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dc.contributor.advisorSimmons, James
dc.contributor.authorMurphy, Samuel T.
dc.contributor.committeememberTrainor-Guitton, Whitney
dc.contributor.committeememberTrudgill, Bruce, 1964-
dc.contributor.committeememberTutuncu, Azra
dc.contributor.committeememberHearon, Thomas E.
dc.date.accessioned2020-02-03T11:28:56Z
dc.date.available2020-02-03T11:28:56Z
dc.date.submitted2019
dc.descriptionIncludes bibliographical references.
dc.description2019 Fall
dc.description.abstractThe unconventional oil and gas industry is convinced that fractures are one of the main differentiators between a good and bad well. Though, fracture delineation within unconventional reservoirs still bares substantial uncertainty. Well logs and surface seismic data try to characterize areas in an effort to populate fracture networks. Unfortunately, logs represent near-wellbore phenomena and 3D seismic data have inherently low frequency content; you are limited to a scale of faulting that can be seen at this resolution. Microseismic data are commonly used to locate induced fractures, but their naturally high temporal frequency content can create reflection images of these “Discrete Fracture Networks” (DFNs), effectively boosting resolution beyond what is observed in 3D seismic. The goal of this research is to use time-lapse microseismic data and image the microseismic reflection information to produce a much higher resolution of the reservoir target area. In addition, we can take this information and propagate it geostatistically throughout a 3D seismic volume, in hopes of achieving better regional insight into the mechanisms that control hydraulic fracturing. Two wells were hydraulically fractured in the Niobrara in 2010 followed by a well placed in the deeper Greenhorn area and subsequently completed in 2014. Vertical distance between the Niobrara and Greenhorn well targets is 500 feet. A vertical monitor well (Bevo) was placed in the center of these treatment wells to maximize coverage (vertically straddling each formation and monitoring as close as 300 feet away) along the mid-lateral area of each well. Research data surrounding these wells consist of 3D seismic, microseismic and well log data in the Hereford Field, Northeastern Colorado, in the Denver-Julesburg Basin. Analyses of time-lapse microseismic data were performed on the Longhorn B3 (Niobrara), B5 (Niobrara) and G4 (Greenhorn) horizontal wells, monitored from a geophone-array in the Bevo vertical well. Microseismic event locations from the G4 completion show propagation upward to the B5 well, indicating preferential growth towards potential depletion of the overlying Niobrara. 3D seismic data show faulting in the area, suggesting hydraulic fracture conduits. Microseismic reflection imaging displays smaller scale fractures coinciding with larger faults in the area. Time-lapse velocity results showed that, over a 4-year time period, significant velocity changes were observed, suggesting that a combination of depletion, pore-pressure and fracture network changes have occurred. The x- and y- dimensions of the microseismic image volumes are 700 x 700 feet, but the determined reliable microseismic imaging area is 300 x 300 feet, due to the geometry of the experiment and associated Kirchhoff depth migration artifacts. This research not only proves that we can achieve higher resolution reservoir insight, but it also tells us that there are many more variables involved and they should be considered when drilling and completing future wells.
dc.identifierMurphy_mines_0052N_11874.pdf
dc.identifierT 8869
dc.identifier.urihttps://hdl.handle.net/11124/174007
dc.languageEnglish
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.rightsCopyright of the original work is retained by the author.
dc.subjectFractures
dc.subjectMicroseismic
dc.subjectTime-lapse velocity modeling
dc.subjectKirchhoff depth migration
dc.subject3D seismic
dc.subjectReflection imaging
dc.titleTime-lapse study of microseismic velocity and reflection imaging, A
dc.typeThesis
thesis.degree.disciplineGeophysics
thesis.degree.grantorColorado School of Mines
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (M.S.)


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