Maximum likelihood borehole corrections for dual-detector density logs

PDF Version Also Available for Download.

Description

This report discusses Dual-detector density logs which have been used in the petroleum industry for years. The tool was designed with a second detector to allow compensation for the effect of a layer of mudcake between the tool and the formation being measured. The compensation algorithm commonly used calculates the correction to apply to the density measured by the long-spaced detector as proportional to the difference in the densities measured by the two detectors. The coefficient of proportionality is determined from experimental data taken with the tool in a fluid-filled hole of 15 to 40 cm diameter, with uniform thickness ... continued below

Physical Description

8 p.

Creation Information

Carlson, R.C. October 1, 1993.

Context

This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. It has been viewed 21 times . More information about this article can be viewed below.

Who

People and organizations associated with either the creation of this article or its content.

Author

Sponsor

Publisher

Provided By

UNT Libraries Government Documents Department

Serving as both a federal and a state depository library, the UNT Libraries Government Documents Department maintains millions of items in a variety of formats. The department is a member of the FDLP Content Partnerships Program and an Affiliated Archive of the National Archives.

Contact Us

What

Descriptive information to help identify this article. Follow the links below to find similar items on the Digital Library.

Description

This report discusses Dual-detector density logs which have been used in the petroleum industry for years. The tool was designed with a second detector to allow compensation for the effect of a layer of mudcake between the tool and the formation being measured. The compensation algorithm commonly used calculates the correction to apply to the density measured by the long-spaced detector as proportional to the difference in the densities measured by the two detectors. The coefficient of proportionality is determined from experimental data taken with the tool in a fluid-filled hole of 15 to 40 cm diameter, with uniform thickness sheets of various materials simulating the mudcake. In applying this technology for the Containment program at the Department of Energy Nevada Test Site (NTS) we have discovered two problems. First, we frequently log in air-filled holes much larger than 40 cm. Second, the gap, or layer, is rarely uniform with depth or vertical position on the face of the tool. We have developed a method to determine the proper amount of correction dynamically. No experimental data on the gap effect are needed as long as the two detectors are calibrated to read the proper density when the gap is zero. The method assumes that the form of the equation used in the standard algorithm is correct, but uses the variation of the two density signals with depth to determine the appropriate value of the coefficient, assuming true density varies more slowly than the gap effects. This new, maximum likelihood, method appears to work better than the standard method in both fluid and air-filled holes where the borehole wall is rough and no mudcake is present. It cannot, however, correct for a uniform mudcake or air gap, and so complements but does not replace the standard method.

Physical Description

8 p.

Notes

OSTI as DE94007027

Source

  • 5. international symposium of Minerals and Geotechnical Logging Society, Tulsa, OK (United States), 24-28 Oct 1993

Language

Item Type

Identifier

Unique identifying numbers for this article in the Digital Library or other systems.

  • Other: DE94007027
  • Report No.: UCRL-JC--113796
  • Report No.: CONF-9310286--1
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 142551
  • Archival Resource Key: ark:/67531/metadc618548

Collections

This article is part of the following collection of related materials.

Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

What responsibilities do I have when using this article?

When

Dates and time periods associated with this article.

Creation Date

  • October 1, 1993

Added to The UNT Digital Library

  • June 16, 2015, 7:43 a.m.

Description Last Updated

  • Feb. 23, 2016, 1:52 p.m.

Usage Statistics

When was this article last used?

Yesterday: 0
Past 30 days: 0
Total Uses: 21

Interact With This Article

Here are some suggestions for what to do next.

Start Reading

PDF Version Also Available for Download.

International Image Interoperability Framework

IIF Logo

We support the IIIF Presentation API

Carlson, R.C. Maximum likelihood borehole corrections for dual-detector density logs, article, October 1, 1993; California. (digital.library.unt.edu/ark:/67531/metadc618548/: accessed July 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.