New Mechanisms of rock-bit wear in geothermal wells

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This paper presents recent results of an investigation on failure mode and wear of rock-bits used to drill geothermal wells located in the area of Larderello (Italy). A new wear mechanism, conceived from drilling records and dull bit evaluation analysis, has been identified and a particular configuration of rock-bit has been developed and tested in order to reduce drilling costs. The role of high Bottom Hole Temperature (BHT) on rock-bit performances seems not yet very well understood: so far, only drillability and formation abrasiveness are generally considered to account for poor drilling performances. In this paper, the detrimental effects of ... continued below

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441-448

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Macini, Paolo January 24, 1996.

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Description

This paper presents recent results of an investigation on failure mode and wear of rock-bits used to drill geothermal wells located in the area of Larderello (Italy). A new wear mechanism, conceived from drilling records and dull bit evaluation analysis, has been identified and a particular configuration of rock-bit has been developed and tested in order to reduce drilling costs. The role of high Bottom Hole Temperature (BHT) on rock-bit performances seems not yet very well understood: so far, only drillability and formation abrasiveness are generally considered to account for poor drilling performances. In this paper, the detrimental effects of high BHT on sealing and reservoir system of Friction Bearing Rock-bits (FBR) have been investigated, and a new bearing wear pattern for FBR's run in high BHT holes has been identified and further verified via laboratory inspections on dull bits. A novel interpretation of flat worn cutting structure has been derived from the above wear pattern, suggesting the design of a particular bit configuration. Test bits, designed in the light of the above criteria, have been prepared and field tested successfully. The paper reports the results of these tests, which yielded a new rock-bit application, today considered as a standad practice in Italian geothermal fields. This application suggests that the correct evaluation of rock-bit wear can help to improve the overall drilling performances and to minimize drilling problems through a better interpretation of the relationships amongst rock-bits, formation properties and downhole temperature.

Physical Description

441-448

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  • Proceedings, Twenty-First Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA, January 22-24, 1996

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  • Report No.: SGP-TR-151-61
  • Grant Number: None
  • Office of Scientific & Technical Information Report Number: 889856
  • Archival Resource Key: ark:/67531/metadc884890

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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.

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  • January 24, 1996

Added to The UNT Digital Library

  • Sept. 21, 2016, 2:29 a.m.

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  • Nov. 30, 2016, 12:56 p.m.

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Macini, Paolo. New Mechanisms of rock-bit wear in geothermal wells, article, January 24, 1996; United States. (digital.library.unt.edu/ark:/67531/metadc884890/: accessed November 20, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.