Method of Establishing Vibration Limits and Determining Accumulative Vibration Damage in Drilling Tools
- Mark Wassell (Alternative Positioning Solutions, LLC) | Brian Stroehlein (APS Technology Inc.)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 19-22 September, Florence, Italy
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 1.12.2 Logging While Drilling, 1.12.1 Measurement While Drilling, 7.2.2 Risk Management Systems, 1.6 Drilling Operations
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- 455 since 2007
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MWD tool life is affected by its operating environment. High vibration, shock and temperature reduce the life of the tool. This paper presents a method for combining vibration, shock and temperature effects to calculate MWD tool life.
Drilling tools operate in a hostile environment. The drilling process subjects tools to varying degrees of shock and vibration at elevated temperatures. Sensitive components, such as those used in MWD and LWD tools, are especially prone to vibration damage. Shock and vibration damage may not manifest itself immediately, but accumulates over time to the point of equipment failure.
Today the most common methods in use for monitoring downhole shock and vibration either measure averaged vibration levels or count shocks above set thresholds. Vibration limits are typically set based on hard-won and costly field experience with a particular design. Most methods only look at the current levels of shock and vibration and do not consider tool history, including damage that may have occurred during previous runs.
Drilling tool designs can now also be qualified in the engineering laboratory using accelerated life testing methods (e.g., Highly Accelerated Life Testing, or HALT). Accelerated life testing entails subjecting a test article to much higher levels of vibration than would normally be expected in operation, over much shorter periods of time. Properly used, accelerated life testing is predictive of long-term tool life in a downhole environment, but saves MWD / LWD suppliers and their customers time and money compared to conventional methods.
The method presented here models and derives accumulated damage and failure thresholds as functions of vibration, shock levels, the number of shocks and the operating temperature. It is based on methods used in other industries, particularly aerospace, where reliability is of critical importance. The benefits of this method are that it more accurately accounts for cumulative damage and gives a good estimate of remaining tool life. Warning levels based on this method help predict the operating time remaining prior to failure and the need for scheduled preventative maintenance.
Statement of Theory and Definitions
Accelerated life testing is a widely used approach for qualifying tool components for service at expected operating conditions based on stressing components at exaggerated levels for shorter periods of time. Aerospace, military, consumer goods and the oilfield all use this approach. The approach presented here uses US Military Standard 810G (MIL-STD-810G)1 to extrapolate predicted operating life.
|File Size||214 KB||Number of Pages||9|