Iterative inversion of data from simultaneous geophysical sources

Patent metadata

Field	Value
Publication number	US-9495487-B2
Application number	US-201313791252-A
Country	US
Kind code	B2
Filing date	Mar 8, 2013
Priority date	Sep 28, 2006
Publication date	Nov 15, 2016
Grant date	Nov 15, 2016

Abstract

Method for reducing the time needed to perform geophysical inversion by using simultaneous encoded sources in the simulation steps of the inversion process. The geophysical survey data are prepared by encoding ( 3 ) a group of source gathers ( 1 ), using for each gather a different encoding signature selected from a set ( 2 ) of non-equivalent encoding signatures. Then, the encoded gathers are summed ( 4 ) by summing all traces corresponding to the same receiver from each gather, resulting in a simultaneous encoded gather. (Alternatively, the geophysical data are acquired from simultaneously encoded sources.) The simulation steps needed for inversion are then calculated using a particular assumed velocity (or other physical property) model ( 5 ) and simultaneously activated encoded sources using the same encoding scheme used on the measured data. The result is an updated physical properties model ( 6 ) that may be further updated ( 7 ) by additional iterations.

First claim

The invention claimed is:

1. A computer-implemented method for inversion of measured geophysical data to determine a physical properties model for a subsurface region, comprising:
(a) obtaining the measured geophysical data from a geophysical survey of the subsurface region;
(b) inverting the measured geophysical data by iterative inversion process, using a computer, to determine an updated physical properties model for the subsurface region from an initial physical properties model, wherein:
(i) at least one iteration of the iterative inversion process comprises:
simultaneous encoded-source simulation of survey data representing a plurality of survey sources, or receivers if source-receiver reciprocity is used,
wherein source or receiver signatures in the simultaneous encoded-source simulation are encoded, resulting in a simulated simultaneous encoded-source or encoded-receiver gather of geophysical data,
the iterative inversion process involving updating the initial physical properties model to reduce misfit between the simulated simultaneous encoded-source or encoded-receiver gather and
a corresponding simultaneous encoded-source or encoded-receiver gather formed by summing gathers of measured survey data encoded with the same encoding functions used in the simultaneous encoded-source simulation, and
the updating includes determining an update to the initial physical properties model from a gradient of a cost function characterizing the misfit with respect to a parameter that describes the initial physical properties model and perturbing the initial physical properties model in direction of the gradient, and

(ii) at least one iteration of the iterative inversion process is performed by sequential source or receiver inversion;

(c) downloading the updated physical properties model or saving it to computer storage; and
(d) generating a subsurface image from the further updated physical properties model.

2. The method of claim 1 , wherein the encoding in (b)(i) is designed to cause the simultaneous encoded-source or encoded-receiver gather of measured data to sum individual gathers incoherently.

3. The method of claim 1 , wherein for one or more of the iterations in (b)(i), different encoding functions are used compared to the preceding iteration.

4. A computer-implemented method for inversion of measured geophysical data to determine a physical properties model for a subsurface region, comprising:
(a) obtaining one or more simultaneous encoded gathers of the measured geophysical data from a geophysical survey in which the one or more simultaneous encoded gathers are acquired from a plurality of simultaneously-operating, encoded sources;
(b) obtaining an initial physical properties model of the subsurface region, said initial physical properties model providing values of at least one physical property at locations throughout the subsurface region;
(c) updating, with a computer, the initial physical properties model so that an updated physical properties model is more consistent with the one or more simultaneous encoded gathers of measured data from step (a), said updating involving one or more encoded simultaneous source forward or reverse simulation operations that use the initial physical properties model and encoded source signatures using the same encoding as the encoded sources, wherein an entire simultaneous encoded gather is simulated in a single simulation operation, and said updating the initial physical properties model is included in an iterative inversion process that updates the initial physical properties model to reduce a misfit between the simultaneous encoded gather that is simulated and the one or more simultaneous encoded gathers that are acquired from the plurality of simultaneously-operating, encoded sources, and the updating includes determining an update to the initial physical properties model from a gradient of a cost function characterizing the misfit with respect to a parameter that describes the initial physical properties model and perturbing the initial physical properties model in direction of the gradient;
(d) repeating step (c) at least one iteration, using the updated physical properties model from the previous iteration of step (c) as the initial model to produce a further updated physical properties model of the subsurface region that is more consistent with the one or more simultaneous encoded gathers of measured data, using the same encoding in the simulation as were used by the source devices in obtaining the simultaneous encoded gather of measured data;
(e) downloading the further updated physical properties model or saving it to computer storage; and
(f) generating a subsurface image from the further updated physical properties model.

Assignees

• Exxonmobil Upstream Res Co

Inventors

• Krebs Jerome R
• Anderson John E
• Neelamani Ramesh
• Jing Charles
• Hinkley David L
• Dickens Thomas A

Classifications

• G01V1/28 Primary

  Processing seismic data, e.g. for interpretation or for event detection (G01V1/48 takes precedence) · CPC title

• G01V2210/67

  Wave propagation modeling · CPC title

• G06F30/20

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title

• G06F17/5009 Primary

  Physics · mapped topic

• G06T12/20

  Inverse problem, i.e. transformations from projection space into object space · CPC title