Vibration Memory Sub (VMS™)
The Vibration Memory Sub (VMS) is a standalone downhole tool that measures, calculates and records axial, lateral and angular down-hole vibrations for retrieval and analysis at the surface. The VMS allows operators to assess the severity of downhole drilling shock and vibration, including stick-slip and whirl, and correlate the data to drilling events and equipment performance or failures. Measurements are stamped by date and time for correlation with other data. The VMS can be used to characterize downhole conditions for future BHA planning, post-well analysis of equipment failures or to provide evidence for use in warranty claim resolution.
The tool provides data in the form of ASCII text files which can analyzed by APS's Vibration Data Viewer software or your own analysis software.
The tool's 32 MB memory is capable of recording up to 1,200 hours of continuous data.
This sonde-based tool is available in 6.75 in. and 4.75 in. drill collar sizes, with standard box and pin connections. The sonde-based design allows this tool to be scaled up or down easily for use with other drill collar sizes. Please inquire with your APS sales representative if you require a different collar size.
Preparing the tool for recording vibration data is straightforward:
- Ensure that a battery is installed with sufficient life for recording the desired bit run.
- Set desired user programmable recording parameters through VMM/VMS interface software installed on a standard Windows-based (2000 or XP) PC.
- Clear memory or ensure that there is sufficient memory remaining.
- Install all covers.
Battery replacement is easily performed in a shop environment using basic hand tools.
Vibration measurements are made using two ± 250 g accelerometers and one fluxgate magnetometer rotation sensor. Vibration and RPM data are collected and stored every 4 seconds. Event-driven raw data "snap shots" collect and store a 20-second data set at the maximum processor speed.
Every four seconds, the microprocessor calculates and stores:
- Maximum lateral acceleration – vector sum of x- and y-accelerometer measurements
- RMS lateral acceleration
- Maximum axial vibration – from z-accelerometer
- RMS axial acceleration
- Maximum and minimum angular speed (RPM)
- Absolute date and time
Raw Data Snapshots
In addition to the maximum and average data, the tool stores seven "snapshots" of the raw accelerometer and magnetomer readings. 20-second sets of 1,000 sample/s raw readings are recorded. Raw data can be collected following several user-selectable events.
- The user can select four different vibration conditions which will trigger raw data "snapshot" collection.
- The user can select three different rotation conditions which will trigger raw data "snapshot" collection.
Data is easily retrieved by accessing the data dump port on the sub and connecting it through the VMS Interface Box to a PC. LabWindows™-based software on the PC converts the stored data to a text file with acceleration levels as a function of real time. The data can be erased when retrieved or left in memory after the download.
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