Method of geophysical exploration including processing and displaying seismic data to obtain a measure of subterranean formation rock properties

Claim 1

A method of geophysical exploration for processing seismic data, including the steps of: (a) fitting seismic signal amplitude variations, as a function of incident angle for selected seismic events to: R.sub.c '(θ)=B.sub.0 'B.sub.1 ' tan .sup.2 θ+B.sub.2 ' sin.sup.2 θ tan .sup.2 θ where R c '(θ) is a first reflection coefficient as a function of incident angle; θ is the incident angle; and obtaining a first set of attributes B 0 ', B 1 ' and B 2 ' descriptive of the seismic signal amplitude variation; and (b) mapping the first set of attributes onto an angle-dependent amplitude diagram and transforming the first set of attributes into a measure of the subterranean formation rock properties associated with each selected seismic event.

Claim 2

A method of geophysical exploration for processing seismic data, including the steps of: (a) fitting seismic signal amplitude variations, as a function of incident angle for selected seismic events to: R.sub.c '(θ)=B.sub.0 'B.sub.1 ' tan .sup.2 θ+B.sub.2 ' sin.sup.2 θ tan .sup.2 θ where R c '(θ) is a first reflection coefficient as a function of incident angle; θ is the incident angle; and obtaining a first set of attributes B 0 ', B 1 ' and B 2 ' descriptive of the seismic signal amplitude variation; and (b) mapping the first set of attributes onto an angle-dependent amplitude diagram and transforming the first set of attributes into a measure of the subterranean formation rock properties associated with each selected seismic event.

Claim 3

A method of geophysical exploration for processing seismic data, including the steps of: (a) fitting seismic signal amplitude, as a function of incident angle for selected seismic events, to: R.sub.c '(θ)=B.sub.0 '+B.sub.1 tan .sup.2 θ where R c ' (θ) is the first reflection coefficient as a function of incident angle; θ is the incident angle; and obtaining a first set of attributes B 0 ' and B 1 ' descriptive of the seismic signal amplitude variation; and (b) mapping the first set of attributes onto an angle-dependent amplitude diagram and transforming the first set of attributes into a measure of the subterranean formation rock properties associated with each selected seismic event.

Claim 4

A method of geophysical exploration for processing seismic data, including the steps of: (a) fitting seismic signal amplitude, as a function of incident angle for selected seismic events, to: R.sub.c '(θ)=B.sub.0 '+B.sub.1 tan .sup.2 θ where R c ' (θ) is the first reflection coefficient as a function of incident angle; θ is the incident angle; and obtaining a first set of attributes B 0 ' and B 1 ' descriptive of the seismic signal amplitude variation; and (b) mapping the first set of attributes onto an angle-dependent amplitude diagram and transforming the first set of attributes into a measure of the subterranean formation rock properties associated with each selected seismic event.

Claim 5

A method of geophysical exploration for processing seismic data, including the steps of: (a) statistically fitting seismic signal amplitude variations, as a function of incident angle, for selected seismic events to a parametric equation relating contrasts in formation rock properties to seismic signal amplitude variations, as a function of incident angle, and obtaining a set of attributes descriptive of such amplitude variations; and (b) mapping the set of attributes onto an angle-dependent amplitude diagram and transforming the set of attributes into a measure of the contrast in subterranean formation rock properties associated with each selected seismic event.

Claim 6

A method of geophysical exploration for processing seismic data, including the steps of: (a) statistically fitting seismic signal amplitude variations, as a function of incident angle, for selected seismic events to a parametric equation relating contrasts in formation rock properties to seismic signal amplitude variations, as a function of incident angle, and obtaining a set of attributes descriptive of such amplitude variations; and (b) mapping the set of attributes onto an angle-dependent amplitude diagram and transforming the set of attributes into a measure of the contrast in subterranean formation rock properties associated with each selected seismic event.

Claim 9

A method of geophysical exploration for displaying and interpreting seismic data including the steps of: (a) preparing a lithology diagram having axes of selected formation rock properties for relating contrasts in formation lithology to contrasts in formation rock properties; (b) plotting contour lines on the lithology diagram representative of contrasts in assumed formation rock properties across a subterranean formation interface; and (c) mapping a first set of attributes on the lithology diagram wherein the attributes are descriptive of variations in amplitude of a seismic signal, as a function of incident angle, for a selected seismic event associated with the subterranean formation interface.

Claim 10

A method of geophysical exploration for displaying and interpreting seismic data including the steps of: (a) preparing a lithology diagram having axes of selected formation rock properties for relating contrasts in formation lithology to contrasts in formation rock properties; (b) plotting contour lines on the lithology diagram representative of contrasts in assumed formation rock properties across a subterranean formation interface; and (c) mapping a first set of attributes on the lithology diagram wherein the attributes are descriptive of variations in amplitude of a seismic signal, as a function of incident angle, for a selected seismic event associated with the subterranean formation interface.

Claim 16

A method of geophysical exploration for obtaining a measure of subterranean formation rock properties including the steps of: obtaining a set of observed attributes descriptive of seismic signal amplitude variations as a function of incident angle for seismic events in the seismic signals; obtaining a set of theoretical attributes descriptive of a plurality of contrasts in assumed formation rock properties across a subterranean formation interface associated with the selected seismic event; plotting a plurality of theoretical attribute contour lines on a lithology diagram having axes of selected formation rock properties for relating contrasts in formation lithology to contrasts in formation rock properties; scaling the observed set of attributes to units of reflection coefficient; and plotting the scaled observed attributes onto the contour lines of the theoretical set of attributes to obtain a measure of the underlying formation rock properties associated with the seismic event.

Claim 17

A method of geophysical exploration for obtaining a measure of subterranean formation rock properties including the steps of: obtaining a set of observed attributes descriptive of seismic signal amplitude variations as a function of incident angle for seismic events in the seismic signals; obtaining a set of theoretical attributes descriptive of a plurality of contrasts in assumed formation rock properties across a subterranean formation interface associated with the selected seismic event; plotting a plurality of theoretical attribute contour lines on a lithology diagram having axes of selected formation rock properties for relating contrasts in formation lithology to contrasts in formation rock properties; scaling the observed set of attributes to units of reflection coefficient; and plotting the scaled observed attributes onto the contour lines of the theoretical set of attributes to obtain a measure of the underlying formation rock properties associated with the seismic event.

Claim 22

A method of geophysical exploration for interpreting seismic data, including the steps of: (a) obtaining a first set of attributes descriptive of seismic signal amplitude variations as a function of incident angle for selected seismic events in incident angle ordered gathers of seismic signals; (b) assuming a set of formation rock properties for an overlying formation associated with each selected seismic event; (c) assuming any other set of formation rock properties for an underlying formation associated with each selected seismic event; (d) wherein the assumed formation rock properties define a plurality of assumed contrasts in the formation rock properties across the subterranean formation interface associated with each selected seismic event; (e) obtaining second sets of attributes from the plurality of assumed contrasts in formation rock properties for each selected seismic event; (f) mapping contour lines of the second sets of attributes onto a lithology diagram; and (g) plotting the first set of attributes onto the respective contour lines of the second set of attributes to obtain a more probable estimate of the underlying formation rock properties.

Claim 23

A method of geophysical exploration for interpreting seismic data, including the steps of: (a) obtaining a first set of attributes descriptive of seismic signal amplitude variations as a function of incident angle for selected seismic events in incident angle ordered gathers of seismic signals; (b) assuming a set of formation rock properties for an overlying formation associated with each selected seismic event; (c) assuming any other set of formation rock properties for an underlying formation associated with each selected seismic event; (d) wherein the assumed formation rock properties define a plurality of assumed contrasts in the formation rock properties across the subterranean formation interface associated with each selected seismic event; (e) obtaining second sets of attributes from the plurality of assumed contrasts in formation rock properties for each selected seismic event; (f) mapping contour lines of the second sets of attributes onto a lithology diagram; and (g) plotting the first set of attributes onto the respective contour lines of the second set of attributes to obtain a more probable estimate of the underlying formation rock properties.