Technical Papers
The following technical papers provide information on reservoir characterization using microseismic monitoring, geological microseismic fracture mapping and more.
Natural Fracture Characterization from Microseismic Source Mechanisms: A Comparison with FMI Data
Jo Ellen Kilpatrick, Leo Eisner, Sherilyn Williams-Stroud, Brian Cornette Microseismic Inc., Morris Hall, Williams
Expanded Abstracts | SEG | 2010Microseismic monitoring of hydraulic fracture stimulations is used to determine the extent of fractured rock resulting from the treatment by mapping the locations of induced microseismic events. Usually the geometry of the event locations is used to infer fracture orientations; e.g. trends of microseismic events concentrated along a particular azimuth (or with a planar distribution in 3D) can indicate fracturing along a plane with that orientation. In this study we use additional parameters extracted from induced microseismic events (source mechanisms) to determine the specific fracturing behavior and compare them with independent observations from an FMI log in the treatment well. In a horizontal well located in the mid-Continental USA, we present the results of source mechanism analysis for the best signal-to-noise events triggered by the fracture stimulation treatment. The microseismic events with source mechanisms have failure planes with very similar orientations to natural fractures in the image log. Our results are consistent with the reactivation of natural fractures during the stimulation treatment, suggesting that it is possible to determine natural fracture orientations in the reservoir in cases where image logs are not available. In addition, the microseismic event source mechanisms allow fracture characterization away from the wellbore, providing critical constraints for building fractured reservoir models.
Techniques to estimate fracture effectiveness when mapping low-magnitude microseismicity
Sherilyn Williams-Stroud, MicroSeismic Inc., Randal L. Billingsley, Tracker Resource Development, llc.
Expanded Abstracts | SEG | 2010Hydraulic fracture mapping by locating microseismic events related to rock fracturing is used to evaluate the effectiveness of the stimulation in low-permeability reservoirs. The geometry of the events is used to infer fracture orientation, particularly in the case where events line up along an azimuth, or have a planar distribution in 3 dimensions. When the induced the microseismic events have a low signal-to-noise ratio (either due to low magnitude or propagation effects) their locations can have a high degree of uncertainty. Low signal-to-noise events are not as accurately located in the reservoir, or are not detected at all, so that the extent of fracture stimulated reservoir may be underestimated. In the Bakken Formation of the Williston Basin, we combine geological analysis with process-based and stochastic fracture modeling to build multiple possible fracture model realizations. Specific parameters in the models can be modified while honoring a realistic range for each parameter in order to explore the range of uncertainty. Fracture flow properties generated from the fracture models are validated via history matching iterations. The validated fracture models, in turn, provide a means to calculate a geometrically-constrained volume of rock and fracture permeability that can be used for estimating production. This paper presents a methodology for deciding which fracture parameters to vary (the high sensitivity parameters) in order to minimize the number of realizations that need to be generated during the model conditioning phase of a reservoir simulation program.
Reservoir characterization using surface microseismic monitoring
Peter M. Duncan and Leo Eisner
Geophysics | Vol. 75 | September-October 2010Microseismic monitoring of reservoir processes can be performed using surface or near-surface arrays. We review the published technical basis for the use of the arrays and the historical development of the method, beginning with locating earthquakes through geothermal exploration to the growing field of hydraulic-fracture monitoring. Practical considerations for the array deployment and data processing are presented. The road ahead for the technology includes a move toward life-of-field buried arrays as well as opportunities for extended interpretation of the data, particularly inversion for source-mechanism estimation and measurement of anisotropy in the monitored subsurface.
Comparison of surface and borehole locations of induced seismicity
Leo Eisner1, B. J. Hulsey, Peter Duncan, Dana Jurick, Heigl Werner and William Keller
Geophysical Prospecting | EAGE | December 2009Monitoring of induced microseismic events has become an important tool in hydraulic fracture diagnostics and understanding fractured reservoirs in general. We compare microseismic event and their uncertainties using data sets obtained with surface and downhole arrays of receivers. We first model the uncertainties to understand the effect of different acquisition geometries on location accuracy. For a vertical array of receivers in a single monitoring borehole, we find that the largest part of the final location uncertainty is related to estimation of the backazimuth. This is followed by uncertainty in the vertical position and radial distance from the receivers. For surface monitoring, the largest uncertainty lies in the vertical position due to the use of only a single phase (usually P-wave) in the estimation of the event location. In surface monitoring results, lateral positions are estimated robustly and are not sensitive to the velocity model.
In this case study, we compare event location solutions from two catalogues of microseismic events; one from a downhole array and the second from a surface array of 1C geophone. Our results show that origin time can be reliably used to find matching events between the downhole and surface catalogues. The locations of the corresponding events display a systematic shift consistent with a poorly calibrated velocity model for downhole dataset. For this case study, locations derived from surface monitoring have less scatter in both vertical and horizontal directions.
Observation of shear-wave splitting from microseismicity induced by hydraulic fracturing: A non-VTI story
Petr Kolinsky, Leo Eisner, Vladimir Grechka, Dana Jurick, Peter Duncan
EAGE | Amsterdam, The Netherlands | June 2009Shear waves from microearthquakes induced by hydraulic fracturing are observed on three-component (3C) accelerometers along a 2 km surface profile. The S-wave waveforms exhibit at least two distinct phases suggesting shear-wave splitting. This observation implies the exis-tence of shear anisotropy between the stimulated reservoir and the surface array. We develop and apply several methods to measure the time delay between the two arrivals. The observed shear-wave splitting suggests that something other than vertical transverse isotropy (VTI) is being encountered at this observation site. This observation may explain why S-waves do not improve location accuracy of microseismic events from surface locations as isotropic or VTI model will not focus S-wave energy recorded at long offsets.
Geological Microseismic Fracture Mapping Methodologies for Improved Interpretations Based on Seismology and Geologic Context
S. C. Williams-Stroud and Leo Eisner
CPSG CSEG CWLS Convention | Alberta, Canada | 2009The results of microseismic monitoring of hydraulic fracture treatments are significantly more valuable when a high-confidence interpretation of results can be done. The most common approach is to look for trends, or directions, along which microseismic events line up that would indicate the direction of induced fractures. This type of interpretation is more difficult when the signal is low or when the events appear to define multiple directions. Analysis of geologic structures in the area of the reservoir can provide useful information to support or eliminate interpretations of apparent trends as stimulated fractures, as well as provide an explanation for fracture trends that deviate from the expected orientation from the in-situ stress directions. In some cases, structural geology observed at the surface can be extrapolated to the subsurface to aid the interpretation. When seismic reflection scale horizon and fault interpretations are available, they can be used to infer that smaller scale faults and fractures of similar orientation may have been activated at the wellbore. Inversion of seismic source mechanisms for microseismic events provides the most wellconstrained parameters to describe the failure mechanisms of the hydraulic fracture treatment, and by combining this information with the geologic context a better understanding of the reservoir rock behavior during the stimulation treatment can be developed. In this paper, examples will be presented that describe interpretations of microseismic monitoring results based on geologic context and confirmed by source mechanism inversions.
Noise suppression for detection and location of microseismic events using a matched filter
Leo Eisner, David Abbott, William B. Barker, James Lakings and Michael P. Thornton, Microseismic Inc.
Expanded Abstracts | SEG | 2008Detection and location of microseismic events is generally limited by seismic noise and inversion velocity model accuracy. These issues can be overcome by using "a matched filter" in order to stack scattered energy and reduce demands on the accuracy of the inversion velocity model for events with similar mechanisms and nearby locations. We have applied the technique to a surface monitoring dataset of the microseismic events induced by hydraulic fracturing to detect and relatively locate events. We have benchmarked detection and relative location with a direct location technique (PSET® technology).
Data Acquisition, Transfer and Processing for Multi Channel Permanent PMM Systems
I. Weir-Jones (Weir-Jones / Terrascience Groups), P.M. Duncan, Ph. D. (Microseismic, Inc.), S.A. Shore, C.D., P.Eng. (Weir-Jones / Terrascience Groups) & S.M.J. Taylor, B.Sc. (Weir-Jones / Terrascience Groups)
EAGE | Dubai, United Arab Emirates | December 2006This 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.
Design Considerations for Cost Effective PMM Systems
I. Weir-Jone (Weir-Jones / Terrascience Groups), P.M. Duncan, Ph.D. (Microseismic, Inc.), S.A. Shore, C.D., P.Eng. (Weir-Jones / Terrascience Groups) & S.M.J. Taylor, B.Sc. (Weir-Jones / Terrascience Groups)
EAGE | Dubai, United Arab Emirates | December 2006This 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.
Frontier Exploration Using Passive Seismic
P. Duncan (MicroSeismic, Inc.) & J. Lakings (MicroSeismic, Inc.)
EAGE | Dubai, United Arab Emirates | December 2006We present a case history of 3D 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.
Microseismic Monitoring with a Surface Array
P. Duncan (MicroSeismic, Inc.) & J. Lakings (MicroSeismic, Inc.)
EAGE | Dubai, United Arab Emirates | December 2006We 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.
