6 Matching Results

Search Results

Advanced search parameters have been applied.

Microseismic monitoring as a tool for mapping fractures in the San Andres dolomite

Description: Microseismic monitoring shows promise of being a practical tool for mapping fractures in the San Andres dolomite in terms of rate of microearthquake occurrence and the areal coverage possible from a single downhole seismometer. Microearthquakes were detected during normal waterflood production but monitoring was not complete enough to correlate injection/production activity with microseismic event recurrence. Constant monitoring time capability with at least 3 downhole seismometers is needed to more accurately locate events, and to reliably characterize seismic recurrence in the field. In addition, modeling pressure variations in the reservoir may help explain the mechanisms that produces the microearthquakes. Data useful in modeling the pressure variations could be from tracer experiments, pressure interference tests and individual well production-injection volume. Understanding the mechanism of producing the microearthquakes should, in turn, allow the correlation of the microseismicity with fluid flow within the reservoir. 2 refs., 3 figs.
Date: December 31, 1991
Creator: Rutledge, J. T.; Fairbanks, T. D.; House, L. S. & Murphy, M. B.
Partner: UNT Libraries Government Documents Department

Vertical arrays for fracture mapping in geothermal systems

Description: In collaboration with UNOCAL Geothermal Operations, Los Alamos National Laboratory assessed the feasibility of using vertical arrays of borehole seismic sensors for mapping of microseismicity in The Geysers geothermal field. Seismicity which arises from minute displacements along fracture or fault surfaces has been shown in studies of seismically active oil reservoirs to be useful in identifying fractures affected by and possibly contributing to production. Use of retrievable borehole seismic packages at The Geysers was found to reduce the threshold for detection of microearthquakes by an estimated 2--3 orders of magnitude in comparison to surface-based sensors. These studies led to the design, materials selection, fabrication, and installation of a permanent array of geophones intended for long term seismic monitoring and mapping of fractures in the vicinity of the array at The Geysers.
Date: December 1, 1998
Creator: Albright, J.N.; Rutledge, J.T.; Fairbanks, T.D.; Thomson, J.C. & Stevenson, M.A.
Partner: UNT Libraries Government Documents Department

Microseismic monitoring of the Chaveroo oil field, New Mexico

Description: Induced microseismicity was monitored in the Chaveroo oil field in southeastern New Mexico during a pressurized stimulation of a well being prepared as an injector for a waterflood operation. In addition, the microseismicity was monitored for 5 weeks following the stimulation while the area was under normal waterflood production. Little seismicity was detected during the 5.5 hour stimulation in which three thousand barrels of water were injected into the reservoir at pressures ranging from 96 to 257 bars in excess of hydrostatic pressure. Intermittent monitoring over the 5-week period indicated detectable seismicity occurred during waterflood production. Monitoring during the 5 weeks, however, was not complete enough to draw general conclusions on temporal variations of observed microseismicity. Seventy-three good quality events recorded over a cumulative 24 hours of intermittent monitoring were located using the hodogram technique. Events were detected at distances up to 1700 m from the monitor well but most occurred within 900 m. The map of microearthquake locations indicated that events occurred in the vicinity of producing wells and away from injection wells. The first half of the sequence of mappable events occurred along linear trends, but the pattern became more scattered during the later half of the sequence. The lack of seismicity during the pressurized injection and the increased seismicity levels occurring away from injection wells during waterflood production, suggest seismicity is not induced by Mohr-Coulomb failure. 6 refs., 6 figs.
Date: January 1, 1990
Creator: Rutledge, J.T.; Albright, J.N.; Fairbanks, T.D.; Murphy, M.B. & Roberts, P.M.
Partner: UNT Libraries Government Documents Department

Reservoir fracture mapping using microearthquakes: Austin chalk, Giddings field, TX and 76 field, Clinton Co., KY

Description: Patterns of microearthquakes detected downhole defined fracture orientation and extent in the Austin chalk, Giddings field, TX and the 76 field, Clinton Co., KY. We collected over 480 and 770 microearthquakes during hydraulic stimulation at two sites in the Austin chalk, and over 3200 during primary production in Clinton Co. Data were of high enough quality that 20%, 31% and 53% of the events could be located, respectively. Reflected waves constrained microearthquakes to the stimulated depths at the base of the Austin chalk. In plan view, microearthquakes defined elongate fracture zones extending from the stimulation wells parallel to the regional fracture trend. However, widths of the stimulated zones differed by a factor of five between the two Austin chalk sites, indicating a large difference in the population of ancillary fractures. Post-stimulation production was much higher from the wider zone. At Clinton Co., microearthquakes defined low-angle, reverse-fault fracture zones above and below a producing zone. Associations with depleted production intervals indicated the mapped fractures had been previously drained. Drilling showed that the fractures currently contain brine. The seismic behavior was consistent with poroelastic models that predicted slight increases in compressive stress above and below the drained volume.
Date: November 1, 1996
Creator: Phillips, W.S.; Rutledge, J.T.; Gardner, T.L.; Fairbanks, T.D.; Miller, M.E. & Schuessler, B.K.
Partner: UNT Libraries Government Documents Department

Downhole Seismic Monitoring at the Geysers

Description: A 500-ft length, 6-level, 3-component, vertical geophone array was permanently deployed within the upper 800 ft of Unocal's well GDCF 63-29 during a plug and abandonment operation on April 7, 1998. The downhole array remains operational after a period of 1 year, at a temperature of about 150 C. Continuous monitoring and analysis of shallow seismicity (<4000 ft deep) has been conducted over that same 1-year period. The downhole array was supplemented with 4 surface stations in late-1998 and early-1999 to help constrain locations of shallow seismicity. Locations occurring within about 1 km ({approximately}3000 ft) of the array have been determined for a subset of high-frequency events detected on the downhole and surface stations for the 10-week period January 6 to March 16, 1999. These events are distinct from surface-monitored seismicity at The Geysers in that they occur predominantly above the producing reservoir, at depths ranging from about 1200 to 4000 ft depth (1450 to -1350 ft elevation). The shallow seismicity shows a northeast striking trend, similar to seismicity trends mapped deeper within the reservoir and the strike of the predominant surface lineament observed over the productive field.
Date: October 17, 1999
Creator: Rutledge, J.T.; Anderson, T.D.; Fairbanks, T.D. & Albright, J.N.
Partner: UNT Libraries Government Documents Department

Microseismic monitoring as a tool for mapping fractures in the San Andres dolomite. [Microearthquakes]

Description: Microseismic monitoring shows promise of being a practical tool for mapping fractures in the San Andres dolomite in terms of rate of microearthquake occurrence and the areal coverage possible from a single downhole seismometer. Microearthquakes were detected during normal waterflood production but monitoring was not complete enough to correlate injection/production activity with microseismic event recurrence. Constant monitoring time capability with at least 3 downhole seismometers is needed to more accurately locate events, and to reliably characterize seismic recurrence in the field. In addition, modeling pressure variations in the reservoir may help explain the mechanisms that produces the microearthquakes. Data useful in modeling the pressure variations could be from tracer experiments, pressure interference tests and individual well production-injection volume. Understanding the mechanism of producing the microearthquakes should, in turn, allow the correlation of the microseismicity with fluid flow within the reservoir. 2 refs., 3 figs.
Date: January 1, 1991
Creator: Rutledge, J.T.; Fairbanks, T.D.; House, L.S. (Los Alamos National Lab., NM (United States)) & Murphy, M.B. (Murphy Operating Corp., Roswell, NM (United States))
Partner: UNT Libraries Government Documents Department