US-12618994-B2 - Data-driven separation of upgoing free-surface multiples for seismic imaging

US12618994B2US 12618994 B2US12618994 B2US 12618994B2US-12618994-B2

Abstract

A method includes receiving seismic data including signals collected using a receiver, the seismic data representing a subsurface volume, identifying a downgoing wavefield and an upgoing wavefield in the seismic data, identifying direct arrivals in the downgoing wavefield, estimating at least first-order multiple reflection signals in the upgoing wavefield based on the downgoing wavefield, the upgoing wavefield, and the direct arrivals, and generating seismic images representing the subsurface volume based at least in part on the at least first-order multiple reflection signals.

Inventors

Philippe Caprioli
Paal Kristiansen

Assignees

SCHLUMBERGER TECHNOLOGY CORPORATION

Dates

Publication Date: 20260505
Application Date: 20210521

Claims (15)

1 . A method, comprising: receiving seismic data comprising signals collected using a receiver, the seismic data representing a subsurface volume; identifying a downgoing wavefield and an upgoing wavefield in the seismic data; identifying direct arrivals in the downgoing wavefield; estimating at least first-order multiple reflection signals in the upgoing wavefield based on the downgoing wavefield, the upgoing wavefield, and the direct arrivals, wherein estimating the at least first-order multiple reflection signals comprises estimating first and higher multiple reflection signals by: generating an intermediate wavefield by subtracting the direct arrivals from the downgoing wavefield; deconvolving the downgoing wavefield from the intermediate wavefield to generate a second intermediate wavefield; and convolving the second intermediate wavefield with the upgoing wavefield; and generating seismic images representing the subsurface volume based at least in part on the at least first-order multiple reflection signals.
2 . The method of claim 1 , further comprising removing source signature and ghosting effects in the at least first-order multiple reflection signals by deconvolving the direct arrivals.
3 . The method of claim 1 , further comprising adaptively subtracting the at least first-order multiple reflection signals from the upgoing wavefield, wherein the seismic images are generated at least partially from a remainder of the upgoing wavefield after the at least first-order multiple reflection signals are subtracted from the upgoing wavefield.
4 . The method of claim 1 , further comprising comparing the at least first-order multiple reflection signals with modeled at least first-order multiple reflection signals generated using a water-propagation model, and determining whether the water-propagation model is accurate based on the comparing.
5 . The method of claim 1 , wherein subtracting the direct arrivals comprises direct muting of the direct arrivals in the downgoing wavefield.
6 . The method of claim 1 , wherein estimating the at least first-order multiple reflection signals is data-driven and does not rely on a water-propagation model, and wherein the seismic images that are generated do not include primary reflections.
7 . The method of claim 1 , further comprising generating a velocity model representing a subterranean domain using the at least first-order multiple reflection signals.
8 . A non-transitory computer-readable medium storing instructions that, when executed by at least one processor of a computing system, cause the computing system to perform operations, the operations comprising: receiving seismic data comprising signals collected using a receiver, the seismic data representing a subsurface volume; identifying a downgoing wavefield and an upgoing wavefield in the seismic data; identifying direct arrivals in the downgoing wavefield; estimating at least first-order multiple reflection signals in the upgoing wavefield based on the downgoing wavefield, the upgoing wavefield, and the direct arrivals, wherein estimating the at least first-order multiple reflection signals comprises: subtracting the direct arrivals from the downgoing wavefield to generate a first intermediate wavefield; deconvolving the downgoing wavefield from the first intermediate wavefield to generate a second intermediate wavefield; deconvolving the downgoing wavefield from the upgoing wavefield to generate a third intermediate wavefield; and convolving the direct arrivals, the second intermediate wavefield, and the third intermediate wavefield, so as to estimate the at least first-order multiple reflection signals in the upgoing wavefield; and generating seismic images representing the subsurface volume based at least in part on the at least first-order multiple reflection signals.
9 . The medium of claim 8 , wherein the operations further comprise removing source signature and ghosting effects in the at least first-order multiple reflection signals by deconvolving the direct arrivals.
10 . The medium of claim 8 , wherein estimating the at least first-order multiple reflection signals comprises estimating second-order multiple reflection signals separately from estimating the at least first-order multiple reflection signals.
11 . The medium of claim 8 , wherein the operations further comprise adaptively subtracting the at least first-order multiple reflection signals from the upgoing wavefield, wherein the seismic images are generated at least partially from a remainder of the upgoing wavefield after the at least first-order multiple reflection signals are subtracted from the upgoing wavefield.
12 . The medium of claim 8 , wherein the operations further comprise comparing the at least first-order multiple reflection signals with modeled at least first-order multiple reflection signals generated using a water-propagation model, and determining whether the water-propagation model is accurate based on the comparing.
13 . The medium of claim 8 , wherein estimating the at least first-order multiple reflection signals is data-driven and does not rely on a water-propagation model, and wherein the seismic images that are generated do not include primary reflections.
14 . The medium of claim 8 , wherein the operations further comprise generating a velocity model representing a subterranean domain using the at least first-order multiple reflection signals.
15 . A computing system, comprising: one or more processors; and a memory system including one or more non-transitory computer-readable media storing instructions that, when executed by at least one of the one or more processors, cause the computing system to perform operations, the operations comprising: receiving seismic data comprising signals collected using a receiver, the seismic data representing a subsurface volume; identifying a downgoing wavefield and an upgoing wavefield in the seismic data; identifying direct arrivals in the downgoing wavefield; estimating at least first-order multiple reflection signals in the upgoing wavefield based on the downgoing wavefield, the upgoing wavefield, and the direct arrivals, wherein estimating the at least first-order multiple reflection signals comprises estimating first and higher multiple reflection signals by: generating an intermediate wavefield by subtracting the direct arrivals from the downgoing wavefield; deconvolving the downgoing wavefield from the intermediate wavefield to generate a second intermediate wavefield; and convolving the second intermediate wavefield with the upgoing wavefield; and generating seismic images representing the subsurface volume based at least in part on the at least first-order multiple reflection signals.

Description

Cross-Reference To Related Applications This application is the National Stage Entry of International Application No. PCT/US2021/033690, filed May 21, 2021. BACKGROUND Ocean Bottom Seismometer (OBS), Ocean Bottom Cable (OBC), and Ocean Bottom Node (OBN) refer to types of marine seismic data acquisition systems. In these systems, generally, seismic receivers (hydrophones, geophones, etc.) are positioned at or near the ocean bottom, and a seismic source sends shots downward, from a shallower depth. This technique is often used to create recordings in a relatively quiet environment (in comparison to streamers) and/or where obstructions are present that may make using a streamer difficult. Seismic data in this context, and in other marine and land-based contexts, may include a combination of several signals or wavefields. Generally, a “primary” reflection is the signal that is sought to be extracted from the recorded signal. The primary represents a seismic wave that is reflected from a subsurface reflector (generally an interface between two types of rock) and then detected by a receiver as it returns upwards. Another signal that may be present is a direct arrival. In the OBS/OBC/OBN context, this may generally be a signal that propagates from the source through the water and directly to the receiver, without being reflected. The seismic signals also generally include multiple reflection signals (or “multiples” for short). Multiple reflections occur when a downgoing seismic wave is reflected by a reflector, but before returning to the receiver, is reflected at least one more time, by a second reflector before finally propagating to the receiver. The second reflector can be subsurface or may be a “free surface”, e.g., the ocean surface. Multiple reflections are often considered a type of noise and have been the subject of many different techniques to identify and remove them from the seismic data, e.g., without removing the desired primary signals. Recently, it has been recognized that multiples also contain complementary information about the reflectivity of the subsurface. Accordingly, separating multiples and primaries is used to image the primaries without the multiples, but now also to image the multiples separately. Imaging of multiples has been shown to add value to the primary imaging particularly in areas where the illumination from the primaries is poor. SUMMARY Embodiments of the disclosure include a method that include receiving seismic data including signals collected using a receiver, the seismic data representing a subsurface volume, identifying a downgoing wavefield and an upgoing wavefield in the seismic data, identifying direct arrivals in the downgoing wavefield, estimating at least first-order multiple reflection signals in the upgoing wavefield based on the downgoing wavefield, the upgoing wavefield, and the direct arrivals, and generating seismic images representing the subsurface volume based at least in part on the at least first-order multiple reflection signals. Embodiments of the disclosure include a non-transitory computer-readable medium storing instructions that, when executed by at least one processor of a computing system, cause the computing system to perform operations that include receiving seismic data including signals collected using a receiver, the seismic data representing a subsurface volume, identifying a downgoing wavefield and an upgoing wavefield in the seismic data, identifying direct arrivals in the downgoing wavefield, estimating at least first-order multiple reflection signals in the upgoing wavefield based on the downgoing wavefield, the upgoing wavefield, and the direct arrivals, and generating seismic images representing the subsurface volume based at least in part on the at least first-order multiple reflection signals. Embodiments of the disclosure include a computing system that includes one or more processors and a memory system that includes one or more non-transitory computer-readable medium storing instructions that, when executed by at least one of the one or more processors, cause the computing system to perform operations that include receiving seismic data including signals collected using a receiver, the seismic data representing a subsurface volume, identifying a downgoing wavefield and an upgoing wavefield in the seismic data, identifying direct arrivals in the downgoing wavefield, estimating at least first-order multiple reflection signals in the upgoing wavefield based on the downgoing wavefield, the upgoing wavefield, and the direct arrivals, and generating seismic images representing the subsurface volume based at least in part on the at least first-order multiple reflection signals. Thus, the computing systems and methods disclosed herein are more effective methods for processing collected data that may, for example, correspond to a surface and a subsurface region. These computing systems and methods increase data processing effectiveness, e