Ultrasonic Reduction of
Wellbore Deposits and
Formation Damage

Photographs of sonoluminescence generated by acoustic cavitation in solutions of water and Luminol. At left, a high-power acoustic horn produces a small region of intense cavitation near the horn's tip. This is undesirable for wellbore cleaning applications because the acoustic energy is wasted in the fluid near the source and very little reaches the wellbore wall or the formation. At right, a single transducer from the prototype cleaning tool, currently being field tested (see below), produces a more diffuse, uniform cloud of cavitation surrounding the source (located in the top middle of the picture). More acoustic energy can be transmitted to the wellbore walls with this type of source, and the uphole power requirements can be reduced significantly.
-photos courtesy of Timothy Jones (SDR)

Laboratory apparatus used for cleaning experiments. Pictures show a Hassler flow cell, which holds a 1-inch diameter core sample and a Branson acoustic horn used to sonicate the cores with high-intensity ultrasound. The left picture shows the equipment before insertion of the horn into the Hassler cell and the right picture shows the horn inserted and ready to begin treatment.

Project Summary

Laboratory work on ultrasonic treatment of simulated damage in core samples has been successful at cleaning drilling mud infiltration, in-situ fines migration, paraffin precipitation and polymer infiltration. The main deliverables of the project are a working prototype downhole ultrasonic cleaning tool and sufficient operating procedures to allow the technology to be transferred to industry. This tool has been built and tested in the field in damaged producing wells to assess its effectiveness for cleaning and to determine optimum operating parameters. Please contact Peter Roberts for more information.

Project Components

• Laboratory Research:
  Please refer to the publications listed below for details of the laboratory research.
  Significant lab results are summarized in this table (250 kb Jpeg).

• Tool Specifications (150 kb Jpeg)

• Tool Field Test Criteria
  A primary goal of this project is to determine the wellbore conditions and field operating procedures required to ensure successful acoustic treatments with the prototype tool. This list (click above) summarizes the most important requirements we have determined to date, based on extensive laboratory research and on initial field experience.

• Tool Field Test Summaries:
  Field testing with the prototype cleaning tool has allowed us to better define the wellbore conditions and operating procedures required for successful downhole treatments, as listed above. As of October, 1996, the tool has been tested in two separate sets of well types.
  • Farmington Methane Wells
    The first tests were performed in coalbed methane wells near Farmington, New Mexico. The aim was to remove coal fines from perforations in the producing zones. Although the tool did produce some curious effects on pressure buildup data in one of the wells (see below), no conclusive data on production changes caused by the tool were obtained from these tests. However, these tests provided useful information about the tool's influence on wellbore pressure buildup rates, its behavior in various fluids at differing temperatures and pressures, and the wellbore parameters that must be controlled to maximize the cleaning effectiveness. Although two methane wells were treated, only the first well was producing significant gas when the treatment was performed. Because the second well was not flowing significantly during treatment, it is unlikely that any fines were removed from the perforations. A summary of the test results on the first methane well is given below.
    • Summary of methane well test #1

  • North Central Texas Oil Wells
    For the second set of field tests, five wells located in the Bend Arch region of north central Texas were treated to remove progressive perforation plugging due to migration of formation fines. These wells were chosen based on their steadily declining production rates and indications from the producers that the cause of the decline was primarily near-wellbore damage. Four of the five wells were in the same producing field and were fairly low-volume producers. Individual-well tank tests were conducted to estimate daily oil and water production for 4 days prior to treatment and for 16 days during the first month after treatment. The combined daily production data for the first 4 wells show that, after an initial pump stabilization period of about 4-5 days, oil production is steadily rising relative to the pre-treatment rates. Post-treatment water production rose sharply at first and is now gradually declining. Currently, total fluid production (oil+water) for the 4 wells combined is reasonably stable at a value approximately twice the average pre-treatment rate. Pre-treatment tank tests for the fifth well were anomalously high, given the well's prior history, and the results of our treatment on this well are inconclusive. The following plot summarizes the combined test tank data for the four low-volume wells.
    • 4-Well Combined Production Data (170 kb Jpeg)

Principal Investigators

• Peter Roberts, LANL
• Mukul Sharma, University of Texas at Austin
• Voldi Maki, The Measurement Group

Project Publications and Presentations

• Roberts, P. M., A. Venkitaraman and M. M. Sharma (1996). Ultrasonic Removal of Organic Deposits and Polymer Induced Formation Damage, Proc. Soc. Petrol. Eng. Intl. Symp. Formation Damage Control, SPE 31129: 8 pp. (PDF file)
• Venkitaraman, A., P. M. Roberts and M. M. Sharma (1995). Ultrasonic Removal of Near-Wellbore Damage Caused by Fines and Mud Solids, SPE Drilling & Completion, 10, No. 3: 193-197.
• Venkitaraman, A., P. M. Roberts and M. M. Sharma (1994). Ultrasonic Removal of Near-Wellbore Damage Caused by Fines and Mud Solids, Proc. Soc. Petrol. Eng. Intl. Symp. Formation Damage Control, SPE 27388: 441-449. (PDF file)

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Mail comments and suggestions to proberts@lanl.gov