Spatial characterization of dysfunction in downhole systems
Methods and systems are provided that determine data characterizing spatial variation of vibrational dysfunction (such as HFTO) along the BHA of a drilling system. In embodiments, such data can be determined from a minimal set of measurements of any or all of four variables that include: vibration amplitude; vibration wavelength; vibration frequency; and the axial position of the first vibrational node. In embodiments, such data can be determined from measurements of vibration amplitude and vibration frequency of a BHA at two fixed positions along the BHA (e.g., with two sensors offset axially along the BHA). In other embodiments, such data can be generated from the estimated position of the first vibrational node and measurements of vibration amplitude and vibration frequency by a single sensor disposed at a fixed axial position along the BHA.
1 . A downhole system, comprising:
a bottomhole assembly (BHA) including a drill bit;
a first sensor disposed at a first distance from the drill bit;
a second sensor disposed at a second distance from the drill bit, wherein the second distance is greater than the first distance; and
at least one processor that is part of or coupled to the BHA, the at least one processor configured to obtain data including respective vibrational amplitudes from the first sensor and the second sensor and use an acoustic velocity and the data to determine data characterizing spatial variation of vibration along at least a portion of a length of the BHA, wherein using the data includes deriving a vibrational frequency.
2 . The downhole system of claim 1 , wherein:
the first and second sensors are configured to measure acceleration or rotation of the BHA.
3 . The downhole system of claim 1 , wherein:
the at least one processor is configured to use an axial position of a vibration node to determine the data characterizing spatial variation of the vibration along the at least a portion of the length of the BHA.
4 . The downhole system of claim 1 , wherein:
the at least one processor is configured to determine a maximum amplitude of the vibration by solving a system of equations that relates the maximum amplitude of the vibration to the respective vibrational amplitudes measured by the first and second sensors.
5 . The downhole system of claim 4 , wherein:
the system of equations further includes a distance to a first vibrational node, the first distance between the first sensor and the drill bit, the second distance between the second sensor and the drill bit, and a wavelength.
6 . The downhole system of claim 5 , wherein:
the wavelength is determined from the vibrational frequency derived from the data from at least one of the first sensor and second sensor.
7 . The downhole system of claim 1 , wherein:
the first and second sensors are configured to measure axial strain.
8 . The downhole system of claim 1 , wherein:
the first and second sensors comprise magnetometers.
9 . The downhole system of claim 8 , wherein:
the at least one processor is configured to differentiate measurement data obtained from the magnetometers to determine collar rotational speed.
10 . A method for determining spatial variation of vibration along a bottomhole assembly (BHA) including a drill bit, the method comprising:
obtaining first data including a first vibrational amplitude with a first sensor at a first distance from the drill bit;
obtaining second data including a second vibrational amplitude with a second sensor at a second distance from the drill bit, the second distance being greater than the first distance; and
using, via at least one processor that is part of or coupled to the BHA, acoustic velocity and the first and second data to determine data characterizing spatial variation of vibration along at least a portion of a length of the BHA, wherein using the first and second data includes deriving a vibrational frequency.
11 . The method of claim 10 , further comprising:
determining, via the at least one processor that is part of or coupled to the BHA, a maximum amplitude of the vibration by solving a system of equations that relates the maximum amplitude of the vibration to the first and second vibrational amplitudes measured by the first and second sensors.
12 . The method of claim 11 , wherein the system of equations further includes a distance to a first vibrational node, the first distance between the first sensor and the drill bit, the second distance between the second sensor and the drill bit, and a wavelength.
13 . The method of claim 12 , wherein:
the wavelength is determined from the vibrational frequency derived from the data from at least one of the first sensor and second sensor.
14 . A downhole system, comprising:
a bottomhole assembly (BHA) including a drill bit;
a first sensor disposed at a first distance from the drill bit;
a second sensor disposed at a second distance from the drill bit, wherein the second distance is greater than the first distance; and
at least one processor that is part of or coupled to the BHA, the at least one processor configured to:
obtain data from the first sensor and the second sensor and use the data to determine data characterizing spatial variation of vibration along at least a portion of a length of the BHA; and
determine a maximum amplitude of the vibration by solving a system of equations that relates the maximum amplitude of the vibration to vibrational amplitudes measured by the first and second sensors, wherein the system of equations further includes a distance to a first vibrational node, the first distance between the first sensor and the drill bit, the second distance between the second sensor and the drill bit, and a wavelength.
15 . The downhole system of claim 14 , wherein:
the wavelength is determined from a vibration frequency derived from the data from at least one of the first sensor and second sensor.
16 . The downhole system of claim 14 , wherein:
the first and second sensors are configured to measure acceleration or rotation of the BHA.
17 . The downhole system of claim 14 , wherein:
the first and second sensors are configured to measure axial strain.
18 . A method for determining spatial variation of vibration along a bottomhole assembly (BHA) including a drill bit, the method comprising:
obtaining first data with a first sensor at a first distance from the drill bit;
obtaining second data with a second sensor at a second distance from the drill bit, the second distance being greater than the first distance;
using, via at least one processor that is part of or coupled to the BHA, the first and second data to determine data characterizing spatial variation of vibration along at least a portion of a length of the BHA; and
determining, via the at least one processor that is part of or coupled to the BHA, a maximum amplitude of the vibration by solving a system of equations that relates the maximum amplitude of the vibration to vibrational amplitudes measured by the first and second sensors, wherein the system of equations further includes a distance to a first vibrational node, the first distance between the first sensor and the drill bit, the second distance between the second sensor and the drill bit, and a wavelength.
19 . The method of claim 18 , wherein:
the first and second sensors are configured to measure acceleration or rotation of the BHA.
20 . The method of claim 18 , wherein:
the first and second sensors are configured to measure axial strain.