Microseismic Source Research Articles

Petroleum reservoir characterization using downhole microseismic monitoring

Imaging of microseismic data is the process by which we use information about the source locations, timing, and mechanisms of the induced seismic events to make inferences about the structure of a petroleum reservoir or the changes that accompany injections into or production from the reservoir. A few key projects were instrumental in the development of downhole microseismic imaging. Most recent microseismic projects involve imaging hydraulic-fracture stimulations, which has grown into a widespread fracture diagnostic technology. This growth in the application of the technology is attributed to the success of imaging the fracture complexity of the Barnett Shale in the Fort Worth basin, Texas, and the commercial value of the information obtained to improvecompletions and ultimately production in the field. The use of commercial imaging in the Barnett is traced back to earlier investigations to prove the technology with the Cotton Valley imaging project and earlier experiments at the M-Site in the Piceance basin, Colorado. Perhaps the earliest example of microseismic imaging using data from downhole recording was a hydraulic fracture monitored in 1974, also in the Piceance basin. However, early work is also documented where investigators focused on identifying microseismic trace characteristics without attempting to locate the microseismic sources. Applications of microseismic reservoir monitoring can be tracked from current steam-injection imaging, deformation associated with reservoir compaction in the Yibal field in Oman and the Ekofisk and Valhall fields in the North Sea, and production-induced activity in Kentucky, U.S.A.

The 1998 Valhall microseismic data set: An integrated study of relocated sources, seismic multiplets, and S-wave splitting

We relocate 303 microseismic events recorded in 1998 by sensors in a single borehole in the North Sea Valhall oil field. A semiautomated array analysis method repicks the P- and S-wave arrival times and P-wave polarizations, which are needed to locate these events. The relocated sources are confined predominantly to a [Formula: see text]-thick zone just above the reservoir, and location uncertainties are half those of previous efforts. Multiplet analysis identifies 40 multiplet groups, which include 208 of the 303 events. The largest group contains 24 events, and five groups contain 10 or more events. Within each multiplet group, we further improve arrival-time picking through crosscorrelation, which enhances the relative accuracy of the relocated events and reveals that more than 99% of the seismic activity lies spatially in three distinct clusters. The spatial distribution of events and wave-form similarities reveal two faultlike structures that match well with north-northwest–south-southeast-trending fault planes interpreted from 3D surface seismic data. Most waveform differences between multiplet groups located on these faults can be attributed to S-wave phase content and polarity or P-to-S amplitude ratio. The range in P-to-S amplitude ratios observed on the faults is explained best in terms of varying source mechanisms. We also find a correlation between multiplet groups and temporal variations in seismic anisotropy, as revealed by S-wave splitting analysis. We explain these findings in the context of a cyclic recharge and dissipation of cap-rock stresses in response to production-driven compaction of the underlying oil reservoir. The cyclic nature of this mechanism drives the short-term variations in seismic anisotropy and the reactivation of microseismic source mechanisms over time.

Microseismic source deconvolution: Wiener filter versus minimax, Fourier versus wavelets, and linear versus nonlinear

Deconvolution is commonly performed on microseismic signals to determine the time history of a dislocation source, usually modeled as combinations of forces or couples. This paper presents a new deconvolution method that uses a nonlinear thresholding estimator, which is based on the minimax framework and operates in the wavelet domain. Experiments were performed on a steel plate using artificially generated microseismic signals, which were recorded by high-fidelity displacement sensors at various locations. The source functions were deconvolved from the recorded signals by Wiener filters and the new method. Results were compared and show that the new method outperforms the other methods in terms of reducing noise while keeping the sharp features of the source functions. Other advantages of the nonlinear thresholding estimator include (1) its performance is close to that of a minimax estimator, (2) it is nonlinear and takes advantage of sparse representations under wavelet bases, and (3) its computation is faster than the fast Fourier transform.

Improvements in mining induced microseismic source locations at the Lucky Friday Mine using an automated whole-waveform analysis system : Dodge, D A; Sprenke, K F Pure Appl GeophysV139, N3/4, 1992, P609–626

Improvements in mining induced microseismic source locations at the Lucky Friday Mine using an automated whole-waveform analysis system : Dodge, D A; Sprenke, K F Pure Appl GeophysV139, N3/4, 1992, P609–626

Microseismic logging: a new hydraulic fracture diagnostic method : Mahrer, K D SPE Form EvalV8, N1, March 1993, P41–49

Hydraulic fracture treatments and fluid injections into fractured wells induce a useful cloud of microseismic sources in the fractured zone. This induced seismicity can last for hours after pumping and pervades the fracture. The source-size population distribution ranges from a countable (50 to 500) number of large, individually distinguishable events to a din of background events. Each source radiates wave motion, which can be recorded only in and near the fracture. A new method uses these motion data, recorded in the cased treatment well, to determine the fracture height and azimuth. The height is found by delineating the location and vertical extent of a spatial anomaly in the background-motion data. The azimuth is derived from the particle-motion polarization of the largest events of the microseismic event population

Practical application of an innovative microseismic source location procedure : Ge, M; Kaiser, P K Int J Geotech Geol EngngV10, N3, Sept 1992, P163–184

Practical application of an innovative microseismic source location procedure : Ge, M; Kaiser, P K Int J Geotech Geol EngngV10, N3, Sept 1992, P163–184

Microseismic Logging: A New Hydraulic Fracture Diagnostic Method

Summary Hydraulic fracture treatments and fluid injections into fractured wells induce a useful cloud of microseismic sources in the fractured zone. This induced seismicity can last for hours after pumping and pervades the fracture. The source-size population distribution ranges from a countable (50 to 500) number of large, individually distinguishable events to a din of background events. Each source radiates wave motion, which can be recorded only in and near the fracture. A new method uses these motion data, recorded in the cased treatment well, to determine the fracture height and azimuth. The height is found by delineating the location and vertical extent of a spatial anomaly in the background-motion data. The azimuth is derived from the particle-motion polarization of the largest events of the microseismic event population. This paper describes the method, exemplary data sets, theory, and simulations that substantiate this method.

Practical application of an innovative microseismic source location procedure

A detailed case study conducted at a Canadian gold mine is presented to demonstrate the practical usefulness of the source location data analysis theory developed by Ge and Kaiser (1990). The basic concept of the theory and the interpretation of the physical status of wave arrival picks is explained through a step-by-step analysis of several microseismic events. The effectiveness of the theory is illustrated by statistical data analysis. It is demonstrated that the theory enhances MP250 systems by providing an automatic microseismic source location technique.

Microseismic source locations: a test of faith : Estey, L H; Swanson, P L; Boler, F M; Billington, S Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18–20 June 1990P939–946. Publ Rotterdam: A A Balkema, 1990

Microseismic source locations: a test of faith : Estey, L H; Swanson, P L; Boler, F M; Billington, S Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18–20 June 1990P939–946. Publ Rotterdam: A A Balkema, 1990

Improvements in mining induced microseismic source locations at the Lucky Friday mine using an automated whole-waveform analysis system

For years, severe rockburst problems at the Lucky Friday mine in northern Idaho have been a persistent safety hazard and an impediment to production. An MP250 based microseismic monitoring system, which uses simple voltage threshold picking of first arrivals, has been used in this mine since 1973 to provide source locations and energy estimates of seismic events. Recently, interest has been expressed in developing a whole waveform microseismic monitoring system for the mine to provide more accurate source locations and information about source characteristics. For this study, we have developed a prototype whole-waveform microseismic monitoring system based on a 80386 computer equipped with a 50 kHz analog-digital convertor board. The software developed includes a data collection program, a data analysis program, and an event detection program. Whole-waveform data collected and analyzed using this system during a three-day test have been employed to investigate sources of error in the hypocenter location process and to develop an automatic phase picker appropriate for microseismic events.

Innovative micro-seismic source location technique : Ge, M; Kaiser, P K Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18–20 June 1990P43–50. Publ Rotterdam: A A Balkema, 1990

Innovative micro-seismic source location technique : Ge, M; Kaiser, P K Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18–20 June 1990P43–50. Publ Rotterdam: A A Balkema, 1990

Interpretation of physical status of arrival picks for microseismic source location

Abstract The automatic recognition of a microseismic event usually relies on two criteria: threshold voltage level and event recognition time window. Current microseismic source location techniques are severaly limited because the physical status of an arrival pick is not known. This paper presents a theory for the identification of the physical status of an arrival pick. It consists of an arrival time difference analysis and a residual analysis. The theory can be used to discriminate various types of arrival picks critical for microseismic source location. An event-based velocity model can then be established and used to determine the source location more accurately. The theory provides a unique approach that may be utilized in various automatic acoustic/seismic processing systems.

Wide‐angle triangulation array study of simultaneous primary microseism sources

Persistent low frequency noise between 10 and 200 mHz due to storm systems is commonly observed as microseisms on seismic records from land and ocean bottom detectors. We report on an analysis of 20‐second microseisms recorded simultaneously on two land‐based long‐period arrays (the Alaskan Long Period Array and the Large Aperture Seismic Array) during November 1973. Azimuths of approach are determined by applying frequency wave‐number analysis and beam‐forming techniques to coherent bandpass‐filtered samples of the microseismic noise field recorded by the arrays. Microseismic source azimuths exhibit sufficient stability over periods of one hour to permit determination of reliable source locations by triangulation with the two arrays. Locations for two microseism noise sources associated with two separate Atlantic and Pacific pelagic storms were found simultaneously with these methods. In both cases, the microseismic noise source appears to be associated with nearshore processes. Although the gross spectral character of the microseisms displays the commonly observed primary‐ and double‐frequency microseism peaks, slight spectral differences are apparent for the two noise sources.

Application of acoustic emission for the evaluation of microseismic source location techniques : Kat, M; Hassani, F P; Momoh, O A Proc 23rd Annual Conference of the Engineering Group of the Geological Society, Engineering Geology of Underground Movements, Nottingham, 13–17 Sept 1987P513–524. Publ Nottingham: University of Nottingham, 1987

This paper discusses the strengths and limitations of various source location techniques. The methods evaluated are; the Least Squares Direct (solving for a source using a constant velocity and solving for and source and velocity), Mount Isa, Simplex, Diminishing Cube and Simplex Combination approaches. Each technique is evaluated on the basis of its ability to accurately determine hypocenters from a variety of imperfect data. The data is a combination of simulated events, with S-wave triggers, P-wave velocity variations, and reliable P-wave arrival times. In addition, the methods were further evaluated using acoustic emissions from blast tests conducted at Brunswick Mining and Smelting Corporation's No. 12 mine

Improved determination of microseismic source location using a simplex technique

The monitoring of microseismic activity in geological formations of underground mines is discussed. The accuracy of a particular monitoring technique is subject to limitations of measurement precision, and errors in the determination of the correct phase of the incoming signal associated with the first arrival of the seismic wave. The value of the simplex technique for microseismic monitoring is illustrated through the presentation of experimental results in the determination of source location for a series of known-source test blasts. It is concluded that a careful analysis of the errors affecting each particular microseismic installation is a necessary step in understanding the capabilities of this particular system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Structural and vibrational bedrock properties in Sweden

Bedrock properties, of great concern in seismology as well as in numerous practical applications, are elucidated by means of short-period seismic wave propagation. Field work in central Sweden revealed the existence of a superficial granitic layer 1.4 km thick with lower wave velocities than the layer below. The brittle nature of the top layer is evidenced by low quality factors and is related to rockbursts in the vicinity of mines. By spectral techniques, the permanent Swedish network is used for quantitative estimation of ground motion (acceleration, regional magnitude, source energy) due to regional seismic events. For localization of teleseismic events and other signal combination, the whole network can be treated as a continental array, because of excellent signal coherence between the stations. Variations of sensitivity among the stations depend mainly upon relation to microseismic sources around the coasts. Our aim has been to elucidate the importance of bedrock properties for a number of different problems in pure and applied seismology.

Iterative approximation techniques for microseismic source location : Dechman, G H; Sun, M C USBM RI 8245, 1977, 13P

iterative approximation techniques for microseismic source location : Dechman, G H; Sun, M C USBM RI 8245, 1977, 13P

Microseismic source locations around block caving at the climax molybdenum mine : 8F. US BUR. MINES, RI 7798, 1973, 13P

Microseismic source locations around block caving at the climax molybdenum mine : 8F. US BUR. MINES, RI 7798, 1973, 13P

On Darbyshire's Method of Analysing Microseims

In a recent paper with the same title as this letter, Hurst (1968) has made some comments on my work on microseisms (Iyer 1958, 1959). He points out an error in Darbyshire’s equations and the ‘ false conclusions ’ I reached from them. Mathematically speaking Hurst is right. For a point source model of microseisms composed of Rayleigh and Love waves, it is true that in the horizontal components, the Rayleigh and Love parts are correlated in an opposite sense. In other words, in the horizontal components when the Rayleigh waves are in phase, the Love waves are out of phase, and vice versa. This leads to the modifications in Darbyshire’s equations as Hurst has pointed out. 1 indicated this effect in my thesis (1959) though I did not use the idea and change Darbyshire’s equations. I developed the equations in which two out of the three correlation coefficients were shown to be adequate to solve for 8 and LIR, mainly because r,, was consistently a smaller quantity than r,, and r,,, and it was often difficult to determine the peak in the correlation functions as plotted by the photoelectric correlationmeter. This was to be expected as the correlation function was the composite of two independent functions, the Rayleigh part and the Love part. Hence it was considered desirable to avoid using r,,, to estimate 0, if possible. When this was found feasible, I decided to use the new equations. After all when a problem can be solved with two measurements, why use three, especially when the third quantity is not as stable as the other two? From another point of view also, it seems I was justified in modifying Darbyshire’s equations. In the light of developments that have taken place in the science of microseisms during the last ten years, a signal-plus-noise model for microseisms seems more realistic than a point Rayleigh-Love source. The fact that r,, M r,,:r,, in many cases seems to point out that the contribution to the correlation function made by what I called ‘ Love waves ’ was small. Work done by Haubrich et al. (1963) has shown that a good part of microseisms recorded at La Jolla consists of Rayleigh waves associated with an extended source, generated, probably by coastal ocean waves. Hence my work was a beginning of the concept of a point source of microseisms ‘ polluted ’ by isotropic noise. I called the noise ‘ Love waves ’, which is probably wrong. It can be seen that ‘ incoherent ’ noise in the horizontal components can lead to a positive value of I,.., which is very nearly equal to the product of r,, and rYz. One can generate models with Love and Rayleigh waves of varying degrees of isotropicity combined together. From our recent knowledge of the structure of microseismic sources gained by the use of extended seismic arrays, the sobering thought emerges that any model for microseismic sources is a beginning and not the end of the problem. Hence I would like to point out that my model of point source of Rayleigh waves mixed with Love waves from wide-angle sources is not ‘ a priori improbable ’, but one way of looking at the problem from data available at that time. I am grateful Of course, this game can be played in more ways also.

On microseismic sources : Proskuryakova T. A., 1965. (In Russian; English abstract). Seism. Issled., Rezult, Issled, Mezhd. Geofiz. Proekt., Mezhd. Geofiz. Komitet. Presidiume Akad. Nauk. SSSR, No. 6: 23–30.

On microseismic sources : Proskuryakova T. A., 1965. (In Russian; English abstract). Seism. Issled., Rezult, Issled, Mezhd. Geofiz. Proekt., Mezhd. Geofiz. Komitet. Presidiume Akad. Nauk. SSSR, No. 6: 23–30.