NEW LOGGING TOOLS AND TECHNIQUES KEY TO ENHANCED RECOVERY

Primarily based on the following PTTC workshops:

 "Wireline Logging Applications for the Michigan Basin," held February 18, 1999, in Mt. Pleasant, MI (Midwest Region)

"Wireline Logging and New Technologies for the Appalachian Basin," held April 7-8, 1999, in Morgantown, WV (Appalachian Region)

BOTTOM LINE

New tool technologies and techniques in wireline logging, analysis, and interpretation—that were successful in mature wells in other parts of the country—have great potential for increasing economic success in the Appalachian and Midwestern regions.

PROBLEM ADDRESSED

Even for operators with substantial expertise in traditional wireline logging technologies, it is difficult to monitor advances and stay abreast of the new tools and methods that could substantially affect the bottom line. Logging technology has advanced rapidly. New specialized tools can measure previously unobtainable reservoir rock and reservoir/ borehole fluid properties. Also, the capability to accurately and efficiently collect, analyze, and interpret the tool response data has greatly increased.

KEY WORDS:

Production Logging, Borehole Imaging Logs, Nuclear Magnetic Resonance Logs, Integrated Reservoir Characterization, Log Analysis Software, Digital Logs

SPEAKERS

Brad Posner and Todd Sutton, Schlumberger

Ken Moss, Baker Atlas

Lynn Watney and Bill Guy, Kansas Geological Survey

James Wood, Michigan Technological University

TECHNOLOGY OVERVIEW

Wireline logging is the major technology available to quantitatively and qualitatively describe the architectural, rock, and fluid properties of the subsurface reservoir. The same logs, interpreted by different professionals, provide a range of information. Geophysicists determine depths, boundaries, and rock/ fluid properties. Geologists study formation tops, environments of deposition, the types and amounts of hydrocarbons present, and potential production and reserves. Engineers examine wellbore irregularities, pay thickness/ uniformity, the best depths to set packers for testing, ideal completion intervals to maximize hydrocarbon and minimize water production, recommended completion techniques, and volume of cement needed.

Among the more important new technologies are formation microimaging tools (for identifying the presence of fractures and sedimentary structures) and nuclear magnetic resonance tools (for identifying the type and movability of reservoir fluids).

With the advent of highly deviated and horizontal wellbores, operators can more efficiently contact and produce hydrocarbons. However, technologies that work for measuring multiphase flow behavior and determining flow profiles in vertical wells do not yield good results in highly deviated wellbores. The gravitational segregation of phases (oil, water, and natural gas) in horizontal and undulating wellbores is responsible for the problem. New flow-meter instrumentation and interpretation techniques relying on arrays of capacitors now allow the measurement of flow regime, holdups (i. e., phase thicknesses/ proportions in the volume of the borehole), and phase velocities across the wellbore. Data from the new tools are combined with data from spinner, pressure, temperature, and nuclear measurement to determine the optimal levels.

For many operators, getting the log data in digital or raster format is the first step. New options for handling data have become available. NeuraLog’s digitizing system—a neural network-based software that transforms scanned paper images into usable digital data—is one solution. An essential quality control feature is the onscreen comparison of scanned data with the original scanned image.

The enhanced processing of wireline log data enables more accurate interpretations of reservoir conditions, but additional insights are gained through digital processing and data handling capabilities. For example, a combination of new induction tools with multiple depths of investigation and advanced data processing is enabling more accurate location of thin pays in interbedded sections. During logging runs, new digital communications capabilities allow critical decision-making based on realtime analysis of logging data. This is done using surface processing facilities, which broadcast encrypted, real-time data to the home office.

In mature reservoirs, the importance of a reservoir-wide approach to log analysis, rather than on a well-by-well basis, cannot be overemphasized. This is required to gauge overall reservoir productivity, determine communicating volumes within the reservoir, target new opportunities, and tailor specific recovery strategies.

New features of the PfEFFER spreadsheet multiwell log analysis software include movable oil plots and forward modeling capabilities for petrophysical properties. The software, which was developed at the University of Kansas, now addresses reservoir zoning, flagging of pay cutoffs, identifying and mapping of flow units, making subsurface cross sections, and gridding for reservoir simulation.

LESSONS LEARNED

Integrating wireline log data with other sources of reservoir information is needed to optimize the interpretation of subsurface parameters. Reservoir mineralogy is an example of unanticipated factors that might significantly affect wireline tool responses. Their calibration against other information compiled from cores, cuttings, fluid samples, existing logs, etc., is especially important when running new tools in a reservoir for the first time.

Multiwell comparisons in a “matrix-like” approach to log analysis allow producers to build more consistent, realistic models to predict reservoir performance under various scenarios. In mature reservoirs, developing an understanding of the entire reservoir as an integrated whole is much more important than it has been in the past.

FIELD RESULTS

There are several examples of how the PfEFFER package can be used to analyze pre-existing log data to decipher subtle and complex pay zones not identified by routine log analysis. In a well in Illinois producing from the Aux Vases Sandstone, a subtle pay zone was indicated where the operator’s criteria for pay were not met. The well was completed in the newly identified zone for 21 bopd and 21 bwpd. A well in the Morrow in Colorado was found to have substantial potential to produce in a zone with increasing reservoir quality, but also water saturation that increased with depth. Production from the well reached 98 bopd and 300 mcfg/ day.

In a low-contrast, low-resistivity reservoir in the Minnelusa formation in Wyoming, a well in a subtle pay zone was completed for 862 bopd, 85 bwpd, and 85 mcfg/ day. In a similar Red Fork well in Oklahoma, the serrated appearance of the gamma ray log suggested that a section consisted of thinly laminated sandstone and shale layers. PfEFFER confirmed the suspicion; a section of productive sandstone zone was not discovered in the field until after 15 wells had been drilled.

CONNECTIONS:

Brad Posner and Todd Sutton
Schlumberger Oil Field Services
3401 East Pike, Zanesville, OH 43701
Phone 740-450-8370, E-mail posner@mount-pleasant.wireline.slb.com

Ken Moss, Baker Atlas
5625 Venture Way
Mt. Plesasant, MI 48858
Phone 517-773-7992, Fax 517-772-5083

James Wood, Dept. of Geological Engineering, Geology and Geophysics, Michigan Technological University
Houghton, MI 49931
Phone 906-487-2894, Fax 906-487-3371, E-mail jrw@mtu.edu

Lynn Watney, Kansas Geological Survey
1930 Constant Ave., Lawrence, KS 66047
Phone 913-864-3695, Fax 913-864-5317, E-mail lwatney@kgs.ukans.edu

For information on PTTC’s regional resource centers and activities contact:

Appalachian:
Douglas Patchen, Program Director
Appalachian Oil & Natural Gas Research Consortium,
West Virginia University
NRCCE-Evansdale Dr., PO Box 6064 Morgantown, WV 26506-6064
Phone 304-293-2867 x-5443, Fax 304-293-7822, E-mail dpatch@wvunrcce.nrcce.wvu.edu

Midwest:
David G. Morse, Petroleum Geologist, Oil and Gas Section Illinois State Geological Survey,
Natural Resources Bldg. 615 E. Peabody Dr., Champaign, IL 61820
Phone 217-244-5527, Fax 217-333-2830, E-mail morse@geoserv.isgs.uiuc.edu

Disclaimer: No specific application of products or services is endorsed by PTTC. Reasonable steps are taken to ensure the reliability of sources for information that PTTC disseminates; individuals and institutions are solely responsible for the consequences of its use.

The not-for-profit Petroleum Technology Transfer Council is funded primarily by the US Department of Energy’s Office of Fossil Energy, with additional funding from universities, state geological surveys, several state governments, and industry donations.

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