Method of processing seismic data
AssigneeWesternGeco L.L.C.
InventorJohan O.A. Robertsson
Life of this patent
Estimating the term…
Abstract
A method of de-ghosting seismic data acquired in a marine seismic survey comprises estimating ∂zp (where p is the fluid pressure) from a time-derivative of p and a derivative of p in a horizontal direction such as the x-direction. The time-derivative of p and the derivative of p in the horizontal direction can be readily obtained from the acquired seismic data, and are used to provide an improved estimate of ∂zp which, in general, cannot be directly determined from the acquired seismic data. Once ∂zp has been estimated it can be used to de-ghost the acquired seismic data.
Claims24
A method of de-ghosting seismic data, the method comprising the steps of:
- a) obtaining seismic data using a seismic source and a seismic receiver disposed within a fluid medium;
- b) determining a derivative with respect to time of the fluid pressure at a point in the vicinity of a selected one of the seismic source and the receiver;
- c) determining a derivative with respect to a first direction of the fluid pressure at a point in the vicinity of the selected one of the seismic source and receiver;
- d) determining a derivative with respect to a second direction of the fluid pressure at a point in the vicinity of the selected one of the seismic source and receiver from the results of steps (b) and (c);
- and
- e) processing the seismic data using the derivative with respect to a second direction of the fluid pressure, thereby to reduce the effects in the processed seismic data of seismic energy reflected and/or scattered at the sea surface.
A method as claimed in any preceding claim wherein the second direction is a substantially vertical direction.
A method as claimed in any preceding claim wherein step (e) comprises determining {tilde over (p)}, where
- 8 p ~ = 1 2 ( p + 1 ik z ∂ z p )
A method as claimed in any preceding claim wherein the seismic data is obtained in the vicinity of an array of receivers;
- and wherein the method comprises using the results of the processing of the seismic data to reduce the effects of seismic energy reflected and/or scattered at the sea surface in the signal emitted by a corresponding array of seismic sources.
A method of calibrating a seismic receiver, the method comprising the steps of:
- a) measuring the particle velocity using a seismic source and a seismic receiver disposed within a fluid medium;
- b) determining a derivative with respect to time of the particle velocity at a point in the vicinity of the receiver;
- c) determining a derivative with respect to a first direction of the particle velocity at a point in the vicinity of the receiver;
- d) determining a derivative with respect to a second direction of the particle velocity at a point in the vicinity of the receiver from the results of steps (b) and (c);
- and
- e) determining a measure of the quality of the measurement of the particle velocity using the derivative with respect to a second direction of the particle velocity.
A method of calibrating a seismic receiver comprising the steps of:
- a) disposing a seismic receiver in a fluid medium;
- b) measuring the fluid pressure and the particle velocity using the seismic receiver;
- c) computing one of the particle velocity and the fluid pressure from the measured value of the other of the particle velocity and the fluid pressure and from the depth of the receiver;
- and
- d) comparing the computed value of the one of the particle velocity and the fluid pressure with the measured value of the one of the particle velocity and the fluid pressure.
A method of determining the depth of a seismic receiver, comprising the steps of:
- a) disposing a seismic receiver in a fluid medium;
- b) measuring the fluid pressure and the particle velocity using the seismic receiver;
- and
- c) determining the distance between the fluid surface and the receiver from the measured values of the particle velocity and the fluid pressure.
Dependencies are inferred from the claim text.