Monitoring a microseismic event
AssigneeABB Offshore Systems Limited
InventorRobert Hughes Jones
Life of this patent
Estimating the term…
Abstract
A method of monitoring a microseismic event includes detecting the event to produce a first signal dependent on the event. The first signal includes noise at a frequency of, for example 50 Hz. A first sample of the first signal is taken. Then a second sample of the first signal is taken, the second sample occurring n/f seconds after the first sample, where n is an integer (e.g. 1). Subtracting the first and second samples from each other produces a farther signal dependent on the event in which the noise has been at least partly compensated for.
Claims10
A method of monitoring a microseismic event, comprising:
- detecting said event to produce a first signal dependent on said event, the first signal including noise at a frequency of f Hz;
- taking a first sample of said first signal;
- taking a second sample of said first signal, the second sample occurring n/f seconds after the first sample, where n is an integer;
- and subtracting the first and second samples from each other to produce a further signal dependent on said event in which said noise has been at least partly compensated for.
A method of monitoring a microseismic event, the method comprising the steps of:
- detecting a microseismic event to produce a first signal dependent on said event, the first signal including a noise signal produced by cathodic protection currents having a frequency of f Hz;
- taking a first sample of said first signal;
- taking a second sample of said first signal, the second sample taken n/f seconds after the first sample;
- and
- determining a difference between the first and second samples to produce a third signal dependent on said microseismic event in which said noise signal has been at least partly removed.
A method of monitoring a microseismic event in a fluid producing well, comprising the steps of:
- rectifying an AC main supply to produce DC current, the DC current containing a noise signal having a base frequency f Hz equivalent to the frequency of the AC main supply and harmonics thereof;
- detecting a microseismic event to produce a first signal dependent on said event, the first signal including the noise signal;
- taking a first sample of said first signal;
- taking a second sample of said first signal, the second sample taken n/f seconds after the first sample;
- determining a difference between the first and second samples to produce a third signal dependent on said microseismic event in which said noise signal has been at least partly removed;
- and
- applying the third signal to an existing trigger detection algorithm to detect the microseismic event.
Dependencies are inferred from the claim text.