US 10,241,218 B2 · Methods and systems for computing notional source signatures from near-field measurements and modeled notional signatures

Abstract

Methods and systems for computing notional source signatures from modeled notional signatures and measured near-field signatures are described. Modeled near-field signatures are calculated from the modeled notional signatures. Low weights are assigned to parts of a source pressure wavefield spectrum where signatures are less reliable and higher weights are assigned to parts of the source pressure wavefield spectrum where signatures are more reliable. The part of the spectrum where both sets of signatures are reliable can be used for quality control and for comparing the measured near-field signatures to modeled near-field signatures. When there are uncertainties in the input parameters to the modeling, the input parameters can be scaled to minimize the differences between measured and modeled near-field signatures. Resultant near-field signatures are computed by a weighted summation of the modeled and measured near-field signatures, and notional source signatures are calculated from the resultant near-field signatures.

Claims27

Dependent claims

In a process for generating an image of a subterranean formation using marine seismic techniques in which a source is activated above the subterranean formation and the reflections from the subterranean formation are recorded as seismic data generated by receivers and a near-field signature of each pressure wave generated by a source element of the source is captured in a recording generated by a pressure sensor located within a near field of each source element, the specific improvement comprising:

generating a modeled near-field signature for each source element, wherein the modeled near-field signature of a source element is a combination of modeled notional source signatures of each source element;
combining a low-frequency portion of the recorded near-field signature with a high-frequency portion of the modeled near-field signature of each source element to generate a new recording corresponding to a new near-field signature of each source element, wherein the new near-field signature of each source element avoids an unreliable high-frequency portion of the recorded near-field signature and an unreliable low-frequency portion of the modeled near-field signature;
computing notional source signatures of the source elements using the new near-field signatures, each notional source signature characterizing an isolated pressure wave generated by a source element without effects of pressure waves generated by other source elements and without free surface reflections;
determining a source pressure wavefield from the notional source signatures;
and
generating an image of the subterranean formation based on the source pressure wavefield and the seismic data.

3 more elements

A computer system for computing an image of a subterranean formation from recorded seismic data collected in a marine seismic survey of the subterranean formation, the system comprising:

one or more processors;
one or more data-storage devices;
and
machine-readable instructions stored in the one or more data-storage devices that when executed using the one or more processors controls the system to carry out
generating a modeled near-field signature for each source element of a source activated above the subterranean formation in a body of water, wherein the modeled near-field signature of each source element is a combination of modeled notional source signatures of each source element;
combining a low-frequency portion of the recorded near-field signature with a high-frequency portion of the modeled near-field signature of each source element to generate a new recording corresponding to a new near-field signature of each source element;
computing notional source signatures of the source elements using the new near-field signatures, each notional source signature characterizing an isolated pressure wave generated by a source element without effects of pressure waves generated by other source elements and without free surface reflections;
determining a source pressure wavefield from the notional source signatures;
and
generating an image of the subterranean formation based on the source pressure wavefield and seismic data generated by receivers that detect reflections from the subterranean formation in response to activation of the source.

7 more elements

Dependencies are inferred from the claim text.

Methods and systems for computing notional source signatures from near-field measurements and modeled notional signatures

Life of this patent

Methods and systems for computing notional source signatures from near-field measurements and modeled notional signatures

Life of this patent

Abstract

Claims27