contributing to microseismic monitoring. Analysing the travel-time and amplitude of the recorded waveforms provides a feasible way to estimate the anisotropy of subsurface, and thus improve the quality of microseismic imaging.
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Integration Of Passive Seismic Methodologies And Its Application On The Maupasacq Dataset
Authors K. Polychronopoulou, C. Orfanos, K. Leontarakis, D. Giannopoulos, A. Lois and N. MartakisSummaryPassive Seismic has always been a potentially prominent exploration tool. In this context, a processing workflow, incorporating the output of different Passive Seismic methodologies, has been developed. This workflow consists of exploiting three different types of Passive Seismic signal (seismic noise, local earthquakes and teleseismic events) extracted form the same Passive Seismic dataset. This procedure has been applied on data acquired in the context of the OROSACQ project, a research project that has been launched early 2017 and consisted of a 6-month Passive Seismic acquisition on a test site in France, near the Pyrenees mountains. The results were very promising, as this technique permitted the maximization of the acquired information.
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Use The Seismic Interferometry Method To Assess The Effects Of Hydro-Fracturing In Wysin Borehole
More LessSummaryThe article’s objective is to show that passive seismic methods, in particular, seismic interference of seismic noise, can be used to evaluate the destructive effects of hydro-fracturing in the rocks surrounding the borehole. The research was done by Institur of Geophisics team on the basis of observations and monitring at the Wysin site (the eighteenth well drilled in shale-gas concession in the so-called shale region of Pomerania, Poland, nearly 4000 m deep).
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A Correlation Analysis Between Injection Rates And Magnitude Distribution In The Geysers Geothermal Field
Authors K. Leptokaropoulos, S. Cielesta and M. StaszekSummaryThe magnitude distribution variation in the north western part of The Geysers geothermal field is studied. Various types of b-value analysis are performed in order to investigate thoroughly the impact of fluid injection to magnitude distribution. Other parameters such as distance from the open hole of the injection well are also investigated. The analysis performed in this study indicated that b-values are significantly positively correlated to injection rate fluctuations whereas no significant influence of the seismicity rates and the distance from the injection well on b-values was detected.
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Uncertainty Of B-Value Estimation In Connection With Magnitude Distribution Properties Of Small Data Sets
Authors K. Leptokaropoulos and A. AdamakiSummaryWe evaluate the efficiency of the maximum likelihood estimator introduced by Aki (1965) , using synthetic datasets exhibiting diverse but well defined properties. The deviation of the b-value estimation from its real value is quantified by Monte Carlo simulations as a function of catalogue features and data properties such as the sample size, the magnitude uncertainties distribution, the round-off interval of reported magnitude values and the magnitude range. Within the objective of this study, algorithms have been compiled for the determination of such observational-theoretical deviations and to facilitate the construction of nomograms corresponding to diverse cases of input parameters. In this way, a more accurate estimation of the uncertainty level for the b-value and MC determination can be achieved, contributing to a more robust seismic hazard assessment, especially at low activity areas and induced seismicity sites. Our results indicate that b-value analysis, especially for small datasets should be carried out together with Magnitude range analysis. Nomograms should be constructed and adjusted to each particular case study in order to achieve a more accurate estimation of the b-value and the corresponding uncertainty.
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The Sheer Approach To Shale Gas Exploration And Exploitation Associated Risks
Authors S. Cielesta, S. Lasocki, K. Leptokaropoulos and S. CescaSummaryThe abstract presents the SHEER project that primarily aims at assessing the environmental impacts of shale gas extraction and exploration, and secondly, at developing best practices to reduce its environmental footprint.
The description of SHEER database comprising multidisciplinary data concerning the shale gas exploitation test sites, processing procedures, results of data interpretation and recommendation as well as other documents describing the state of the art is included.
One of the test sites is the real-time research monitoring field at Wysin, Pomerania, where the hydraulic fracturing took place. The seismic monitoring main aim was to detect microseismic events at the fracturing site and therefore contribute to a better characterization of the induced seismicity related to the shale gas extraction Finally, a collaboration between SHEER and IS-EPOS project is presented within the Thematic Core Services – Anthropogenic Hazard e-Platform.
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Active Mapping Of Geologic Structures Using Microseismicity And Their Role In Large Magnitude Occurrences Associated With Water Flooding
Authors I. Nizkous and T. UrbancicSummaryCapturing information on geologic structures in reservoirs into geo-cellular models traditionally has relied on the use of seismic data when no surficial evidence is found. In many ways, the resolution of these data sets may be insufficient to identify not only structures that could affect reservoir performance but the dynamic response to the common production and enhanced oil recovery. Conventional seismic structural interpretation has no additional information about how these structures behave in the presence of a dynamic stress field resulting from different injection based EOR approaches, for example, water flood, steam or gas operations.
In this paper, we outline how long term micro-earthquake monitoring of a reservoir can not only be used to identify these potentially hazardous geologic structures, but through collective behavior of micro-earthquakes we can identify the spatial variability in deformation and stress associated with any particular fault zone, which consists of several active parts that can behave differently over time.
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Aftershocks And Seismic Efficiency For The Cooper Basin (Australia) Geothermal Stimulation
Authors E. Caffagni, G. Bokelmann and F. FuchsSummaryUsing data from the geothermal field in the Cooper Basin (South Australia), we study the relationship between the horizontal and vertical relative location of consecutive events (RLCE) and magnitude.
The obtained spatial distribution of RLCE shows a striking shape, in that it suggests a magnitude dependence, with smaller event separations towards higher magnitudes. This effect is real, and apparently caused by the existence of aftershocks for low to moderate energy events.
In order to understand the factors controlling induced seismicity, we investigate the relation between the injected volume and seismic moment. Seismicity appears predominantly controlled by the fault area rather than the injected volume.
Finally, estimations of the seismic efficiency provide the basis for a distinction between “triggered” and “induced” events.
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Laboratory Acoustic Emission Test With A Brittle Shale Cap-Rock
Authors J. Park, L. Grande, M. Soldal, G. Sauvin and B. BohloliSummaryThe integrity of cap-rock is a critical issue for both injection and production operations and we need to make sure that any induced alteration in the subsurface is within acceptable range. For such a purpose, micro-seismic is a useful technique. However, it is not always the case that we can record events, as shown in the current study. Therefore, it is recommended to perform extensive laboratory-based AE tests with different lithology and all possible stress conditions (path, rate, etc.). From such datasets and experiences, we can have better and confident ideas of how to interpret acquired field-scale micro-seismic data by linking to geomechanical behaviors of cap-rock.
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A New Conceptual Model For Enhancement And Inhibition Of Low-Magnitude Microseismic Events Related To Fluid Injection
Authors B. Bohloli, T.I. Bjørnarå, V. Oye and B. Goertz-AllmannSummaryMicroseismic events have been observed during many fluid injection projects and are generally related to hydraulic fracturing or re-activation of pre-existing, critically stressed weakness zones. However, microseismic events have also been recorded in several cases where injection pressure is quite low and below the estimated fracture pressure. The primarily assumed mechanism for such events is that the rock was critically stressed and brought to failure by small stress changes, related to the load changes and/or pore pressure changes. This paper explains a new and additional possibility to enhance or inhibit the generation of small microseismic events through an interdisciplinary approach based on the Lugeon test analysis. We analyze the successive evolution of injection pressure versus injection rate of CO2. Based on the type of flow patterns, fluid flow is classified into characteristic groups proposed by Houlsby (1976) . Different flow patterns such as turbulent, laminar, and washout were observed throughout the CO2 injection at e.g. In Salah. Mobilization (wash-out) of fines and clogging of pores affect the pore pressure and may destabilize rock blocks. Effective stress acting on fractures also changes upon injection shut-in/restart, possibly causing small displacements of a rock block and result in a low-magnitude microseismic event.
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Toward Offshore Microseismic Data Source Mechanism Determination - A Synthetic Sensitivity Study
Authors N. Langet, A. Wüstefeld and V. OyeSummaryWe propose in this paper to test the sensitivity of the inversion of wave amplitudes for the source parameters determination.
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Downhole Microseismic Monitoring At A Pilot Hydraulic Fracturing Site In Poland
Authors W. Gajek, J. Trojanowski and M. MalinowskiSummaryA precise velocity model is necessary to obtain reliable locations of microseismic events, which provide information about the effectiveness of the hydraulic stimulation. Seismic anisotropy plays an important role in microseismic event location by imposing the dependency between wave velocities and its propagation direction. Building an anisotropic velocity model allows for more accurate location of microseismic events. In this paper we develop a workflow for a VTI velocity model construction in the absence of SH-waves in perforation shots data. SH-waves carry information about Thomsen’s γ parameter and provide constraints for microseismic events locations. We extract effective ε, δ and VP0, VS0 for each layer from P- and SV-waves arrivals of perforation shots, while the unresolved γ is retrieved from selected microseismic events’ SH-SV-waves delay time, afterwards. Finally we present an accurate locations of microseismic events recorded during a pilot stimulation job located in Northern Poland.
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Developing An Inversion Algorithm For A Velocity And Location Of Microseismic Events Using The Maximum Intersection Method In Linear Velocity Gradient Model
More LessSummaryWe suggest a simple inversion algorithm to find the location of microseismic event. We used a linear velocity gradient model to simplify the algorithm. It can estimate the vertical velocity gradient of model and the location of microseismic events using the Maximum Intersection (MAXI) method. It can remove the effect of origin time and increase the number of data. We also modified the forward problem equations to solve the numerical instability of previous forward problem by using the definition of ray parameter. We verified our algorithm using the synthetic data set which is generated by mimicking the well logging data. We could obtain the velocity information and meaningful location of microseismic event.
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The Largest Event Of The Dfw Seismicity 3 Years After The Injection Termination - Is It An Evidence for Natural Origins Of Dfw Seismicity?
Authors P. Woźniakowska, L. Eisner and M. MusilSummaryThe study showed that the largest seismic event in the DFW area occurred more than 2 years after stopping of 9 months long salt water disposal injection. The largest event of September 30, 2012 with magnitude 3.4 (mblg) is similar to events occurring during the years 2008 and 2009. The events observed during the years of 2008 and 2009 became known as triggered by salt water disposal in the immediate vicinity of the DFW airport. However, seismological evidence shows that seismicity continues for more than 2 years after the waste water disposal was terminated, that the seismicity occurs along natural pre-existing fault, magnitudes of these events increase. These observations seem to be more consistent with natural creep along a slowly slipping fault.
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Seismic Attenuation In The Delaware Basin
Authors M. Drwila, L. Eisner, Z. Jechumtálová and D. AnikievSummaryInduced seismicity in Delaware Basin (West Texas and New Mexico, USA) has recently gained attention of the geoscience community. The knowledge about seismic attenuation in this sedimentary basin is poor. The peak frequency method was applied to the selected seismic events with high signal-to-noise ratio from the Delaware Basin to estimate effective quality factors of the basin sediments. The observed attenuation can be characterized by Q factors of approximately 90 and 100 (with uncertainty of 30) for P-wave and S-waves, respectively. The ratio between Qp and Qs is common for saturated sedimentary basins as they are less attenuating the S-waves.
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A Comparison Of Microseismic Source Location Methods: Probabilistic Vs. Migration-Based Approaches
By I. AbakumovSummaryLocalization of induced microseismic events is a vital element of passive seismic monitoring. Currently, a variety of techniques for localization of microseismic events are available in the literature. These techniques employ various information from the recorded wavefields and are based on different theoretical considerations. In this report, we compared the location results, obtained by three different techniques, namely traveltime inversion, diffraction stacking and cross-correlation stacking. We found out that for the majority of events the location results obtained with three different methods almost perfectly coincide. Furthermore, we observed that the mismatch of the location results can be used as a quality control tool to identify misinterpretation of phases, errors of arrival time picking, multiple events, etc.
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Recent Seismicity in West Texas
Authors A. Savvaidis, D. Huang, A. Lomax and B. YoungSummaryIn recent years, possible induced seismicity has been detected in the southern mid-continent of the U.S., including Texas. These events have led to substantial public discussion regarding the cause and potential risks of damage to infrastructure and to public safety. In an effort to better understand the seismogenesis of these events and to monitor earthquake activity, a statewide seismic monitoring program, known as TexNet, has been funded by the 84th Texas Legislature to deploy seismic stations in Texas. The goal of TexNet is to provide authenticated data to evaluate the location, frequency, and likely causes of natural and induced seismicity. It is suggested that seismicity is associated with oil and gas production (e.g., development of hydrocarbon extraction) and/or wastewater injection. A better understanding of these seismic events will help stakeholders avoid operational procedures that may lead to the occurrence of induced earthquakes.
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Synthetic Modelling Of A DAS Cable’s Sensitivity And Performance In Microseismic Monitoring Applications
Authors M. Wilks and A. WuestefeldSummaryWe assume two DAS cable geometries of 300 recording channels that replicate the Oseberg PRM (seafloor array) and a deviated well (akin to that used in hydraulic fracturing). We calculate the longitudinal strain at each channel, subject to the amplitude relationships described by Kuvshinov (2016) , for P-waves and a coupled-cable to-medium case. The DAS cable’s sensitivity across the medium is investigated for differing wrapping angles of helical fibre. We then test how a 3D event location performs in these scenarios and create probability density estimates of the mislocations. These findings and the future implications for DAS as a viable microseismic monitoring technique are then discussed.
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Application Of Tomography And Dynamic Parameter Analysis In A Block Caving Mine
Authors G. Viegas, K. Bosman, D. Angus and T. UrbancicSummaryWe use seismic passive tomography and micro-seismic clustering techniques (Dynamic Parameter Analysis — DPA) as interpretive tools to understand the continual time and spatial evolution of local stresses in a block caving mine. We perform weekly analysis using a rich micro-seismic dataset recorded with a local system. In DPA we combine the collective behavior of many micro-seismic events that occur in the same rock volume, to describe the temporal-spatial deformation of the rockmass and identify dynamic stress changes. In Tomography we use micro-seismic event travel time information to resolve subtle variations in the velocity structure which can be related to stress changes and rock damage. Combining the information from the two methods allows for a more robust interpretation of the results. We illustrate the applicability of the two methods by showing an example of stress loading on a lateral cave wall during cave development and subsequent de-stressing. This information is extremely useful in the control of the block cave development, the geometry of the associated surface subsidence, and for block caving managing operations including load support, blast sequencing to redistribute concentrated loads (high stress regions).
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Origins Of Rayleigh Wave Overtones In Ambient Noise
Authors A. Kazantsev, M. Peruzzetto, H. Chauris, P. Dublanchet and F. HuguetSummary2D spectral element simulations in the frequency range 0.1–3 Hz were performed on a large-scale model (1200×50 km). Ocean water, sediments, granitic crust and mantle were included. Two seismic arrays were modeled on the continent in order to analyze the wavefield composition on the granitic crust and above a sedimentary basin. Four source locations were tested: ocean surface in deep and shallow water, ocean bottom and continental surface near the array. Finally, the effect of removing the mantle from the simulation was investigated. The deep-water surface source was able to excite a clear Lg phase, which disappeared when the mantle was removed. The Lg phase, in turn, excited the overtones above the sedimentary basin. The Rayleigh fundamental mode was dominant for the other investigated source locations. This might explain the presence of the Lg phase and Rayleigh overtones in the short-period seismic noise, which is probably a signature of shortperiod sources near the surface in deep ocean.
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How The Choice Of Location Algorithm Affect Results: A Synthetic Comparison
Authors A. Wuestefeld, S.P. Näsholm and S.M. GreveSummaryA priori assessment of the expected location accuracy of a sensor network is typically done through inversion of the travel-time spatial gradients. This approach assumes that the applied location algorithm successfully recovers the global minimum of the objective function. However even for phase-picks without errors, complexity in the velocity model and limitations in network layout may inhibit the finding of a global minimum. The location algorithms may end up in a local minimum instead. This study focuses solely on the algorithmic aspects of the event location procedure. For a series of synthetic microseismic event locations, we calculate arrival times, add picking errors, and then feed these synthetic picks into a set of different location routines which look for minima in selected misfit objective functions. While most of the analyzed location approaches mainly lead to good location results, none of the analyzed approaches recovered the correct location for all event locations.
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Remote Real-Time Processing Of Hydraulic Fracture Treatment Microseismic Data Using Large Arrays
More LessSummaryReal-time processing of microseismic downhole data has been performed for many years, see for example Maxwell et al. (2000) . Downhole data lends itself to real-time processing, because the data volume is relatively small, typically less than 200 channels, and the relative high signal/noise ratios of downhole data makes it possible to perform “event triggering” to identify isolated segments of data that contain events, which can be remote transmitted to remote processing centers. Real-time microseismic processing of surface data is also not new, see for example Furong et al. (2017) . But real-time microseismic processing of surface data is generally done by placing large and expensive compute resources in the field, such as specialized trucks that are outfitted to house clusters of computers. Here we describe a workflow whereby data from large surface arrays with over 2,000 channels are processed in real time remotely, and we describe the benefits of this workflow for hydraulic fracture treatments.
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The Enigma Of Dip-Slip And Aligned Strike-Slip Events Within The Same Event Cloud
Authors W.M. Heigl, D.E. Diller, B. Fish, T. Shuck and S. WilsonSummaryOver the past decade, various authors have observed a dominance of dip-slip or strike-slip P-wave first motion patterns and the juxtaposition of both within the same microseismic event cloud (e.g. Eisner & Stanek, 2017 ; Tan & Engelder, 2016 ; Wilson & Diller, 2016 ; Diller et al., 2015 ; and references therein). The steeper, and sometimes near vertical, nodal plane of these dip-slip first motion patterns is often found to strike approximately parallel to the direction of maximum horizontal stress ( Fig. 1 ). Aligned strike-slip first motion patterns show a similar behavior: steeply dipping nodal planes and one of them striking parallel to the direction of maximum horizontal stress ( Fig. 2 ). Moreover, Rutledge et al. (2015) showed that both dip-slip and strike-slip events can concentrate in discrete depth intervals. One type of mechanism tends to dominate in a given reservoir, presumably reflecting different regional stress states. Tan and Engelder (2016) demonstrate that events in neighboring clusters can have opposing P and S wave polarities …
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Microseismicity To Production - What Do We Need To Measure First?
More LessSummaryCurrently there are four widely discussed theories how microseismicity interacts with hydraulic fracturing. Each theory has different implication for interpretation of microseismicity in the reservoir modeling. Therefore, better understanding of relationship between microseismicity and hydraulic fracture stimulation is needed before further reservoir models are developed and applied. That would lead to more precise estimation of hydrocarbon production and give greater value to microseismic. We may use either seismic or non-seismic methods. While non-seismic methods provide independent view on hydraulic fracture they seem to be limited in the amount of information on the relationship between hydraulic fracture and microseismicity. We propose microseismic monitoring of directivity as the most promising way to find out the orientation of fault planes and determine a slip vector on them. It seems to be the most suitable method but requires sensors in multiple azimuths and well coupled due to high frequency signals. We suggest using DAS sensors which are capable of sampling high frequency and may provide continuous data along long offset at reasonable costs.
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